Bisphenol A and indicators of obesity, DM and CVD.BPA与肥胖,糖尿病和心血管疾病指标。
5 厌氧消化碱性预处理
Effect of alkaline pretreatment on anaerobic digestion of solid wastesM.Lo´pez Torres *,Ma.del C.Espinosa Llore ´ns National Center for Scientific Researcher (CNIC),Environmental Pollution Department (DECA),Ave.25y 158,Cubanacan,Playa,Havana City,CubaAccepted 19October 2007Available online 18December 2007AbstractThe introduction of the anaerobic digestion for the treatment of the organic fraction of municipal solid waste (OFMSW)is currently of special interest.The main difficulty in the treatment of this waste fraction is its biotransformation,due to the complexity of organic material.Therefore,the first step must be its physical,chemical and biological pretreatment for breaking complex molecules into simple monomers,to increase solubilization of organic material and improve the efficiency of the anaerobic treatment in the second step.This paper describes chemical pretreatment based on lime addition (Ca(OH)2),in order to enhance chemical oxygen demand (COD)solubi-lization,followed by anaerobic digestion of the OFMSW.Laboratory-scale experiments were carried out in completely mixed reactors,1L capacity.Optimal conditions for COD solubilization in the first step of pretreatment were 62.0mEq Ca(OH)2/L for 6.0h.Under these conditions,11.5%of the COD was solubilized.The anaerobic digestion efficiency of the OFMSW,with and without pretreatment,was evaluated.The highest methane yield under anaerobic digestion of the pretreated waste was 0.15m 3CH 4/kg volatile solids (VS),172.0%of the control.Under that condition the soluble COD and VS removal were 93.0%and 94.0%,respectively.The results have shown that chemical pretreatment with lime,followed by anaer-obic digestion,provides the best results for stabilizing the OFMSW.Ó2007Elsevier Ltd.All rights reserved.1.IntroductionIn Cuba,municipal solid waste management is currently facing serious problems involving a lack of adequate trans-portation,environmental pollution as a result of the use of horse-driven cars,potential biohazards in landfill places after disposal without any treatment,and urbanization in existing landfills.In order to solve such problems,the Cuban government has been working on a master plan for integrated manage-ment of municipal solid waste.Only a very short-term plan,basically an annual one,is currently available and the for-mulation of an integrated master plan having long-term perspectives is an urgent necessity.Since municipal solid wastes are rapidly increasing,thus provoking huge waste disposal problems,the government is mainly concerned with the incorporation of solutions for the treatment of such complex wastes (JICA,2004).Anaerobic digestion can be an attractive option,both asa disposal route and as a source of alternative energy.In the last few years,much effort has been made at introduc-ing anaerobic digestion processes for treating the organic fraction of municipal solid waste (OFMSW)(Wu et al.,2006).However,the main obstacle in spreading this tech-nology is the lower biodegradation rate of solid wastes (due to the chemical composition and structure of lignocel-lulosic materials)in comparison to liquid ones.It is recog-nized that the rate-limiting step of anaerobic processes for wastes with a high solids content is the hydrolysis of the complex organic matter to soluble compounds (Pavlostas-this and Gosset,1985;Delgenes et al.,1999;Chulhwan et al.,2005).Therefore,physical,chemical or biological pretreatment methods (or their combination)are required,in order to reduce the rate of such a limiting step.Previous studies have pointed out that alkali pretreat-ment is the best known method for enhancing the biodeg-radation of complex materials,thus rendering the most significant benefits (Hoon,2004).In the last years,the use of ozone in chemical pretreatment is gaining great0956-053X/$-see front matter Ó2007Elsevier Ltd.All rights reserved.doi:10.1016/j.wasman.2007.10.006*Corresponding author.Tel.:+5372718897;fax:+5372080497.E-mail address:matilde.lopez@.cu (M.Lo´pez Torres)/locate/wasmanAvailable online at Waste Management 28(2008)2229–2234interest in the scientific community,not only by removing recalcitrant and toxic compounds but also by increasing the biodegradability of waste.However,this process is con-sidered to be very expensive if intended to eliminate all of the contaminants of the waste(Momenti and Cleto, 2006).Special attention is afforded to the use of combined pretreatment,including alkaline pretreatment for increas-ing the efficiency of anaerobic digestion of complex wastes (Bill et al.,1990;Rodrı´guez-Va´zquez et al.,1992;Delgenes et al.,1999;Chulhwan et al.,2005).The preferred chemical, in all cases,was sodium hydroxide(NaOH),which was reported to yield greater solubilization efficiency than cal-cium hydroxide(Ca(OH)2).Although NaOH enhancesanaerobic digestion performance,the use of this reagent involves higher chemical costs and,therefore,a possible increase of pretreatment cost.Nevertheless,Ca(OH)2is less expensive,US$0.07/kg(GECA,2004),than many other materials and has been thoroughly applied in pretreatment studies from various biomass sources such as corn stover, wood,sugar-mill-mud waste(SMMW),municipal waste and sludge(Bill et al.,1990;Espinosa et al.,1995;Hoon, 2004;Lo´pez et al.,2005).Besides,the availability of lime must favor studying and expanding this alternative under Cuban conditions.The government has made a great effort to introduce the adequate management of solid wastes,with the assistance of various developed countries.A study to prepare an inte-grated solid waste management plan was carried out,with the capital(Havana)being the reference because it has the highest population in Cuba.Currently,a study is being conducted on the feasibility and selection of recommended projects,leading to thefinal formulation of appropriate pilot projects.Thus,lime pretreatment might be an economical option as afirst step,in order to improve biodegradation of ligno-cellulosic materials.The objective of the present work is to evaluate the effect of alkaline pretreatment with lime in anaerobic digestion of solid wastes,especially on the organic fraction of municipal solid waste.2.Methodsanic fraction of municipal solid waste(OFMSW)For this study,samples fromfive municipalities of Havana were collected and separated into fractions,that is,plastics,glass,rubber,textiles,aluminum,general met-als,paper–cardboard,wood,yard waste,and kitchen waste.A10kg sample of each organic fraction,mainly kitchen waste and other small organic materials,were placed in nylon bags and transported to the laboratory, where the OFMSW was mixed with water to obtain a con-centration of8%total solids(TS).The characteristics of OFMSW from all of the analyses are shown in Table1.The data represent the average of three independent determinations from three independent samples.Differences among the observedfigures were less than3%in all cases.2.2.Alkaline pretreatmentDespite the chemical characteristics of lime,it was employed as a chemical agent for hydrolyzing in the OFMSW pretreatment.The higher lime availability and low cost compared to any other chemical may allow scale-up of the process and further introduction of results.The pretreatment was performed in batch,in a1-L reac-tor,at room temperature under anoxic condition.A mechanical stirrer was used for continuous mixing of the components.The experiments were conducted in triplicate.The experimental work was designed to study the effects of lime in OFMSW solubilization.Two independent vari-ables were considered:concentration of lime and time of solubilization.Furthermore,alkali concentration levels of 40and100mEq/L and solubilization times of1and6h were considered in the statistical experimental design. The optimal parameters were obtained from a32factorial plan.The effectiveness of the pretreatment was evaluated by the solubilization degree,based on the quantity of solu-ble organic matter and expressed as a function of chemical oxygen demand(COD)Sð%Þ¼SCOD fÀSCOD iTCODÃ100whereS=Solubilization(%)SCOD=Soluble chemical oxygen demand(f–final and i–initial)(mg/L)TCOD=Total chemical oxygen demand(mg/L)2.3.Anaerobic bioreactorThe effects of the OFMSW solubilization on the anaer-obic digestion process,with respect to a control digester (fed with no pretreated wastes),were evaluated in this sequence.Both digesters consisted of1L stirred reactors,operated on a batch basis,fed with loads of40,60,80and100mL. Table1Characteristics of organic fraction of municipal solid waste used in the experimentsParameter Concentration(mg/L)a Total COD49,429Soluble COD13,675Total solids81,150Volatile solids54,401Total dissolved solids12,903Volatile dissolved solids8154pH7.5a Except pH.2230M.Lo´pez Torres,Ma.d.C.Espinosa Llore´ns/Waste Management28(2008)2229–2234In all of the experiments,the digesters were run in afill-and-drawn mode,with volumes of the settled supernatant removed equal to volumes of feed added.The settlement period was2h,which was enough for separating and retaining biomass.Each experiment lasted the interval for maximum gas production,and COD removal in each load andfigures represent the mean of two runs.The volume of methane was measured by using a1-L Boyle–Mariotte reservoir,which was connected to the digesters.To remove the CO2produced,a tightly closed bubbler,holding a KOH solution(10%),was connected between the two elements.The methane produced displaces a measurable volume of water from the reservoir,which was equivalent to the methane volume.2.4.Analytical methodsAll analyses were done by triplicate,following validated sources such as the American Public Health Association (APHA,1998)and involved chemical oxygen demand (COD),total solids(TS),volatile solids(VS),total dis-solved solids(TDS),volatile dissolved solids(VDS)and pH.Total and soluble COD were determined by the color-imetric method.The samples were centrifuged at 10,000rpm for20min.2.5.Statistical processingTo study the effects of the different factors and to test the statistical significance,the Analysis of Variance (ANOVA)and the t-Student were conducted,using the software Statgraphic(Statgraphic,2000).3.Results and discussionThe most remarkable characteristic of this waste was the high content of organic matter,expressed as total COD and the fractions VS/TS and VDS/TDS(Table1).The per-centages of VS in TS and VDS in TDS are67.0%and 63.0%,respectively.Anyway,the large amount of sus-pended solids(more than80.0%)and the relatively low content of dissolved matter make pretreatment necessary, in order to enhance the chemical oxygen demand(COD) solubilization.As a result,a higher efficiency of the anaer-obic digestion process must be achieved.3.1.PretreatmentThe increase of the soluble chemical oxygen demand (SCOD)from13,675to20,101mg/L was noticed when the lime concentration was increased up to70mEq Ca(OH)2/L.Under this condition,a solubilization of 13.0%of was observed.On the other hand,the concentra-tion of volatile dissolved solids(VDS)was increased slightly(5.8%)after the pretreatment,which may be due to the progressive hydrolysis of the complex organic matter present in the feeding.Throughout the assays,the addition of lime caused a sudden increase in pH followed by a grad-ual drop,which can be attributed to neutralization of the acidic products,previously formed.Such behavior was also noticed by other authors(Pavlostasthis and Gosset,1985; Rajan et al.,1989;Espinosa et al.,1995).The statistical results for the optimization of COD solu-bilization are summarized in Table2.The analysis of var-iance(ANOVA,p<0.05)involving three effects(alkali concentration,time and second-order interaction among concentration itself)indicates that they are statistically sig-nificant.Furthermore,the R-squared statistic indicates that thefitted model explains92.4%of the variability in solubilization.The analysis shown in the Pareto chart(Fig.1)suggests that interaction among the alkali concentration itself,alkali concentration and time are the factors contributing signif-icantly to solubilization.All of them cross the vertical line, representing a significance of95%.The equation of thefit-ted model,considering the values of the variables in their original units and only the significant coefficients,isS¼À5:7351þ0:6777ÃCÀ4:6436ÃtÀ0:0049ÃC2 whereS=Solubilization(%)C=Alkali concentration(mEq Ca(OH)2/L)t=Solubilization time(h)Table2Summary of the statistical analysis(ANOVA)Source Sum ofsquaresDf MeansquareF-Ratio p-ValueA:Concentration20.944120.94411.590.0272a B:Time17.34117.349.600.0363a AA46.4732146.473225.730.0071a AB0.83722510.8372250.460.5334 BB 6.139811 6.13981 3.400.1390 Total error7.225974 1.80649Total(correlation)94.6729R-squared=92.3674%.a Statistical signification at95%confidencelevel.M.Lo´pez Torres,Ma.d.C.Espinosa Llore´ns/Waste Management28(2008)2229–22342231A positive correlation (r =0.961)was also demonstrated among observed and fitted data (Fig.2),which supports the model.The optimal solubilization condition for OFMSW was 62.0mEq Ca(OH)2/L (equivalent to 2.3g Ca(OH)2/L)and 6.0h (Fig.3).Under these conditions,solubilization reached levels up to 11.5%.The characterization of the pre-treated OFMSW is shown in Table 3.Further addition of Ca(OH)2has shown a decrease in solubilization,which may be associated with instability and formation of com-plex,non-soluble compounds.As a result,hydrolysis of organic matter becomes unfeasible.Moreover,if alkali concentration was increased beyond the optimal concentra-tion (100mEq Ca(OH)2/L),soluble COD decreased from 19,359to 14,664mg/L,a finding that also supports the above results.Our results of alkaline pretreatment were compared to those from other authors (Table 4).Rajan et al.(1989)reported a solubilization of 14%(20mEq/L of alkali)and only 18%(40mEq/L),for the same alkali (Ca(OH)2),1%TS solids.However,it is important to clarify that these data represent the average values without any optimizationstudy.On the other hand,Espinosa et al.(1995)and Lo´pez et al.(2005)found similar results by treating sewage sludge from a wastewater treatment plant and sugar-mill-mud waste (SMMW)from a sugar factory,respectively.In the present study,optimal levels of solubilization were also similar to those results,irrespective of the type of waste.All of the above results support the positive effect of alkaline pretreatment with Ca(OH)2on the organic frac-tion of municipal solid wastes.Not only was the level of soluble COD increased but also surface area of complex organic matter,due to swelling.This fact makes these wastes more susceptible to enzymatic attack by microor-ganisms,so that anaerobic digestion processes must be fur-ther enhanced.3.2.Anaerobic digestionAnaerobic digestion performance in both reactors is shown in Table 5.An initial OFMSW concentration of 8%TS (adjusted prior to each feeding or pretreatment)was used.One of the reactors was loaded with the pre-treated waste with alkali at 62.0mEq Ca(OH)2/L,equiva-lent to 2.8g Ca(OH)2/100g TS.The effect of pretreatment on VS and SCOD removal was tested by applying t -Stu-dent,paired samples (two tails),p <0.05.Differences between digesters for VS (p =0.000005)and SCOD (p =0.00042)removals were statistically significant,so that pretreatment must improve digestibility of complex wastes.The structural properties of the waste withoutpretreatment41.2152.433.6464.8616.0767.2918.5069.72110.93712.152aboveFig.3.Surface plot.Chemical pretreatment of OFMSW (organic fraction of municipal solid waste).Table 3Characteristics of organic fraction of municipal solid waste after pretreatment under optimal conditions ParameterConcentration (mg/L)a Total COD 47,445Soluble COD 19,359Total solids80,035Volatile dissolved solids 12,861pH8.5aExcept pH.Table 4Comparison of the solubilization levels using lime pretreatment for different solid wastesRajan et al.(1989)Espinosa et al.(1995)Lo´pez et al.(2005)This study Waste Waste activated sludge Sewage sludge SMMW OFMSW Concentration (mEq/L)40608662TS (%)1388Solubilization (%)1811.714.511.52232M.Lo´pez Torres,Ma.d.C.Espinosa Llore ´ns /Waste Management 28(2008)2229–2234hamper anaerobic degradation,thus limiting surface area for microbial attack and anaerobic decomposition.Similar results were summarized for gas yield.The pre-treated digester yielded higher methane amounts than con-trol (significant differences,p =0.0019),which suggests that pretreatment should improve anaerobic digestion,not only increasing organic solubilization but also surface area available for enzymatic action as a result of fiber swell-ing.The maximum increase in methane yield was 172.7%over the control for a feeding of 100mL of pretreated waste.However,the methane yields were lower than those from other authors (Table 6).As a whole,they have stud-ied various pretreatment combinations of different solid wastes,but very expensive ones (Del Borghi et al.,1999;Tiehm et al.,2001;Chulhwan et al.,2005).On the other hand,the composition of the waste and the unavoidable small pieces of non-biodegradable materials present in the waste (since it is not source-selected)contributed to the results presented in this work.Mata-Alvarez et al.(1990)found similar results when compared source-selected OFMSW and mechanically-selected OFMSW.Neverthe-less,when economic considerations are made,the pretreat-ment alternative studied in this work shows positive results,being affordable from the economic point of view,consid-ering the low cost (US$0.07/kg)of the Ca(OH)2,(GECA,2004).Fig.4.shows the variation of the cumulated methane volumes as a function of time for different feed volumes in the control digester without pretreatment.The anaerobic digestion of the OFMSW follows a step-wise reaction or diauxic performance,as described by Aiba et al.,1970.In contrast with that,Fig.5.shows methane production inthe pretreated waste digester.It was observed,in all cases,a concomitant,gradual and continuous enhancement in methane production with the increase of the volume of waste added.This result clearly demonstrates the advan-tage of this approach.During the experiment,as consequence of the degrada-tion of low molecular weight compounds to final products (that might be acidic ones),it was necessary to continuously add alkali in the control digester.In contrast,the digester fed with pretreated waste maintained its alkalinity and neu-tral pH,thus helping the biotransformation process.The above results suggest that under appropriate alkali treatment,complex organic matter becomes moreTable 5Summary of digester performanceLoad (mL/L reactor )Without pretreatment With pretreatment 406080100406080100VS removal (%)7876767595959494SCOD removal (%)9494929096969593(m 3CH 4/kg VS)000.0530.0550.0410.0530.1010.150Maximum increase (%)90.56172.70pH7.07.27.27.57.37.07.07.0Table 6Comparison of the methane yield under different conditionsDel Borghi et al.(1999)Tiehm et al.(2001)Chulhwan et al.(2005)Chulhwan et al.(2005)This study WasteOFMSW +SSWASWASWASOFMSW PretreatmentChemical and bacterial a Ultrasonic b Biological c Thermochemical d Chemical e CH 4yield (m 3CH 4/kg VS)0.390.30.290.520.15a Organic fraction of municipal solid waste +sewage sludge (OFMSW +SS).Chemical hydrolysis with NaOH and selected hydrolytic bacteria.b Waste activated sludge (WAS).Ultrasonic disintegration.c Waste activated sludge (WAS).Aerobic bacteria and acidogenic process with selected bacteria.d Waste activated sludge (WAS).Thermal treatment with NaOH.eOrganic fraction of municipal solid waste (OFMSW).Chemical hydrolysis with Ca(OH)2.M.Lo´pez Torres,Ma.d.C.Espinosa Llore ´ns /Waste Management 28(2008)2229–22342233biodegradable by roughly changing chemical structure.The treatment may also induce swelling,thus enhancing surface area available for further microbial enzymatic attack.Thus,these results could be an alternative to include into the master plan for the integrated management of municipal solid waste in Cuba.4.ConclusionsThe alkaline pretreatment renders a significant increase in the soluble COD,11.5%of the total COD,thus improv-ing anaerobic digestion,measured by an increase of meth-ane yields up to172%over the control without pretreatment.From the above results,a procedure for the treatment of the organic fraction of the municipal solid waste can be designed.The two-stage design must involve lime alkaline pretreatment,followed by anaerobic digestion. AcknowledgmentsThe authors wish to thanks Mrs.Janis Zral and Mr.Celso Pe´rez by their careful proofreading of and recommendations to improve the manuscript.Also,the authors are grateful to their colleagues Rigoberto Escobedo Acosta,Oneida Correa Senciales,Xiomara Rodrı´guez Petit,Yadiana Leo´n Herna´n-dez,Yamile´A´lvarez Llaguno,Rosario Morejo´n Montano, Jacqueline Gutie´rrez Navarrete,and Antonio On˜a,for con-ducting the analysis and collecting the samples. ReferencesAiba,S.,Humphrey A.,Millis N.,1970.Biochemical Engineering.Instituto del Libro.Ciencia y Te´cnica(Book Institute.Science and Technical).La Habana.Cuba.APHA,AWWA,WPCF,1998.Standard Methods for analysis of water and wastewater.20th ed.American Public Health Association, Washington,DC,USA.Bill,T.,Jih-Gaw,L.,Rajan,R.V.,1990.Low-level alkaline solubilization for enhanced anaerobic digestion.Journal Water Pollution Control Federation62(1),81–87.Chulhwan,P.,Chunyeon,L.,Sangyong,K.,Yu,Ch.,Howard,C.H., 2005.Upgrading of anaerobic digestion by incorporating two different hydrolysis processes.Journal of Bioscience and Bioengineering100(2), 164–167.Del Borghi, A.,Converti, A.,Palazzi, E.,Del Borghi,M.,1999.Hydrolysis and thermophilic anaerobic digestion of sewage sludge.Bioprocess Engineering20,553–566.Delgenes,J.P.,Penaud,V.,Torrijos,M.,Moletta,R.,1999.Thermo-chemical pretreatment of an industrial microbial biomasa:Effect of sodium hydroxide addition on COD solubilization,anaerobic biode-gradability and generation of soluble inhibitory compounds.In: Proceeding II International Symposium on anaerobic digestion of solid waste.Barcelona,Espan˜a.pp.121–128.Espinosa,M.C.,Lo´pez,M.,Montalvo,S.,Escobedo,R.,Ruı´z,M., Correa,O.,1995.Chemical solubilization and anaerobic treatment of sewage sludge.In:Proceeding Earth Conference on Biomass for energy,development and the environment.Havana,Cuba.p.103. GECA,2004.Directorio de productores,industriales,agropecuarios y de servicios de la Repu´blica de Cuba.(Cuban producers,industrialists, farming and services directory.)Third ed.<www.chasqui.cu> (accessed26.04.07).Hoon,K.S.,2004.Lime pretreatment and enzymatic hydrolysis of corn stover.Dissertation for the Degree of Doctor of Philosophy.Texas A&M University.JICA,2004.Study on Integrated Management Plan of Municipal Solid Waste in Havana City.Progress Report.Part1.Cuba.Lo´pez,M.,Espinosa,M.C.,Escobedo,R.,2005.Estudio comparativo del pretratamiento quı´mico para mejorar la digestio´n anaerobia de residuos so´lidos(Comparative study of chemical pretreatment to improve the anaerobic digestion of solid wastes).Revista CNIC.vol.36,Nu´mero Habana.Cuba.Mata-Alvarez,J.,Cecchi, F.,Pavan,P.,1990.The Performance of digesters treating the organic fraction of municipal solid wastes differently sorted.Biological Wastes33,181–199.Momenti,T.J.,Cleto,E.,bination of an anaerobic process and ozonation in the treatment of cellulosic pulp bleaching effluent.In: Proceeding of the Second International Meeting on Environmental Biotechnology and Engineering(2IMEBE).Edited by He´ctor Mario Poggi-Varaldo,Elvira rı´os-Leal,Jaime Garcı´a-Mena,Fernando Espa-rza-Garcı´a,Ma Teresa Ponce-Noyola,Ireri Robles-Gonza´lez,Isabel Sastre-Conde,Herver Macarie,Jose´Luis Sanz,Irene Watson-Craik, Eugenio Foresti,Danny Reible and Claudio Garibay-Orijel.Me´xico. Pavlostasthis,S.G.,Gosset,J.M.,1985.Modeling alkali consumption and digestibility improvement from alkaline treatment of wheat straw.Biotechnology and Bioengineering27,345–354.Rajan,R.V.,Lin,J.G.,Ray,B.T.,1989.Low-level chemical pretreatment for enhanced sludge solubilization.Journal Water Pollution Federa-tion64(11/12),1678–1683.Rodrı´guez-Va´zquez,R.,Villanueva-Ventura,G.,Rios-Leal, E.,1992.Sugarcane Bagasse pith dry pretreatment for single cell protein production.Bioresource Technology39,17–22.STATGRAPHIC plus5,2000.Statistical Graphics Corp.,USA. Tiehm,A.,Nickel,K.,Zellhorn,M.,Neis,U.,2001.Ultrasonic waste activated Sludge Disintegration for improving anaerobic stabilization.Water Research35,2003–2009.WU,M.,Sun,K.,Zhang,Y.,2006.Influence of temperaturefluctuation on thermophilic anaerobic digestion of municipal organic solid waste.Journal of Zhejiang University SCIENCE B.ISSN1673-1581(Print);ISSN1862-1783(Online).2234M.Lo´pez Torres,Ma.d.C.Espinosa Llore´ns/Waste Management28(2008)2229–2234。
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Determination of Bisphenol A Migrating from Epoxy CanCoatings to Infant Formula Liquid Concentrates
Determination of Bisphenol A Migrating from Epoxy Can Coatings to Infant Formula Liquid ConcentratesJ.E.Biles,*T.P.McNeal,and T.H.BegleyOffice of Premarket Approval,HFS-248,U.S.Food and Drug Administration,200C Street S.W.,Washington,D.C.20204Migration of bisphenol A(BPA)from epoxy-coated can surfaces to infant formula concentrates isreported.Levels of BPA in the undiluted concentrates surveyed in this study range from0.1to13parts per billion(ppb)as determined by solid phase extraction/high-pressure liquid chromatographywith fluorescence detection and confirmation by gas chromatography with mass selective detection.Fourier transform infrared spectroscopy with30°specular reflectance/transmittance was used toscreen formula cans for epoxy coatings.Keywords:Bisphenol A;epoxy;can coating;migration;infant formulaINTRODUCTIONEpoxy polymers are resistant to solvents and can bondto a variety of substrates,especially metals(Gannon,1990).These properties make epoxy resins a popularchoice for use in enamel coatings on the food contactsurfaces(FCS)of metal food and beverage cans.When-ever a polymeric material is in contact with food,theresidues and additives in the polymer may migrate tothe food.This is especially true for polymers exposedto food at elevated temperatures,i.e.heat-processedcanned foods.Bisphenol A(4,4′-isopropylidenediphenol,CAS Registry No.80-05-7,more commonly known asBPA)is a principal reactant in the preparation of manyepoxy polymer resins,including those used in foodcontact can enamels.Recently,BPA has been associ-ated with estrogen-like behavior in in-vitro cell culturestudies(Krishnan et al.,1993).The effects of BPA invivo are still unclear.We have developed a protocol to screen for BPA-basedepoxy can coatings on the FCS and determine BPA ininfant formula concentrates.If a can coating is screenedusing Fourier transform infrared spectroscopy(FT-IR)and identified as an epoxy,migrated BPA in the formulais concentrated by solid phase extraction(SPE)anddetermined in the extract by high-pressure liquid chro-matography(HPLC)with fluorescence detection.BPA is then confirmed in selected formula extracts by gas chromatography with mass selective detection(GC-MS). To determine BPA in infant formulas,a protocol was needed to determine low parts per billion(ppb)levels. Methods reported in the literature for determination of BPA,bisphenol F(BPF),the diglycidyl ether of BPA (DGEBA or BADGE in Europe),and the diglycidyl ether of BPF(DGEBF)(Brotons et al.,1995;Begley et al., 1991;Losada et al.,1991;Crathorne et al.,1986;Gan-dara et al.,1990;Henriks-Eckermanand and Laijoki, 1988)were not suitable for our goals.The protocol described in this paper provides greater specificity and sensitivity for BPA than the methods reported in the literature.EXPERIMENTAL PROCEDURESReagents.All solvents were of HPLC grade and purchased from Burdick and Jackson,Inc.(Muskegon,MI).BPA was of 99+%purity purchased from Aldrich Chemical Co.(St.Louis, MO).Water was distilled and then purified by a Milli-Q water purification system(Millipore Corp.,Milford,MA).A pow-dered infant formula concentrate(Gerber Products Co.,Free-mont,MI)was purchased from a local supermarket and prepared daily as needed(for an analytical blank)according to instructions on the label.Infant Formula Concentrates.At least three cans from each of four major manufacturers of infant formula in the United States were surveyed using the protocol presented here. All of the canned formula concentrates were purchased in suburban Maryland and Virginia near Washington,DC,dur-ing January and February1996.One exception was a single 945mL can of ready-to-feed formula,ca.3years old at the time of testing(as noted in Table1.).Each manufacturer in the test group has several formulations of milk-and soy-based products.The variety of formulations ranges from those*Author to whom correspondence should be ad-dressed[fax(202)401-8531].Table1.Amount of BPA in Undiluted Canned Infant Formula ConcentratesBPA determined cformulabrand a can type b ppb ng/cm2%recov A113.211.675A112.110.690E39.58.590B18.37.479A4 5.1 4.583B4 4.8 4.267C d5 4.5 4.0104D d4 3.9 3.5109B4 3.6 3.295C2 1.510.180C2 1.38.889C d2 1.38.8100D40.70.6106D40.10.197a At least three examples of each major manufacturer’s formula were purchased.An example of one other brand is included(E).b Can types:1,two piece,384mL volume,epoxy-coated lid, modified epoxy-coated body;2,two piece,384mL volume,epoxy-coated lid,PVC-coated body;3,three piece,384mL volume,epoxy-coated ends,modified epoxy side(body);4,three piece,384mL volume,epoxy-coated ends and side(body);5,three piece,945mL volume,epoxy-coated ends,modified epoxy side(body)(this can contained ready-to-feed formula,ca.3years old at time of analysis).c Area(cm2)is calculated for epoxy-coated surfaces only.d Soy-based products;all others are milk-based.4697J.Agric.Food Chem.1997,45,4697−4700S0021-8561(97)00518-9This article not subject to U.S.Copyright.Published1997by the American Chemical Societyfortified with nutrients such as iron to products intended for consumption by different age groups.All of the formula concentrates contained between7%and8%(w/v)fat and were intended for a1:1dilution(v/v)with water.Except as noted, all of the cans in the survey were made to contain384mL and were of two-or three-piece design(two-piece having a top and seamless body and three-piece having two ends joined by a seamed body).FT-IR Apparatus and Operating Conditions.A Nicolet Magna550Series II(Nicolet Analytical Instruments,Madison, WI)FT-IR equipped with a30°horizontal specular reflectance/ transmittance attachment(Janos Optical Corp.,Townshend, VT)and interfaced with a personal computer running Omnic (Nicolet Analytical Instruments)software was used to pre-screen all of the cans surveyed in this study.The FT-IR was set to average32scans.Qualitative Analysis of Can Coatings by FT-IR.The lot number and any relevant description of the can such as design,volume,formula type(soy-based or milk-based,iron fortified,etc.),and manufacturers were recorded.(All were analyzed prior to the expiration date except as noted in Table1.)The formula concentrate was transferred from the can toa clean Erlenmeyer flask and reserved for later analysis.The inside of the empty can was cleaned with soap and water to remove any food residues and rinsed.The inside surface of the can was dried with a clean towel and then air-dried for several hours.When the can had been thoroughly dried,a coupon measuring ca.5cm×1.5cm was removed from each side(body and lid or ends)of the can with tin snips.One coupon at a time was then placed flat on the horizontal specular reflectance/transmittance attachment mounted in the FT-IR so the infrared radiation was incident on the food contact surface of the can coupon.The can coupons were analyzed and the spectra compared to infrared spectra of known epoxies and other polymers.SPE.SPE tubes were6mL styrene/divinylbenzene porous polymer packing available as Supelclean Envi-chrom P(Su-pelco,Inc.,Bellefonte,PA).HPLC Apparatus and Operating Conditions.The HPLC System consisted of a Spectra Physics Model8800pump (Spectra-Physics,San Jose,CA),a Rheodyne Model7125 injector valve(Rheodyne,Inc.,Cotati,CA)equipped with a50-µL injection loop,a second Rheodyne7125injector valve equipped with a Shandon Hypercarb S7µm guard column (Keystone Scientific,Inc.,Bellefonte,PA)as the injection loop, a Spectra-Physics SP8792column heater set at40°C,a7µm particle size,150mm× 4.6mm Shandon Hypercarb S graphitized carbon column(Keystone Scientific,Inc.),a Waters Model470fluorescence detector(Waters Division of Millipore Corp.,Milford,MA)operated at235nm excitation and317 nm emission,and a Spectra-Physics Chromstation/2data system interfaced to an IBM PS/2Model80personal computer. The HPLC mobile phases were as follows:solvent A,water/ methanol/acetonitrile(90:5:5);solvent B,water/methanol/ acetonitrile(5:90:5);and solvent C,water/methanol/acetonitrile (5:5:90).A mobile phase program was run as follows at a flow of0.5mL/min:isocratic30%A,30%B,and40%C to12min; linear gradient to10%A,10%B,and90%C in1min;isocratic for3min;linear gradient to30%A,30%B,and40%C in1 min;isocratic for10min to re-equilibrate the column.HPLC Quantitation.External calibration was performed using chromatographic responses of at least five standard concentrations of BPA ranging from1to50ng/mL.The standard curve of the concentrations versus chromatographic peak areas was calculated from a linear regression program.Quantitative Analysis by HPLC.A10.0-30.0mL ali-quot(optimum volume of aliquot will vary depending on the concentration of BPA in the test formula)of the test formula was removed and the remainder reserved for additional testing in an Erlenmeyer flask in a refrigerator at4°C.The aliquot was diluted to100.0mL with distilled deionized water(DDW) and transferred to a100mL buret.An SPE cartridge was rinsed and prewetted with a total of20mL of DDW.Enough DDW was retained on the cartridge so that the bed remained completely covered.The buret was placed above the cartridge, and a flow from the buret to the cartridge was adjusted to be compatible with a flow of ca.10mL/min through the cartridge produced from a vacuum source.The total volume of diluted formula was passed through the cartridge.The buret was washed with15mL of DDW and the wash allowed to pass completely through the cartridge.The total aqueous eluate was drained and discarded,and the residual water was removed from the cartridge by air-drying with vacuum for5 min.The buret was then washed with15mL of hexane and the wash allowed to pass through the cartridge.BPA was eluted from the cartridge into a calibrated15mL conical tube with three5mL volumes of chloroform.The cartridge was drained between each volume.The chloroform was evaporated (by gentle heating over a steam bath with the addition of two or three carborundum boiling chips to ease bumping)to ca. 50µL.The concentrated extract was then diluted with up to 4.0mL(amount of dilution depends on the concentration of BPA in the formula)of mobile phase(30%A,30%B,and40% C)and analyzed for BPA by HPLC.This extraction/concentra-tion was performed in triplicate for each canned formula tested.Recoveries were calculated by fortifying the formula (in duplicate)with an amount of BPA equal to the average amount quantitated in the same formula.The average BPA concentration in the unfortified formula was subtracted from the total BPA concentration in the fortified formula to deter-mine the net amount of BPA recovered.An analytical blank was analyzed as described above using formula prepared from dry powdered mix and HPLC grade water.GC-MS Apparatus and Operating Conditions.The GC-MS system consisted of a Hewlett-Packard(HP)5890B gas chromatograph(GC)with an HP7673automated liquid sampler,a capillary split-splitless injector,a30m×0.25mm i.d.Rt x-5(cross-linked95%dimethyl-5%diphenyl polysilox-ane)FSOT capillary column with1.0µm film thickness(Restek Corp.,Bellefonte,PA),and an HP5970B mass selective detector(MSD)with capillary direct interface to GC.The GC operating parameters were as follows:UHP helium carrier gas at ca.10psi column head pressure(1mL/min);injection volume,2µL;split vent open after1min;injector temperature, 280°C;interface temperature,290°C;oven program,initial temperature100°C,program at10°C/min to280°C,and hold 3min(BPA t r,ca.19.1min).The MSD was operated in the selected ion monitoring mode;ions m/z119,213,and228were monitored at2.6scans/s from18.8to19.3min,dwell100ms. The GC-MS system was controlled with a Pascal Chemstation data system.A2µL injection of concentrated infant formula extract in chloroform was made,and confirmation of BPA was based on retention time and relative response ratios of the ions listed above.RESULTSInfrared analysis showed all cans to have at least one of the FCSs coated with an epoxy or“modified”epoxy enamel based on BPA.In three cases,only the lids of two-piece cans were found to be coated with an epoxy. All spectra were compared(visually and by a matching algorithm)with standards in the High Resolution Hum-mel Polymer Library and spectra acquired from the FCS of epoxy-coated“customer ready”(unused)cans obtained from a major supplier(Figure1).The matching algorithm identified some epoxy coatings as modified with fatty acid esters and oils(Figure2and Table1). The incorporation of flexibility-enhancing modifiers in epoxy resins based on BPA is common(Savla,1977). The presence of BPA was confirmed in selected formula extracts by GC-MS.The ion ratios of the extracts agreed with those of authentic BPA standards to within(20%.The highest amount of BPA measured in any of the infant formula concentrates was13.2ppb and the lowest was0.1ppb.Levels of BPA consumed in prepared formula would be lower because directions on the labels call for a1:1dilution(v/v)of formula concentrate with4698J.Agric.Food Chem.,Vol.45,No.12,1997Biles et al.water.Recoveries for milk-based formulas averaged 86%,while recoveries for soy-based formulas averaged 104%.Coefficients of variation for the triplicate runs ranged from 2%to 27%for milk-based products and from 9%to 27%for soy-based products.The limit of detection,defined as 3times the standard deviation of the baseline produced by the detector when measuring a blank prepared from powdered formula after concen-tration by a factor of 30,was 0.9ppb.BPA was extracted from formula and concentrated by as much as 30-fold by using SPE before HPLC analysis.An obvious correlation between the product’s expiration date and the level of BPA determined in the formula was not observed.The data in Table 1are reported in terms of both concentration (ppb)and mass of BPA per unit areaofFigure 1.Infrared spectrum of unused epoxy-coated can food contactsurface.Figure 2.Infrared reflectance/transmittance spectrum of BPA-based epoxy can coating,typical of those encountered in this investigation.Migration of Bisphenol A from Can Coatings J.Agric.Food Chem.,Vol.45,No.12,19974699epoxy-coated FCS(ng/cm2);the latter accounts for differences in can construction.DISCUSSIONThe qualitative FT-IR data presented here show that epoxy is used as an enamel coating on at least one of the FCSs of all of the infant formula cans in the test group.Specular reflectance/transmittance FT-IR pro-vides a quick and easy means to screen can coatings. This information is essential in conjunction with quan-titative techniques to determine the total amount of BPA migration to the formula on a surface area basis. The protocol for HPLC determination of BPA de-scribed here is preferred to those for BPA,BPF,DGE-BA,and DGEBF in aqueous-based food simulants (Gandara et al.,1990;Crathorne et al.,1986)and organic solvents(Losada et al.,1991;Henriks-Eckerman and Laijoki,1988).The food matrix and migration levels of DGEBA investigated by Begley et al.(1991) differed significantly from those investigated here for BPA.Brotons et al.(1995)reported BPA in canned vegetables at levels from1to6times greater than the highest level reported here in infant formula and with higher coefficients of variation.The sensitivity reported here for BPA in formula concentrates is comparable to that reported in less complicated organic and aqueous matrices in the earlier studies.This survey of canned infant formula liquid concen-trates has shown that low parts per billion levels of BPA can be extracted,concentrated,determined,and con-firmed using the combined techniques of SPE,HPLC with fluorescence detection,and GC-MS. ACKNOWLEDGMENTWe thank Stanley Cichowicz,Nicholas Duy,and Gracia Perfetti of the U.S.Food and Drug Administra-tion and Kestutis Chesonis and Philip Patterson of the U.S.Army Research Laboratory for their contributions to this study.LITERATURE CITEDBegley,T.;Biles,J.;Hollifield,H.Migration of an epoxy adhesive compound into a food-simulating liquid and food from microwave susceptor packaging.J.Agric.Food Chem.1991,39(11),1944-1945.Brotons,J.;Olea-Serrano,M.;Villalbos,M.;Pedraza,V.;Olea, N.Xenoestrogens released from lacquer coatings in food cans.Environ.Health Perspect.1995,103(6),608-612. Crathorne,B.;Palmer,C.;Stanley,J.High-performance liquid chromatographic determination of bisphenol-A diglycidyl ether and bisphenol-F diglycidyl ether in water.J.Chro-matogr.1986,360,266-270.Gandara,J.;Abuin,S.;Losada,P.;Lozano,J.Determination of bisphenols A and F in noncured epoxy resins by RP-HPLC-fluorescence techniques.J.Chromatogr.Sci.1990, 31,450-454.Gannon,J.Epoxy,Resins and Compounds.In Modern Plastics Encyclopedia;Juran,R.,Ed.;McGraw Hill:New York,1990. Henriks-Eckerman,M.;Laijoki,T.Determination of oligomer 340and polyamines in cured epoxy resins by extraction and high-performance liquid chromatography.Analyst1988,13, 239-242.Krishnan,A.;Stathis,P.;Permuth,S.;Tokes,L.;Feldman,D.An estrogenic substance is released from polycarbonateflasks during autoclaving.Endocrinology1993,132(6), 2279-2286.Losada,P.;Mahia,P.;Oderiz,L.;Lozano,J.;Gandara,J.Sensitive and rapid reversed-phase liquid chromatography-fluorescence method for determining bisphenol A diglycidyl ether in aqueous-based food simulants.J.Assoc.Off.Anal.Chem.1991,74(6),925-928.Savla,M.Epoxy resin adhesives.In Handbook of Adhesives, 2nd ed.;Skiest,I.,Ed.;Van Nostrand Reinhold:New York, 1977.Received for review June23,1997.Revised manuscript received September15,1997.Accepted Spetember17,1997.X JF970518VX Abstract published in Advance ACS Abstracts,No-vember1,1997.4700J.Agric.Food Chem.,Vol.45,No.12,1997Biles et al.。
novolac epoxy和Phenolic Epoxy 酚醛环氧浅谈
Novolac epoxy 和Phenolic Epoxy 浅谈陆坤宏Novolac epoxy与Phenolic Epoxy虽然都翻译为酚醛环氧树脂。
酚醛环氧涂层：Novolac的比Phenolic的高级一点，耐高温性能更好一点（国内资料总结）。
英文分别为Epoxy novolac resins 和epoxy Phenolic Resins1.Epoxy novolac resinsNovolacs are modifications of bisphenol F resins formed using excess phenol。
The viscosity of novolac resins is significantly higher than that of bisphenol F resins. As important, the functionality is considerably greater. The higher viscosity and greater functionality of the novolacs make their heat and chemical resistance properties superior to those of bisphenol F.Increasing the functionality in epoxy resins by using epoxy novolac precursors instead of bisphenol A backbones allows formulators to achieve higher crosslinking densities and significant performance enhancements. A variety of epoxy resins are available with functionalities in excess of 2 up to 8. Epoxy novolac resins are broadly utilized as primary epoxy resins or as modifiers in multi-resin systems。
Principles of Plasma Discharges and Materials Processing9
CHAPTER8MOLECULAR COLLISIONS8.1INTRODUCTIONBasic concepts of gas-phase collisions were introduced in Chapter3,where we described only those processes needed to model the simplest noble gas discharges: electron–atom ionization,excitation,and elastic scattering;and ion–atom elastic scattering and resonant charge transfer.In this chapter we introduce other collisional processes that are central to the description of chemically reactive discharges.These include the dissociation of molecules,the generation and destruction of negative ions,and gas-phase chemical reactions.Whereas the cross sections have been measured reasonably well for the noble gases,with measurements in reasonable agreement with theory,this is not the case for collisions in molecular gases.Hundreds of potentially significant collisional reactions must be examined in simple diatomic gas discharges such as oxygen.For feedstocks such as CF4/O2,SiH4/O2,etc.,the complexity can be overwhelming.Furthermore,even when the significant processes have been identified,most of the cross sections have been neither measured nor calculated. Hence,one must often rely on estimates based on semiempirical or semiclassical methods,or on measurements made on molecules analogous to those of interest. As might be expected,data are most readily available for simple diatomic and polyatomic gases.Principles of Plasma Discharges and Materials Processing,by M.A.Lieberman and A.J.Lichtenberg. ISBN0-471-72001-1Copyright#2005John Wiley&Sons,Inc.235236MOLECULAR COLLISIONS8.2MOLECULAR STRUCTUREThe energy levels for the electronic states of a single atom were described in Chapter3.The energy levels of molecules are more complicated for two reasons. First,molecules have additional vibrational and rotational degrees of freedom due to the motions of their nuclei,with corresponding quantized energies E v and E J. Second,the energy E e of each electronic state depends on the instantaneous con-figuration of the nuclei.For a diatomic molecule,E e depends on a single coordinate R,the spacing between the two nuclei.Since the nuclear motions are slow compared to the electronic motions,the electronic state can be determined for anyfixed spacing.We can therefore represent each quantized electronic level for a frozen set of nuclear positions as a graph of E e versus R,as shown in Figure8.1.For a mole-cule to be stable,the ground(minimum energy)electronic state must have a minimum at some value R1corresponding to the mean intermolecular separation (curve1).In this case,energy must be supplied in order to separate the atoms (R!1).An excited electronic state can either have a minimum( R2for curve2) or not(curve3).Note that R2and R1do not generally coincide.As for atoms, excited states may be short lived(unstable to electric dipole radiation)or may be metastable.Various electronic levels may tend to the same energy in the unbound (R!1)limit. Array FIGURE8.1.Potential energy curves for the electronic states of a diatomic molecule.For diatomic molecules,the electronic states are specifiedfirst by the component (in units of hÀ)L of the total orbital angular momentum along the internuclear axis, with the symbols S,P,D,and F corresponding to L¼0,+1,+2,and+3,in analogy with atomic nomenclature.All but the S states are doubly degenerate in L.For S states,þandÀsuperscripts are often used to denote whether the wave function is symmetric or antisymmetric with respect to reflection at any plane through the internuclear axis.The total electron spin angular momentum S (in units of hÀ)is also specified,with the multiplicity2Sþ1written as a prefixed superscript,as for atomic states.Finally,for homonuclear molecules(H2,N2,O2, etc.)the subscripts g or u are written to denote whether the wave function is sym-metric or antisymmetric with respect to interchange of the nuclei.In this notation, the ground states of H2and N2are both singlets,1Sþg,and that of O2is a triplet,3SÀg .For polyatomic molecules,the electronic energy levels depend on more thanone nuclear coordinate,so Figure8.1must be generalized.Furthermore,since there is generally no axis of symmetry,the states cannot be characterized by the quantum number L,and other naming conventions are used.Such states are often specified empirically through characterization of measured optical emission spectra.Typical spacings of low-lying electronic energy levels range from a few to tens of volts,as for atoms.Vibrational and Rotational MotionsUnfreezing the nuclear vibrational and rotational motions leads to additional quan-tized structure on smaller energy scales,as illustrated in Figure8.2.The simplest (harmonic oscillator)model for the vibration of diatomic molecules leads to equally spaced quantized,nondegenerate energy levelse E v¼hÀv vib vþ1 2(8:2:1)where v¼0,1,2,...is the vibrational quantum number and v vib is the linearized vibration frequency.Fitting a quadratic functione E v¼12k vib(RÀ R)2(8:2:2)near the minimum of a stable energy level curve such as those shown in Figure8.1, we can estimatev vib%k vibm Rmol1=2(8:2:3)where k vib is the“spring constant”and m Rmol is the reduced mass of the AB molecule.The spacing hÀv vib between vibrational energy levels for a low-lying8.2MOLECULAR STRUCTURE237stable electronic state is typically a few tenths of a volt.Hence for molecules in equi-librium at room temperature (0.026V),only the v ¼0level is significantly popula-ted.However,collisional processes can excite strongly nonequilibrium vibrational energy levels.We indicate by the short horizontal line segments in Figure 8.1a few of the vibrational energy levels for the stable electronic states.The length of each segment gives the range of classically allowed vibrational motions.Note that even the ground state (v ¼0)has a finite width D R 1as shown,because from(8.2.1),the v ¼0state has a nonzero vibrational energy 1h Àv vib .The actual separ-ation D R about Rfor the ground state has a Gaussian distribution,and tends toward a distribution peaked at the classical turning points for the vibrational motion as v !1.The vibrational motion becomes anharmonic and the level spa-cings tend to zero as the unbound vibrational energy is approached (E v !D E 1).FIGURE 8.2.Vibrational and rotational levels of two electronic states A and B of a molecule;the three double arrows indicate examples of transitions in the pure rotation spectrum,the rotation–vibration spectrum,and the electronic spectrum (after Herzberg,1971).238MOLECULAR COLLISIONSFor E v.D E1,the vibrational states form a continuum,corresponding to unbound classical motion of the nuclei(breakup of the molecule).For a polyatomic molecule there are many degrees of freedom for vibrational motion,leading to a very compli-cated structure for the vibrational levels.The simplest(dumbbell)model for the rotation of diatomic molecules leads to the nonuniform quantized energy levelse E J¼hÀ22I molJ(Jþ1)(8:2:4)where I mol¼m Rmol R2is the moment of inertia and J¼0,1,2,...is the rotational quantum number.The levels are degenerate,with2Jþ1states for the J th level. The spacing between rotational levels increases with J(see Figure8.2).The spacing between the lowest(J¼0to J¼1)levels typically corresponds to an energy of0.001–0.01V;hence,many low-lying levels are populated in thermal equilibrium at room temperature.Optical EmissionAn excited molecular state can decay to a lower energy state by emission of a photon or by breakup of the molecule.As shown in Figure8.2,the radiation can be emitted by a transition between electronic levels,between vibrational levels of the same electronic state,or between rotational levels of the same electronic and vibrational state;the radiation typically lies within the optical,infrared,or microwave frequency range,respectively.Electric dipole radiation is the strongest mechanism for photon emission,having typical transition times of t rad 10À9s,as obtained in (3.4.13).The selection rules for electric dipole radiation areDL¼0,+1(8:2:5a)D S¼0(8:2:5b) In addition,for transitions between S states the only allowed transitions areSþÀ!Sþand SÀÀ!SÀ(8:2:6) and for homonuclear molecules,the only allowed transitions aregÀ!u and uÀ!g(8:2:7) Hence homonuclear diatomic molecules do not have a pure vibrational or rotational spectrum.Radiative transitions between electronic levels having many different vibrational and rotational initial andfinal states give rise to a structure of emission and absorption bands within which a set of closely spaced frequencies appear.These give rise to characteristic molecular emission and absorption bands when observed8.2MOLECULAR STRUCTURE239using low-resolution optical spectrometers.As for atoms,metastable molecular states having no electric dipole transitions to lower levels also exist.These have life-times much exceeding10À6s;they can give rise to weak optical band structures due to magnetic dipole or electric quadrupole radiation.Electric dipole radiation between vibrational levels of the same electronic state is permitted for molecules having permanent dipole moments.In the harmonic oscillator approximation,the selection rule is D v¼+1;weaker transitions D v¼+2,+3,...are permitted for anharmonic vibrational motion.The preceding description of molecular structure applies to molecules having arbi-trary electronic charge.This includes neutral molecules AB,positive molecular ions ABþ,AB2þ,etc.and negative molecular ions ABÀ.The potential energy curves for the various electronic states,regardless of molecular charge,are commonly plotted on the same diagram.Figures8.3and8.4give these for some important electronic statesof HÀ2,H2,and Hþ2,and of OÀ2,O2,and Oþ2,respectively.Examples of both attractive(having a potential energy minimum)and repulsive(having no minimum)states can be seen.The vibrational levels are labeled with the quantum number v for the attrac-tive levels.The ground states of both Hþ2and Oþ2are attractive;hence these molecular ions are stable against autodissociation(ABþ!AþBþor AþþB).Similarly,the ground states of H2and O2are attractive and lie below those of Hþ2and Oþ2;hence they are stable against autodissociation and autoionization(AB!ABþþe).For some molecules,for example,diatomic argon,the ABþion is stable but the AB neutral is not stable.For all molecules,the AB ground state lies below the ABþground state and is stable against autoionization.Excited states can be attractive or repulsive.A few of the attractive states may be metastable;some examples are the 3P u state of H2and the1D g,1Sþgand3D u states of O2.Negative IonsRecall from Section7.2that many neutral atoms have a positive electron affinity E aff;that is,the reactionAþeÀ!AÀis exothermic with energy E aff(in volts).If E aff is negative,then AÀis unstable to autodetachment,AÀ!Aþe.A similar phenomenon is found for negative molecular ions.A stable ABÀion exists if its ground(lowest energy)state has a potential minimum that lies below the ground state of AB.This is generally true only for strongly electronegative gases having large electron affinities,such as O2 (E aff%1:463V for O atoms)and the halogens(E aff.3V for the atoms).For example,Figure8.4shows that the2P g ground state of OÀ2is stable,with E aff% 0:43V for O2.For weakly electronegative or for electropositive gases,the minimum of the ground state of ABÀgenerally lies above the ground state of AB,and ABÀis unstable to autodetachment.An example is hydrogen,which is weakly electronegative(E aff%0:754V for H atoms).Figure8.3shows that the2Sþu ground state of HÀ2is unstable,although the HÀion itself is stable.In an elec-tropositive gas such as N2(E aff.0),both NÀ2and NÀare unstable. 240MOLECULAR COLLISIONS8.3ELECTRON COLLISIONS WITH MOLECULESThe interaction time for the collision of a typical (1–10V)electron with a molecule is short,t c 2a 0=v e 10À16–10À15s,compared to the typical time for a molecule to vibrate,t vib 10À14–10À13s.Hence for electron collisional excitation of a mole-cule to an excited electronic state,the new vibrational (and rotational)state canbeFIGURE 8.3.Potential energy curves for H À2,H 2,and H þ2.(From Jeffery I.Steinfeld,Molecules and Radiation:An Introduction to Modern Molecular Spectroscopy ,2d ed.#MIT Press,1985.)8.3ELECTRON COLLISIONS WITH MOLECULES 241FIGURE 8.4.Potential energy curves for O À2,O 2,and O þ2.(From Jeffery I.Steinfeld,Molecules and Radiation:An Introduction to Modern Molecular Spectroscopy ,2d ed.#MIT Press,1985.)242MOLECULAR COLLISIONS8.3ELECTRON COLLISIONS WITH MOLECULES243 determined by freezing the nuclear motions during the collision.This is known as the Franck–Condon principle and is illustrated in Figure8.1by the vertical line a,showing the collisional excitation atfixed R to a high quantum number bound vibrational state and by the vertical line b,showing excitation atfixed R to a vibra-tionally unbound state,in which breakup of the molecule is energetically permitted. Since the typical transition time for electric dipole radiation(t rad 10À9–10À8s)is long compared to the dissociation( vibrational)time t diss,excitation to an excited state will generally lead to dissociation when it is energetically permitted.Finally, we note that the time between collisions t c)t rad in typical low-pressure processing discharges.Summarizing the ordering of timescales for electron–molecule collisions,we havet at t c(t vib t diss(t rad(t cDissociationElectron impact dissociation,eþABÀ!AþBþeof feedstock gases plays a central role in the chemistry of low-pressure reactive discharges.The variety of possible dissociation processes is illustrated in Figure8.5.In collisions a or a0,the v¼0ground state of AB is excited to a repulsive state of AB.The required threshold energy E thr is E a for collision a and E a0for Array FIGURE8.5.Illustrating the variety of dissociation processes for electron collisions with molecules.collision a0,and it leads to an energy after dissociation lying between E aÀE diss and E a0ÀE diss that is shared among the dissociation products(here,A and B). Typically,E aÀE diss few volts;consequently,hot neutral fragments are typically generated by dissociation processes.If these hot fragments hit the substrate surface, they can profoundly affect the process chemistry.In collision b,the ground state AB is excited to an attractive state of AB at an energy E b that exceeds the binding energy E diss of the AB molecule,resulting in dissociation of AB with frag-ment energy E bÀE diss.In collision b0,the excitation energy E b0¼E diss,and the fragments have low energies;hence this process creates fragments having energies ranging from essentially thermal energies up to E bÀE diss few volts.In collision c,the AB atom is excited to the bound excited state ABÃ(labeled5),which sub-sequently radiates to the unbound AB state(labeled3),which then dissociates.The threshold energy required is large,and the fragments are hot.Collision c can also lead to dissociation of an excited state by a radiationless transfer from state5to state4near the point where the two states cross:ABÃðboundÞÀ!ABÃðunboundÞÀ!AþBÃThe fragments can be both hot and in excited states.We discuss such radiationless electronic transitions in the next section.This phenomenon is known as predisso-ciation.Finally,a collision(not labeled in thefigure)to state4can lead to dis-sociation of ABÃ,again resulting in hot excited fragments.The process of electron impact excitation of a molecule is similar to that of an atom,and,consequently,the cross sections have a similar form.A simple classical estimate of the dissociation cross section for a level having excitation energy U1can be found by requiring that an incident electron having energy W transfer an energy W L lying between U1and U2to a valence electron.Here,U2is the energy of the next higher level.Then integrating the differential cross section d s[given in(3.4.20)and repeated here],d s¼pe24021Wd W LW2L(3:4:20)over W L,we obtains diss¼0W,U1pe24pe021W1U1À1WU1,W,U2pe24021W1U1À1U2W.U28>>>>>><>>>>>>:(8:3:1)244MOLECULAR COLLISIONSLetting U2ÀU1(U1and introducing voltage units W¼e E,U1¼e E1and U2¼e E2,we haves diss¼0E,E1s0EÀE11E1,E,E2s0E2ÀE1EE.E28>>>><>>>>:(8:3:2)wheres0¼pe4pe0E12(8:3:3)We see that the dissociation cross section rises linearly from the threshold energy E thr%E1to a maximum value s0(E2ÀE1)=E thr at E2and then falls off as1=E. Actually,E1and E2can depend on the nuclear separation R.In this case,(8.3.2) should be averaged over the range of R s corresponding to the ground-state vibrational energy,leading to a broadened dependence of the average cross section on energy E.The maximum cross section is typically of order10À15cm2. Typical rate constants for a single dissociation process with E thr&T e have an Arrhenius formK diss/K diss0expÀE thr T e(8:3:4)where K diss0 10À7cm3=s.However,in some cases E thr.T e.For excitation to an attractive state,an appropriate average over the fraction of the ground-state vibration that leads to dissociation must be taken.Dissociative IonizationIn addition to normal ionization,eþABÀ!ABþþ2eelectron–molecule collisions can lead to dissociative ionizationeþABÀ!AþBþþ2eThese processes,common for polyatomic molecules,are illustrated in Figure8.6.In collision a having threshold energy E iz,the molecular ion ABþis formed.Collisionsb andc occur at higher threshold energies E diz and result in dissociative ionization,8.3ELECTRON COLLISIONS WITH MOLECULES245leading to the formation of fast,positively charged ions and neutrals.These cross sections have a similar form to the Thompson ionization cross section for atoms.Dissociative RecombinationThe electron collision,e þAB þÀ!A þB Ãillustrated as d and d 0in Figure 8.6,destroys an electron–ion pair and leads to the production of fast excited neutral fragments.Since the electron is captured,it is not available to carry away a part of the reaction energy.Consequently,the collision cross section has a resonant character,falling to very low values for E ,E d and E .E d 0.However,a large number of excited states A Ãand B Ãhaving increasing principal quantum numbers n and energies can be among the reaction products.Consequently,the rate constants can be large,of order 10À7–10À6cm 3=s.Dissocia-tive recombination to the ground states of A and B cannot occur because the potential energy curve for AB þis always greater than the potential energycurveFIGURE 8.6.Illustration of dissociative ionization and dissociative recombination for electron collisions with molecules.246MOLECULAR COLLISIONSfor the repulsive state of AB.Two-body recombination for atomic ions or for mol-ecular ions that do not subsequently dissociate can only occur with emission of a photon:eþAþÀ!Aþh n:As shown in Section9.2,the rate constants are typically three tofive orders of magnitude lower than for dissociative recombination.Example of HydrogenThe example of H2illustrates some of the inelastic electron collision phenomena we have discussed.In order of increasing electron impact energy,at a threshold energy of 8:8V,there is excitation to the repulsive3Sþu state followed by dissociation into two fast H fragments carrying 2:2V/atom.At11.5V,the1Sþu bound state is excited,with subsequent electric dipole radiation in the ultraviolet region to the1Sþg ground state.At11.8V,there is excitation to the3Sþg bound state,followedby electric dipole radiation to the3Sþu repulsive state,followed by dissociation with 2:2V/atom.At12.6V,the1P u bound state is excited,with UV emission tothe ground state.At15.4V,the2Sþg ground state of Hþ2is excited,leading to the pro-duction of Hþ2ions.At28V,excitation of the repulsive2Sþu state of Hþ2leads to thedissociative ionization of H2,with 5V each for the H and Hþfragments.Dissociative Electron AttachmentThe processes,eþABÀ!AþBÀproduce negative ion fragments as well as neutrals.They are important in discharges containing atoms having positive electron affinities,not only because of the pro-duction of negative ions,but because the threshold energy for production of negative ion fragments is usually lower than for pure dissociation processes.A variety of pro-cesses are possible,as shown in Figure8.7.Since the impacting electron is captured and is not available to carry excess collision energy away,dissociative attachment is a resonant process that is important only within a narrow energy range.The maximum cross sections are generally much smaller than the hard-sphere cross section of the molecule.Attachment generally proceeds by collisional excitation from the ground AB state to a repulsive ABÀstate,which subsequently either auto-detaches or dissociates.The attachment cross section is determined by the balance between these processes.For most molecules,the dissociation energy E diss of AB is greater than the electron affinity E affB of B,leading to the potential energy curves shown in Figure8.7a.In this case,the cross section is large only for impact energies lying between a minimum value E thr,for collision a,and a maximum value E0thr for8.3ELECTRON COLLISIONS WITH MOLECULES247FIGURE 8.7.Illustration of a variety of electron attachment processes for electron collisions with molecules:(a )capture into a repulsive state;(b )capture into an attractive state;(c )capture of slow electrons into a repulsive state;(d )polar dissociation.248MOLECULAR COLLISIONScollision a 0.The fragments are hot,having energies lying between minimum and maximum values E min ¼E thr þE affB ÀE diss and E max ¼E 0thr þE af fB ÀE diss .Since the AB Àstate lies above the AB state for R ,R x ,autodetachment can occur as the mol-ecules begin to separate:AB À!AB þe.Hence the cross section for production of negative ions can be much smaller than that for excitation of the AB Àrepulsive state.As a crude estimate,for the same energy,the autodetachment rate is ffiffiffiffiffiffiffiffiffiffiffiffiffiM R =m p 100times the dissociation rate of the repulsive AB Àmolecule,where M R is the reduced mass.Hence only one out of 100excitations lead to dissociative attachment.Excitation to the AB Àbound state can also lead to dissociative attachment,as shown in Figure 8.7b .Here the cross section is significant only for E thr ,E ,E 0thr ,but the fragments can have low energies,with a minimum energy of zero and a maximum energy of E 0thr þE affB ÀE diss .Collision b,e þAB À!AB ÀÃdoes not lead to production of AB Àions because energy and momentum are not gen-erally conserved when two bodies collide elastically to form one body (see Problem3.12).Hence the excited AB ÀÃion separates,AB ÀÃÀ!e þABunless vibrational radiation or collision with a third body carries off the excess energy.These processes are both slow in low-pressure discharges (see Section 9.2).At high pressures (say,atmospheric),three-body attachment to form AB Àcan be very important.For a few molecules,such as some halogens,the electron affinity of the atom exceeds the dissociation energy of the neutral molecule,leading to the potential energy curves shown in Figure 8.7c .In this case the range of electron impact ener-gies E for excitation of the AB Àrepulsive state includes E ¼0.Consequently,there is no threshold energy,and very slow electrons can produce dissociative attachment,resulting in hot neutral and negative ion fragments.The range of R s over which auto-detachment can occur is small;hence the maximum cross sections for dissociative attachment can be as high as 10À16cm 2.A simple classical estimate of electron capture can be made using the differential scattering cross section for energy loss (3.4.20),in a manner similar to that done for dissociation.For electron capture to an energy level E 1that is unstable to autode-tachment,and with the additional constraint for capture that the incident electron energy lie within E 1and E 2¼E 1þD E ,where D E is a small energy difference characteristic of the dissociative attachment timescale,we obtain,in place of (8.3.2),s att¼0E ,E 1s 0E ÀE 1E 1E 1,E ,E 20E .E 28>><>>:(8:3:5)8.3ELECTRON COLLISIONS WITH MOLECULES 249wheres 0%p m M R 1=2e 4pe 0E 1 2(8:3:6)The factor of (m =M R )1=2roughly gives the fraction of excited states that do not auto-detach.We see that the dissociative attachment cross section rises linearly at E 1to a maximum value s 0D E =E 1and then falls abruptly to zero.As for dissociation,E 1can depend strongly on the nuclear separation R ,and (8.3.5)must be averaged over the range of E 1s corresponding to the ground state vibrational motion;e.g.,from E thr to E 0thr in Figure 8.7a .Because generally D E (E 0thr ÀE thr ,we can write (8.3.5)in the forms att %p m M R 1=2e 4pe 0 2(D E )22E 1d (E ÀE 1)(8:3:7)where d is the Dirac delta ing (8.3.7),the average over the vibrational motion can be performed,leading to a cross section that is strongly peaked lying between E thr and E 0thr .We leave the details of the calculation to a problem.Polar DissociationThe process,e þAB À!A þþB Àþeproduces negative ions without electron capture.As shown in Figure 8.7d ,the process proceeds by excitation of a polar state A þand B Àof AB Ãthat has a separ-ated atom limit of A þand B À.Hence at large R ,this state lies above the A þB ground state by the difference between the ionization potential of A and the electron affinity of B.The polar state is weakly bound at large R by the Coulomb attraction force,but is repulsive at small R .The maximum cross section and the dependence of the cross section on electron impact energy are similar to that of pure dissociation.The threshold energy E thr for polar dissociation is generally large.The measured cross section for negative ion production by electron impact in O 2is shown in Figure 8.8.The sharp peak at 6.5V is due to dissociative attachment.The variation of the cross section with energy is typical of a resonant capture process.The maximum cross section of 10À18cm 2is quite low because autode-tachment from the repulsive O À2state is strong,inhibiting dissociative attachment.The second gradual maximum near 35V is due to polar dissociation;the variation of the cross section with energy is typical of a nonresonant process.250MOLECULAR COLLISIONS。
8种东西尽量别买：空气清新剂伤肺 香水或致癌
1.空气清新剂。
它不能从源头清除臭味，喷出的化学微粒还容易被人吸入肺部。
改善室内空气的最好办法是通风，或在室内放一些植物。
The 1 air freshener. It can not remove the odor from the source, but also easy to chemical particles ejected are / inhaled into the lungs. The best way to improve indoor air ventilation, or put some plants indoors.2.下水道、马桶等卫生洁具专用清洁剂。
这些东西易灼伤皮肤、眼睛和身体组织，清洁这些地方最好用小苏打加醋，先浸泡，再用热水冲干净即可。
2 the sewer, toilet sanitary ware, special cleaning agent. These things are easy to burn the skin, eyes and body / tissues, where the best cleaning with baking soda and vinegar, soak in hot water, and then clean.3.听装食品。
听装食品的包装涂有含双酚A的环氧树脂。
这种化学物质与荷尔蒙分泌紊乱、肥胖、心脏病等有关。
最好吃新鲜、冷冻或者玻璃瓶装的食品。
3 cans of food. Canned food packaging coated with epoxy resin containing bisphenolA. The chemicals and hormones / related disorders, obesity, heart disease. It is best to eat fresh, frozen or glass bottled food.4.杀虫剂。
BPA(双酚A介绍)英文版
the intercept of the regression line
the concentration of BPA in the food stimulant in given by:
C=(y-b)/a
●If I am concerned, what can I do to prevent exposure to BPA?
②Apparatus
High performance liquid chromatography HPLC column Mechanical shaker (vortex) Micro syringes Test tubes
③Procedure
HPLC analysis Calibration Execution of determination HPLC interferences
④Expression of results
1. Graphical determination
④Expression of results
2. Calculation from the regression parameters. If the regression line equation is:
●Determination of BPA in food simulants
①Reagents
②Apparatus ③Procedure
④Expression of results
①Reagents
BPA n-Hexane Methanol Deionized water Extraction solvent, methanol/water=1:1 Mobile phase for HPLC methanol/water=70:30 Stock solution of BPA in methanol at a defined concentration of approximately 0.38mg/ml
塑料的危害 英语作文
塑料的危害英语作文The Detrimental Impact of Plastic on Our Planet and its Inhabitants.Plastic, a ubiquitous material in modern society, has become an indispensable part of our daily lives. From packaging to clothing to electronics, plastic has revolutionized many industries and improved our convenience. However, this extensive use of plastic has come at a significant environmental cost, raising concerns about its detrimental impact on our planet and its inhabitants.Environmental Degradation.One of the most pressing issues associated with plastic pollution is environmental degradation. Plastic takes hundreds of years to decompose, meaning that it accumulates in our landfills and ecosystems. This accumulation disrupts natural habitats, damages biodiversity, and pollutes our air, water, and soil.Landfills: Plastic waste accounts for a significant portion of landfill space, leading to overflowing landfills and the release of harmful leachate into the environment.Marine Ecosystems: Plastic pollution is a major threat to marine life. Marine animals often ingest or become entangled in plastic debris, leading to injuries, starvation, and even death. Plastic also accumulates in the ocean food chain, posing a risk to human health.Air Pollution: The incineration of plastic releases toxic chemicals into the air, including dioxins and furans, which are known carcinogens.Human Health Risks.In addition to environmental degradation, plastic pollution also poses significant health risks to humans. Many plastic products contain chemicals known as phthalates, bisphenol A (BPA), and polychlorinated biphenyls (PCBs), which have been linked to a range of health problems,including:Developmental Disorders: Exposure to phthalates inearly life has been associated with developmental disorders such as autism spectrum disorder and attention deficit hyperactivity disorder (ADHD).Hormonal Disruption: BPA mimics the hormone estrogenin the body, potentially disrupting the endocrine systemand leading to problems such as infertility and obesity.Cancer: Some chemicals found in plastics, such as PCBs, are classified as probable human carcinogens and have been linked to various types of cancer.Microplastic Pollution.Plastic pollution is not limited to large items. Microplastics, small pieces of plastic less than 5 millimeters in length, are also a major environmental and health concern. Microplastics are formed when largerplastic items break down over time or are intentionallymanufactured for use in personal care products and industrial processes.Microplastics have been found in a wide range of environmental samples, including water, soil, and air. They can be ingested by humans and other animals, where they can accumulate in the body and cause adverse health effects. Studies have shown that microplastics can disrupt the immune system, alter hormone levels, and even damage DNA.Solutions and Mitigation Strategies.Addressing the plastic pollution crisis requires a comprehensive approach that involves individual actions, government regulations, and industrial innovation. Here are some key measures that can be taken:Reduce Single-Use Plastics: One of the most effective ways to reduce plastic pollution is to reduce our consumption of single-use plastics, such as plastic bags, straws, and utensils.Promote Recycling and Composting: Recycling and composting plastic waste can help divert it from landfills and reduce the environmental impact.Support Sustainable Alternatives: Consumers can support businesses and industries that are developing sustainable alternatives to plastic, such as biodegradable or reusable materials.Government Regulations: Governments can implement regulations to restrict the production and use of single-use plastics and promote the adoption of sustainable practices.Research and Innovation: Continued research and innovation are essential for developing new materials and technologies that minimize the environmental and health impacts of plastics.Conclusion.Plastic pollution is a complex and urgent environmentalissue that poses significant risks to our planet and its inhabitants. The detrimental impact of plastic on our ecosystems, wildlife, and human health necessitates immediate action. By reducing our consumption of single-use plastics, promoting recycling and composting, supporting sustainable alternatives, implementing government regulations, and investing in research and innovation, we can work together to mitigate the plastic pollution crisis and create a healthier and more sustainable future for generations to come.。
美国FDA分析方法验证指引中英文对照
美国FDA分析方法验证指南中英文对照美国FDA分析方法验证指南中英文对照八、、I.INTRODUCTIONThis guida nee provides recomme ndati ons to applica nts on submitt ing an alytical procedures, validati on data, and samples to support the docume ntati on of the identity, strength, quality, purity, and potency of drug substances and drug products.1.绪论本指南旨在为申请者提供建议，以帮助其提交分析方法，方法验证资料和样品用于支持原料药和制剂的认定，剂量，质量，纯度和效力方面的文件。
This guida nce is in ten ded to assist applica nts in assembli ng in formati on, submitt ing samples, and prese nti ng data to support an alytical methodologies. The recomme ndati ons apply to drug substa nces and drug products covered in new drug applicati ons (NDAs), abbreviated new drug applicati ons (ANDAs), biologics license applications (BLAs), product license applications (PLAs), and supplements to these即plicatio ns.本指南旨在帮助申请者收集资料，递交样品并资料以支持分析方法。
邻苯二甲酸二(2-乙基)己酯与胰岛素抵抗的研究进展
E-mail:zgqkyx@·993·•新进展•邻苯二甲酸二（2-乙基）己酯与胰岛素抵抗的研究进展张敏1，何继瑞2*【摘要】 邻苯二甲酸二（2-乙基）己酯（DEHP ）是一种广泛分布于日常生活中的塑化剂。
流行病学研究表明，DEHP 暴露与胰岛素抵抗相关，而胰岛素抵抗又影响2型糖尿病和代谢综合征的发生。
DEHP 可通过胰岛素信号转导通路、转录因子过氧化物酶体增殖物激活受体γ（PPAR-γ）途径、氧化应激、溶酶体-线粒体轴途径及其他代谢危险因素导致胰岛素抵抗。
【关键词】 胰岛素抵抗；二乙基己基邻苯二甲酸；胰岛素敏感性；胰岛素信号转导【中图分类号】 R 347.8 【文献标识码】 A DOI ：10.3969/j.issn.1007-9572.2017.00.262张敏，何继瑞.邻苯二甲酸二（2-乙基）己酯与胰岛素抵抗的研究进展［J ］．中国全科医学，2018，21（8）：993-997.［ ］ZHANG M ，HE J R ．Research progress on Di-（2-ethylhexyl ） phthalate and insulin resistance ［J ］．Chinese GeneralPractice ，2018，21（8）：993-997．Research Progress on Di-（2-ethylhexyl ） Phthalate and Insulin Resistance ZHANG Min 1，HE Ji-rui 2*1.Second Clinical School of Medicine ，Lanzhou University ，Lanzhou 730030，China2.Department 3 of Endocrinology and Metabolism ，Second Hospital of Lanzhou University ，Lanzhou 730030，China*Corresponding author ：HE Ji-rui ，Professor ；E-mail ：hjrlzys63@【Abstract 】 Di-（2-ethylhexyl ） phthalate （DEHP ） is a plasticizer that is widely distributed in the environment.Epidemiological studies have shown that DEHP exposure is associated with insulin resistance ，which in turn affects the occurrence of type 2 diabetes as well as metabolic syndrome.DEHP leads to insulin resistance through the insulin signalingpathway ，the transcription factor peroxisome proliferators-activated receptor gamma （PPAR-γ） pathway ，oxidative stress ，lysosome-mitochondrial axis pathways and other metabolic risk factors.【Key words 】 Insulin resistance ；Diethylhexyl phthalate ；Insulin sensitivity ；Insulin signaling pathway基金项目：甘肃省自然科学基金资助项目（1308RJZA246）1.730030 甘肃省兰州市，兰州大学第二临床医学院2.730030 甘肃省兰州市，兰州大学第二医院内分泌代谢3科*通信作者：何继瑞，教授；E-mail ：hjrlzys63@邻苯二甲酸二（2-乙基）己酯（DEHP ）是一种环境内分泌干扰物，被广泛用作塑化剂添加于食品包装袋、医疗设备等聚氯乙烯（PVC ）材料中使得产品具有更好的柔韧性［1-2］。
有关塑料环保的新闻报道英语作文
有关塑料环保的新闻报道英语作文英文回答：Plastic Pollution: A Global Crisis.Plastic pollution has emerged as a pressing environmental concern, threatening both marine and terrestrial ecosystems. The durability and non-biodegradable nature of plastic materials have led to their accumulation in oceans, landfills, and even remote areas of the planet.Environmental Impacts.The presence of plastic in the environment has severe consequences for wildlife. Marine animals, such as sea turtles, seabirds, and marine mammals, are particularly susceptible to plastic ingestion and entanglement. Ingested plastic can cause physical blockages, malnutrition, and even death. Plastic debris also provides a breeding groundfor harmful bacteria and can accumulate toxic substances, which are transferred up the food chain.Terrestrial ecosystems are also affected by plastic pollution. Plastic fragments can alter soil properties, impede plant growth, and attract pests. Microplastics, tiny particles of plastic, can be transported by wind and water, contaminating soil and groundwater.Health Impacts.Plastic pollution can also pose risks to human health. Exposure to phthalates, a type of plasticizer used to soften plastics, has been linked to endocrine disruption and reproductive toxicity. Bisphenol A (BPA), another common plasticizer, has been associated with cardiovascular disease, diabetes, and obesity.Solutions.Addressing plastic pollution requires a comprehensive approach involving government, industry, and individuals.Governments must implement policies to reduce plastic production, increase recycling, and promote sustainable alternatives. Industry must invest in innovation to develop biodegradable and reusable materials. Individuals can play a significant role by reducing their plastic consumption, recycling properly, and supporting sustainable practices.Chinese Translation:塑料污染，全球危机。
一次性塑料制品的问题英语作文高中
一次性塑料制品的问题英语作文高中全文共3篇示例，供读者参考篇1The Issue of Single-Use Plastic ProductsIntroductionIn recent years, the issue of single-use plastic products has gained widespread attention due to its harmful effects on the environment. These products, such as plastic bags, bottles, and utensils, are used once and then discarded, leading to pollution and threats to wildlife. This essay will explore the problems associated with single-use plastic products and suggest possible solutions to address this issue.The ProblemsOne of the main problems with single-use plastic products is their impact on the environment. These products are often not recycled and end up in landfills or oceans, where they can take hundreds of years to decompose. The accumulation of plastic waste in the environment poses a significant threat to wildlife, as animals can ingest or become entangled in plastic debris.Another issue with single-use plastic products is their contribution to climate change. The production and disposal of these products require the use of fossil fuels, which release greenhouse gases into the atmosphere. These gases contribute to global warming, leading to more frequent and severe weather events.Furthermore, the extraction of oil and natural gas for the production of plastic products can have detrimental effects on ecosystems and communities. Oil spills, deforestation, and water pollution are just some of the negative consequences of the extraction industry.SolutionsTo address the issue of single-use plastic products, a combination of government regulations, corporate responsibility, and individual action is needed. One possible solution is to ban or restrict the use of certain single-use plastic products, such as plastic bags or straws, and promote the use of reusable alternatives.Another solution is for companies to take responsibility for the lifecycle of their products, from production to disposal. This can include using biodegradable materials, designing productsthat are easily recyclable, and implementing take-back programs for used items.Individuals can also help reduce the use of single-use plastic products by adopting sustainable habits, such as bringing reusable bags and water bottles, avoiding products with excessive plastic packaging, and properly disposing of plastics through recycling programs.ConclusionIn conclusion, the issue of single-use plastic products is a pressing environmental concern that requires action at various levels. By implementing regulations, promoting corporate responsibility, and adopting sustainable practices, we can reduce the impact of plastic waste on the environment and create a more sustainable future for generations to come. It is essential that we all do our part to address this issue and work towards a cleaner and healthier planet.篇2The Issue of Single-Use Plastic ProductsIntroductionSingle-use plastic products have become a major environmental challenge in recent years. These products are used once and then thrown away, contributing to the global plastic pollution crisis. In this essay, we will explore the problems associated with single-use plastic products and discuss possible solutions to this pressing issue.The Environmental Impact of Single-Use Plastic ProductsSingle-use plastic products, such as plastic bags, bottles, and straws, are produced in large quantities and are often used for a very short period of time before being discarded. These products take hundreds of years to decompose, and during this time, they release harmful chemicals into the environment. Plastic pollution is a growing problem that is damaging ecosystems, harming wildlife, and polluting our oceans and waterways. The accumulation of plastic waste is also contributing to climate change by releasing greenhouse gases into the atmosphere.The Human Health Impact of Single-Use Plastic ProductsIn addition to harming the environment, single-use plastic products also pose a threat to human health. Many of these products contain harmful chemicals, such as bisphenol A (BPA) and phthalates, which can leach into food and water and be ingested by humans. These chemicals have been linked to arange of health problems, including cancer, reproductive issues, and neurological disorders. By using single-use plastic products, we are putting our health at risk and exposing ourselves to potentially dangerous toxins.Solutions to the Single-Use Plastic ProblemTo address the problem of single-use plastic products, we need to take action at both individual and societal levels. One of the most effective ways to reduce plastic waste is to minimize our use of single-use plastic products. This can be done by using reusable alternatives, such as shopping bags, water bottles, and straws. By making small changes to our daily habits, we can significantly reduce our plastic consumption and lessen our impact on the environment.In addition to individual efforts, governments and businesses also have a role to play in tackling the single-use plastic problem. Many countries have implemented bans or restrictions on single-use plastic products, such as plastic bags and straws. These policies help to reduce plastic waste and encourage the use of more sustainable alternatives. Businesses can also take steps to reduce their plastic footprint by using biodegradable or compostable packaging materials and incentivizing customers to bring their own reusable containers.ConclusionThe issue of single-use plastic products is a complex and multifaceted problem that requires a coordinated and collaborative effort to address. By raising awareness about the environmental and health impacts of plastic pollution, and taking concrete actions to reduce our use of single-use plastic products, we can work together to create a more sustainable and healthier future for our planet. It is up to each and every one of us to play our part in protecting the environment and reducing our reliance on harmful plastics. Together, we can make a difference and create a world free from the burden of single-use plastic waste.篇3The Problem of Single-Use Plastic ProductsSingle-use plastic products have become an integral part of our daily lives. From plastic bags and straws to water bottles and food containers, these items are convenient and inexpensive, making them a popular choice for consumers. However, the prevalence of single-use plastics has led to a range of environmental and health issues that cannot be ignored.One of the biggest problems with single-use plastic products is their impact on the environment. These items aremade from non-biodegradable materials, which means that they do not break down naturally and can persist in the environment for hundreds of years. As a result, plastic pollution has become a major issue in oceans, rivers, and landfills around the world. Marine animals often mistake plastic debris for food, leading to ingestion and entanglement, which can be fatal. Additionally, when plastics break down into smaller pieces, they can release harmful chemicals into the environment, posing a threat to wildlife and human health.Single-use plastics also contribute to climate change. The production and disposal of these products require the use of fossil fuels, which release greenhouse gases into the atmosphere. Furthermore, the transportation of plastic items to consumers adds to their carbon footprint. As a result, the widespread use of single-use plastics is exacerbating the global climate crisis.In addition to their environmental impact, single-use plastics also pose health risks to humans. Many plastic products contain harmful chemicals such as bisphenol A (BPA) and phthalates, which can leach into food and beverages, especially when exposed to heat or sunlight. These chemicals have been linked to a range of health problems, including hormone disruption, obesity, and cancer. Furthermore, microplastics – tiny plasticparticles – have been found in air, water, and food sources, raising concerns about their potential impact on human health.To address the problem of single-use plastic products, governments, businesses, and individuals must take action. Legislation banning or restricting the use of certain plastic items, such as plastic bags and straws, can help reduce plastic pollution and encourage the transition to more sustainable alternatives. Businesses can also play a role by adopting more environmentally friendly packaging options and promoting reusable products. Finally, individuals can make a difference by reducing their reliance on single-use plastics, recycling whenever possible, and advocating for a cleaner, healthier planet.In conclusion, the widespread use of single-use plastic products is a pressing issue that requires urgent attention. From plastic pollution in the environment to health risks for humans, the negative impacts of single-use plastics are far-reaching and cannot be ignored. By taking collective action to reduce our consumption of these items and promote more sustainable alternatives, we can work towards a cleaner, healthier future for our planet and all its inhabitants.。
食物过度包装的危害英文作文
食物过度包装的危害英文作文英文回答：Excessive food packaging poses a significant threat to the environment and human health. Its consequences can be observed locally and on a global scale, affecting ecosystems, human health, and the overall well-being of our planet.Environmental Impact:Pollution: Food packaging materials, such as plastics, metals, and glass, can contribute to pollution. Production, disposal, and incineration of these materials release harmful chemicals and greenhouse gases into the environment, polluting air, water, and soil.Landfill Buildup: Non-biodegradable packaging takes up considerable space in landfills, contributing to waste accumulation. Decomposing food waste within landfills alsogenerates harmful methane gas.Ocean Pollution: Plastic packaging often ends up in oceans, posing a threat to marine life. Ingestion or entanglement in plastic debris can lead to injury, starvation, or death for animals.Deforestation: To produce paper and cardboard packaging, forests are cleared, leading to habitat loss for wildlife and contributing to climate change.Human Health Impact:Chemical Contamination: Some packaging materialscontain harmful chemicals that can leach into food. These chemicals, such as bisphenol A (BPA), can disrupt hormones and have been linked to health issues like obesity and reproductive problems.Foodborne Illnesses: Improper or excessive packagingcan create a breeding ground for bacteria and other pathogens, increasing the risk of foodborne illnesses.Nutritional Deficiency: Overly packaged foods often contain artificial ingredients, additives, and preservatives that have low nutritional value. Reliance on these foods can contribute to nutrient deficiencies.Global Implications:Increased Carbon Footprint: The production, transportation, and disposal of food packaging contribute to greenhouse gas emissions, further exacerbating climate change.International Waste Trade: Developed countries often export their plastic waste to developing nations, where it may end up in landfills or leak into the environment.Inequality in Waste Management: Disparities in waste management infrastructure and resources lead to unequal distribution of the negative impacts of food packaging.Solutions:To mitigate the harms of excessive food packaging, several solutions are available:Reduce and Redesign Packaging: Manufacturers should reduce the amount of packaging used and redesign it to be more sustainable. Reusable, biodegradable, and compostable materials should be prioritized.Improve Waste Management: Governments and organizations must invest in waste management infrastructure, including recycling programs and waste-to-energy facilities.Consumer Behavior Change: Consumers can make informed choices by purchasing products with minimal packaging, supporting bulk purchases, and properly disposing of packaging waste.Awareness and Education: Raising awareness about the negative impacts of excessive food packaging is crucial to drive change at the consumer, industry, and policy levels.中文回答：食物过度包装对环境和人类健康构成严峻威胁。
食品过度包装的危害和建议英语作文
食品过度包装的危害和建议英语作文英文回答：Excessive food packaging has become an alarming global issue, posing significant environmental, economic, and health risks. This essay will delve into the multifaceted harms of excessive food packaging and propose sustainable solutions to mitigate its negative impacts.Environmental Consequences:Excessive food packaging contributes significantly to plastic waste pollution. Single-use plastics, such as bags, wraps, and containers, account for a vast majority of packaging materials, and their slow decomposition rate poses a long-term threat to ecosystems. They leach toxic chemicals into soil and water bodies, harming wildlife and potentially compromising human health.Moreover, the production of food packaging requiressubstantial resources, including fossil fuels, water, and energy. The extraction and processing of these materials further exacerbates environmental degradation. Additionally, landfills and waste incineration facilities struggle to manage the sheer volume of food packaging waste,contributing to greenhouse gas emissions.Economic Implications:Excessive food packaging inflates food prices for consumers. Manufacturers pass on the costs of packaging materials, production, and waste disposal to end users.This can disproportionately impact low-income households, who may struggle to afford food essentials due to inflated prices caused by excessive packaging.Furthermore, the disposal and recycling of food packaging waste can be costly for municipalities and waste management companies. In many cases, the cost of recycling outweighs the value of the recycled materials, leading to additional economic burdens on taxpayers.Health Concerns:Certain food packaging materials contain harmful chemicals that can leach into food. For instance, bisphenol A (BPA), a common component of plastic packaging, has been linked to reproductive problems, developmental disorders, and certain types of cancer. Other chemicals, such as phthalates and perfluorinated compounds (PFCs), have also raised concerns due to their potential health effects.In addition, excessive packaging can create a false sense of freshness and shelf life, leading to food waste and potential health risks from consuming spoiled food. Furthermore, the convenience of single-use packaging may promote overconsumption and contribute to obesity and other diet-related health issues.Sustainable Solutions:Mitigating the harms of excessive food packaging requires a comprehensive approach involving consumers, manufacturers, retailers, and policymakers. Here areseveral key solutions:Reduce and redesign: Manufacturers should explore alternative packaging materials, such as biodegradable plastics, paper, or reusable containers. They should also strive to minimize packaging size and optimize its design for efficiency and recyclability.Encourage reuse and refill: Consumers should opt for reusable bags, containers, and water bottles. Retailers can offer incentives for customers who bring their own containers or participate in refill programs.Promote sustainable packaging practices: Retailers should prioritize products with minimal packaging and encourage consumers to make informed choices about packaging materials. Governments can implement policiesthat incentivize sustainable packaging and hold manufacturers accountable for excessive packaging.Improve waste management: Municipalities should invest in recycling and composting infrastructure to efficientlyprocess food packaging waste. Education campaigns can help consumers understand proper waste disposal practices.中文回答：食品过度包装的危害：食品过度包装已成为一个令人担忧的全球性问题，对环境、经济和健康构成重大风险。
塑料制品危害英文作文
塑料制品危害英文作文英文：Plastic products have become an integral part of our daily lives. From the packaging of food to the construction of buildings, plastic is used everywhere. However, the convenience of plastic comes with a price – its harmful effects on the environment and human health.Firstly, plastic pollution is a major problem. Plastic products take hundreds of years to decompose, and theyoften end up in the ocean, harming marine life. For example, sea turtles often mistake plastic bags for jellyfish and ingest them, leading to their death. Additionally, plastic waste can also clog drainage systems and cause flooding during heavy rainfall.Furthermore, plastic products contain harmful chemicals that can leach into food and water, posing a health risk to humans. For example, bisphenol A (BPA) is a chemicalcommonly found in plastic products such as water bottlesand food containers. Studies have shown that BPA candisrupt hormones and potentially lead to health problems such as cancer, diabetes, and obesity.In conclusion, while plastic products may be convenient, their negative impact on the environment and human health cannot be ignored. It is important for individuals toreduce their use of plastic products and for governments to implement policies to regulate and reduce plastic waste.中文：塑料制品已经成为我们日常生活中不可或缺的一部分。
英语作文塑料瓶的危害事件
英语作文塑料瓶的危害事件Plastic bottles have become an integral part of our daily lives. They are convenient, lightweight, and easily disposable. However, their widespread usage has led to a significant increase in plastic waste, causing severe environmental and health hazards. In this article, we will explore the dangers associated with plastic bottles and the urgent need to find sustainable alternatives.One of the primary concerns related to plastic bottles is their contribution to pollution. It is estimated that over 8 million metric tons of plastic end up in our oceans every year, with plastic bottles being a significant contributor. These bottles take hundreds of years to decompose, releasing harmful chemicals into the environment in the process. Marine life often mistakes plastic bottles for food, leading to ingestion and entanglement, which can be fatal.Moreover, the production of plastic bottles requireslarge amounts of fossil fuels, contributing to greenhouse gas emissions and climate change. The extraction andrefining of petroleum, the main raw material for plastic production, release harmful pollutants into the air,further deteriorating air quality. The carbon footprint associated with plastic bottle production andtransportation is substantial, exacerbating the global climate crisis.In addition to environmental concerns, plastic bottles pose a significant threat to human health. Many plastic bottles contain bisphenol A (BPA) and phthalates, which are known to be endocrine disruptors. These chemicals can leach into the liquid stored in the bottles, especially when exposed to heat or sunlight. When consumed, they candisrupt hormonal balance and have been linked to various health issues, including reproductive problems, obesity,and certain types of cancer.Furthermore, the disposal of plastic bottles presents a significant challenge. Despite efforts to promote recycling, the majority of plastic bottles end up in landfills or aslitter. Plastic waste takes centuries to decompose, and during this process, it releases toxic chemicals that contaminate soil and water sources. This not only affects ecosystems but also poses risks to human health through the consumption of contaminated food and water.To address these concerns, it is crucial to reduce our reliance on plastic bottles and adopt sustainable alternatives. One such alternative is the use of reusable water bottles made from materials like glass, stainless steel, or BPA-free plastic. These bottles can be refilled multiple times, reducing the need for single-use plastic bottles. Additionally, governments and industries should invest in the development and promotion of biodegradable and compostable packaging materials to replace traditional plastic bottles.Education and awareness campaigns are also essential to change consumer behavior and promote responsible plastic bottle use. By educating individuals about the dangers of plastic bottles and the importance of recycling, we can encourage them to make more sustainable choices.Governments should implement stricter regulations and incentives to promote recycling and discourage the production and consumption of single-use plastics.In conclusion, plastic bottles pose significant risks to the environment and human health. Their production, disposal, and chemical composition contribute to pollution, climate change, and various health issues. It is imperative that we take immediate action to reduce our dependence on plastic bottles and embrace sustainable alternatives. By doing so, we can protect our planet and safeguard the well-being of current and future generations.。
吃罐头鱼的利与弊英语作文
Canned fish is a staple in many households,appreciated for its convenience and long shelf life.However,the consumption of canned fish comes with both benefits and drawbacks that are worth examining in detail.On the positive side,canned fish is a convenient food option that requires no preparation time.It can be opened and consumed immediately,making it an ideal choice for busy individuals or those who may not have access to fresh fish.The canning process also helps to preserve the nutritional content of the fish,ensuring that consumers receive a good source of protein,omega3fatty acids,and various essential vitamins and minerals. Omega3s,in particular,are known for their heart health benefits and their role in brain function and development.Moreover,canned fish is often more affordable than fresh fish,making it accessible to a wider range of consumers.This affordability is especially important in areas where fresh seafood is scarce or expensive.The versatility of canned fish also allows it to be incorporated into a variety of dishes,from salads to pasta,offering a quick and easy way to add flavor and nutrition to meals.However,the drawbacks of consuming canned fish cannot be ignored. One of the primary concerns is the potential presence of bisphenol A BPA in the lining of some cans.BPA is a chemical that has been linked to various health issues,including hormonal imbalances and an increased risk of certain cancers.While many manufacturers have moved away from using BPA in their cans,it is still important for consumers to be aware ofthis potential risk.Another concern with canned fish is the high sodium content often found in the brine used to preserve the fish.High sodium intake has been linked to increased blood pressure and a higher risk of heart disease.For individuals monitoring their sodium intake,this can be a significant drawback.Additionally,the canning process can sometimes affect the taste and texture of the fish.Some consumers find that canned fish has a softer texture and a less fresh taste compared to fresh or frozen options.This can be a deterrent for those who prioritize the sensory experience of their food.Environmental considerations also play a role in the debate surrounding canned fish.The production and disposal of cans contribute to waste and pollution,which can have negative impacts on the environment.While recycling programs can help mitigate this issue,it is still an important factor to consider.In conclusion,while canned fish offers convenience,affordability,and nutritional benefits,it also comes with potential health risks and environmental concerns.Consumers should weigh these factors carefully when deciding whether to incorporate canned fish into their diets.It may be beneficial to seek out cans that are BPAfree and to balance consumption with fresh or frozen fish options to ensure a varied and nutritious diet.。
环境新兴污染物双酚A暴露加重非酒精性脂肪性肝病大鼠脂质代谢异常
环境新兴污染物双酚A暴露加重非酒精性脂肪性肝病大鼠脂质代谢异常丁雯瑾;孙超;桑玉尔;陈梅梅;范建高;袁涛【摘要】目的探讨在非酒精性脂肪性肝病(NAFLD)背景下新兴环境污染物双酚A(BPA)对机体脂质代谢的影响.方法将18只SD大鼠随机分为正常饮食组、高脂饮食(NAFLD)组和NAFLD/BPA处理组,饲养12w.采用Western blot法检测血清和肝组织脂代谢相关蛋白的变化.结果 NAFLD组和NAFLD/BPA组肝质量分别为(20.5±2.8)g和(20.9±1.9)g、体质量为(500.1±19.1)g和(511.1±20.5)g、血清甘油三酯分别为(2.5±0.5)mmol/L和(2.8±0.9)mmol/L、胆固醇为(2.4±0.7)mmol/L和(2.8±0.6)mmol/L,游离脂肪酸(FFA)分别为(578.6±48.7)mmol/L和(602.2±50.3)mmol/L,均显著高于正常组[(15.2±2.3)g、(432.5±13.2)g、(2.0±0.8)mmol/L、(1.0±0.6)mmol/L和(487.4±14.9)mmol/L,P<0.05];与正常组比,NAFLD组和NAFLD/BPA组肝组织脂肪酸合成酶(FAS)分别上调了2.45倍和1.91倍,靶基因乙酰辅酶A合成酶(ACS)蛋白表达量分别下降了1.54倍和1.5倍(P<0.05).结论 BPA的长期摄入可加重机体肥胖,促进血脂异常.【期刊名称】《实用肝脏病杂志》【年(卷),期】2017(020)006【总页数】3页(P785-787)【关键词】非酒精性脂肪性肝病;双酚A;脂质代谢;大鼠【作者】丁雯瑾;孙超;桑玉尔;陈梅梅;范建高;袁涛【作者单位】200092上海市上海交通大学医学院附属新华医院消化科;200092上海市上海交通大学医学院附属新华医院消化科;200092上海市上海交通大学医学院附属新华医院消化科;200092上海市上海交通大学医学院附属新华医院消化科;200092上海市上海交通大学医学院附属新华医院消化科;200092上海市上海交通大学医学院附属新华医院环境科学与工程学院【正文语种】中文双酚A（bisphenol A，BPA）、邻苯二甲酸酯和烷基酚是一类新兴环境污染物，亦称环境内分泌干扰物，世界卫生组织将其定义为：能使内分泌功能发生变化，从而对个体及子孙或者群体产生有害影响的外因性化学物质或混合物[1-3]。
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双酚A与肥胖，糖代谢异常/2型糖尿病和心血管疾病指标的关系：流行病学调查的系统综述摘要介绍：双酚A是一种大量使用的化学物质，它具有类似雌激素的作用，而且它与肥胖心血管疾病和糖尿病有关系。
这篇综述评价了流行病学验证双酚A暴露是这些疾病风险因素的一致性与质量。
方法：我们根据现行的系统综述评估方法指南，选择两位独立的人员对有关BPA与肥胖，心血管疾病，糖尿病和相关标志物关系的流行病学文献进行鉴定，检阅与总结。
每篇文献的总结都考虑到了它的方法与结果，特别是研究设计与暴露评估，这方面被认为是BPA流行病学研究的主要弱项。
由于定量meta分析不可行，研究结果被定性分类为正相关，反相关，无相关或混合相关。
结果：几乎所有有关BPA与肥胖，糖尿病以及心血管疾病关系的研究都是横断面研究，而且依靠单一的BPA暴露测量，这可能会导致严重的暴露五分类。
所有的结果与研究都不一致。
虽然一些研究用了同样的数据和同样或相似的统计方法，但是当方法稍微变化就会产生不同的结果。
结论：流行病学研究的设计严重限制我们对BPA暴露与健康效应关系的理解。
就现存的流行病学文献来看，说BPA与肥胖，糖尿病或心血管疾病具有因果关系是没有证据的。
关键词：双酚A，生物监测，BPA，心血管疾病，糖尿病，肥胖，流行病学，系统综述介绍环境肥胖因子的意思是“能够不适当地改变脂质代谢，脂肪储存，代谢定位点和能量平衡，或者调解食欲和饱腹感以促进脂肪积累与肥胖的化学物质”(Kirchner et al., 2010)。
据猜测肥胖因子的暴露会使人患肥胖症，2型糖尿病和心血管疾病的风险增加(Cameron, 2010)。
船舶防污漆中的三丁基锡和人工合成的己烯雌酚通常被认为是肥胖因子，但是越来越多的环境化学物质被认为对内分泌系统有影响，而且最终会导致代谢综合征(MetS)（这包括胰岛素抵抗(IR)，高胰岛素血症，腹部肥胖，糖耐量异常，糖尿病DM，微量蛋白尿，高水平甘油三酯(TG)，低水平高密度脂蛋白胆固醇(HDL)，血压上升，炎症与血栓前期[Pacholczyk et al., 2008]）以及一些相关不利的健康结果。
正如Diamanti-Kandarakis等人所说的“有关内分泌干扰物作为肥胖因子的机制的知识还十分欠缺，尤其是作用的过程。
”一个复杂因素是饮食可能是主要的肥胖因子相关化合物的暴露途径。
这引起了一个问题：肥胖（以及相关疾病）是由于摄入了偶然含有这些化学物质的食物，还是这些化学物质自己导致了肥胖和相关疾病。
Sharpe & Drake (2013)建议流行病学研究会使我们在两方面收货颇丰：首先，流行病学研究提供的信息是人们的实际暴露水平，而毒理学研究通常用较高的剂量；其次，这种研究可以分解出各种因素，如饮食，对肥胖及相关疾病的影响。
在这篇综述中，我们首先检查现有可用的有关BPA与肥胖，糖尿病和心血管疾病关系的流行病学证据。
BPA或者双酚基丙烷在工业上大量被用来制造聚碳酸酯塑料和环氧树脂，然后被用来制造瓶子，食物容器和牙科密封剂(Arnichet al., 2011; Calafat et al., 2005)。
生物监测数据表明大多数人尿样中具有可测水平的结合BPA，少数人具有可测水平的非结合BPA（具有生物活性的单体），而且饮食被认为是一般人群的主要暴露方式(Calafat et al., 2008;Kang et al., 2006; LaKind & Naiman, 2008; LaKind et al.,2012a, 2011; Mahalingaiah et al., 2008)。
一般人群血清中是否有可测水平的BPA却是个争论激烈的难题(Calafat et al., 2013)，尽管最近一项研究发现高饮食暴露人群血清中无可检测水平的非结合BPA(Teeguarden et al., 2011)。
由于BPA的暴露十分广泛和它的雌激素特性，低剂量BPA暴露对健康的影响引起了很大的关注(Goodman et al., 2009; Melnick et al., 2002)。
由于雌激素化合物在生物学上可以影响各种器官与组织，所以其健康效应也是十分广泛的。
尽管大多数都在关注BPA的生殖发育毒性(Braun & Hauser, 2011; Golub et al.,2010; Hauser & Sokol, 2008; Goodman et al., 2006, 2009; Meeker, 2010)，但是最近人们开始关注BPA的代谢效应，人们猜测BPA会增加患肥胖症，心血管疾病和糖尿病的风险(Alonso-Magdalena et al., 2011; Thayer et al., 2012)。
对于这些结果，人们猜测BPA作用的机制是激活雌激素受体alpha，以调节胰岛bata细胞(Livingstone &Collison, 2002; Ropero et al., 2008)。
据猜测，BPA促进产生过度的胰岛素信号，最终导致胰岛素抵抗，并且增加糖尿病，高血压和血脂异常的风险(Alonso-Magdalena et al., 2006;Nadal et al., 2009)。
目前讨论环境化学物（包括BPA）的内分泌效应主要集中在体外实验和动物体内模型(European Food Safety Authority, 2010; Hengstleret al., 2011; Rhomberg et al., 2012; Talsness et al., 2009;Thayer et al., 2012; Vandenberg et al., 2012)。
相反的是，BPA效应的流行病学综合评价数据却十分不足(Dash et al., 2006; Tang-Peronardet al., 2011)。
据我们所知，之前只有一篇综述精细地评估了人群中BPA与心血管，糖尿病以及其它疾病的关系。
BPA的流行病学研究是一个发展迅速的领域，每个月都有许多评估其各种效应的论文发表。
但是之前提到的综述(Braun et al., 2011a)只评估了两篇有关BPA与糖尿病和心血管疾病关系的文献(Lang et al., 2008;Melzer et al., 2010)，还有一篇有关体重指数的(Wolff et al.,2007)。
现在有40多篇相关文献可供使用，所以建立新的流行病学证据的评估是可行的。
这篇综述系统地评价了流行病学验证双酚A暴露是肥胖，心血管疾病和糖尿病的风险因素的一致性与质量。
方法方法导论在此研究中，我们参阅了现行的系统综述方法指导(Moher et al., 2009; Shea et al., 2007; Sutton et al., 1998)。
另外，我们根据“多重系统综述评估工具”（即AMSTAR，是之前方法(Delaney et al.,2007; Moher et al., 1999)的扩展）(Shea et al., 2007)交叉检查了我们的研究方法。
AMSTAR工具包含以下11个项目：（1）在系统评价开展以前，应该确定研究问题及纳入排除标准；(2)至少要有两名独立的数据提取员；（3）至少检索2种电子数据库，另外还要检索综述教科书和二次参考文献，并在方法部分附上关键词和医学主题词(MESH)；（4）发表情况是否已考虑在纳入标准中（如灰色文献，是指未发表的文献）；（5）提供排除的研究文献清单；（6）描述纳入研究的特征；（7）有条理地评估单个研究的局限性；（8）在推论时要考虑证据的可靠性；（9）可能的话，研究结果要以定量meta分析呈现，并且要检验它的异质性；（10）评估发表偏倚；（11）资料来源声明(Shea et al., 2007)。
除了第9和第10项取决于正式meta分析的可行性，AMSTAR清单被用于所有的系统综述。
文献的识别与选择初始文献检索使用的电子数据库包括PubMed和EMBASE。
使用的关键词有‘‘BPA,’’‘‘bisphenol A,’’ ‘‘toxicity,’’ ‘‘humans,’’‘‘health,’’ ‘‘health outcomes,’’ ‘‘obesity’’,‘‘overweight’’,‘‘DM, ’’ ‘‘diabetes,’’ ‘‘epidemiology,’’ ‘‘heart disease(s),’’‘‘CVD(s),’’‘‘myocardial infarction (MI),’’ ‘‘heart attack,’’‘‘coronary disease(s),’’ ‘‘coronary heart disease(s) (CHD),’’‘‘coronary artery disease(s) (CAD),’’ ‘‘epidemiology’’以及一些相关关键词。
我们选择那些研究人群BPA暴露与健康效应关系的文献。
检索到文献的二次引用文献也被评估了。
为了识别未在同行审查文献发表的相关文献，我们执行了附加的文献检索。
由于许多研究没有特别的集中在研究肥胖，心血管疾病和糖尿病，但是也包含了相关数据，所以我们试图检索所有有关BPA和健康关系的流行病学研究。
然后，审阅这些文献，以提取与现在研究问题相关的信息。
检索到与考虑到的流行病学研究的完整清单附在补充材料中。
相关研究的搜索与选择是由两名独立的研究人员(J.L. and M.G.)执行的，且对于不同的意见采取合适的方法达成一致。
纳入综述的标准如下：（1）通过对生物样品的检测，研究不同水平BPA暴露的人群。
（2）相关结果被分为5大类：（a）超重或肥胖的指标：体重指数（BMI），腰围（WC），体重（WC），脂肪量（FM），非脂肪部分（FFM），臀围（HC），腰臀比（WHR）和脂肪比率（%BF）。
（b）反应糖代谢受损的情况：糖尿病和胰岛素抵抗。
（c）糖代谢的生物标志：循环空腹血糖水平（FG），胰岛素水平（I），糖化血红蛋白水平（HbA1C）和其他指标，如对beta细胞功能的测量。
（d）反应心血管疾病的情况：心肌梗死MI，冠心病CHD/CAD，高血压，心绞痛，中风等其他各种能够影响心脏与血管健康的疾病与原因，如劲动脉超声存在斑块或外周动脉疾病（PAD）。
（e）反应心血管健康的指标：血液总胆固醇（TC），低密度脂蛋白（LDL），高密度脂蛋白（HDL）和甘油三酯（TG）;测量的舒张收缩压（DBP andSBP）和其他反应心血管功能的指标，如弗雷明汉风险得分（FRS）或心率变异性（HRV）。
（3）BPA暴露与以上结局的关系的评估是由出版作者评估的，或者基于出版物提供的信息评估的。