给排水英语论文

PARTICLE EXPOSURE THROUGH THE INDOOR AIR ENVIRONMENTGYULA DURA∗ and BRIGITTA SZALAYFodor Jozsef National Centre for Public Health, NationalInstitute of Environmental Health, Gyali ut 2-6, Budapest 1097,HungaryAbstract: Sources, exposure and measuring techniques for indoor particulate matters (PM) are overviewed. To evaluate indoor air quality in two subway sta-tions in Budapest, concentrations of PM10, PM2.5 and total suspended particu-lates (TSP) were measured during a 5-day period in a preliminary study. The following results were found: PM10 pollution was 2–3 times higher in the metro station than in matched sampling in the street. The levels of PM2.5 were much less. PM pollution level was not influenced by the depth of the platforms. Keywords: indoor environment, particulate matter, exposure, PM on subway1.IntroductionIt is well known that air quality has a significant impact on human health. We can drink bottled water if piped water contains too much chlorine. We can select higher-quality food, so-called bio-products currently on the market, if we are afraid of chemical residuals. However, we cannot choose the air we breathe. We spend a large part of our life indoors, at home, or other public environ-ments, such as schools or restaurants. Having clean indoor air is very important for the health of the population as a whole and it becomes particularly impor-tant for infants, children and the elderly or people predisposed to disease, parti-cularly respiratory or cardiovascular diseases.The public health significance of indoor air pollutants, including particulate matter (PM), is studied worldwide and scientific evidence shows a significant impact on the health of the population (/pages/publica-tions/factsheets.asp). Environmental tobacco smoke (ETS), combustion products, volatile organic compounds and biological pollutants are all responsible for, or increasing respiratory diseases and in some cases, cardiovascular diseases ∗ To whom correspondence should be addressed.271P.P. Simeonova et al. eds.,Nanotechnology – Toxicological Issues and Environmental Safety, 271–276.© 2007 Springer.PARTICLES AND THE INDOOR AIR ENVIRONMENT272(Gamble, 1998). When exposures are sufficient to cause acute health effects in a population (as may occur in certain accidental catastrophes) causal rela-tionships are easier to demonstrate. However, low-level exposure environ-mental or occupational exposure is difficult to investigate. In principle, there are two basic approaches commonly used to address indoor air issues. The most obvious is to reduce indoor exposure to known air pollutants for which health impacts have been established or are strongly suspected. The second is to promote investigations aimed at a better understanding the exposure – health effect relationship in order to support policy development and implementation (WHO/Euro, 2006). Regarding PM, we have to reduce sources of emissions or take measures, such as optimizing building design and ventilation, to keep indoor concentrations of pollutants as low as possible. There is also a need to conduct investigations on the source, hazard, exposure and effect of different types of airborne particles and informing the populations at risk on behaviours that minimizes exposure. This strategy is already followed by many national and international organizations such as WHO and EU.2.Sources of Indoor PMThe major indoor source of fine-particle exposure, besides smoking, is cooking, particularly from frying and broiling. For ultra-fine particles, gas-burners, gas ovens, and electric toasters are also important point sources (Ott and Siegmann 2006). Other sources of indoors air polluatants are derived from the day-to-day activities of humans and dosmestic animals, as well as handling of organic materials like firewood. Biological particles that have settled indoors, along with other particulate matter, may become resuspended into the ambient air through normal household activities and other mechanical disturbances. The relative importance of these sources depends on the environment and lifestyle of the occupants. Particles present in the indoor environment may also be bound to surfaces, attached to dust accumulated in the building, or present in internal parts of the building structure or their operating system, such as air-condi-tioning units, and ducts (Morawska and Salthammer 2003).Besides active indoor sources, particles generated by outdoor sources can penetrate from outdoor into indoor air either through open windows or doors, or through cracks, gas or holes in the building envelope. Particle deposition on indoor surfaces is related to particle size and surface characteristics, with rough surfaces resulting in higher deposition than smooth ones. The depositing parti-cles contribute to the surface accumulation, and thus the process of deposition can also be described in terms of an increase in deposited materials on the sur-faces. The deposition of house dust has been the subject of many studies.There is a significant difference in the role of outdoor air, as a source of indoor particles, compared to the role of indoor sources. Indoor sources, whilePARTICLES AND THE INDOOR AIR ENVIRONMENT 273 affecting outdoor characteristics to varying degrees, have a direct effect only in houses in which they are present. Since the characteristics of the sources and pattern of their usage differ from house to house, the resulting particle-concen-tration levels and other characteristics will differ from house to house as well. Outdoor air, however, provides the same background levels for all houses in the area. Although the fraction of outdoor particles penetrating a building differs due to differences in air-exchange rates or the filtering systems, the time variation of this background tends to remain the same.The indoor/outdoor (I/O) relationship for mechanically ventilated buildings is even more complex than that for naturally ventilated buildings. The mechani-cally ventilated buildings investigated, in most cases, have been non-industrial workplaces or public buildings, such as offices, hospitals, restaurants, schools, shopping centers or public transport buildings (Poupard et al. 2005). A common characteristic of indoor areas in all such buildings is that the mechanical venti-lation and filtration systems affect the characteristics of PM entering the build-ing in terms of concentration and size distribution.3.Exposure to Indoor PMHuman movement has frequently been shown to result in an increase in particle-mass concentration. Activities such as walking, cleaning or dressing can significantly increase the concentration of PM in the air. It has been demon-strated that even light activities could be a significant source of PM. However, such physical activities do not contribute to PM in the air, which are basically non-resuspendable under conditions present in residential environments.In addition, the impact of cigarette smoking on particle concentrations has been investigated in terms of the increase in particle concentrations in the houses of smokers compared to the houses of non-smokers based upon various averaging periods, number of cigarettes smoked and indoor/outdoor ratios for houses with and without smokers. Increased concentrations of PM2.5, as a result of cigarette smoking, have been found in many places. Moreover like smoking, the effect of cooking on indoor particle mass concentration levels has been in-vestigated and expressed in a number of ways (Saraga et al. 2006).For the assessment of human exposure to indoor pollutants, the analysis of settled house dust and adsorbed organic, inorganic, and biologically active compounds is of increasing scientific and medical interest. Particulates pass into the body through oral and dermal intake. The main mechanism for intake of airborne particles by the human body is through inhalation of particulates and deposition in the respiratory tract (Morawska et al. 2005). Large-sized particulates mainly deposit in the upper part of the respiratory tract due to impaction, interception, gravitational sedimentation as well as turbulent dispersion (Oberdorster et al. 2005). Very fine particles, such as those generatedPARTICLES AND THE INDOOR AIR ENVIRONMENT274 through combustion processes, have a high probability of deposition in deeper parts of the respiratory tract, due to their high diffusivities. An understanding of the mechanisms of particle deposition in the human respiratory tract and the ability to quantify the deposition in individual parts of the respiratory tract is of fundamental importance for dose assessment from inhalation of particles, which can then be used for risk assessment (Gwinn and Vallyathan 2006). Over the last three decades, a large number of studies have been conducted to investi-gate particle deposition in the human respiratory tract (Donaldson et al. 1998, Oberdorster et al. 2005).4. Measurement Techniques for Indoor PMElectronmicroscopy is the most common technique used for particle analysis at both the morphological and chemical levels. Scanning electron microscopy men. Characterization of indoor PM, by combining scanning and transmission et al. 2005). It should be noted, however, that no single electron-microscope technique will provide a total elemental characterization of a specimen and a synergistic approach is generally required, which includes several other micro- analytical techniques.5. Preliminary Results on Indoor Air-Quality Assessmenton Underground Platforms in BudapestAs people spend about 10% of their time per day with transportation, and a large number of people are exposed to traffic-related pollution in big cities every day (http://www.levego.hu/caag.htm). Nowadays the underground trans-port mode has an important role in Budapest as 23% of the inhabitants make use of the metro. This represents 863,140 persons travelling by underground lines on average in 1 day last year. The main sources of respirable tunnel dust in the underground rail system are particles from abrasive forces acting on rails and wheels from traction and braking. These are likely to contain iron and par-ticles shed from humans and their clothes. The results of a study by Hurley et al. (2003) showed that dust in the London Underground differs from outdoor particles and accordingly risks from outdoor particles are misdirecting for esti-mating its health effects. Tunnel dust is coarser, being generated by interaction(SEM) can provide information on particle surface structures or 3D interpre-tations. The added advantage of SEM is the capacity to determine the elemental levels that yield specific information about the elemental features of a speci-composition of airborne particles at both the individual and bulk-particle electron-microscopy, yields additional information about the size, morpho-logy, and the chemical and phase composition of individual particles (HoflichPARTICLES AND THE INDOOR AIR ENVIRONMENT 275 of brakes, wheels and rails rather than by combustion, with higher-mass con-centrations and lower-particle numbers. It contains about 90% iron, 1–2% quartz and the remains of other metals. One of the main aims of their work was to characterize the physical quality and composition of the dust and to make measurement that would allow evaluation of the exposure levels of the London underground workers.The goal of our investigation was to establish the passenger’s exposure to PM on two metro platforms being at different depths (deep and subsurface) of stations in Budapest. Manual sampling was carried out using a high-volume sampler (TSP) and a Harvard impactor (PM10 and PM2.5) during 24 h on 5 con-secutive days. Gravimetry analysis was performed. Energy-dispersive x-ray SEM was used for the characterization of particles morphology as well as for the elemental composition.It was found that the differences for PM2.5 between the metro stations and the above-ground sampling location were less than for PM10. Five-day means of the PM10 were 200 ug/m3 on the subsurface and deep metro stations. The outdoor (ambient-air) concentrations were between 55 and 95 ug/m3. Five-day means of the PM2.5 were 60 and 80 ug/m3 on the subsurface and deep metro stations, respectively. The ambient air concentrations were under 50 ug/m3. Hourly TSP concentrations exceeded the national standard (200 ug/m3) for ambient-air.Morphology and element composition was analysed by SEM. Regarding the composition of particulates the major components of PM10 fractions sampled in metro stations were Fe (30%), O (23%) and C (29%). PM2.5 fractions contained less Fe (10%) and more C (50%) than PM10 particles. These outcomes in some ways are similar to the composition of tunnel dust received in the London underground. Morphology of particles with iron content was found in amor-phous and needle forms as well. Mutagenicity assay of TSP samples taken on metro platforms showed moderate mutagenic activity with responses varying from 1,47 (1,19) to 4,42 (3,31) revertants per metric cube depending on depth of the station.Our preliminary results indicate absences of elevated risk to the traveling public from exposure to PM in Budapest metro and have firmed that the dust metro is mainly from abrasion comprised of iron. Since concentrations of PM found in the subway indicate meaningful presence of these contaminants, fur-ther control measures should be considered.AcknowledgmentsAuthors thank Mrs. Eva Vaskövi for kindly providing data of the measurements on metro stations.PARTICLES AND THE INDOOR AIR ENVIRONMENT276ReferencesDonaldson, K., Li, X.Y., and MacNee, W., 1998, Ultrafine (nanometre) particle mediated lung injury, J. Aerosol. Sci.29(5/6):553–560.Gamble, J.F., 1998, PM2.5 and mortality in long-term prospective cohort studies: cause-effect or statistical associations? Environ. Health Perspect.106(9):535–549.Gwinn, M. and Vallyathan, V., 2006, Nanoparticulates: Health Effects - Pros and Cons, Environ.Health Perspect. 114:1818–1825.Hoflich, B.L., Weinbruch, S., Theissmann, R., Gorzawski, H., Ebert, M., Ortner, H.M., Skogstad,A., Ellingsen, D.G., Drablos, P.A., and Thomassen, Y., 2005, Characterization of individualaerosol particles in workroom air of aluminium smelter potrooms, J. Environ. Monit.7(5):419–424.Hurley, J.F., Cherrie, J.W., Donaldson, K., Seaton, A., and Tran, C.L., 2003, Assessment of health effects of long-term occupational exposure to tunnel dust in the London Underground, Institute of Occupational Medicine Research Report TM/03/02.Morawska, L., Hofmann, W., Hitchins-Loveday, J., Swanson, C., and Mengersen, K., 2005, Ex-perimental study of the deposition of combustion aerosol in the human respiratory tract, J. Aerosol Sci.36:939–957.Morawska, L. and Salthammer, T., 2003, Indoor Environment, Airborne Particles and Settled Dust. Wiley-VCH, Weinheim, Germany.Oberdorster, G., Oberdorster, E., Oberdorster, J., 2005, Nanotoxicology: An Emerging Discipline Evolving from Studies of Ultrafine Particles, Environ. Health Perspect. 113:823–839.Ott, W.R. and Siegmann, H.C., 2006, Using multiple continuous fine particle monitors to charac-terize tobacco, incense, candle, cooking, wood burning, and vehicular sources in indoor, out-door and in-transit settings, J. Atmos. Env.40:821–843.Poupard, O., Blondeau, P., Iordache, V., and Allard, F., 2005, Statistical analysis of parameters influencing the relationship between outdoor and indoor air quality in schools, J. Atmos. Env.39:2071–2080.Saraga, D., Maggos, T., Vassilakos, C., Michopoulos, J., Helmis, C.G., and Bartzis, J.G., 2006, Contribution from smoking to PM2.5, PM1 particles and VOCs concentrations in residential houses in Athens, Greece WIT, Trans. Ecol. Environ.86:355–364.WHO/Euro, 2006, Health risk of particulate matter from long range transboundary air pollution.ECEH, Bonn, Germany. http://www.euro.who.int/document/E88189.pdf/pages/publications/factsheets.aspParticulates small but dangerous, 2006, Environmental Fact Sheet No 20.http://www.levego.hu/caag.htm。