Air pollution mixtures

TABLE 8-1 Effects of Photochemical-Oxidant Air Pollution Mixtures (in Irradiated Auto Exhaust) and Some Individual Constituents in Single Short (6-h) Exposures ... 

Grosjean, D. and Parmar, S.S. (1991) Removal of air pollutant mixtures from museum display cases. Studies in Conservation, 36,... 

Mautz WJ, Kleinman MT, Bhalla DK, et al. 2001. Respiratory tract responses to repeated inhalation of an oxicant and acid gas-particle air pollutant mixture. Toxicol Sci 61(2) 331-341. 

Natural gas is attractive as a fuel ia many appHcatioas because of its relatively clean burning characteristics and low air pollution (qv) potential compared to other fossil fuels. Combustion of natural gas iavolves mixing with air or oxygen and igniting the mixture. The overall combustion process does not iavolve particulate combustion or the vaporization of Hquid droplets. With proper burner design and operation, the combustion of natural gas is essentially complete. No unbumed hydrocarbon or carbon monoxide is present ia the products of combustioa. 

Carbon monoxide was discovered in 1776 by heating a mixture of charcoal and 2inc oxide. It provided a source of heat to industry and homes as a component of town gas and was used as a primary raw material in German synthetic fuel manufacture during World War II its compounds with transition metals have been studied extensively (see Carbonyls). Most recently, carbon monoxide emission from vehicle exhausts has been recognized as a primary source of air pollution (qv). 

Sufficient evidence is available to indicate that atmospheric pollution in vaiying degrees does affect health adversely. [Amdur, Melvin, and Drinker, Effec t of Inhalation of Sulfur Dioxide by Man, Lancet, 2, 758 (1953) Barton, Corn, Gee, VassaUo, and Thomas, Response of Healthy Men to Inhaled Low Concentrations of Gas-Aerosol Mixtures, Arch. Lnviron. Health, 18, 681 (1969) Bates, Bell, Burnham, Hazucha, and Mantha, Problems in Studies of Human Exposure to Air Pollutants, Can. Med. A.s.soc. J., 103, 833 (1970) Ciocco and... 

The effects of atmospheric pollution are chemical, and concentration, specific. However, additive, and sometimes synergistic, effects arising from mixtures are important. A sutmuary of the potential effects of common air pollutants is given in Table 16.10. 

Indoor air often contains a variety of contaminants at concentrations that are far below any standards or guidelines for occupational exposure. Given our present knowledge, it is difficult to relate complaints of specific health effects to exposures to specific pollutant concentrations, especially since the significant exposures may be to low levels of pollutant mixtures. 

Smog a mixture of air pollutants, principally ground-level ozone, produced by chemical reactions involving smog-forming chemicals. See also haze. 

Smog commonly refers to air pollution it implies an air mixture of smoke particles, mists, and fog droplets of such concentration and composition as to impair visibility, in addition to being irritating or harmful. Smog is often associated with temperature inversion in the atmosphere that prevent normal dispersion of contaminants. 

In a report comparing community responses to low-level exposure to a mixture of air pollutants from pulp mills, Jaakkola et al. (1990) reported significant differences in respiratory symptoms between polluted and unpolluted communities. The pollutant mixture associated with the pulp mills included particulates, sulfur dioxide, and a series of malodorous sulfur compounds. Major contributors in the latter mixture include hydrogen sulfide, methyl mercaptan, and methyl sulfides. In this study the responses of populations from three communities were compared, a nonpolluted community, a moderately polluted community, and a severely polluted community. Initial exposure estimates were derived from dispersion modeling these estimates were subsequently confirmed with measurements taken from monitoring stations located in the two polluted communities. These measurements indicated that both the mean and the maximum 4-hour concentrations of hydrogen sulfide were higher in the more severely polluted community (4 and 56 g/m3 2.9 and 40 ppb) than in the moderately polluted one (2 and 22 g/m3 1.4 and 16 ppb). Particulate measurements made concurrently, and sulfur dioxide measurements made subsequently, showed a similar difference in the concentrations of these two pollutants between the two polluted communities. 

Because of the exposures to mixtures of air pollutants, it is difficult to predict whether the symptoms seen in these studies would be experienced by populations exposed to low levels of hydrogen sulfide near NPL sites. However, pollution patterns in geothermally active areas and near industrial facilities such as pulp mills and sour gas production facilities are likely to be similar to those reported in these studies, suggesting that populations living near such facilities could experience similar symptoms. 

Polycyclic aromatic hydrocarbons (PAH) are important air pollutants that have to be detected at very low concentrations. Fig. 2.4h shows the separation of a synthetic mixture of very low levels of PAH. They are barely detectable using uv absorption, but are easily monitored by fluorescence. 

A 2-value smaller than 1 means that there is an excess of fuel in the mixture. In this case the air/fuel mixture is called rich. If more air is in the mixture than needed for a complete fuel combustion (2 > 1) the term lean mixture is used. Ideally the combustion is complete at 2 = 1. Real fuel cannot be combusted without an increase in CO and soot at 2-values smaller than 1.05. Due to changing operation conditions, for example a soiled burner, wear of the nozzle or leaky flaps, change of gas quality or changes of temperature and air pressure in the ambient atmosphere, the air/fuel ratio and thus flue gas composition can change over time. In order to minimize the risk of intoxication (see also chapter 5333), explosion and pollution real (uncontrolled) fuel burners are adjusted to operate far beyond this limit in the excess (lean mixture) region. However, unfortunately effi-... 

Carbonyl sulfide is an intermediate in this reaction. A mixture of sulfur dioxide and oxygen was blown into the bottom of coke-fired reduction furnace and sulfur vapor condensed from the off-gases. Trail is the location of a large mine and smelter in British Columbia. The process was originally used in the 1930s for abating air pollution from the smelter, but when the demand for sulfuric acid for fertilizer production increased in 1943 it became obsolete. See also Boliden (1), RESOX. 

Photochemical air pollution consists of a complex mixture of gaseous pollutants and aerosols, some of which are photochemically produced. Among the gaseous compounds are the oxidizing species ozone, nitrogen dioxide, and peroxyacyl nitrate ... 

Laboratory experiments of this type have the great advantage that the initial conditions can be well defined (although often they are not ), in contrast with the average sample of urban air, which is a mixture of new and old pollutants. Also, in laboratory experiments, the same sample of air is observed over a long period, which is not possible with most air pollution monitoring networks. For these reasons, most attempts to understand the chemistry of oxidant formation have concentrated on smog-chamber experiments, rather than the real atmosphere. 

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