Solvents urban pollutants

The sources of urban pollutants are municipal sewage, runoff from city streets and landfills, and industrial effluents. Indirectly solvents contribute to municipal sewage, insofar as they comprise part of the landfill and runoffs. Mostly, industrial effluents have solvent components. 

The CAA of 1990 contains six titles and related provisions designed to encourage air pollution abatement and reduction. These provisions address several environmental pollution problems that affect us all, such as tropospheric ozone, hazardous pollution, mobile emissions, urban pollution, acid deposition, and stratospheric ozone depletion. Because the scope of this chapter is on solvents and the regulations that impact their use, only Titles I, III, V, and VI and their relevance to solvents will be discussed. 

Although both types of pollution sources present a serious problem, point sources can be controlled, at least in principle. Nonpoint sources, however, are difficult to control. Sources and types of nonpoint pollution in impacted rivers and lakes in the United States include agriculture, land disposal, construction, hydromodification, urban runoff, and silviculture, resource extraction. The pollutants in these sources include sediment, nutrients, toxins, pesticides, salinity, and acidity (Institute, 1988). Looking at these lists, one can easily deduce that solvents play roles in the pollution of water. 

The vapors of this highly toxic synthetic solvent (it s a nasal irritant and a neurotoxin) contribute to the formation of urban ozone pollution. Ethylene glycol is listed in the 1990 Clean Air Act as a hazardous air pollutant and is on the EPA s Community Right-to-Know list. 

One of the major uses of activated carbon is in the recovery of solvents from industrial process effluents. Dry cleaning, paints, adhesives, polymer manufacturing, and printing are some examples. Since, as a result of the highly volatile character of many solvents, they cannot be emitted directly into the atmosphere. Typical solvents recovered by active carbon are acetone, benzene, ethanol, ethyl ether, pentane, methylene chloride, tetrahydrofuran, toluene, xylene, chlorinated hydrocarbons, and other aromatic compounds [78], Besides, automotive emissions make a large contribution to urban and global air pollution. Some VOCs and other air contaminants are emitted by automobiles through the exhaust system and also by the fuel system, and activated carbons are used to control these emissions [77,78],... 

It should be noted that workers exposed to benzene by dermal contact also may inhale vapors and thus receive a dual exposure. The air in many polluted areas often contains significant benzene levels as a result of the combustion of petroleum fuels. The ambient air over Los Angeles, California, in the decade 1990-2000, for example, typically contained greater than 1.0 ppm benzene.I18 Tobacco smokers and those exposed to secondhand (or environmental) smoke are further exposed to benzene. It is reasonable to anticipate that benzene-containing solvents will be used in urban and industrial areas where the air is polluted with benzene and that smokers will be among those who use such solvents. Such conditions further dictate the need for lowering the allowable benzene concentration in solvents. 

The third principal source of nitrobenzene is the atmospheric photo-chemical reaction of nitrogen oxides with benzene, which presumably is derived from automobile fuels and, to a lesser extent, solvent uses of benzene (Dorigan and Hushon 1976). As benzene releases decline, this source (not quantified) should diminish as well. The contribution of this source is difficult to estimate since most measurements of ambient atmospheric nitrobenzene have been made in urban areas near sites of nitrobenzene manufacture, use, and disposal (see Section 5.4.1). Seasonal variations and those associated with air pollution episodes suggest that this source, although limited, may form a significant proportion of nonoccupational human exposure. 

Since the beginning of this century, synthetic organic compounds have been produced either for domestic (detergents, plastics, etc.), industrial (solvents, additives, dyes, etc.) or agricultural (pesticides, etc.) uses. Around 60,000 compounds are widely used in human activities and could be found in the environment, especially in water (surface water, groundwater, industrial or urban wastewater) or polluted soils [1-4]. 

---