Academic journal article Environmental Health Perspectives

Origin and Health Impacts of Emissions of Toxic By-Products and Fine Particles from Combustion and Thermal Treatment of Hazardous Wastes and Materials

Academic journal article Environmental Health Perspectives

Origin and Health Impacts of Emissions of Toxic By-Products and Fine Particles from Combustion and Thermal Treatment of Hazardous Wastes and Materials

Article excerpt

High-temperature, controlled incineration and thermal treatment of contaminated soils, sediments, and wastes at Superfund sites are often preferred methods of remediation of contaminated sites under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 and related legislation. Although these methods may be executed safely, formation of toxic combustion or reaction by-products is still a cause of concern. Emissions of polycyclic aromatic hydrocarbons (PAHs); chlorinated hydrocarbons (CHCs), including polychlorinated dibenzo-p-dioxins and dibenzofurans; and toxic metals (e.g., chromium VI) have historically been the focus of combustion and health effects research. However, fine particulate matter (PM) and ultrafine PM, which have been documented to be related to cardiovascular disease, pulmonary disease, and cancer, have more recently become the focus of research. Fine PM and ultrafine PM are effective delivery agents for PAHs, CHCs, and toxic metals. In addition, it has recently been realized that brominated hydrocarbons (including brominated/chlorinated dioxins), redox-active metals, and redox-active persistent free radicals are also associated with PM emissions from combustion and thermal processes. In this article, we discuss the origin of each of these classes of pollutants, the nature of their association with combustion-generated PM, and the mechanisms of their known and potential health impacts. Key words: cardiovascular health, environmental health, fine and ultrafine particulate matter, persistent free radicals, respiratory health, thermal remediation. Environ Health Perspect 114:810-817 (2006). doi:10.1289/ehp.8629 available via http://dx.doi.org/ [Online 26 January 2006]

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In 1980, Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act (1980; more commonly known as Superfund) that was designed to deal with abandoned and uncontrolled waste sites. Two classes of presumptive remedies exist to deal with Superfund sites: containment and treatment. Containment simply prevents the spread of contaminants to the soil, air, and water, whereas treatment employs technologies to rid the area of contaminants. The treatment regimens for soils and solid wastes most often employed are some form of combustion or thermal treatment, including a) incineration, which uses high temperatures to degrade contaminants; b) on-site thermal destruction, which is, in effect, a low-grade incineration process; and c) thermal desorption, in which toxic chemicals are first desorbed from the medium, collected, transported off-site, and then usually incinerated.

Combustion and thermal processes are dominant sources of air pollution. Although much attention is still paid to their contribution to priority air pollutants [i.e. ozone, volatile organic compounds (VOCs), and nitrogen oxides (NOx)], they also produce chronically toxic products of incomplete combustion (PICs). The greenhouse gas carbon dioxide is a product of complete combustion of carbon, and the ozone promoter N[O.sub.x] is a product of complete combustion of nitrogen. However, chronically toxic organic pollutants, such as benzene, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), acrylonitrile, and methyl bromide, are products of incomplete combustion of carbon, carbon and chlorine, carbon and nitrogen, and carbon and bromine compounds, respectively. Although these toxic combustion by-products are formed in many types of combustion and thermal processes, they have historically been of particular concern for incineration of hazardous wastes and soils/sediments contaminated with hazardous wastes. For this reason, on-site incineration, defined as direct contact of the waste material with a flame, has come into disfavor. Instead, thermal destruction or desorption (in which the waste does not directly contact the flame) has been frequently substituted. Unfortunately, low- or moderate-temperature treatment has the potential to form more toxic by-products than does incineration. …

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