Impacts and control of air toxics from combustion

Abstract

The debate over the contribution of air toxics to adverse human and ecosystem health effects continues in both scientific and policy arenas. While the primary concern in the 1970s and 80s was the criteria pollutants and the nonmethane volatile organics which contribute to ozone formation, concern in the late 1980s was directed to air toxics as well. Major changes in regulatory legislation occurred in the early 1990s resulting in increased demand for emissions reductions. Air toxics in combustion emissions include volatile and semivolatile organics such as benzene, dioxins, and furans, as well as inorganic species such as HCl, many metals (including metal oxides and chlorides), and aerosols with particles less than 10 μm in diameter. Air toxic are of concern for their potential to impact both human and ecosystem health. While carcinogenic potential was of greatest concern initially, other health impacts including reproductive effects and endocrine system disruption are receiving increasing attention. Within the combustion community, research efforts focused initially on air toxics emissions from incinerators. More recently, air toxics emissions from other combustion processes have come under scrutiny. The relationships among the feedstock, the combustion process, and postcombustion processes all influence the emissions of air toxics and the distribution or transfer of pollutant species among environmental media. This paper reviews impacts by air toxics from combustion on human health and ecosystem health, reviews the factors that contribute to the formation of air toxics, and considers how the impacts can guide combustion research to focus on those factors most crucial to control of air toxics.