ABSTRACT

Combustion technologies continue to be significant for many human activ­ ities; yet combustion-derived air toxics contribute to adverse human and ecosystem health effects. Combustion-generated pollutants represent one of the major problems associated with the energy supply, waste incineration, transportation, forest fires, and crop burning. When hazardous air pollu­ tants (HAPs) were first identified as a potential human health issue, expec­ tations among scientists and regulators were that a few air toxics would be identified, and hence easily controlled. As the potential threats of air toxics became of greater concern to the public, the focus of much air toxics research was to understand the chemistry and physics of waste incineration. Research has demonstrated that toxic combustion byproducts with environ­ mental impacts are not generated solely or even largely by incinerators [1]. An emerging and serious issue is the previously overlooked contribution of some air toxics-namely nonmethane hydrocarbons (NMHCs) and lightabsorbing carbon (LAC)—to the overall burden of greenhouse gases [2-4]. The challenges of identifying, reducing, and controlling air toxics in com­ bustion are known now to be complex. Fuels, combustion technologies, modes of operation, and postcombustion processes all influence the emis­ sions of air toxics, and affect the distribution, transport, and transformation of pollutant species in the environment.