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Mutagenicity and Carcinogenicity of Combustion Emissions are impacted more by combustor technology than by fuel composition a brief review
Citation:
DeMarini, D. Mutagenicity and Carcinogenicity of Combustion Emissions are impacted more by combustor technology than by fuel composition a brief review. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS. John Wiley & Sons, Inc, Hoboken, NJ, 63(3):135-150, (2022).
Impact/Purpose:
The U.S.EPA needs clear guidance regarding the health risks associated with certain types of combustion technologies versus the types of materials burned using those various technologies. This review summarizes ~50 years of research on the mutagenicity and carcinogenicity of combustion emissions and draws some fundamental principles that can inform the Agency regarding this issue. The primary contributor to air pollution is combustion emissions, and particulate matter (PM), especially the extractable organic material (EOM) of PM, is associated with lung cancer risk to humans. Due to the ubiquitous presence of several key chemical classes in PM, especially polycyclic aromatic hydrocarbons (PAHs), as well as nitroarenes and aromatic amines, all EOM from PM from a wide array of combustion emissions or polluted air are mutagenic. This review of 51 different combustion emissions, and previous analyses of PM from >3,000 air samples, show that it is the concentration of particulate matter (PM) in terms of PM/m3 of air and not so much the nature of the PM itself that is associated with the mutagenicity of air and combustion emissions. A mutagenicity emission factor is the amount of mutagenicity produced per unit of activity, such as burning a kg of wood. The fundamental features of good combustion (minimizing kinetic and mass-transfer limitations by promoting high residence times, temperatures, and turbulence), which are found in well-designed combustion systems such as utility boilers, produce the lowest mutagenicity emission factors, whereas poor combustion conditions (low temperatures and poor mixing of fuel and atmospheric oxygen), which are typical of open burning, produce the highest mutagenicity emission factors. PAHs play a predominant role in the mutagenicity emission factor, as shown by the high correlation (r = 0.80) between mutagenicity and PAH emission factors for a wide variety of combustion emissions. How materials are combusted is more critical than the material itself in terms of the resulting mutagenicity emission factor. This fundamental engineering principle can inform environmental and public health assessments of combustion emissions.
Description:
Studies during the past 50 years have characterized the carcinogenicity and mutagenicity of extractable organic material (EOM) of particulate matter (PM) in ambient air and from combustion emissions. We have summarized conclusions from these studies and present data supporting those conclusions for 51 combustion emissions, including carcinogenic potencies on mouse skin (papillomas/mouse/mg EOM), mutagenic potencies (revertants/µg EOM) in the Salmonella (Ames) mutagenicity assay, and mutagenicity emission factors (revertants/kg fuel or revertants/MJthermal) in Salmonella. Mutagenic potencies of EOM from PM from ambient air and combustion emissions span 1-2 orders of magnitude, respectively. In contrast, the revertants/m3 span >5 orders of magnitude due to variable PM concentrations in ambient air. Carcinogenic potencies of EOM from combustion emissions on mouse skin and EOM-associated human lung cancer risk from those emissions both span ~3 orders of magnitude and are highly associated. The ubiquitous presence of polycyclic aromatic hydrocarbons (PAHs), nitroarenes, and aromatic amines results in mutagenic and carcinogenic potencies of PM that span only 1-3 orders of magnitude; most PM induces primarily G to T mutations. Mutagenicity emission factors of combustion emissions span 3-5 orders of magnitude and correlate with PAH emission factors (r = 0.8). Mutagenicity emission factors were largely a function of how material was burned (highly efficient modern combustors versus open burning) rather than what materials were burned. Combustion systems that minimize kinetic and mass-transfer limitations and promote complete oxidation also minimize the mutagenicity of their emissions. This fundamental engineering principle can inform environmental and public health assessments of combustion emissions.
