Comments on: Using CALPUFF to evaluate the impacts of power plant emissions in Illinois: model sensitivity and implications

Levy et al. (2002) describe portions of their analysis of the public health impacts of emissions from nine power plants in Illinois. This and similar analyses (Levy and Spengler, 2002; Freeman, 2001; Abt, 2000) use dataintensive models of air quality and health risks to estimate the number of deaths caused by increases in ambient particulate matter (PM) concentrations due to emissions from specific sources. As modeled by Levy et al. (2002), 87% of the population-weighted, powerplant-derived PM2.5 increment exists as sub-microgram per cubic meter concentrations of secondary sulfates and nitrates, which, together with modeled primary PM, are estimated to cause ‘‘320 premature deaths per year y due to current emissions from the nine Illinois power plants’’. As explained below, several crucial but difficultto-recognize problems with the Levy et al. (2002) analysis compromise its reliability. We thank Dr. Levy and coworkers for sharing with us the input files that control the CALMET and CALPUFF runs, that we might explore these issues.