A Comparison of Hourly with Annual Air Pollutant Emissions: Implications for Estimating Acute Exposure and Public Health Risk
Assessing the potential for non-cancer health risks following inhalation of chemicals is important to informing air pollution risk management. Health risks from air pollutants are calculated by comparing exposure estimates from chronic (i.e., an average over one year or greater) or acute (typically 1-hour) durations to chemical- and duration-specific reference values or standards when available. However, modeled estimates of acute chemical exposure concentrations based on emissions data can be uncertain for many air pollutants. This uncertainty is largely due to a lack of hourly emissions data being reported from most industrial sources, compared to the availability of long-term data (e.g., annual emissions). In this study, we analyze some of the rare hourly air pollutant emissions information reported from industrial sources. We examine and discuss differences between these reported hourly emission rates and average hourly emission rates for reduced sulfur compounds from kraft pulp mill operations, and sulfur dioxide and oxides of nitrogen from a large U.S. power plant. We then discuss the additional challenge of assessing health risks based on hourly exposures, particularly the lack of acute reference values for many air pollutants applicable to the general population.