A multiple source approach to acute human health risk assessments

Abstract

The US Army Center for Health Promotion and Preventive Medicine (USACHPPM) has developed a three-tiered approach to perform an acute noncarcinogenic health risk assessment to comply with requirements contained in USEPA’s ‘Addendum to the Methodology for Assessing Health Risks Associated with Indirect Exposure to Combustor Emissions' (USEPA, Draft strategy for combustion of hazardous waste, May 1993). The addendum document drafted in November 1993 suggests evaluation of short-term emissions and exposures, but it does not provide necessary guidance or methodology. This evaluation becomes extremely complex when several sources contribute to the overall concentration of contaminants in the air. Because each source has a different emission rate, location, and dispersion profile, the compound-specific maximum concentrations are rarely located at the same receptor location, as determined by using the Industrial Source Complex Short Term (ISCST3) dispersion model. Furthermore, evaluation of hazard quotients at various receptor locations from a large number of contaminants from multiple sources is an extremely complex and tedious process. This paper will detail a three-tiered approach which was developed to perform the acute risk assessment, quantify possible advantages and disadvantages associated with each tier, and demonstrate the effects of contributing factors, such as distance, emission rate variability, population/exposure scenarios, and compound speciation. In order to accomplish this task, a sample facility with four different combustion sources was modeled and processed according to the three-tiered approach.