The Partnership for Environmental Research and Community Health (PERCH) Phase III, Part 1: Community-scale risk assessment in greater Pensacola, Florida

The Partnership for Environmental Research and Community Health (PERCH) is a comprehensive, multi-partner, and multi-disciplinary study to determine if a connection exists between elevated levels of illness in Northwest Florida and the levels of ambient air pollutants. Initial phases of the project investigated regional scale threats to public health and welfare by reviewing existing information on emission sources and air quality, and subsequently deploying mobile air monitoring equipment to collect data on ambient pollutant concentrations on a local scale in the greater Pensacola, Florida area. These seminal analyses found that high levels of fine particulate matter likely pose the greatest risk to human health, and that sulfates, organic carbon, and secondary organic aerosols dominate the PM2.5 mass distribution. Locally high concentrations of certain air toxic pollutants appear to result from gasoline combustion, suggesting that mobile sources contribute significantly to potentially dangerous levels of both fine particulate matter and toxic air pollutants. Phase III of the PERCH continues the investigation of air quality in Northwest Florida in two parts: (1) community-scale risk assessment for toxic pollutants and (2) source apportionment of PM2.5, ozone, and mercury.

This paper presents an update on continuing efforts to develop a community-scale risk assessment for hazardous air pollutants in greater Pensacola area through an application of the U.S. EPA's Regional Air Impact Modeling Initiative (RAIMI). RAIMI is a set of software tools developed by the U.S. EPA Region 6 to integrate emissions inventories, an air dispersion model, risk model, and population distributions within a Geographic Information System (GIS) interface enabling the user to model and visualize anticipated health risks due to toxic air pollutants. This analysis was formulated in a manner consistent with the U.S. EPA's Air Toxics Risk Assessment Reference Library and its Volume 3, Community-scale Assessment, which is currently under ongoing development. In addition to the preliminary risk assessment results for greater Pensacola, this paper offers a demonstration of the application of RAIMI and lessons learned for improvement of future community-scale risk assessments.

The PERCH analysis utilized emissions data from the 1999 final National Emissions Inventory (NEI) (Version 3.0) of Hazardous Air Pollutants for point, non-point, and off-road sources. Where appropriate and informative, data from the 2002 draft NEI were used to update and confirm inputs from the 1999 NEI. Air dispersion modeling was performed using the U.S. EPA's Industrial Source Complex Short Term version 3 model (ISCST3) and regulatory default processing methods to compute ambient air concentrations in residential areas, commercial developments, and other sensitive receptors such as schools. Representative geophysical data (i.e., terrain, land use and cover, meteorological conditions) were used in the dispersion model and to delineate sensitive areas within RAIMI for the risk assessment calculations. Risk data for acute (short-term, 1-hour average) impacts and chronic (long-term, annual average) impacts due to toxic pollutant exposure via the inhalation pathway were drawn from RAIMI's integrated risk library, which was developed from the U.S. EPA's Integrated Risk Information System (IRIS) and various other human health risk assessment protocols.

The results of the RAIMI analyses for greater Pensacola indicate the sources and pollutants that pose the greatest risk to residents and suggest the priority in which emissions controls and other mitigating measures might be implemented to improve air quality on a local scale.