Air Toxic Emissions and Associated Health Risks in Cook County, IL

Objectives: The goal of this study is to characterize emissions of air toxics in Illinois and Cook County, IL spatially and temporally, and delineate areas with higher inhalation cancer risk burden in Cook County. Methods: U.S. EPA’s NEI and NATA data for 1999, 2002, 2005, and 2011 were downloaded from the U.S. EPA website. For each set of data, air emissions from four common source categories (i.e., point/major; non-point/area; on-road; non-road) and chemical contribution to air pollution were analyzed. Arc Geographic Information System (GIS) was used to spatially analyze the U.S. EPA NEI air emissions data for Illinois and U.S. EPA NATA inhalation excess cancer risk data for Cook County. Results: NEI data indicated that area/non-point (from 21% in 1999 to 48% in 2011) and non-road (14% in 1999 and 21% in 2011) sources contributed the most to the overall emissions with an increasing trend over the years. Chemical-specific emissions indicate that BTEX, hydrochloric acid, hexane, and 2,2,4-trimethylpentane contributed the most to the overall emissions in Illinois. In terms of distribution of total air toxics emissions in Illinois, the highest contributions in tons per year were observed in Cook (28%), followed by DuPage (7%), and Lake (4%) counties that represent urbanized counties in Illinois. Similar to Illinois, Cook County has a high influence of area/non-point and mobile with an increasing trend in their contribution. In the category of total, on-road, and non-road emissions of air toxics, BTEX constituents were predominant. In terms of NATA, the higher inhalation cancer risk areas were more widespread in 1999 with exceedances observed in industrial areas in the southeast side of Cook County, in areas near O’Hare international airport, urban core and highway/freeway corridors/subareas. Benzene was the top contributor to total cancer risk in Cook County in 1999-2002 and the second highest in 2005-2011, constituting 16% - 24% of total excess inhalation cancer risks, followed by similar low molecular weight VOCs found in transportation fuel. Changes in methodologies employed for NATA estimates by the U.S. EPA prevented a temporal analysis of the cancer risk data. Conclusions: Reduction in benzene air emissions through implementation of MACT standards, voluntary emissions control programs and mobile fleet turn-over over time have resulted in significant improvement in associated benzene emissions and associated inhalation cancer risk. However, certain pockets of Cook County with highly diverse populations, particularly, urban core of Chicago, still have subareas with higher cancer risks and further efforts towards air emissions control for public health protection is necessary. In addition, there are other carcinogens with increased emissions over time as illustrated by formaldehyde, as the top contributor (39%) to total cancer risk in 2005, increasing its contribution to 45% to total cancer risk in 2011.