Development of Historical National Emissions Inventory Data of Criteria Air Pollutants at the County Level from 1990 to 2017 in the United States

Abstract

Understanding the location and concentration of pollutants is critical to developing regulations that preserve human health by limiting exposure to harmful chemical compounds. Quantifying and tracking exposure to air contamination, specifically, poses an issue, due to the mobile and reactive nature of these chemicals and particles. The Environmental Protection Agency (EPA) releases a National Emissions Inventory (NEI) on a semi-annual basis, beginning in 1990, based on submissions of county-level reports. The NEI offers quantitative estimates of emissions of Criteria Air Pollutants (CAPs) and Hazardous Air Pollutants (HAPs) from both man-made and natural sources. While national-level and state-level trends of NEI data over the past 30 years are easily accessible by the public, long-term NEI data has not yet been compiled at a county level, leading us to compile this data to allow for targeted trend analysis at a finer scale. To match data across each release of the NEI from 1990 to 2017, we parsed through the available county data based on the unique identifiers for each entry, such as the Federal Information Processing System (FIPS) code, Source Classification Code (SCC), sector, and pollutant. Further, we included estimates for years between reports, connecting the years of historical CAP NEI data. We believe that this consecutive NEI dataset can both assist long-term air quality and climate studies and help facilitate analyses of climate change-related policies by examining finer-scale long-term emissions trends.