US EPA

1323655 

Technical Report 

Analysis of recent U.S. ozone air quality data to support the O3 NAAQS review and quadratic rollback simulations to support the first draft of the risk and exposure assessment 

Wells, B; Wesson, K; Jenkins, S 

2012 

U.S. Environmental Protection Agency 

Research Triangle Park, NC 

http://www.epa.gov/ttnnaaqs/standards/o3/data/20120814wells.pdf 

Ambient air quality information is an important element of the 03 NAAQS Health and Welfare Risk and Exposure Assessments (REAs; U.S. EPA, 2012a, b), as well as the Policy Assessment (PA; U.S. EPA, 2012c). This memorandum provides information about the ambient 03 monitoring data, modeling data, and spatial fusion technique analyzed in both REAs, as well as information on the ambient 03 concentrations in locations and time periods of the health studies discussed in the PA.

In addition, this memorandum also provides information on the "quadratic rollback" method, which uses a quadratic equation to reduce high concentrations at a greater rate than low concentrations in simulations of just meeting the current 03 standard. In this review, quadratic rollback was used to simulate reductions in 03 concentrations in areas that did not meet the current 03 standard of 0.075 ppm (75 ppb). This memorandum discusses the application of the quadratic rollback to simulate just meeting the current standard in 12 case study areas for the Health REA (U.S. EPA, 2012a) and in the national-scale analysis for the Welfare REA (U.S. EPA, 2012b). An evaluation of the rollback approach is also discussed for the urban case study analysis, as well as the national-scale application.