In 2006 DEQ completed an air quality modeling study called the Portland Air Toxics Assessment or PATA. This study used local meteorology, topography and emission information about population, neighborhood, car, truck, industrial and smaller sources to predict the level of 12 air toxics (hazardous air pollutants). Levels of ten of these pollutants are estimated to be above benchmark concentrations recommended by the Air Toxics Science Advisory Committee and recently adopted by the Environmental Quality Commission.
Benchmarks are not standards, but rather planning goals and triggers for our program. We compare benchmarks to ambient monitoring and exposure modeling to address risk and to communicate modeling and monitoring results. See the EQC staff report Oregon Air Toxics Program: Benchmarks
for information on benchmarks.
PATA included risk assessment modeling with results described and shown in maps and charts. This comprehensive assessment by DEQ is a key step in a community planning process to reduce air toxics in the Portland area. Sections of the report are below.
The initial modeling for the report was done by
ICF consulting. They used information provided by Metro, EPA, DEQ and
others for the modeling. The model estimated daily pollution levels
under various weather conditions at the neighborhood level.