As part of the exposure reconstruction, a material balance model was developed to estimate the mass of PFOA released to air, water, landfills, and off-site disposal from the mass of the same materials used at the facility from 1951 to 2003. Using these estimated air emissions, for each year from 1951 to 2003, PFOA air concentrations and total deposition to soil were estimated using the ISCST3 air dispersion model.
PFOA concentrations leaching from soil to groundwater were estimated using the PRZM model using the deposition estimates from the air dispersion modeling, and groundwater concentrations were estimated using the results of the PRZM model. The estimated air, soil, and groundwater concentrations were then used to estimate the Average Daily Doses (ADDs) of PFOA for residents living in five water districts in the vicinity of the facility from 1951 to 2003. The results of this exposure reconstruction were published in the peer-reviewed literature in Paustenbach et al. (2007).