EVALUATION OF A PROBABILISTIC EXPOSURE MODEL APPLIED TO CARBON-MONOXIDE (PNEM CO) USING DENVER PERSONAL EXPOSURE MONITORING DATA/

The probabilistic National Ambient Air Quality Standards (NAAQS) Expos ure Model applied to carbon monoxide (pNEM/CO) was developed by the U. S. Environmental Protection Agency (EPA) to estimate frequency distrib utions of population exposure to carbon monoxide (GO) and the resultin g carboxyhemoglobin (COHb) levels. To evaluate pNEM/CO, the model was set up to simulate CO exposure data collected during a Denver Personal Exposure Monitoring Study (PEM) conducted during the winter of 1982-1 983. This paper compares computer-simulated exposure distributions obt ained by pNEM/CO with the observed cumulative relative frequency distr ibutions of population exposure to CO from 779 people in the Denver PE M study. The subjects were disaggregated into two categories depending upon whether they Lived in a home with a gas stove or an electric sto ve. The observed and predicted population exposure frequency distribut ions were compared in terms of 1-hr daily maximum exposure (1DME) and 8-hr daily maximum moving average exposure (8DME) for people Living in homes with gas stove or an electric stove. For 1DME, the computer-sim ulated results from pNEM/CO agreed most closely within the range of 6- 13 ppm, but overestimated occurrences at low exposure (<6 ppm) and und erestimated occurrences at high exposure (>13 ppm). For 8DME, the pred icted exposures agreed best with observed exposures in the range of CO concentration between 5.5 and 7 ppm, and over-predicted occurrences b elow 5.5 ppm and under-predicted occurrences above 7 ppm.