WP11 Risk Management
E145-146
1:20 PM - 4:40 PM, Wednesday
() Use of Subchronic versus Chronic Toxicity Criteria in EPA′s Construction Worker Scenario for Risk Assessment.
Quiring, S1, Scheffler, L1, Boge, H1, 1 URS, Seattle, WA, USA
ABSTRACT- Critical decisions to remediate hazardous waste sites are now sometimes being made based on health risks to construction workers using EPA′s recently developed construction worker exposure scenario. For the construction worker scenario, EPA recommends use of subchronic toxicity criteria, rather than chronic criteria; however, EPA has developed subchronic criteria for few chemicals. Therefore, the more widely available chronic criteria are frequently used in lieu of subchronic values. Toxicity criteria in this context are estimates of a safe dose of a chemical to which a person would be exposed under chronic or subchronic exposure conditions. In EPA′s development of toxicity criteria, EPA initially selects the no-observed-adverse-effect-level or lowest-observed-adverse-effect-level from an applicable toxicological study to form the basis of the criteria. Uncertainty factors are applied to adjust the no-observed-adverse-effect-level or lowest-observed-adverse-effect-level downwards from the principal toxicity study. These factors are applied as precautionary measures to account for various types of uncertainties. We examined specific chronic toxicity criteria uncertainties for six common noncarcinogenic chemicals found at diesel-contaminated sites: toluene, 1,3,5-trimethylbenzene, naphthalene, ethylbenzene, xylenes, and fluoranthene. We derived subchronic criteria applicable to a working adult population for all six chemicals by removing some of the adjustments and uncertainty factors used by EPA in their derivation of chronic criteria. We performed sample hazard calculations using EPA′s default construction worker exposure parameters combined with our derived subchronic toxicity criteria. In addition, we also calculated hazard quotients using the more commonly available chronic criteria. Using subchronic criteria, hazards were significantly reduced, in some cases by as much as 80 percent. We concluded that using subchronic, rather than chronic, criteria would better support decisions to remediate hazardous waste sites based on predicted construction worker health risks for short-term chemical exposures.
Key words: construction worker, risk assessment, subchronic, toxicity criteria