Assessment of cumulative risk from pesticides with the scenario-model-parameter uncertainty analysis

This study assesses risks from multiple route and multimedia residential exposure to chlorpyrifos and diazinon, using the cumulative risk assessment method and an original method: the Scenario-Model-Parameter (SMP) uncertainty analysis. This combination of methods addresses three weaknesses of the conventional risk assessment practice, which may lead to underestimation of risks. The first and the second weaknesses are the separate treatment of exposures via different routes and exposure to different pollutants, respectively. The third weakness concerns the current uncertainty analysis that focuses only on parameter uncertainty and assumes that the other two uncertainty types, scenario and model, are negligible. This study employs two estimation approaches, deterministic and probabilistic, and data from the National Human Exposure Assessment Survey (NHEXAS) in Arizona. Significant findings are that the 90th percentile cumulative risk does not exceed the level of concern. The cumulative risk is caused mainly by ingestion route, followed by the inhalation route and the dermal absorption route. Major parameter uncertainty sources include concentration data and body weight. The SMP uncertainty analysis points out that the risk would be underestimated if scenario or model uncertainties were not accounted for. Insights obtained from this study may be used by others to better design and perform cumulative risk assessments.