Exposure endpoint selection in acute dietary risk assessment.

Abstract

Current USEPA Office of Pesticide Program approaches to acute dietary risk assessment do not adequately address uncertainty in the distributional analysis of exposure. This is especially true with respect to regulatory decision points (bright lines) located at the far extreme of the cumulative output distribution. Use of the 99.9th centile as a risk assessment endpoint necessitates confidence in food consumption and residue input distributions that cannot be demonstrated with currently available data and analysis approaches. Even for a pesticide with a rich residue database, data limitations are sufficient to skew results to significantly overestimate exposure. This is compounded when extremes in food consumption are used that go beyond the stated error bounds for the database used. Risk management decision making need not consider endpoints at extremes of exposure output distributions in order for mitigation to be protective of sensitive populations. In fact, such decision making is better informed by utilizing more statistically reliable endpoint selection in the risk assessment process. The richest data content in cumulative exposure distributions occurs in regions well removed from output tails, where the pattern of exposure distribution is driven by the effects of residue concentrations. In contrast, the extreme upper tail of the exposure distribution is data poor and is characterized by high uncertainty reflecting extremes in food consumption patterns. At present, risk managers are better served with exposure endpoints removed from the highly uncertain tails of exposure distributions such as the 99.9th centile bright line. The selection of more appropriate risk management decision points should consider the nature of the distribution, the severity of the effect being assessed, and robustness of the data available for assessing acute dietary risk.