On the assessment of the maximally exposed individual (MEI) at superfund sites using Monte Carlo simulations

Abstract

In this paper, the methodology used by the United States Environmental Protection Agency (EPA) to protect a small population that may be at high risk, referred to as the “maximally exposed individual”; (MEI) is assessed. Monte Carlo techniques and more reasonable values for exposure parameters are used to determine a more physiologically reasonable MEI. The Monte Carlo MEI is compared to the EPA's quantification of the MEI as well as the results of a standard MC assessment.

In general, the EPA's estimate of MEI risks were found to be much larger (one to three orders of magnitude) than the Monte Carlo MEI risk estimates, showing that using default maximum values results in overestimated risks. In comparing the risk distributions of the Monte Carlo MEI with the Monte Carlo nominal population, one can conclude that the existence of a MEI in the nominal population is highly unlikely. However, by regulating at a higher percentile risk value of the nominal population, a small percentage of the MEI population may be protected. Nonetheless, it is important to consider the MEI in the decision‐making process.

Key words:

• Health risk
• Superfund Sites
• uncertainty
• variability
• Monte Carlo simulations
• probability distributions
• maximally exposed individual