ABSTRACT

Scenario evaluation is the most common means of exposure assessment. Estimates of factors in the behavioral realm that bring a receptor into contact with a contaminated medium are used, along with measurements of the chemical concentration in that medium, to estimate external dose. The Reasonable Maximum Exposure concept was also presented in the 1992 Final Guidelines for Exposure Assessment. Point-of-contact exposure assessment measures the chemical or stressor concentration at the interface between the body and the environment. The value of this method is that exposure is directly measured rather than estimated, with the proviso that the measurements are accurate. One area of probabilistic risk assessment that continues to provide difficulties is the specification of distributions. A long-held assumption in risk assessment is that children may receive their entire daily amount of soil ingestion from a single contact with soil. The mature and senescent keratinocytes that comprise the stratum corneum are organized into a “brick and mortar” pattern.