basis of limited information on chemical contamination and assumptions about the
population. Exposure assessments should not be based on a hypothetical maximally
exposed individual (MEI). Screening risk assessments should rely on more representative
estimates. Risk-management decisions should be based on refined exposure assessments
that evaluate the distribution of a population's varied exposures and should address
explicitly for any segments of the population that have unusually high exposures.
Whenever possible, measurements should be obtained to support or validate any generic
values used in exposure assessments, to check modeling results, or to provide more-
realistic estimates of exposure than can be obtained with models. Such measurements
might include collecting data at locations where exposures are anticipated, monitoring the
exposures experienced by individuals, collecting data on the physical and chemical
conditions that affect the movement and availability of chemicals, and providing
information that relates exposure to effects, possibly using biologic markers.
Measurements of exposure can be very different from estimated exposures based on
source characteristics "(Risk Assessment and Risk Management in Regulatory Decision-
There are two broad types of mathematical models used in exposure assessment: those
that predict exposure to the agent, and those that predict the concentration of the agent.
Exposure models can be used to estimate the exposures of populations based on small
numbers of representative measurements. Models that predict concentration can be
combined with information on human time-activity patterns to estimate exposures.
Modeling may be done on long-term and short-term exposures, both of...
Bernard Goldstein, Director, Environmental and Occupational Health Sciences Institute and Chairman, Department of Environmental and Community Medicine, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ