EHP~Issues/Approaches~Low Dose–Response Extrapolation~Environmental Health

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_http://www.ehponline.org/members/2008/11502/11502.pdf_

(http://www.ehponline.org/members/2008/11502/11502.pdf)

" Topics included: the need for formalized approaches and criteria to assess

the evidence for mode of action; the use of human vs. animal data; the use of

mode of action information in biologically-based models; and the implications

of interindividual variability, background disease processes and background

exposures in threshold vs. nonthreshold model choice. Approaches that differ

from current practice were recommended for extrapolating high-dose animal

data to low-dose human exposures, including categorical approaches for

integrating information on mode of action, statistical approaches such as model

averaging, and inference-based models that explicitly consider uncertainty and

interindividual variability. "

Over the past half-century, methodological advances have provided an

increasingly strong

quantitative basis for estimating the human health risks associated with

exposures to

environmental contaminants. Estimation of the dose-response function is one

of four critical

elements of the now paradigmatic approach to health risk assessment

developed in 1983 by the

National Research Council (NRC 1983). Establishing dose-response functions

frequently

requires extrapolating limited amounts of data from high-concentration

animal toxicological

studies to the relatively lower concentrations typically experienced by

humans. Statistical

methods, known as “low-dose extrapolation†models, have been developed for

this purpose, and

their merits and limitations have been debated since the earliest efforts in

environmental

contaminant risk assessment.

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