Science and exposure assessment Earlier this year I attended a risk assessment conference held at a major university. During the first day speakers on various topics relating to risk assessment presented their ideas and research. The second day was to follow the format of a workshop. As a charge to the workshop groups, the conference chairman shared his observations of the first day with the plenary session during the second morning of the conference. He went through his notes on the different topics until he got to exposure assessment, when he reported “there is no science in exposure assessment.” Not unpredictably, the exposure assessors took instant and unanimous umbrage at this statement. There is plenty of science in exposure assessment; in fact, so many sciences contribute to this field that it may be the last bastion of the generalist. And herein lies a problem. Because of its interdisciplinary nature, exposure assessment does not fit neatly into current university curricula. The need for exposure assessment expertise is becoming more and more important. A carefully done exposure assessment can translate into millions of dollars worth of action, dollars either spent or saved in cleanups, for example. But where will these exposure assessors be educated? Exposure assessments usually attempt to quantify the contact of a chemical (or toxic agent) with an organism, such as a human, and often include the absorption step to quantify dose. Assessors today generally use three approaches as tools: direct measurement, which tries to measure the contact while it is happening; prediction, which uses monitoring data, models, and population activity patterns to estimate exposure; and reconstruction, in which indicators of past exposure, such as tissue levels or biomarkers, are used along with such tools as pharmacokinetics to try to reconstruct past exposures. The best exposure assessments usually employ a combination of these basic a p proaches to add credibility and reduce uncertainty. The knowledge and skills needed for different aspects of the assessment include several branches of chemistry, engineering, biology, statistics, geology, meteorology, computer science, and pharmacokinetics and other health sciences, as well as experience in field
work. Obviously, many specialities are also involved, but the interdisciplinary nature of the problem is clear. As an indication of the availability of exposure assessment training in this country, I asked a consultant to do a quick, admittedly “nonstatistically representative” look at what is being offered. He contacted 12 schools of public health and 11 environmental engineering schools. These schools were the most likely to have courses in exposure assessment, according to guidebooks, reports, and recommendations from professional societies. Only one full-semester course on exposure assessment was offered in these 23 schools, although several universities covered the topic in a lecture or two as part of an overall risk assessment course or offered a short course on some aspect of exposure assessment through their continuing education departments. As a colleague at a university recently told me, “Interdisciplinary, interdepartmental projects are not things that universities do easily.” If we in the scientific community want to be sure there is science in exposure assessment, it is time to get exposure assessment into the teaching of environmental science.
This ankle rvll subjea 10 US. copyright Published 1987 American Chemical Saiety
,$L&Qa. Michael A. CaUahan is director of the Erposure Assessment Group in EPA’s m c e of Research and Development. His group is active in developing exposure assessment methods and guidelines and in performing exposure assessments and reviewing them for other organizations. Callahan has spent the past 10 years in the exposure assessmentfield for EPA’s research and regulatory oflces. Envimn. Sci.Technol..Vol. 21. No. 12.1987 1139