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Epidemiology and the EPA Dioxin Reassessment
Dick Clapp, D.Sc.
Associate Professor of Environmental Health
Boston University School of Public Health
Summary: The evidence from human epidemiological studies for
the toxicity and, more specifically, the carcinogenicity of the dioxins
and related compounds has vastly increased during the last 10-15 years.
Investigations of (1) dioxin-exposed workers; (2) the residents of Seveso,
Italy; (3) Air Force Ranch Hands (the subset of the U.S. military exposed
to Agent Orange during the Vietnam War); and, (4) the offspring of women
exposed to dioxin from incinerators or in the diet have deepened our understanding
of the health effects of these hazardous compounds. The scientific evidence
from these studies was summarized and utilized in the draft EPA dioxin
reassessments of 1994 and 2000. In the Science Advisory Board review,
various members of the assessment team commented on the strengths and
weaknesses of the human data and offered widely divergent interpretations
of that data's meaning. Interestingly, some of these individuals suggested
that there was evidence in a number of the cancer studies for a threshold
and even a protective effect of dioxin exposure at low doses. I will critique
and examine the scientific basis for these arguments and, in addition,
examine the affiliations, orientations, and potential biases of those
board members who argued in favor of a threshold or protective effect.
Biography: Dr. Clapp received his M.P.H. degree from the Harvard
School of Public Health in 1974 and his D.Sc. degree, in epidemiology,
from the Boston University School of Public Health in 1989. From that
time until just last year, he worked at the John Snow Institute's Center
for Environmental Health Studies, first as its director and, more recently,
as a consultant. In 1993, Dr. Clapp joined the B.U. School of Public Health's
Environmental Health Department as a full-time faculty member. Currently,
as an associate professor at the school, he teaches courses in epidemiology
and environmental health.
Dr. Clapp has been heavily involved in conducting epidemiological studies,
including the investigation of cancer in Vietnam veterans and of leukemia
in the children who were part of the Woburn, Massachusetts childhood leukemia
cluster. He served as a consultant to the EPA Science Advisory Board Dioxin
Reassessment Review Subcommittee and, in that capacity, was especially
involved in the interpretation of epidemiological studies used in the
dioxin reassessment. Dr. Clapp is a member of several professional organizations
and currently sits on the Governing Council of the International Society
for Environmental Epidemiology and serves as Vice-Chair of the Steering
Committee of Greater Boston Physicians for Social Responsibility.
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