Environmental Factors in Breast Cancer
Supplement to Cancer
Environmental Pollutants and Breast Cancer
Epidemiologic Studies
Julia Green Brody, PhD1
Kirsten B. Moysich, PhD2
Olivier Humblet, MS1
Kathleen R. Attfield, BS1
Gregory P. Beehler, MA2
Ruthann A. Rudel, MS1
1 Silent Spring Institute, Newton, Massachusetts.
2 Department of Epidemiology, Roswell Park Can-
cer Institute, Buffalo, New York.
Laboratory research has shown that numerous environmental pollutants cause
mammary gland tumors in animals; are hormonally active, specifically mimick-
ing estrogen, which is a breast cancer risk factor; or affect susceptibility of the
mammary gland to carcinogenesis. An assessment of epidemiologic research on
these pollutants identified in toxicologic studies can guide future research and
exposure reduction aimed at prevention. The PubMed database was searched
for relevant literature and systematic critical reviews were entered in a data-
base available at URL: www.silentspring.org/sciencereview and URL: www.
komen.org/environment (accessed April 10, 2007). Based on a relatively small
number of studies, the evidence to date generally supports an association
between breast cancer and polycyclic aromatic hydrocarbons (PAHs) and poly-
chlorinated biphenyls (PCBs) in conjunction with certain genetic polymorph-
isms involved in carcinogen activation and steroid hormone metabolism.
Evidence regarding dioxins and organic solvents is sparse and methodologically
limited but suggestive of an association. Methodologic problems include inade-
quate exposure assessment, a lack of access to highly exposed and unexposed
populations, and a lack of preclinical markers to identify associations that may
be obscured by disease latency. Among chemicals identified in toxicologic
research as relevant to breast cancer, many have not been investigated in
humans. The development of better exposure assessment methods is needed to
fill this gap. In the interim, weaknesses in the epidemiologic literature argue
for greater reliance on toxicologic stu