AP, P Grandjean, T Jørgensen, JW Brock and HB Hartvig. 1998.
Organochlorine exposure and risk of breast cancer. Lancet
studies of the relationship between breast cancer and organochlorines
have focused on the classic suspects, DDT or its metabolites and
PCBs. This research by an international group of scientists (including
the US Centers for Disease Control) expands this body of research
by assessing links between dieldrin exposures and breast cancer
risk. They find that women with the highest serum concentration
of dieldrin had more than a two-fold increased risk of developing
breast cancer compared to those with the lowest concentration.
from subjects enrolled in the "Copenhagen City Heart Study,"
a study population selected randomly from around Copenhagen, Denmark,
were analyzed. Women were enrolled in 1976, at which time serum
samples were obtained. The health of the participants was then tracked
for the next 17 years. During that time, 268 of the 7712 participants
developed invasive breast cancer. For this analysis, each woman
with breast cancer was matched with two breast cancer free women
also in the study, and a comparison was made of the chemical constituents
of the serum stored in 1976.
study has several strengths: prospective design, long-term follow-up,
and random selection of participants independent of the occurrence
of breast cancer.
was associated with a significant increase in the risk of
breast cancer. The result for dieldrin showed a dose-related
increase in risk with an adjusted odds ratio of 2.05. The
risk of breast cancer was twice as high in women with the
highest serum concentrations of dieldrin compared to women
with the lowest concentrations.
right, the reference group (R) is compared with quartiles
of dieldrin exposure (adapted from Høyer et al.
1998). Vertical bars indicate 95% confidence interval. The
dose response relationship is statistically significant (p=0.01).
result is especially important because dieldrin is unequivocally
an estrogen mimic, shown to interact with the estrogen receptor
in analyses using Soto and Sonneschein's E-screen test.
study also examined DDT (and its metabolites) and PCB. No risk increase
was detected for these compounds.
exposure to estrogen has been identified as a significant risk factor
for breast cancer in people. While DDT is slightly estrogenic, its
principle metabolite, DDE, anti-androgenic in human tissue. With
respect to DDT, the authors of this article state: "Information
on o,p'-DDT was insufficient because only 20% of the serum
samples contained this compound in detectable amounts."
negative results were more definitive on p,p'-DDE, the most
common metabolite of DDT. Much confusion has been generated in the
popular media about the failure of DDE to yield positive links.
As an anti-androgen, DDE would not be predicted to increase the
risk of breast cancer on the basis of its hormonal activity. Hence
it is particularly inappropriate for industry spokes-scientists
like Steven Safe to claim that the failure of research to reveal
links between DDT and breast cancer proves that estrogenic organochlorines
do not cause breast cancer. He knows better.