study indicates that PCBs and DDE contamination levels in adult
women are not associated with increased risk of breast cancer.
If anything, there is a slight but statistically insignificant decrease
in risk associated with increasing levels of PCB and DDE in women's
question is how to interpret this result.
one level it is very positive and reassuring. Taken at
face value, women with higher levels of these two organochlorine
contaminants during adulthood are not at greater risk as a result
of that exposure.
does not mean, however, that PCBs and DDE (or its parent
compound, DDT) are absolved of involvement in the causation of
breast cancer. The study examines only the relationship
between adult contamination levels and risk. It gives no
insight into risk and fetal or developmental exposure. One of
the central theses of endocrine disruption is that developing stages
of a person (or animal's) life cycle are more vulnerable than are
adult stages. The 1999 assessment
by the US National Academy of Sciences of health risks related to
endocrine disruption explicitly acknowledges that research on human
health impacts has failed to address this issue, concluding that
the relevant studies simply haven't been done.
does the paper by Hunter et al. say very much about other
organochlorines, or about "xeno-estrogens" (synthetic
compounds that mimic estrogen).
in fact is an "xeno-anti-androgen," not a xeno-estrogen.
Under certain experimental circumstances it can have effects superficially
similar to xeno-estrogens because exposure to it causes experimentally
exposed male mammals to develop characteristics that are more feminine
than expected. The mechanism of action, however, is through its
interference with androgens like testosterone (hence anti-androgen)
instead of its enhancement of estrogens.
it turns out that the forms of PCBs that accumulate and persist
in the human body are anti-estrogens, not estrogens. So
forget trying to reach sweeping conclusions about "weak xenoestrogens"
from studies of DDE and PCBs measured in adult women. More...