endocrine disruption is of no concern to human health because the chemicals implicated are weak in comparison to natural estrogen
This myth is wrong for several reasons, but it begins (as do many initially-credible myths) with a grain of truth.
Estrogenic substances like bisphenol A, DDT, nonylphenol, etc., are thousands of times weaker than the human estrogen estradiol at binding with estrogen receptors within the nucleus, the 'nuclear hormone receptors.' That's the grain of truth.
But it's misleading for two reasons. First, natural chemicals called 'serum binding proteins' circulate in the bloodstream and bind with estradiol. As a result, only a very small portion of estradiol in serum is available for binding with the nuclear hormone receptors. These serum binding proteins are much less effecting at soaking up circulating xenoestrogens like BPA. Hence even if xenoestrogens are weaker, they are much more available. Calculations show that if you take into account both the relative weakness of the xenoestrogens and their much greater bioavailability, even at relatively low doses they should have biological effects. And experiments with animals prove that they do.
The second reason is that estrogens also bind with receptors on the cell membrane surface. When they do, they initiate signaling pathways that control a number of important physiological and genetic pathways. It turns out that some xenoestrogens are just as powerful as estradiol at binding with these membrane receptors.
Hence to call them 'weak estrogens' is factually incorrect. From the perspective of membrane receptors, they are quite powerful. This research detects impacts at doses as low as parts per trillion.
The third reason why this myth is misleading is that estrogenicity is just one part of endocrine disruption. Contaminants also interfere with thyroid, testosterone, and many other hormones.
DDT hasn't been linked to human harm
does not appear to cause immediate toxic effects in people,
at least at the levels likely to be encountered today in malaria
vector control programs.
study published in July 2001 by scientists from the US Centers
for Disease Control and the National Institute of Environmental
Health Sciences, however, clearly repudiates any notion
that DDT is without human health risk.
research, published in The Lancet, reveals a strong
link between DDT exposure and the likelihood of pre-term birth:
the greater a mother's exposure, the more likely it is that
her infant will be born prematurely. Premature birth itself
is linked to a wide array of health problems later in life.
And the pattern found by the scientists was so strong that
they concluded there had been an epidemic of pre-term birth
in the US due to DDT exposure during the decades of heavy
DDT application. More...
study, by scientists at the National Institute of Environmental
Health Sciences, indicates that DDT's effect on infant mortality,
both by increasing preterm birth and by decreasing the length
of time that mothers breast feed, is very substantial. More...
gaggle of conservative ideologues nonetheless pushes for DDT
use even in the US. Example...
In fact, the NY Times published an
op-ed calling for DDT use in the US in August 2003.
studies now prove that compounds like DDT and PCBs are not risk
factors for breast cancer.
studies indicate there is no association between PCBs
and DDE (a persistent break-down product of DDT) levels in
adult women and their risk of breast cancer.
overcome severe obstacles that epidemiology faces when confronting
address the question of whether developmental exposure (fetal
or pubertal) increases breast cancer risk. More...
- None incorporated information about genetic susceptibility (see below)
studies, moreover, say
nothing about whether weakly estrogenic contaminants cause
Other studies reveal that a less studied xenoestrogendieldrinis
a risk factor for breast cancer and another recent
study reinforces concerns about dioxin.
In late 2004, scientists reported that a strong association between PCBs and breast cancer risk in women with a specific variant of an allele whose gene product is important to PCB detoxification. This discovery is especially insightful because it was the third study of this population of women. The first two found no association. Only the third, with information about genetic type, was able to detect the strong association. It had been masked by mixing women with different susceptibilities in the same analysis.
arsenic treated wood becomes safe for children as it ages.
research by the Environmental Working Group and the University
of North Carolina demonstrates that old arsenic-treated wood
structures are as dangerous as new ones. Arsenic continues
to leach out of this wood for many years. And what had been
thought to be protective—coating it with sealant—
only works for 6 months or less. Some of the soil around decks
and playgrounds where arsenic treated wood has been used actually
is so contaminated that it qualifies for SuperFund. More...
used in products sold to consumers have been tested and found
safe from health effects.
Most chemicals in modern use have simply not been tested for
their impacts on human health, even very basic effects. If
tests have been carried out, they usually are far too simplistic
to anticipate many important health effects. More...
Stolen Future is nothing but hypothesis masquerading as fact
and it risks generating public hysteria over exposure to chemicals
whose risks may be uncertain.
the book and on this web site we carefully distinguish between
what is known and what is plausible but uncertain. One of the
book's main conclusions is a call for new scientific research
to answer unresolved questions. And one of the most gratifying
impacts of the book has been to contribute to interest (and
funding) for that new research, the results of which are building
rapidly. These new results
are providing dramatic support for the issues raised in Our
risk assessment standards based upon tests using adult human
subjects will provide safe guidelines for exposure.
are not little adults. Tests on adults give few
insights into the health risks created by pesticide exposure
for the fetus and for children, who are usually far more sensitive
to contamination than adults. More...
the final scientific word on frog deformities proves they are
a result of natural processes, not human activity.
latest research on frog deformities implicates a combination
of natural and human causes. Parasitic infections clearly can
induce deformities, although they appear to be absent in some
cases. Agricultural fertilizers create conditions in ponds that allow the parasites to become more numerous. And pesticides, undermine the frog's capacity to
resist infection. Thus deformities are more common where both agricultural chemicals and parasites co-occur.