Myths... versus reality.

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 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.

A 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.

This 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...

Another 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...

A 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.

Several recent 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.

• None overcome severe obstacles that epidemiology faces when confronting mixtures.
• None address the question of whether developmental exposure (fetal or pubertal) increases breast cancer risk. More...
• None incorporated information about genetic susceptibility (see below)

These studies, moreover, say nothing about whether weakly estrogenic contaminants cause breast cancer.

Other studies reveal that a less studied xenoestrogen—dieldrin—is 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.

New 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...

Wrong. 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...