BPA: From bad to worse

The first major study of health effects in people from a chemical used in plastic baby bottles, food cans and a host of other products links it with possible risks for heart disease and diabetes. (AP)

See also: This is your fetus' brain on plastics

And here, for your enjoyment (coff), an excerpt of my undergrad paper on BPA. This stuff ain't good for you.

During the past thirty years, certain chemicals have been found to disrupt the endocrine systems of wildlife, lab animals, and humans. Bisphenol A (BPA) is an organic compound, first synthesized in 1905, that is made from two moles of phenol and acetone (hence its name). In 1936, Dodds and Lawson fed BPA to ovariectomized rats and found that it could act as a weak estrogen. But its principal use was created in 1953, when researchers found that they could combine BPA and the poison gas phosgene to form a hard, clear polycarbonate plastic. Bisphenol A-based polycarbonate, commonly referred to as just "polycarbonate," has a variety of uses. Most important for the purposes of its biological effects are the uses in which BPA can be ingested. BPA is used the lining of cans, in tooth sealants and in "white filling" composites, and it has been found to leach into saliva (Brotons et al., 1995; Olea et al., 1996). The chemical's old reputation as an estrogen re-emerged seven years ago, when scientists at Stanford University reported that their experiments had been tainted by BPA leaching from plastic flasks they were using. The cells reacted even though the amounts were too small to be detected by the maker's safety testing procedures (Krishnan et al., 1993).

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The levels of BPA exposure determined safe by the FDA have been shown in many experiments to be unsafe for consumption. More studies will be needed to validate these effects. But most importantly, more basic research is needed on how BPA mimics estrogen and binds to its receptor; how that binding triggers estrogenic effects; and what those effects mean in terms of organ (including brain) development. In the meantime, it seems that women of childbearing age should avoid, as much as possible, exposure to polycarbonate plastics.

Pitt husband-and-wife team discovers cancer-linked virus

A husband-and-wife team at the University of Pittsburgh Cancer Institute have discovered a virus strongly linked to Merkel cell carcinoma, an aggressive skin cancer that used to be very rare but has become increasingly common in the past two decades, particularly among those with compromised immune systems.

Yuan Chang and Patrick Moore reported their findings in this week's Science.

Interestingly, Merkel cell polyomavirus (MCV) is the second cancer-associated virus discovered by the pair. In 1993, they found the virus that causes the most common cancer in Africa, Kaposi's sarcoma.

Chang and Moore spent nearly a decade developing a new technology that was instrumental in discovering the virus. "Digital transcriptome subtraction" is so called because it subtracts genetic sequences known to be human from the genome of the tumor under study, leaving only genetic transcripts that might have come from a foreign organism.

Using the technique in Merkel cell tumors, they found one sequence that was similar to, but distinct from, known viruses. They went on to show that this sequence belonged to a new polyomavirus that was present in almost all the Merkel cell tumors they tested, but few other tissues.

Their discovery could lead to a blood test or vaccine, similar to the recently developed vaccines against human papillomavirus (HPV) to prevent cervical cancer.

Researchers had suspected the existence of MCV, which is genetically similar to an African green monkey virus. Up to a quarter of adults--one billion people--could be infected with the human relative of this monkey virus. However, just as with HPV, most people with the virus will not develop the associated cancer.

More: NYT, Reuters