Wednesday, June 29, 2011

Another attack on BPA

Journal article here. The critical factor in such studies is the level of exposure. A basic principle of toxicology is that the toxicity is in the dose. And humans get very tiny exposures to BPA through packaging -- just a few molecules at a time. So the key factor in this study is whether or not the mice were given even tinier does (given that mice are much much smaller than humans). It seems hard to imagine. The authors state that the dose they administered was "likely to provide circulating serum concentrations close to those observed for humans" but this does not seem to have been tested and the sampling used to assess normal human levels was not mentioned. On the whole, it seems likely that the mice were given a much heavier dose than humans would normally receive.

One also notes that many other studies have shown no ill effects and if you do enough studies (and this field is an obsessional one) you will get some apparently significant effects by chance alone

UPDATE: Just a very quick note made without re-reading the article. The reported effects were not "ex hypothesi". In fact the original hypotheses were comprehensively disconfirmed. The authors apparently then went on a data dredging spree, examining a very large number of possible differences. Under those circumstances some significant contrasts are likely to be found by chance alone. That is of course very poor science -- with the results being suitable for hypothesis generation but unable to justify any firm findings

A gender-bending chemical found in food packaging may reduce a man's ability to attract a female, researchers warn. A study from the University of Missouri found male mice who were exposed to bisphenol A as babies became demasculanised and 'behaved more like females.'

Study author associate professor Cheryl Rosenfeld, said the chemical had suppressed the early production of testosterone, which the females could sense. 'The BPA-exposed deer mice in our study look normal; there is nothing obviously wrong with them. Yet, they are clearly different,' she said. 'Females do not want to mate with BPA-exposed male deer mice, and BPA-exposed males perform worse on spatial navigation tasks that assess their ability to find female partners in the wild. '

The research could have implications on how BPA affects human development and behaviour. 'These findings presumably have broad implications to other species, including humans, where there are also innate differences between males and females in cognitive and behavioral patterns,' Rosenfeld said.

Bisphenol A, or BPA, which is used to harden plastics, is one of the world’s most widely manufactured chemicals and can be found in dozens of everyday items including baby bottles, CD cases and food and drink packaging. Because the chemical mimics oestrogen, many scientists believe it interferes with the way hormones are processed by the body.

Although several animal studies have shown it to be safe, others have linked Bisphenol A to breast cancer, liver damage, obesity, diabetes and fertility problems.

In the study, female deer mice were fed BPA-supplemented diets two weeks prior to breeding and throughout lactation.

The mothers were given a dosage equivalent to what the U.S. Food and Drug Administration considers a non-toxic dose and safe for mothers to ingest. At weaning the deer mice offspring were placed on a non-supplemented BPA diet and their behavior tested when they matured into adults.

Male deer mice exposed to BPA were less desirable to female deer mice, who literally turned their noses up at them. This meant the females did not consider them genetically suitable mates.

'We can use this evolutionary approach to the study of BPA to determine to best way to assess differences in the risks to boys and girls to early exposure to this chemical,' said David Geary MU Curators' Professor of Psychological Sciences.


Television creates 'perfect storm' of childhood obesity

This is a "policy statement", not science. There have been many gravely mistaken policies in medical science

Television creates a "perfect storm" of childhood obesity, paediatricians warn today. The mixture of long-hours sitting doing nothing in front of the box, exposed to advertising for unhealthy products, means today's children both get too little exercise and end up consuming foods which make them put on weight.

The caution comes from the American Association of Pediatrics (AAP), in a policy statement about children, obesity and television.

It advises parents to limit their time their children spend watching non-educational programmes to two hours per day, and take the television screeens and computers out of their sons' and daughters' bedrooms.

Commenting on the statement, the lead author, Dr Victor Strasburger, said: "We’ve created a perfect storm for childhood obesity – media, advertising, and inactivity. "American society couldn’t do a worse job at the moment of keeping children fit and healthy – too much TV, too many food ads, not enough exercise, and not enough sleep."

Although the warning was about American children, it could almost as easily apply to British ones as well. Studies show that British children watch on average almost as much as their American counterparts.

Dr Strasburger said children saw £5,000 to 10,000 food ads per year, most of them for junk food and fast food."

The policy statement is published in Monday's edition of the AAP's journal, Pediatrics.


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