Cleanliness is a virtue, but it’s possible to overdo it–that’s the message from a new study, which found that antibacterial soap may be doing teenagers more harm than good. The study found that the more teenagers are exposed to the antibiotic triclosan, the more likely they are to suffer from allergies and hayfever.

The researchers also looked at the effects of the widely used plastic chemical Bisphenol A (BPA), and found signs that teenagers with more BPA exposure may have immune system problems. The study was the first of its kind to examine the link between these two chemicals and immune dysfunction, which had only previously been studied in animals. Both chemicals are endocrine-disruptors, which means they may mimic or interfere with the body’s natural hormones.

“Many research studies show an association between exposure to environmental chemicals and different disease outcomes. There is a lack of data, however, examining whether exposure to these chemicals may affect our immune systems,” Erin Rees Clayton, a researcher from the University of Michigan school of public health said in an email. [The Montreal Gazette]

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A new study of 218 Chinese men found that even low levels of the controversial plastics chemical bisphenol A (BPA) can lower sperm quality and count.

For the study, which was published in the journal Fertility and Sterility, researchers noted the participants’ sperm quality and urine BPA levels over five years. When compared to participants without detectable levels of the chemical, men with BPA in their urine were three times more likely to have low quality sperm.

“This adds additional human evidence that BPA is bad,” said [the study's first author] De-Kun Li…. “The general public should probably try to avoid exposure to BPA as much as they can.” [Washington Post]

That’s a tough order, because BPA is all over the place. It’s found in everything from sports equipment to medical devices to the plastic lining in canned foods.

Li’s previous studies have shown sexual effects of high levels of BPA, including inducing impotence in male factory workers exposed to it. Those studies were done with men exposed to about 50 times as much BPA as the average U.S. man, so the results might not apply to your average Joe.

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Remember the sunscreen speech? The Chicago Tribune column, which became an urban legend and then a bizarre spoken word hit for Baz Luhrmann, began

Wear sunscreen.

If I could offer you only one tip for the future, sunscreen would be it. The long-term benefits of sunscreen have been proved by scientists, whereas the rest of my advice has no basis more reliable than my own meandering experience.

But is even this sage advice subject to the “it’ll cause cancer, no wait, it’ll cure cancer” back-and-forth that plagues medical studies? Reading some headlines today, you might think so. Don’t toss out your tube of Banana Boat just yet, though.

The non-profit Environmental Working Group released another of its reports on the sunscreen industry, coming down hard on the chemicals it uses and the claims it makes in its advertising. Some stories about the report drew headlines like “Sunscreen May Hurt, Not Help;” “Your Sunscreen May Give You Cancer: Study;” and “Study: Many Sunscreens May Be Accelerating Cancer.”

EWG’s report claims that a Vitamin A compound called retinyl palmitate, used in some 40 percent of sunscreens, breaks down and causes skin damage under exposure to sunlight. The report cites research done under the Food and Drug Administration. But, according to dermatologist Henry W. Lim of Henry Ford Hospital:

These claims, says Lim, are based on a study in mice, which are far more susceptible to skin cancer than humans. “It’s dangerous to apply a finding in mice to humans, and I’ve spoken with a number of my colleagues about this and we all agree that it’s very premature to even cast doubt about the safety of this chemical.” The EWG also flagged products with oxybenzone, which it calls a “hormone-disrupting” compound. This, too, is based on mice data, says Lim; the animals were fed significantly greater amounts of the chemical than what’s commonly applied in sunscreen. Other research found no significant changes in blood hormone levels in human volunteers who were told to apply sunscreens containing oxybenzone every day for two weeks [U.S. News & World Report].

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The storm of news about the BP oil spill in the Gulf of Mexico has reached a relative lull today, as the oil company preps for its containment dome project that it will try to execute over the next several days. With a moment to take a break from the constant news updates, reports are starting to ask: What’s with all that chemical dispersant responders have been dumping on this spill?

The stuff is called Corexit, made by the Nalco Company, and BP has now dumped about 160,000 gallons of it in the Gulf (as well as pumping 6,000 gallons more all the way down to the leak location). The dispersant particles bind to oil, sink, and are carried away by ocean currents. But while that could help keep a spill from reaching the shores en masse, it means the oil isn’t actually “cleaned up,” but rather diluted. And the dispersant chemicals themselves can be dangerous, as Nalco’s own documents (pdf) show.

The 10-page documents go into detail about compounds that must be handled with great care in their original form, that should not touch the skin and can damage lungs. Although the documents state that the potential environmental hazard is “moderate,” they say that when used as directed at sea in the recommended amounts the potential environmental exposure is “low” [The New York Times].

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China has dished out justice in the tainted milk case, and severe justice at that. The country has executed two men, Zhang Yujun and Geng Jinping, convicted  in January of crimes connected to last summer’s powered milk and infant formula contamination incident, which killed six children and sickened about 300,000 people in total.

Zhang, a farmer, produced some 770 tonnes of the powder from July 2007 to August 2008 which was laced with an industrial chemical, melamine, used in the manufacture of plastics and fertiliser [The Telegraph]. Geng was convicted of selling the powder to dairy brokers. The Supreme Court reviewed the cases before the executions, now done with lethal injection, took place. Nineteen other people were convicted of crimes; three got life sentences.

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Chemicals that prevent your house, sofa, and clothes from bursting into flames are ending up in coastal waters all around the United States, and could be damaging the health of both sea creatures and the humans who consume those animals, according to a new study from the National Oceanic and Atmospheric Administration (NOAA). Says the NOAA’s John Dunnigan: “This is a wake-up call for Americans concerned about the health of our coastal waters and their personal health…. Scientific evidence strongly documents that these contaminants impact the food web and action is needed to reduce the threats posed to aquatic resources and human health” [The Oregonian].

Polybrominated Diphenyl Ethers (PBDEs) are a class of flame retardant chemicals that have been widely used in consumer products since the 1970s. The chemicals are credited with saving hundreds of lives each year from the spread of fire, federal scientists said…. But studies on animals have shown that flame retardants can cause thyroid hormone disruption and interfere with developing reproductive and nervous systems [Los Angeles Times].

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