Soto and her colleagues exposed pregnant rats to bisphenol A at doses ranging from 2.5 to 1,000 µg per kg of body weight per day. By the time the pups exposed at the lowest dose reached the equivalent of puberty (50 days old), about 25% of their mammary ducts had precancerous lesions, a proportion three to four times higher than among the nonexposed controls. Mammary ducts from all other exposure groups showed elevated levels of lesions. Cancerous lesions were found in the mammary glands of one-third of the rats exposed to 250 µg/kg/day.
Bisphenol A is used in the manufacture of polycarbonate plastics and epoxy resins. It is found in many food and beverage containers, including baby bottles. It is also found in canned food linings and dental composites, and it leaches from all of these products. In one study, Soto notes, urine samples from 95% of the human subjects contained the chemical.
The Environmental Protection Agency has set a safe human intake dose of 50 µg/kg/day for bisphenol A. “On the basis of the effects observed in recent studies, this seems to be an unsafe level,” Soto says.
Bisphenol A is old news, BTW, people have known for a while about this chemical’s propensity to carcinogenicity. Of course, there’s that whole argument about pregnant mice being more susceptible to chemicals than humans, etc. So, the jury is still out. but Soto is right, 50 µg/kg/day seems to not provide enough of a safety factor. The EU uses 10 µg/kg/day, though they do say that
realistic worst-case estimates of consumer exposure via foodstuffs, range from 0.00048 mg/kg bw/day for adults to 0.0016 mg/kg bw/day for infants, which is well below the maximum exposure level
Of course, who knows what additive effects this chemical may have with the multitude of other chemicals floating around. Doing tests of single chemicals and trying to link that to epidemiological data is a perilous undertaking, the connections are tenuous most of the time and the plastics companies routinely fund studies that prove otherwise, because as you know, if you know what you’re going to find before you study it, you will find it!
Read the wikipedia stub on polycarbonates. Us yuppies who drink religiously from Nalgene bottles to avoid phthalates and nasty tastes would do good to take note! I guess glass is the best, though it does have that annoying tendency to shatter when dropped… Water from glass bottles do have the best taste, though.