By Jocelyn Kaiser
ScienceNOW Daily News
16 April 2008
A U.S. federal agency's draft report on the health risks of bisphenol-A, a chemical found in some plastics, is stirring new controversy about the hormonelike substance. Although the report, released yesterday, mostly mirrors an outside group's conclusions last year, it ratchets up concerns about certain risks to fetuses and children. That has environmentalists praising the report, but it's not clear whether the findings will trigger regulatory action.
Bisphenol-A (BPA) is found in polycarbonate bottles, including some water and baby bottles, as well as the liners of some metal food cans. It has been detected in the blood of most Americans. At high levels, BPA acts like a hormone in animal experiments, causing effects such as lower birthweight and delayed puberty in offspring. The controversy centers on studies over the last 10 years finding effects on developing animals at the much lower levels to which humans are exposed. A panel of outside experts convened by the federal National Toxicology Program (NTP) last summer found many of these studies unconvincing (ScienceNOW, 8 August 2007). However, it had "some concern" about neurological effects on the developing fetus, such as changes in the brain and behavior. Environmentalists and several lawmakers slammed the report as biased, because a contractor hired to help draft the report had received industry funding.
Now the NTP's own scientists have found "some concern" not only for neurobehavioral effects, but for potential effects such as precancerous breast and prostate lesions, and delayed puberty in females. This is a notch more worrisome than the "minimal concern" about these effects in the outside panel's report. (The NTP uses a 5-point scale, ranging from "negligible concern" to "serious concern.") Michael Shelby, director of the NTP Center for the Evaluation of Risks to Human Reproduction, explains that new papers led NTP to "give a little more credence" to reports of prostate changes in newborn animals. The NTP also noted flaws in studies finding that low-level BPA does not alter breast development. And it concluded that certain mouse studies on accelerated puberty in females were convincing.
Although Shelby says it is unusual for the NTP to depart from an outside panels' conclusions, it is not unprecedented. "The comments and controversy sure were an impetus to look a little closer," he says. However, as Shelby notes, overall both panels had only "some concern," about BPA, which is less likely to trigger regulatory action than a higher level of concern.
Sonya Lunder thinks the new report has big implications. A senior analyst at the Environmental Working Group, an advocacy group, Lunder lauds the NTP's decision to include many studies discarded by the earlier panel. She thinks the Food and Drug Administration, which has told Congress it is not relying on these low-dose studies to determine BPA's risks, "will have to take another look at the literature."
The NTP draft report will now go through a comment period and peer review. Meanwhile, BPA is getting a tougher rap in Canada, where Health Canada scientists are expected to issue a report soon finding more serious concerns about the risks. That could lead to the first national limit or ban on the chemical [标签:content1][标签:content2]
作者:admin@医学,生命科学 2011-01-04 05:14