WASHINGTON — A panel of scientists looking at why some young girls are entering puberty earlier than ever tossed out a variety of answers: obesity, diet, lifestyle, the media and even plastics.
Some studies suggest that two key additives to plastics, bisphenol A and phthalates, could be contributing to the early onset of puberty. But plastics industry officials were quick to say that other scientific evidence contradicts those claims.
While the claims are startling, none of the evidence is conclusive, according to several scientists speaking at a Feb. 7 news conference in Washington sponsored by environmental organizations.
"I'll begin right at the outset by saying there are no certain answers," said John Peterson Myers, director of the W. Alton Jones Foundation and the co-author of "Our Stolen Futures," a book that launched the debate about endocrine disrupters.
Myers pointed to a September study in Puerto Rico. That study said there is a "possible association" between premature breast development in young girls and exposure to phthalates, although it said it "cannot be interpreted as the cause."
The study by the University of Puerto Rico said that island is believed to have the highest incidence of premature thelarche, or the beginning of breast development during puberty, in the world, a fact that has puzzled researchers for two decades.
Myers said the study offers the first "statistically significant" link. Forty-one blood samples from girls without thelarche had no phthalates, while a majority of 28 samples from girls with the condition had "significantly high" levels of phthalates, the study said.
The Phthalate Esters Panel of the American Chemistry Council said the study's own data supports the conclusion that there is no link: It showed that the levels of phthalates in individual patients did not show any correlation.
Phthalates have been used for decades without evidence of human harm, said Marian Stanley, director of the Arlington, Va., phthalates panel.
The panel of scientists also pointed to a 1999 study in Nature magazine that found exposure to low levels of BPA brings on early puberty in mice.
But Steve Hentges, executive director of the American Plastics Council's polycarbonate business unit, also in Arlington, said much larger studies have not come to similar conclusions.
Premature puberty appears to be a serious public health problem, he said. He added, however, "We think, based on the weight of evidence, that there is no role" for BPA, he said. BPA is a building block of polycarbonate.