(CNN) -- The U.S. Environmental Protection Agency and other regulators are not using the best available science in their assessment of bisphenol-A's (BPA) safety, according to a statement released Tuesday by the Endocrine Society.
"Testing needs to include models of developmental exposure during critical life periods when organisms may be most vulnerable to even very low-dose exposure," says the world's largest group of researchers and clinicians who study how hormones function.
For a typical poison, a higher dose correlates directly with greater toxicity, but endocrine disrupting chemicals like BPA may be counter-intuitively more potent at lower levels, and during "windows of vulnerability" such as pregnancy, explains a 2009 scientific statement by the Endocrine Society.
That poses a problem for regulatory agencies' screening tests, which are based on traditional toxicology and do not detect the low-dose effects of chemicals on the endocrine system, said Frederick vom Saal, who co-authored the Endocrine Society's new statement.
The Endocrine Society also issued a revised definition for endocrine-disrupting chemicals, saying that any chemicals "that interfere with any aspect of hormone action should be presumed to produce adverse effects," regardless of whether the adverse effects are well understood.
Earlier this year, the FDA denied a petition by the Natural Resources Defense Council to ban BPA in food packaging, where the chemical is used in plastics and the lining of cans.
"FDA is constantly monitoring the science on the substances or products it regulates, including BPA," the FDA said in a statement to CNN. "The FDA does not have sufficient evidence at this time to show harm to humans at low levels of exposure to BPA."
The EPA has declined to comment.
"The FDA is using approaches to regulate endocrine disrupting chemicals that violate basic endocrine principles," said Vom Saal. "They are not so incompetent that they cannot understand this. It is just inconvenient to do so."