That is a main finding of a report, three years in the making, published Wednesday by a team of 12 scientists who study hormone-altering chemicals.
Dozens of substances that can mimic or block estrogen, testosterone and other hormones are found in the environment, the food supply and consumer products, including plastics, pesticides and cosmetics. One of the biggest, longest-lasting controversies about these chemicals is whether the tiny doses that most people are exposed to are harmful.
In the new report, researchers led by Tufts University's Laura Vandenberg concluded after examining hundreds of studies that health effects "are remarkably common" when people or animals are exposed to low doses of endocrine-disrupting compounds. As examples, they provide evidence for several controversial chemicals, including bisphenol A, found in polycarbonate plastic, canned foods and paper receipts, and the pesticide atrazine, used in large volumes mainly on corn.
The scientists concluded that scientific evidence "clearly indicates that low doses cannot be ignored." They cited evidence of a wide range of health effects in people – from fetuses to aging adults – including links to infertility, cardiovascular disease, obesity, cancer and other disorders.
"Whether low doses of endocrine-disrupting compounds influence human disorders is no longer conjecture, as epidemiological studies show that environmental exposures are associated with human diseases and disabilities," they wrote.
In addition, the scientists took on the issue of whether a decades-old strategy for testing most chemicals – exposing lab rodents to high doses then extrapolating down for real-life human exposures – is adequate to protect people.
They concluded that it is not, and so they urged reforms. Some hormone-like chemicals have health effects at low doses that do not occur at high doses.
"Current testing paradigms are missing important, sensitive endpoints" for human health, they said. "The effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health."
The report was published online Wednesday in the scientific journal Endocrine Reviews. Authors include scientists University of Missouri's Frederick vom Saal, who has linked low doses of bisphenol A to a variety of effects, Theo Colborn, who is credited with first spreading the word about hormone-disrupting chemicals in the late 1980s and University of California, Berkeley's Tyrone Hayes, who has documented effects of atrazine on frogs.
The senior author is Pete Myers, the founder of Environmental Health News and chief scientist of Environmental Health Sciences.
Linda Birnbaum, director of the National Institute of Environmental Health Sciences, said the new report is valuable "because it pulls a tremendous amount of information together" about endocrine-disrupting compounds. Her agency is the main one that studies health effects of contaminants in the environment.
Birnbaum said she agrees with their main finding: All chemicals that can disrupt hormones should be tested in ultra-low doses relevant to real human exposures, she said.
In many cases, chemical manufacturers still are asking "old questions" when they test the safety of chemicals even though "science has moved on," she said. "Some of the testing paradigms have not advanced with the state of the science." Birnbaum wrote an editorial on Wednesday referencing the new report.