EPA defends chemical testing of low-dose hormone effects
June 27, 2013
The U.S. Environmental Protection Agency has concluded that current testing of hormone-altering chemicals is adequate for detecting low-dose effects that may jeopardize health.
This comes in response to a report written last year by 12 scientists who criticized the government’s decades old-strategy for testing the safety of many chemicals found in the environment and in consumer products.
The scientists specifically focused on a phenomenon called “nonmonotonic dose response,” which means that hormone-like chemicals often do not act in a typical way; they can have health effects at low doses but no effects or different effects at high doses. The EPA frequently evaluates the risks of chemicals with tests that expose lab animals to high doses, then extrapolating to lower doses that people and wildlife encounter.
Dozens of substances that mimic or block estrogen, testosterone or thyroid hormones are found in the environment, food, pesticides and consumer products. The idea that these chemicals harm people at tiny doses remains controversial.
The EPA’s draft “State of the Science” report, completed last week, found that such low-dose responses “do occur in biological systems but are generally not common.”
“There currently is no reproducible evidence” that the low-dose effects seen in lab tests “are predictive of adverse outcomes that may be seen in humans or wildlife populations for estrogen, androgen or thyroid endpoints,” the agency report said.
“Therefore, current testing strategies are unlikely to mischaracterize...a chemical that has the potential for adverse perturbations of the estrogen, androgen or thyroid pathways.”
The report was written by EPA officials with input from a team of scientists and managers from the Food and Drug Administration, the National Institute of Environmental Health Sciences and the National Institute of Child Health and Development that reviewed the science on endocrine-disrupting chemicals. It was signed by Robert Kavlock, the EPA’s Deputy Assistant Administrator for Science.
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The federal team was commissioned last June in response to the scientists’ report published a few months earlier by lead author Laura Vandenberg, a Tufts University researcher, and colleagues. Pete Myers, founder of Environmental Health News and chief scientist at Environmental Health Sciences, was the senior author of that report.
The EPA's draft report will be peer-reviewed by a panel of the National Academies of Sciences.
The American Chemistry Council, which represents chemical companies, praised the EPA’s conclusion.
The EPA “affirms what mainstream scientists have expressed for years: the purported scientific evidence for non-monotonic low dose exposures leading to endocrine disruption and adverse effects is, at best, very weak,” the industry group said in a prepared statement.
Vandenberg said although the debate over how to assess the risks of these chemicals remains, the EPA’s acknowledgement that nonmonotonic dose responses exist is a step forward, culminating years of science.
But she added that the EPA made some “odd, and possibly political decisions” in the new report.
The EPA’s belief that high dose testing can predict safety at low doses “flies in the face of our knowledge of how hormones work,” Vandenberg told EHN in an email. “They [endocrine disrupting chemicals] are overtly toxic at high doses but act like hormones, with completely different actions, at low doses.”
In the 2012 report, Vandenberg and colleagues pointed to chemicals such as bisphenol A (BPA) – which is found in polycarbonate plastic and some canned foods and paper receipts – and atrazine, a pesticide used mostly on corn, as examples of chemicals that are inadequately tested to protect human health.
“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,” the scientists said in their report published in the journal Endocrine Reviews.
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.
Vandenberg said the EPA used out-of-date studies on atrazine, when they should have used a new publication with dozens of authors from around the world showing the “consistent, low-dose effects of this chemical on amphibians, reptiles, fish, birds and mammals.”
Their discussion of the low-dose effects of BPA on the prostate “are also about a decade out of date, and give credence to industry funded studies that had flawed experimental designs and failed positive controls,” she said.
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