Polybrominated diphenyl ethers or PBDEs, which are flame-retardants added to polyurethane foam furniture cushions, mattresses, carpet pads and automobile seats, also are widespread.
The plastics industry maintains that its products are safe after decades of testing.
“Every additive that we use is very carefully evaluated, not just by the industry, but also independently by government agencies to look at all the materials we use in plastics,” said Mike Neal, a consumer and environmental affairs specialist at PlasticsEurope, an industry trade association, and a co-author of the report.
But some of these chemicals have been shown to affect reproduction and development in animal studies, according to the report. Some studies also have linked these chemicals with adverse effects in people, including reproductive abnormalities.
“We have animal literature, which shows direct links between exposure and adverse health outcomes, the limited human studies, and the fact that 90 to 100 percent of the population has measurable levels of these compounds in their bodies,” said John Meeker, an assistant professor of environmental health sciences at the University of Michigan School of Public Health and a lead author. “You take the whole picture and it does raise concerns, but more research is needed.”
Shanna Swan, director of the University of Rochester's Center for Reproductive Epidemiology, conducted studies that found an association between pregnant women’s exposure to phthalates and altered genital development in their baby boys.
Also, people with the highest exposure to BPA have an increased rate of heart disease and diabetes, according to one recent study. Animal tests studies of PBDEs have revealed the potential for damaging the developing brain and the reproductive system.
Yet the effects on human health remain largely unknown. To help shed more light on the issue, the report recommends more sophisticated human studies.
“It’s tough to have a smoking gun with a single animal study or observational human study,” Meeker said. “We need to have different types of studies indicating a consistent pattern to more definitively determine health effects resulting from these chemicals.”
But testing humans for endocrine disruptors can be tricky because phthalates and BPA pass through the body so quickly. In addition, tests for each chemical cost about $100 a pop.
Deciding which chemicals to test and at what dose is also an issue. To date, most studies have addressed single chemicals, and there are limited data on the interactions between chemicals. Compounding the problem is the discovery that endocrine disrupting chemicals may have effects at doses lower than those used in the Environmental Protection Agency’s standard toxicity tests.
Swan said the old model of testing should be thrown out and that the new goal should be tests that mimic real human exposure.
“It’s a very complicated picture and the laboratory model of just taking one isolated chemical and giving it to a genetically pure strain of rats in clean cages, clean air and clean water and seeing what it does just doesn’t come close to mimicking the human situation,” she said.
Many researchers recommend studies that test pregnant women as well as their children. The National Children’s Study will do just that by examining environmental influences on more than 100,000 children across the United States, following them from before birth until age 21.
“There are so many questions now with these chemicals in relation to cardiovascular disease, age and puberty, obesity, developmental disorders,” said Swan. “We don’t know what’s causing it, only hints, so the beauty of the National Children’s Study is that we can look at all of these endpoints and it should reveal a lot of answers.”