CUMULATIVE RISK: Plastic softening phthalates, like those found in some rubber ducks, pose risks to developing children.
©iStockphoto.com/Doug Cannell

Concluding that nearly everybody is exposed to a mix of chemicals that could be damaging male reproductive health, a national panel of scientists on Thursday advised the U.S. Environmental Protection Agency to shift its focus and group them together when judging how much of a danger they pose.

The committee, assembled by the National Academy of Sciences, looked specifically at phthalates, controversial compounds widely found in consumer products. Phthalates soften plastic to make vinyl for toys, building materials, medical devices and other items, and they also are used in fragrances and other beauty products.

The recommendation to combine the compounds when analyzing their threats to human health would mark a critical change in EPA strategy. It would likely lower the total amount of phthalates the agency considers safe for people and ultimately could lead to strict regulations on their use.

By analyzing each chemical individually, the EPA underestimates the health risks of phthalates, the committee reported. In human bodies, phthalates combine, amplifying the effects on male reproduction.

By only doing one, we underestimate the risk," said Deborah Cory-Slechta, a professor of environmental medicine at University of Rochester School of Medicine and Dentistry who chaired the National Research Council's phthalates committee.

The recommendations could have far-reaching implications beyond phthalates, transforming how the EPA determines to what degree people will be exposed to a variety of chemicals and pollutants.

The committee said other compounds, such as pesticides, also linked to effects on male hormones should be grouped with phthalates in the EPA's risk analysis.

"A focus solely on phthalates to the exclusion of other antiandrogens would be artificial and could seriously underestimate cumulative risk," the report says.

EPA scientists asked the National Academy of Sciences for advice on how to assess phthalates because they know many have the same effects.

Peter Preuss, director of the EPA's National Center for Environmental Assessment, said his "best guess" is that the agency will conduct the recommended cumulative assessment for phthalates. But he said his staff just received the 160-page report and it must first analyze the technical details of how the committee says to proceed.

"The Academy said very clearly that they think there is sufficient information to do this, so that is our next step," Preuss said.

"There are many chemicals that act by many different mechanisms but the final result is a series of impacts on the developing male reproductive system," he said. "The Academy said these things are important—focus on the endpoint, the [health] effect, and work from that. They are trying to simplify this process."

Going even further, the scientists urged the EPA to consider broadening all its assessments to include cumulative effects of compounds with the same health effects.

That, for example, might lead to combined analysis of compounds that affect the brain, female reproduction, lung cancer, or heart disease.

The report bolsters a relatively new scientific argument that cumulative exposure to chemicals and pollutants should be considered when setting safe doses for each.

Many environmental groups and public health experts have urged EPA to conduct risk assessments that combine chemicals, so they welcomed the committee's findings.

Shanna Swan, director of the University of Rochester's Center for Reproductive Epidemiology and one of the leading scientific experts on phthalates, called the cumulative approach "the crucial next step" in addressing environmental chemicals that disrupt hormones.