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Toxic Chemicals—Looking at the Big Picture

Science

Natural Resources Defense Council

By Gina Solomon

Used with permission of NRDC – Switchboard

There are so many toxic chemicals and pollutants in our air, water, food and consumer products that it's easy to just focus on one at a time and get stuck in the details of each specific case. But sometimes it's helpful to step back and look at the big picture.The National Academies of Science (NAS) did precisely that nearly three years ago in a landmark report on protecting people from toxic chemicals. The report, entitled Science and Decisions: Advancing Risk Assessment, contained a series of clear recommendations directed at government agencies such as the U.S. Environmental Protection Agency (EPA) and the Food & Drug Administration (FDA), about how to use science to protect health. Unfortunately, the NAS recommendations have largely been ignored by both the EPA and the FDA. As we approach the third anniversary of the NAS report, it's a good time to look at the four most important recommendations from this impressive panel of scientists. Here's a summary based on their recommendations:

  1. Identify and incorporate variability in human exposure and vulnerability into health assessments, so that all people are better protected.
  2. When information is missing or unreliable, use science-based default assumptions that protect health, rather than waiting for more data, to speed up the chemical assessment and decision-making processes. There should be a clear set of criteria for when to depart from default assumptions.
  3. In assessing the risk of chemicals, incorporate information about the potential impacts of exposure to multiple chemicals. Consider other factors, such as exposure to biological and radiological agents, and social conditions.
  4. Because the population is exposed to multiple chemicals and there is a wide range of susceptibility to chemical exposures, it cannot be presumed that any—even low level—exposures are risk-free. It should be assumed that low levels of exposures are associated with some level of risk, unless there are sufficient data to contradict this assumption.

Since not very many people will want to read the full 424 page NAS report, the committee's recommendations are summarized and interpreted in a new NRDC and SEHN issue paper entitled, Strengthening Toxic Chemical Risk Assessments to Protect Human Health. Incorporating the recommendations of the NAS scientists into current decisions would substantially change the way the EPA and FDA are approaching a host of key issues.

For example:

  • I have previously blogged about hexavalent chromium, the chemical made famous in the movie Erin Brockovich. This widespread drinking water contaminant is known to cause cancer in humans, but one popular industry argument asserts that the substance is detoxified to a non-cancer-causing form of chromium in the acidic environment of the stomach. The industry argument is that the EPA shouldn't regulate hex chrome as a carcinogen because most people can detoxify it. The NAS report urges greater caution—Identify and incorporate variability in human exposure and vulnerability into health assessments, so that all people are better protected. There are at least 20 million prescriptions each year for acid-reducing medications. People on these medications are not able to effectively detoxify cancer-causing chromium in their drinking water. EPA needs to protect these people when it moves forward to assess the risks from hex chrome and ultimately to set a drinking water standard. 
  • After the Gulf oil spill, the FDA assessed seafood safety and concluded that there were no health risks. Their calculations relied on a series of default assumptions that were not consistent with the NAS recommendations. As described more fully in this blog, and this peer-reviewed publication, the FDA adopted unrealistically low assumptions about how much seafood people eat, assumed that the most common contaminant was not a carcinogen even though it is officially designated as such, and assumed that the average consumer weighs 176 pounds, therefore failing to protect many women and all children. These assumptions should be revised to be health-protective. It's hard to justify consumer confidence in Gulf seafood without reasonable default assumptions. 
  • Phthalates are chemicals that interfere with normal male hormones such as testosterone, and they have been linked to genital abnormalities in baby boys. These chemicals are widespread in certain plastics and other consumer products. Until Congress acted, these chemicals were also widespread in toys. My colleague Sarah Janssen discusses the science in her blog on phthalates. Although it's easy to just focus on one chemical at a time, a study of phthalates and pesticides found that in test animals, a mixture of up to 10 chemicals that disrupt male reproductive development by multiple mechanisms resulted in more frequent and severe birth defects than with any of the chemicals individually. This science underscores that EPA needs to heed the recommendation by the NAS to consider the cumulative effects of multiple chemicals and other stressors together as it completes its assessment of phthalates. 
  • Mercury, another important and widespread environmental contaminant, is a particular hazard to people who eat fish. Because it does not cause cancer, the FDA and EPA assume that there is a threshold below which mercury is non-toxic to humans. In fact, this assumption is universal for non-carcinogens, even for chemicals such as mercury that affect the normal functioning of the brain and for which no safe level has been determined, despite numerous large studies in humans. The NAS instead recommended that the scientific assumption should not be so different for neurotoxins and other toxic chemicals than it is for carcinogens; if no safe level is demonstrated in human or laboratory studies, then a safe level should not be assumed.This is yet another reason why the EPA and FDA should not back away from—and should instead strengthen—recommendations that pregnant women and children limit consumption of mercury-containing fish. It's also another reason to applaud recent EPA efforts to reduce or eliminate important sources of mercury pollution such as power plants, as described by my colleague Peter Lehner in his blog. Learn more about mercury at NRDC's guide to Staying Healthy and Fighting Back.

Just this week, the President of the American Association for the Advancement of Science (AAAS) stated that she was "scared to death" by the anti-science movement ...spreading, uncontrolled, across the U.S. and the rest of the western world." It is becoming increasingly clear that the anti-science movement is fueled and funded by a small group of major corporate interests and individuals. Read more in this recent expose in the Guardian. The goal of the attack on science is to stop much-needed government regulations on toxic chemicals and other pollutants (such as greenhouse gases) that harm health. One sign of the success of the anti-science movement is that this important NAS science report has been sitting unheeded for nearly three years. It's time for the EPA and FDA to sit up and take notice.

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