Environmental Pollutants Are Pervasive, Persistent in Their Damage

People living in disadvantaged communities are often exposed to a range of factors that contribute to health problems, such as limited access to healthy foods and health services. During a session at IPS: The Mental Health Services Conference in Chicago in October, researchers sought to educate psychiatrists about the role the environment plays in health disparities.

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Studies show that poor and minority children are often exposed to more indoor lead, outdoor pollution, and chemical-containing processed foods, among others. Some of this exposure comes when the children are still in utero and their rapidly developing brains are extremely sensitive to adverse chemicals.

These pollutants are hard to avoid, Frederica Perera, Ph.D., a professor of Environmental Health Sciences at Columbia University and director of Columbia’s Center for Children’s Environmental Health (CCCEH), told the audience.

“America has had a love affair with chemicals since World War II,” she said. While about 80,000 chemicals are currently licensed for industrial use, she said it is hard to know how many of these chemicals pose developmental risks, since only a small fraction have been tested for neurodevelopmental toxicity.

Studies of blood and urine samples taken as part of the Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey have shown that individuals of lower socioeconomic status on average have higher levels of harmful pollutants in their bodies compared with those of higher socioeconomic status, said Irva Hertz-Picciotto, Ph.D., a professor of epidemiology at the University of California, Davis.

These pollutants include well-known biological toxins such as lead and pesticides, but also items that many people may not think about, such as dental fillings, said Mark Mitchell, M.D., M.P.H., an associate professor of Climate Change, Energy, and Environmental Health Equity at George Mason University. Older dental fillings were typically made out of amalgam, a metallic mixture that contains mercury—which is known to damage the nervous system. (The FDA lists amalgam as a Class II device denoting moderate health risk, but Mitchell said that the research into amalgam is outdated, and it may pose more risks than once believed if a filling cracks or breaks.)

Amalgam is being phased out at many dental practices due to the availability of better and safer materials such as resin, but some dentists still use amalgam regularly. According to Mitchell, patients who receive amalgam fillings are more likely to be low income. Mitchell added that because children from low-income families may have poorer nutrition, they may get more cavities on average and thus have more amalgam in their mouths. Additionally, in the event some mercury leaches out of the fillings, these children are at greater risk of damage since they deal with greater psychosocial stressors, and stress hinders the body’s defenses, including the immune system, he said.

Together, the inequities faced by disadvantaged children create a vicious cycle that affects normal development.

“This is a case of environmental justice,” Mitchell told the audience. “No group should have to bear an undue burden from the effects of industrial or other pollutants.”

When a chemical is banned from use—as occurred with DDT and other pesticides in the 1970s—it is usually just replaced with another chemical. “This is a whack-a-mole problem,” Perera said. Meanwhile, because many chemicals have long half-lives, the older compounds remain present in the environment.

She continued, “Environmental pollutants are especially harmful because they have so many ways to damage the brain.” Studies show these molecules can cause DNA mutations, alter the regulation of genes, and even directly kill brain cells. “The damage they cause can have lifelong effects that have even been shown to be transgenerational.”

Perera highlighted a large, multinational cohort study that the CCCEH has been conducting in New York, Poland, and China to assess the effects of exposure to phthalates (chemicals that make plastics flexible). In this diverse racial and geographical population, phthalate exposure among mothers was consistently associated with lower IQ in children. Previous studies have found that children whose mothers were exposed to lead also had lower IQs than those who were not exposed to the chemical.

Perera noted that while exposure to one chemical may pose some neurodevelopmental risks such as reduced IQ, research shows that a clinically relevant outcome such as autism often occurs only when a person is exposed to a combination of pollutants. “We therefore do not have to tackle all the causal agents [at once], just a few key ones.”

The good news is that the right policies—such as pollution reforms and sustainable energy initiatives—can make a difference, she said. Perera said that a coal plant in one of the China study regions had recently closed, and recent data show that health outcomes in the area are improving. ■