Proof of Burden

Scores of contaminants course through people's veins
Science News, Feb 22, 2003, by Ben Harder

         Farm-field runoff, raw sewage, and smokestack emissions may contain a slew of poisonous chemicals. But how about a healthy person's blood? Two independent teams of scientists report that bodily fluids carry chemical cocktails that include toxic metals, artificial hormones, and ingredients of plastics, flame retardants, pesticides, herbicides, and disinfectants. "The bottom line of both studies is that a whole raft of synthetic chemicals that simply did not exist 40 or 50 years ago is now in the bodies and in the bloodstreams of most Americans," says pediatrician Philip J. Landrigan of Mount Sinai School of Medicine in New York.

        The studies--one from the Centers for Disease Control and Prevention (CDC) in Atlanta and the other from the Environmental Working Group, an advocacy group in Washington, D.C.--focused on determining the prevalence in the body, or the so-called body burden, of more than 100 chemicals. Neither group specifically assessed the chemicals' health effects.

        Nevertheless, environmental-health scientists who reviewed the new caches of data told Science News that they carry many disturbing implications. The pervasiveness of pollutants known to harm or suspected of harming health underscores the need for stronger regulations on chemicals, these scientists say. "As a society, we are still treating chemicals as if they are innocent until proven guilty," says Ana Soto, an endocrinologist at Tufts University School of Medicine in Boston.

        In the CDC study, which cost $6.5 million, Jim Pirkle and his colleagues collected blood and urine samples from thousands of volunteers selected to form a demographic microcosm of U.S. residents. The researchers tested at least 2,500 volunteers for each of 116 contaminants. Of those chemicals, 89 had never been systematically measured in the U.S. population.

        The researchers' tests turned up all 116 pollutants, which include 13 metals, 14 combustion byproducts known as polycyclic aromatic hydrocarbons, and 10 byproducts of organophosphate pesticides. The scientists detected many of the substances in at least half the people they tested. These include 11 of the metals, 8 of the combustion byproducts, and 6 of the organophosphate pesticide byproducts, and 8 other pesticides, repellants, and herbicides.

        The study results indicate that about 425,000 children 1 to 5 years old nationwide have dangerously elevated blood-lead concentrations. Infants and children are thought to carry greater burdens of lead and many other pollutants than most adults because youngsters have different metabolic rates, have more contact with contaminated floors and ground, and are more likely to transfer harmful chemicals into their mouths. Furthermore, because pollutants in the body can harm development, fetuses and children are most at risk, says Lynn Goldman, an environmental health researcher at the Johns Hopkins University in Baltimore.

        Children and teenagers also have heavier burdens than older people of cotinine, a product of secondhand tobacco smoke, CDC finds. In the study, more than half of all nonsmokers in the United States older than 3 had detectable amounts of cotinine in their blood.

        The CDC data will help other environmental investigators identify groups of people that have received unusually high exposures to specific chemicals, Pirkle says. The CDC study itself found greater burdens of certain chemicals in Mexican Americans and blacks than in the population at large.

 HEALTH ISSUES   Even people with typical exposures to the chemicals in the survey could face health risks from their body burden. Pirkle notes that in the 1970s, U.S. residents typically had amounts of lead in their blood that only later were deemed dangerous. "We would have been very wrong" to have assumed back then that an average lead burden was a safe burden, he says.

        That logic applies today to pollutants whose health effects are only beginning to be understood, other researchers say. In urine samples, CDC found ubiquitous evidence of 6 phthalates, chemicals unregulated in the United States and widely used in plastics and cosmetics (SN: 7/20/02, p. 36). "The [CDC's] phthalate data are truly frightening," says reproductive biologist Fred vom Saal of the University of Missouri in Columbia. "There is a clear and convincing set of animal data on the health hazards," which include cancer and reproductive abnormalities, he says.

        The body burdens of currently banned or restricted chemicals, such as DDT, lead, and polychlorinated biphenyls, appear to have dropped since earlier studies. Those trends show that proper environmental regulation does work to reduce people's chemical burdens, says Jane Houlihan of the Environmental Working Group.

        In the second new study, Houlihan and her colleagues found 167 contaminants in blood and urine samples from nine adult volunteers without known unusual exposures to pollutants. Bisphenol A and flame retardant polybrominated diphenyl ethers, which act like hormones in the body, were among numerous synthetic compounds that these scientists detected but that weren't assessed by CDC. Some of Houlihan's data appeared in the July-August 2002 Public Health Reports; her group released the full report in a press briefing on Jan. 30.

        Certain consumer choices may cut individuals' chemical exposures. Children who eat organically grown fruits and vegetables have only one-sixth the concentrations of organophosphate pesticide byproducts in their urine as children who eat conventionally grown produce have, says Cynthia L. Cud of the University of Washington in Seattle. She and her colleagues report that finding in the March Environmental Health Perspectives.


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