How polluted we are

Though toxic compounds pervade the air we breathe, the water we drink, and the foods we eat, they only pose risks if they enter our bodies in biologically active quantities. To evaluate people’s uptake of 27 would-be poisons, federal scientists surveyed blood and urine from 3,800 randomly chosen children and adults. The findings, released March 21, show that most people carry traces of the toxic pollutants.

Researchers with the Centers for Disease Control and Prevention (CDC) in Atlanta analyzed samples collected in 1999 as part of its ongoing National Health and Nutrition Examination Survey (NHANES).

Earlier, federal scientists surveyed a cross-section of the U.S. population for lead, cadmium, and cotinine (a marker of nicotine). This time, the CDC also assayed 24 other metals, pesticides, and phthalates, ubiquitous compounds that are used as solvents and as softeners in plastics.

The new data show that over just one decade, the average blood concentration of cotinine fell a whopping 75 percent–to 0.05 nanograms per milliliter. Residues of lead in blood fell about 26 percent, with concentrations in children now averaging 2 micrograms per deciliter. Though no amount of lead in blood is deemed safe, most concern focuses on values above 10 micrograms per deciliter.

Among the most eagerly awaited findings from this study were values for phthalates. These chemicals have gained notoriety for being able to impair male sexual development in animals (SN: 9/2/00, p. 152) and possibly to foster breast development in preschool girls (SN: 9/9/00, p. 165).

Phthalate urine residues were highest for diethyl phthalate (DEP), a solvent used in cosmetics. Average concentrations hovered about 171 micrograms per liter in urine, with 10 percent of people carrying concentrations 7 times that. Dibutyl phthalate (DBP), a solvent used in dyes, fingernail polish, and some plastics, was the second most prevalent of these compounds. Its residues averaged 28 micrograms per liter. Ironically, commercial production of both the phthalates pales next to that of diethyl hexyl phthalate and other such plasticizers. CDC scientists found that the diethyl hexyl residues average just 3.3 micrograms per liter.

The agency says its new data have prompted it to launch studies of why people are picking up such comparatively high concentrations of DEP and DBP.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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