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Pollutants in boys' blood tied to lower growth
NEW YORK |
NEW YORK (Reuters Health) - Russian boys exposed to unusually high levels of environmental pollutants are smaller than their peers, a new study reports.
After following nearly 500 boys for three years, an international group of researchers found that those with the highest levels of polychlorinated biphenyls (PCBs) in their blood were nearly three centimeters (more than an inch) shorter than boys from the same region with the lowest amount of PCBs in their bodies.
Boys with the highest exposures also averaged two points lower in body mass index (BMI), a measure of weight relative to height.
The authors found a similar pattern in boys with the highest exposure to the pollutant dioxin.
"You're always a little surprised to see such a dramatic effect," study author Jane Burns of the Harvard School of Public Health told Reuters Health, but the findings are "consistent" with some other research about the effect of these chemicals.
Burns explained that the boys included in the study have much higher exposures to these pollutants than the general U.S. population, likely a result of their proximity to a chemical plant that generated dioxin as a byproduct. But a small number of people in the U.S. and other developed countries live in regions with exposures that match - or even exceed - those seen here, she added.
PCBs were once used in everything from appliances and fluorescent lighting to insulation and insecticides. While the chemicals were banned in the 1970s as potential health hazards, they remain a public-health concern because they linger in the environment and accumulate in the fat of fish, mammals and birds.
Research has linked PCBs to an elevated risk of cancer, type 2 diabetes and other ailments. A study of children in Taiwan also found that those exposed in utero to PCBs from contaminated cooking oil were shorter than their peers.
Dioxins are toxic substances formed by burning -- for example in waste incinerators or forest fires -- and in some industrial processes. Airborne dioxins are deposited onto plants, soils and water, and they enter the food chain when ingested by livestock and fish. Dioxin exposure has been shown to lead to both higher cancer rates and changes in birth rates resulting in more female babies and fewer males.
To further investigate the impact of high exposures to PCBs and dioxins on growth, Burns and her colleagues took blood samples from 499 boys ages 8 and 9 living in Chapaevsk, Russia, an area known to be highly contaminated.
Indeed, the highest levels of PCBs and dioxins in the boys' blood far exceeded those found in the average U.S. population, Burns noted.
Prenatal exposure to PCBs, but not dioxins, has been linked to low birth weight. And along with differences in the prepubescent boys' height and weight, the authors found that those with the highest blood levels of PCBs were growing significantly more slowly than boys with the least exposure - by about 0.2 centimeters a year over the three-year study period.
The findings appear in the journal Pediatrics.
It's not entirely clear why PCBs or dioxins might affect growth, Burns said in an interview. "We're not really sure of what the mechanisms are." Research suggests dioxins interfere with genes that regulate normal development, while PCBs disrupt the regulation of thyroid hormones, which could impact growth.
SOURCE: link.reuters.com/vab24r Pediatrics, online December 27, 2010.
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