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Leaden streets

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11:06am, March 21, 2006

From San Diego, at a meeting of the Society of Toxicology

When Arlene L. Weiss and her colleagues found that urban house dust tends to contain more lead the closer it is to a frequently opened window, they reasoned that most of the heavy metal arrives from outside. Their new survey now confirms that street grit is the probable source of lead in urban homes and that flaking paint from overpasses and bridges is a major contributor.

The researchers sampled soil and street sweepings from 255 sites throughout New York City's five boroughs. The highest lead contamination occurred directly beneath elevated train trestles, where concentrations of the metal routinely reached many thousands of parts per million (ppm). The federal limit for lead in U.S. soil is 400 ppm.

Samples of outdoor dust were much less tainted just two to three blocks away from bridges and trestles, with lead loads in the range of 200 to 500 ppm, notes Weiss, a consulting toxicologist with Env

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