By Janet Raloff
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.