In children, even trace residues of lead can wreak harm. One recent study reported evidence of IQ deficits in children with blood concentrations of the metal below 5 micrograms per deciliter (g/dl) (SN: 4/26/03, p. 269: Available to subscribers at Traces of lead cause outsize harm), an amount found in 90 percent of U.S. kids. Now, epidemiologists have turned up evidence that similarly low lead concentrations delay puberty in girls.
Tiejian Wu of East Tennessee State University in Johnson City and his colleagues correlated signs of puberty in a nationally representative sample of 1,700 girls, ages 8 to 16, with the kids' blood-lead concentrations. The data came from a federal health and nutrition survey of the U.S. population.
Wu's group divided girls at each age into three groups on the basis of blood-lead concentrations: under 2 g/dl, at least 5 g/dl, or somewhere between those values. Among 10-year-olds, the share with pubic hair was 60 percen