Lead levels affect IQ and puberty

Children exposed to lead in their homes may suffer toxic effects even at levels once thought too low to cause harm, according to latest research. Even low blood levels of lead are associated with lower IQ scores in young children and delayed onset of puberty in girls. Most lead poisoning occurs because children ingest chips or dust from lead-based paints. Sources include water pipes containing lead, paint, ceramic glazes, pewter and some types of metal utensils. Researchers at the University in Ithaca, New York, periodically evaluated blood lead levels in 172 children starting when they were 6 months old and ending at the age of 5 years. IQ was checked at ages 3 and 5. They took into account a number of factors known to influence IQ, including birth weight, the mother's education level and smoking during pregnancy. The average blood levels of lead in the 5 year old children was 7.4 mcg/dL and their average IQ was 90. Overall, children with the highest blood levels of lead had the lowest IQs. The researchers were able to estimate an approximate 5 point drop in IQ for each 10 mcg/dL increase in blood lead level. Among children with initially lower levels of lead, the effect of rising lead was even more striking. There was a decrease of 7.4 points in IQ for children who started the study with the lowest lead levels (1 mcg/dL) but then had higher exposure (10 mcg/dL). These findings suggest that more children may be adversely affected by environmental lead than previously estimated. Children are especially susceptible to the toxic effects of lead, experiencing neurological problems, including learning disabilities and a drop in IQ if lead levels climb above 10 mcg/dL of blood.

In another study researchers at the US Environmental Protection Agency evaluated levels of lead in the blood and the onset of puberty among 2,186 girls between the ages of 8 and 18. Measurements of puberty included growth of pubic hair, breast development and age when menstruation began. Among the entire group, blood lead concentrations were, on average, below 3 mcg/dL of blood. However, differences were seen between girls with blood lead levels of 1 mcg/dL compared to those with lead concentrations of 3 mcg/dL. Higher blood lead concentrations were associated with significant delay in all pubertal measures. Although the findings cannot prove a causal relation between mildly elevated lead concentrations and delayed puberty, they suggest that even a relatively low level of exposure to lead may influence growth and sexual development in girls.