Exposure to lead in early childhood may delay puberty in girls, a new study from the US National Institute of Child Health and Human Development has found.
Researchers from the institute analysed the findings of blood samples taken from more than 700 girls aged six to 11. They found that those with elevated levels of lead (five or more micrograms of lead per decilitre of blood) were 75% less likely than those with low levels of lead to have adolescence-related hormones at levels associated with the start of puberty.
This difference in hormone levels was even greater in girls with elevated levels of both lead and cadmium, which can damage the kidneys, lungs and bones and increase the risk of cancer.
Children are usually exposed to lead through old, deteriorating lead-based paint and lead-contaminated dust and soil, while breathing in cigarette smoke is a leading source of cadmium exposure, the researchers noted.
Damage even at low levels
Lead, alone or together with cadmium, may suppress the ovaries' production of hormones that prepare a young girl's body to release an egg (ovulate) for the first time, said researchers.
The US Centers for Disease Control and Prevention advises treatment for blood lead levels higher than 10 micrograms per decilitre, the researchers said, but warned that the findings indicate damage can occur at even lower levels.
"Our findings suggest childhood exposure to lead has worrisome effects as children age and reach adolescence. These issues are of concern in some parts of the United States as well as in countries where children are exposed to leaded gasoline, paint or industrial pollutants," study author Audra L. Gollenberg said.
She and her colleagues also found that lead-related delay of puberty was more common in girls with iron deficiency.
"Iron deficiency appears to be a critical factor in the context of lead exposure. Health-care providers may wish to pay particular attention to the importance of screening for iron deficiency among girls at high risk for exposure to lead," Gollenberg said.
The study appears in the current issue of the journal Environmental Health Perspectives.
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