A new study conducted by the U.S. National Institute of Child Health and Human Development suggests that exposure to lead in early childhood could delay puberty amongst girls.

A team of researchers at the institute collected and analyzed the blood samples taken from more than 700 girls in the six to 11 age groups. They found that those with a high level of lead in their blood were at a higher risk of having a late start to their puberty.

The study found that children who had five or more micrograms of lead per deciliter of blood were seen to have a 75 percent lower chance than those with low levels of lead to get adolescence-related hormones at levels that signal the start of puberty.

The study, published in the latest issue of Environmental Health Perspectives, found that the difference in hormone levels was greater among girls with elevated levels of both lead and cadmium, elements that could damage the kidneys, bones and lungs too.

The usual suspects of lead exposure are old lead-based paint and lead-contaminated dust and soil. In addition, children who inhale second-hand smoke from cigarettes could also end up with cadmium exposure.

The researchers concluded that exposure to lead, with or without cadmium, could suppress the production of hormones in the ovaries that causes ovulation for the first time.

"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," says study author Audra L. Gollenberg in press release.

The team also found that lead-related delay of puberty was more common among girls diagnosed previously 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.