Lead Exposure May Cause Cataracts

Common sources of lead include leaded gasoline paint water contamination and air pollution. A study has found a link between lead exposure and the development of cataracts in older men adding to the list of harmful effects blamed on the heavy metal. To measure the men s long-term cumulative exposure to lead the researchers analyzed their shin bones where lead is believed to remain for up to 20 years.

The men with the highest lead levels were found to be 2.7 times more likely to have cataracts than those with the lowest levels. "These are to our knowledge the first data suggesting that accumulated lead exposure such as that commonly experienced by adults in North America may be an important unrecognized risk factor for cataract " said the researchers led by Debra Schaumberg assistant professor of medicine and ophthalmology at Harvard Medical School.

The researchers said the highest levels of lead were not outside the range of what would be found in the general North American population of older adults. The study gave no information about how the participants were exposed to lead but common sources include leaded gasoline paint water contamination and air pollution.

Nearly every North American adult has accumulated some lead in the bones which reflect long-term exposure. By contrast lead levels in the blood reflect more recent exposure. And the researchers found no connection between cataracts and the lead levels in the study participants blood.

The study of 795 men (age 60 and older) appears in the latest Journal of the American Medical Association. Cataracts were identified in 122 of the men. The researchers theorized that over time lead may contribute to a change in the cells that make up the eye lens resulting in the clouding that characterizes cataracts. Cataracts affect nearly 25 million North Americans 65 and older and are one of the world s leading causes of blindness. Advancing age smoking diabetes and excessive exposure to sunlight are known risk factors. Surgery can prevent vision loss.

Previous studies have linked lead exposure with high blood pressure and dementia in adults. Lead can hamper children s development and at high levels cause mental retardation and death. Environmental health researcher Ellen Silbergeld of Johns Hopkins University s Bloomberg School of Public Health called the study extremely interesting. But she said one drawback is that the researchers could not pinpoint whether the increased risk was associated with exposure to lead at a key moment in life or to chronic exposure.

With files from ABC News