Magazine article Science News

Blood-Lead Climbs as Old Bones Decline

Magazine article Science News

Blood-Lead Climbs as Old Bones Decline

Article excerpt

Blood-lead climbs as old bones decline

Young children tend to suffer more from lead's toxic effects--ranging from IQ deficits to gastrointestinal distress--than their parents do. But two new studies suggest an adult's reduced lead sensitivity is a transient stage that diminishes and may even disappear in the elderly. Reported last week at a federally sponsored lead conference in Columbia, Md., these and other new findings are contributing to a growing appreciation of bones' role in lead toxicity.

Though the body may store 95 percent of its lead burden in bone, physicians usually gauge contamination by blood levels -- that circulating pool of the contaminant available to poison soft tissues such as the brain. In fact, scientists have generally considered bone's sequestration of lead as a detoxifying mechanism. However, data now indicate bone is anything but a permanent, inert lead-storage site.

How long the skeleton binds lead depends largely upon bone type, researchers from the University of Lund Hospital in Sweden reported at the conference. Their X-ray fluorescence assays of male lead-smelter workers put the usual half-life of lead in spongy bone, like vertebrae, at less than five years, while its half-life in dense, compact bone, like fingers, can last two to four times longer.

However, certain physiological conditions -- mainly pregnancy, lactation and menopause -- can foster dramatice bone loss. To indirectly investigate the effects on lead release, researchers from the Environmental Protection Agency, the National Institute of Environmental Health Sciences and the Environmental Defense Fund compared blood-lead levels recorded in 2,981 U.S. women during the second National Health and Nutrition Evaluation Survey (NHANES II). They found that women who never had children -- and therefore never shed significant bone and bone-bound lead to developing offspring -- carry far more lead into old age than those who had been pregnant. …

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