U.S. Water News Online
WASHINGTON -- According to two studies recently published by The Journal of the American Medical Association, lead may be even more dangerous than previously thought, causing high blood pressure and kidney impairment at unexpectedly low levels.
The authors of these studies, both made on adult men, suggest current safety standards for lead exposure in both adults and children may need to be further tightened.
The men studied, who ranged from middle-aged to elderly, had the same exposure to lead as most Americans had in the past 40 or 50 years, said Dr. Howard Hu, a researcher at the Harvard School of Public Health and a co-author of both studies. The men in the study were participants in a long-term study on aging conducted by the Department of Veterans Affairs, giving researchers considerable data about their health.
"Few of them had occupational exposures," Hu said. Rather, they had picked up lead from other sources in the environment, including lead-soldered food cans and water pipes, and fumes from leaded gasoline.
In the first study of 590 men, Hu's research team found a connection between high blood pressure and the amount of lead in the shinbone. They used the bone level rather than a blood test because bone more accurately reflects long-term lead exposure. That is because lead slowly accumulates in bone and stays there long after it leaves the bloodstream, providing evidence of what happened in the past, according to researchers.
The lead level proved more closely linked to hypertension than several other factors that have been implicated in other studies, including smoking, alcohol, and salt in the diet.
"I think the study has two ramifications for public health," Hu said. "First, it might be possible that we could treat certain cases of hypertension by neutralizing lead in the body, with drugs called chelating agents, which remove lead and other metals." But Hu explained this would only work if lead were still playing an active role, not if a permanent effect had already occurred.
The second implication of the study concerns federal standards for exposure. "Adults can now have four times the lead exposure of kids," Hu said. "Maybe that should be revised." Children should have a blood level under 10 micrograms per deciliter. For adults, the Occupational Safety and Health Administration (OSHA) says up to 40 or 50 micrograms is acceptable.
"The men in our study probably have levels well under the OSHA standard," Hu said, "but we feel the lead is contributing to their hypertension. Maybe it's time to rethink the OSHA standard."
The other study found that increasing levels of lead in the blood, even within a range considered low, impaired kidney function in adult men.
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