'Safe' Blood Lead Levels Linked To Risk Of Death

Researchers studied lead levels below 10 micrograms per deciliter (µg/dL) which previously has been considered safe.

The levels studied are common and considerably lower than lead levels perceived by the government as a concern to public health, said Paul Muntner, Ph.D., author of the study and an associate professor of epidemiology and medicine at Tulane University School of Public Health and Tropical Medicine in New Orleans.

"Our study found the association of blood lead with cardiovascular death to be evident at levels as low as 2 ìg/dL," he said. "Since 38 percent of U.S. adults had lead levels above 2 ìg/dL in 1999--2002, the public health implications of these findings are substantial."

The Occupational Safety and Health Administration (OSHA) defines high blood lead in adults as higher than 40 µg/dL. The Centers for Disease Control and Prevention recommend that women of child-bearing age have blood lead levels below 10 µg/dL.

Researchers said the study questions the current belief about what lead levels are safe in the population.

"We wanted to know whether there was an association between the current blood lead levels among U.S. adults and coronary heart disease, stroke or cancer," Muntner said.

Since the mid-1970s, when lead was no longer added to gasoline or household paint and lead was banned for use in soldering food cans, average blood lead levels in American adults have decreased from 13.1 µg/dL to 1.6 µg/dL.

"Even though lead levels are much lower than before, the current levels are still orders of magnitude higher than pre-industrial levels," Muntner said.

Today lead is mostly used to make batteries. It is also used to make ammunition (bullets), pipes and roofing materials. According to OSHA, exposure to lead can occur in at least 120 occupations including lead smelting, battery manufacturing, ship building/repair, auto manufacturing and printing. Breathing contaminated air, eating contaminated food or soil, or drinking contaminated water are ways people can be exposed to lead. Inhalation of airborne lead is generally the most significant source of occupational lead absorption.

The researchers used data from the Third National Health and Nutrition Examination Survey Mortality Follow-Up Study, involving 13,946 adults whose blood lead levels were collected and measured between 1988 and 1994.

When researchers studied those who died by Dec. 31, 2000, they found that death from any cause, cardiovascular disease, heart attack and stroke increased progressively at higher lead levels.

Compared to participants with blood lead below 1.9 µg/dL, participants with blood lead between 3.6 µg/dL and 10 µg/dL had:

• a 25 percent higher risk of death from any cause
• a 55 percent higher risk of death from cardiovascular diseases
• an 89 percent higher risk of death from heart attack
• two and a half times the risk of death from stroke

"The increased risk of all-cause and cardiovascular deaths with increased lead levels affected all groups we studied: non-Hispanic whites, non-Hispanic blacks and Mexican Americans, as well as males and females," Muntner said. "The risk of death from cancer did not increase at the blood lead levels that our study investigated.

"Our study had limited ability to evaluate the risks of lead exposure associated with blood lead levels below 2 µg/dL. Future research is needed to identify the level of lead exposure that is not associated with major health outcomes. Although markedly reduced, the current blood lead levels may not be low enough, and we believe that practical and cost-effective methods for reducing lead exposure in the general U.S. population are needed."

Co-authors are: Andy Menke, M.P.H.; Vecihi Batuman, M.D.; Ellen K. Silbergeld, Ph.D.; and Eliseo Guallar, M.D., Dr.P.H. The National Institutes of Health partially funded the study.