CHICAGO — Bone loss at menopause can cause elevated blood-lead levels that may increase women's risk of high blood pressure, a study found.
Previous studies have linked lead exposure in men with high blood pressure. But the new research is the first to suggest that thinning bones can release lead acquired from decades-earlier exposure and cause health problems, said co-author Ellen Silbergeld, an environmental health researcher at Johns Hopkins University's Bloomberg School of Public Health.
Lead exposure from paint, water, air pollution and other environmental sources elevates blood-lead levels and in large doses can cause poisoning, especially in children. The metallic chemical ultimately accumulates in bones, and in low-level exposure may remain there for decades without serious effects.
But when aging bones start to thin, lead can leak back into the blood, where it is more likely to cause damage, the researchers said.
"Loss of bone at menopause can essentially result in a latent or re-exposure to lead," said Denis Nash, the lead author and a researcher with New York City's health department.
About one-fourth of the study participants had the highest blood-lead levels — averaging 6.4 micrograms per deciliter. They were 40 percent more likely to have high blood pressure than those with the lowest blood-lead levels, 1 microgram per deciliter on average.
That suggests lead in the blood has a damaging effect on blood pressure even when it's below the government's "level of concern" for childhood exposure, 10 micrograms per deciliter, Nash said. The federal limit for occupational exposure is 40 micrograms per deciliter.
Low levels of lead exposure and hypertension are both common in U.S. adults, so "even if lead is not a main cause of hypertension, it could still be responsible for a significant number of cases of hypertension in the general population," Nash said.
The study appears in Wednesday's Journal of the American Medical Association.
The researchers examined data on 2,165 women aged 40 to 59 who participated in a national health survey conducted from 1988 to 1994.
Even though Americans' blood-lead levels have fallen in recent decades with efforts to remove lead from environmental sources including paint and gasoline, the study underscores reasons to remain concerned about lead exposure, said Dr. Howard Hu of Harvard's School of Public Health.
"It's a pretty important paper," said Hu, who was not involved in the research. "The issue of bone as a source of lead that will cause problems later in life is a huge issue."
Hu's own research suggests that getting adequate amounts of calcium might offset lead's damaging effects on blood pressure.