March 25, 2003 -- Exposure to lead at levels well below federal safety standards may still be enough to raise the blood pressure of older women. A new study shows that women approaching menopause as well as postmenopausal women may be especially vulnerable to the long-term effects of lead exposure and have an increased risk of hypertension, the leading cause of heart disease death.
Lead exposure, as measured by lead levels found in the blood, has already been linked to elevated blood pressure and an increased risk of hypertension in men. But researchers say women may experience a surge in blood lead levels during menopause and perimenopause (pre-menopause) as skeletal stores of lead are released during periods of bone loss, which is greatly accelerated during this transition.
The study, published in the March 26 issue of The Journal of the American Medical Association, found high blood lead levels among more than 2,000 women aged 40 to 59 were significantly related to blood pressure levels and the risk of hypertension.
For example, women who had the highest blood lead levels were more than three times as likely to have elevated diastolic (the bottom number in a blood pressure reading) pressure than those who had the lowest blood lead levels.
The diastolic reading measures the resting pressure in between beats. The systolic blood pressure is the pressure of blood in the artery when the heart contracts.
Researchers say the risks of high blood pressure linked to lead exposure were especially pronounced among postmenopausal women. In these women, blood lead levels were a significant predictor of both elevated diastolic and systolic (the top number in a blood pressure reading) blood pressure.
Comparing women who had the lowest blood lead levels with those who had the highest, the study found the difference in lead levels was associated with a difference in 1.7 mm Hg in systolic blood pressure and 1.4 mm Hg in diastolic blood pressure.
"From a public health perspective, the most important and troubling finding is that lead appears to increase blood pressure in women at very small increments above 1.0 ug/dL, well below what is considered deleterious in adults," writes researcher Denis Nash, PhD, MPH, of the University of Maryland School of Medicine and colleagues.
"These results demonstrate effects of lead at levels less than the U.S. occupational blood lead exposure limits (40 ug/dL) and even less that the current Centers for Disease Control and Prevention level of concern for preventing lead poisoning in children (10 ug/dL)," they conclude.
Researchers say the study provides support for continued efforts to reduce lead levels in the general population, especially among women.
Potential sources of lead exposure include having lead-based paint in the home, living near a lead smeltering plant, or working in a battery manufacturing or welding facility.
SOURCE: The Journal of the American Medical Association, March 26, 2003.