Reduced Blood Lead Levels Tied to Lower Blood Pressure: Study

The reduction in lead exposure positively affects blood pressure in the study population, suggesting consequential improvements in heart health.

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Long-term decline in the blood lead levels of American Indians has been found to improve the population’s cardiovascular health, including reduced blood pressure levels, a new study reports.

According to the research, supported by the National Institutes of Health (NIH) and published in the Journal of the American Heart Association, adults with the greatest reductions in blood lead levels saw their systolic blood pressure fall by about 7 millimeters of mercury (mm Hg).

In children, lead exposure damages the brain and nervous system while slowing growth and development. Additionally, it has been linked to increased risks for heart disease in adults. The U.S. Food and Drug Administration (FDA) notes that while lead is found naturally in the environment, there is no known safe level of exposure. It is also impossible to completely prevent lead from entering the food supply.

For the Strong Heart Family Study, an extension of the Strong Heart Study, the most comprehensive study on cardiovascular health and risk factors among American Indian adults, the research team partnered with 285 American Indian adults. The participants live in tribal communities in Arizona, Oklahoma, North Dakota, or South Dakota, where communities have historically been exposed to high lead levels. Lead exposure happened through myriad ways, the team noted, including well water, local waterways, paint, dust, and consumption of canned goods, herbs, and spices.

The research team examined the participants’ historical medical data, including blood lead levels and blood pressure readings. Specifically, they compared data collected between 1996 and 1997 with that from 2006 to 2009. At the beginning of the study, the average blood lead level was 2.04 microliters per deciliter (µg/dL). Throughout the study, the average blood lead level dropped by 0.67 µg/dL, or roughly 33 percent. In the most significant cases, blood lead levels of patients with a baseline of 3.21 µg/dL experienced a 55 percent reduction of 1.78 µg/dL over time. The drop was linked to a 7 mm Hg reduction in systolic blood pressure.

“This is a huge win for public health, especially since many American Indians can face higher risks for elevated lead levels,” Anne E. Nigra, the senior study author and an assistant professor of environmental health sciences at Columbia University Mailman School of Public Health in New York, said in an NIH press release. “Compared to the general U.S. population, American Indian communities experience both a higher burden of cardiovascular disease and elevated metal exposure. We saw that even small decreases in a person’s blood lead levels can have meaningful health outcomes.”

Policy Changes Account for Drop in Lead Levels

The drop in lead levels is most likely attributed to public health policies implemented in recent years to reduce lead exposure through everyday items, such as water and plumbing, and bans on lead in paint, gasoline, and canned food. The study noted that canned foods, which used to be soldered with lead, are commonly consumed on American Indian reservations.

For example, in 1991, the Environmental Protection Agency (EPA) implemented a rule to control both lead and copper in drinking water. Known as the Lead and Copper Rule, it prohibits lead concentrations in public drinking water from exceeding 15 parts per billion (ppb) and requires action if that level is surpassed.

The team noted that “lead exposure remains an important concern in American Indian communities” despite the observed decline. In some areas of North Dakota and South Dakota where lead exposure persists in private and public water systems, American Indian communities have higher blood lead levels than those in Arizona and Oklahoma.

“More research needs to be done to determine how environmental agents exacerbate cardiovascular and other diseases, and more needs to be done to improve the environmental health of American Indians,” said Lindsey A. Martin, a health science administrator at the National Institute of Environmental Health Sciences (NIEHS), also part of the NIH.