Medical researchers have long known that lead-poisoning damages children’s brains and increases the risks of all sorts of health problems from high blood pressure to heart disease. Now new research has found that the deaths of an estimated 250,000 Americans from cardiovascular disease each year may be linked to lead exposure — a number far higher than previous estimates.
The study was based on a national health survey that tracked more than 14,000 participants across the country over nearly two decades. In previous studies, researchers had assumed that low levels of lead in people’s blood wouldn’t increase the risk of death. But the new study found that even minute levels of lead substantially increase the risk of death, especially from heart disease.
“We saw risk down to the lowest measurable levels,” said Bruce Lanphear, a lead-poisoning researcher at Simon Fraser University in British Columbia who led the study. “It’s a big deal and it’s largely been ignored when it comes to cardiovascular disease deaths.”
Lead levels in the air have declined dramatically in the United States since the country began phasing out leaded gasoline in the 1970s. But lead water pipes are still being used in communities scattered across the country, and lead paint remains in many old houses.
Workers at construction sites and auto shops may be exposed to lead. It’s released into the air by coal-fired power plants, lead smelters and other industrial facilities, including recyclers that work with lead batteries. Lead can be found in products like fishing weights, lead-glazed ceramics and some children’s toys. It also continues to turn up in some foods, including baby foods.
The new study, which was published Monday in The Lancet Public Health journal, is the first to estimate the number of deaths in the U.S. linked to low-level lead exposure using data from a nationally representative sample.
Cardiovascular disease is the leading cause of death for Americans, and the study’s findings indicate that lead is a major factor contributing to those deaths. The research focused on 14,289 people who were followed in the national health survey between 1988 and 1994, and again in 2011. Their health data included a blood test for lead.
At the end of the period, 4,422 people had died, including 1,801 from cardiovascular disease, out of which 988 deaths were from coronary heart disease. The researchers adjusted the results for a list of factors such as age, sex, alcohol consumption, smoking and diet, and estimated the proportion of deaths in U.S. adults ages 44 or older whose premature deaths could have been prevented if they hadn’t been exposed to lead.
They estimated that 256,000 deaths — nearly 29 percent of premature deaths from cardiovascular disease — could be linked to lead exposure each year. That included 185,000 deaths from coronary heart disease, or about 37 percent of all deaths from that cause, as well as other types of cardiovascular disease, such as strokes and peripheral artery disease.
Previous studies had assumed that there was no harm when patients had lead at concentrations of less than 50 parts per billion in their blood. About four out of five people in the survey had lead concentrations in their blood below that level, yet their cases still showed increasing risks with incremental rises in lead levels.
Lanphear said the results point to a need for the federal Environmental Protection Agency, as well as other federal and state agencies, to ratchet down the allowable levels of lead under their standards.
“The levels of lead in standards right now are too high to protect kids,” Lanphear said. “And this new study would suggest that they’re too high — whether it’s lead in water, lead in house dust, lead in air — all of those things should be reevaluated based upon this study because it suggests that there’s no safe level of lead.”
Lanphear and his colleagues also looked at deaths from all causes and estimated that about 400,000 deaths per year are attributable to lead exposure in the United States. That’s 10 times larger than the current estimate and about 18 percent of all deaths. It’s also comparable to the approximately 480,000 current smokers who die in a given year.
Those numbers are based on the amounts of lead that older Americans were exposed to decades ago. Lanphear pointed out that most Americans are exposed to less lead nowadays because of lead has been taken out of gasoline and paint.
“So the number of deaths from lead exposure will be lower in younger generations,” he said. “Still, lead represents a leading cause of disease and death, and it is important to continue our efforts to reduce environmental lead exposure.”