New research suggests that even low levels of lead exposure may be playing a much larger role in deaths due to heart disease than previously believed.
In a study published this month in the medical journal The Lancet Public Health, researchers from Simon Fraser University in Vancouver estimate that lead exposure contributes to about 412,000 deaths in the United States each year, which is 10 times larger than previous estimates.
Researchers set out to better quantify lead exposure as a risk factor for cardiovascular disease mortality in the U.S., as the link between lead poisoning and heart disease death has been known for some time, but its effects have been poorly defined.
This study looked at data on adults 20 years old or older who enrolled in the Third National Health and Nutrition Examination Survey (NHANES-III) from 1988 through 1994. Resaerchers followed up with 14,289 adults that were part of the study up to December 31, 2011.
Participants completed a medical examination and home interview, and researchers looked for concentrations of lead in the blood, as well as cadmium levels in their urine.
According to the findings, while a blood lead level of 5 μg/dL for adults is generally considered safe, researchers said no level should actually be considered safe. Of the adults involved in the study, 3,632 of them had blood levels exceeding 5 μg/dL. Researchers found that increases in concentration of lead in blood was associated with a significant increase in all causes of death, cardiovascular disease mortality, and ischaemic heart disease deaths.
The study calculated that about 18% of all-cause mortalities in the U.S. had lead as a contributing factor, which translates to about 412,000 deaths annually.
“Our findings suggest that, of 2.3 million deaths very year in the USA, about 400,000 are attributable to lead exposure, an estimate that is about ten times larger than the current one,” the researchers concluded. “The key reason for this difference is because the previous estimate assumed cardiovascular disease was only evident at concentrations of lead in blood as low as 5 μg/dL.”
The findings are similar to concerns over the years over the effects of lead exposure in children. Over time, health experts have had to lower the blood lead levels considered safe, until many say that there is no safe level.
While lead exposure has been linked to heart disease in adults, elevated blood lead levels are an indicator that children may be at risk for side effects of lead poisoning, which can lead to serious nervous system injury, brain damage, seizures, growth or mental disability, as well as other severe health problems throughout the rest of their childhood and life.
One of the more common causes of of lead poisoning is lead-based paint, which was banned in the United States in 1978 due to the risk of severe and permanent brain damage and developmental problems, particularly in children. However, a number of older homes still contain the toxic paint on the walls, and if it flakes or peals off, young children could ingest the paint chips or breathe dust that comes from the paint, resulting in lead poisoning. Many of those homes are owned by HUD or receive HUD assistance.
In recent years, there has also been an increased focus on lead in drinking water, stemming from the recent and ongoing Flint water crisis, during which a change to the water system in the Michigan city resulted in high levels of lead in residents’ drinking water, causing thousands of children to suffer lead exposure and, potentially, lead poisoning.
The U.S. Centers for Disease Control and Prevention (CDC) estimates that 535,000 children ages 1-5, or about 2.6% of such children in the U.S., have levels of lead in their blood that place them at risk for adverse health effects. To come up with that number, the CDC analyzed data from the National Health and Nutrition Examination Survey from the years 1999 to 2002, and 2007 through 2010.
The majority of those children are poor and live in older urban areas, mainly in the inner city. Most are minorities, meaning such exposures add to numerous problems already plaguing inner city black and Latino youths, such as poverty, high crime and poor schools.