Global lead exposure greater CVD risk factor than smoking, cholesterol
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Key takeaways:
- Modeling data suggest more than 5.5 million adults worldwide died of CVD due to lead exposure in 2019.
- More than 90% of those deaths occurred in low- and middle-income countries.
World Bank data suggest lead exposure in 2019 alone was attributable to more than 5.5 million CVD deaths and the loss of 765 million IQ points for young children globally, with the greatest impact in low- and middle-income countries.
Although global lead exposure has declined substantially since the phasing out of leaded gasoline, sources of lead exposure remain plentiful, especially in low-income and middle-income countries, Bjorn Larsen, an international development economist and consultant to the World Bank, and Ernesto Sanchez-Triana, PhD, global lead for pollution management and circular economy for the World Bank, wrote in The Lancet Planetary Health.
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“Global exposure to lead, especially in low- and middle-income countries, has substantially larger health effects in both children and adults than previously understood,” Larsen told Healio. “The estimated magnitude and cost brings lead exposure to the top of the list of environmental health risk factors along with PM2.5 ambient and household air pollution. As a recognized risk factor for CVD, our estimates suggest that lead exposure may be the third largest CVD risk factor after hypertension and dietary risks, ahead of tobacco smoking and cholesterol.”
Novel health impact model
In a modeling study, Larsen and Sanchez-Traina assessed country blood lead level estimates from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019. The researchers estimated IQ loss in the global population of children younger than 5 years using the blood lead level-IQ loss function from an international pooled analysis. Researchers also estimated the cost of IQ loss, calculated only for the proportion of children expected to enter the labor force, as the present value of loss in lifetime income from the IQ loss (presented as cost in U.S. dollars and percentage of gross domestic product with a range).
Researchers then estimated CV deaths due to lead exposure among people aged 25 years or older using a health impact model that captures the effect of lead exposure on CVD mortality, mediated through mechanisms other than hypertension.
All estimates were calculated by World Bank income classification and region (for low-income and middle-income countries only) for 2019.
The findings were published in The Lancet Planetary Health.
Children younger than 5 years lost an estimated 765 million (95% CI, 443 million-1.098 billion) IQ points and an estimated 5,545,000 (95% CI, 2,305,000-8,271,000) adults died of CVD in 2019 due to lead exposure.
“The estimate of the global health burden of lead exposure in this study places lead exposure as an environmental risk factor at par with PM2.5 ambient and household air pollution combined, and ahead of unsafe household drinking water, sanitation and handwashing,” the researchers wrote. “This finding is in contrast to that of GBD 2019, which ranked lead exposure as a distant fourth environmental risk factor, due to not accounting for IQ loss in children, other than idiopathic developmental intellectual disability in a small subset of children and reporting a substantially lower estimate of adult CVD mortality.”
Models also demonstrated that 95.3% of the total global IQ loss and 90.2% of the total CVD deaths due to lead exposure occurred in low- and middle-income countries.
“CVD deaths were six times higher than the GBD 2019 estimate,” the researchers wrote.
High cost of lead exposure
Globally, the cost of lead exposure was $6 trillion in 2019, equivalent to 6.9% (95% CI, 3.1-10.4) of the global gross domestic product. Of that cost, an estimated 77% was the welfare cost of CVD mortality and 23% was the present value of future income losses from IQ loss, according to the researchers.
“The first and foremost priority is institutionalizing routine nationwide blood lead level measurements in both children and adults in low- and middle-income countries as well as in high-income countries without routine measurements,” Larsen told Healio. “This must be accompanied by comprehensive identification of sources of lead exposure, especially in locations and regions with elevated blood lead levels.”
Larsen noted that sources of lead exposure — and their relative contribution to blood lead levels — are far from adequately understood in low- to middle-income countries but include lead acid battery recycling, metal mining, food, soil and dust, water, leaded paint, cookware from recycled materials, lead-glazed pottery and ceramics, spices, toys, cosmetics, electronic waste, fertilizers and cultured fish feed.
“The presence of each of these sources varies greatly across countries, and each source’s contribution to population blood lead levels needs to be better understood in most low- to middle-income countries in order to develop effective exposure mitigation plans,” Larsen told Healio.
For more information:
Bjorn Larsen can be reached at bl@bjorn-larsen.com.
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