Lead exposure likely behind 5.5 million CVD deaths: study

Cardiovascular disease (CVD) deaths and IQ loss caused by lead exposure could be far higher than previous estimates, according to analysis published in The Lancet Planetary Health.

The analysis indicates that lead might have caused 5.5 million adult deaths from cardiovascular disease and the loss of 765 million IQ points in children under the age of five worldwide in 2019.

The global health effects of lead exposure could be similar to the estimated health effects of PM2.5 outdoor ambient and household air pollution combined, and three times greater than the health effects of unsafe drinking water, sanitation and handwashing, the study suggests.

Exposure to lead can seriously harm young children’s health, including damage to the brain, slowed development and learning difficulties. In adults, lead exposure can increase people’s risk of cardiovascular disease — which accounts for almost 95% of deaths linked to lead exposure — as well as chronic kidney disease and learning disabilities.

Exposure sources

Despite the fact that lead-containing petrol has been phased out around the world, exposure to the toxic metal still poses major global health risks, especially in low- and middle-income countries (LMICs).

Key sources of exposure include lead acid battery recycling, metal mining, food, soil and dust, leaded paint, cookware from recycled materials, lead-glazed pottery and ceramics, spices, toys, cosmetics, electronic waste, fertilisers 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 (BLLs) needs to be better understood in most LMICs to develop effective exposure mitigation plans.

Lead author Bjorn Larsen said: “We know that lead exposure has continued to cause huge impacts on human health, despite most countries banning the use of leaded petrol more than 20 years ago. What is concerning about our study is that it indicates these damaging health effects are much greater than we previously thought and that they come at a very high economic cost, especially in low- and middle-income countries. Efforts to address the impacts of lead exposure must reflect that these are as significant as those posed by PM2.5 outdoor ambient and household air pollution.”

The true number of deaths

The authors analysed the data using a health impact model that estimated lead exposure’s effect on deaths from cardiovascular disease caused by factors other than high blood pressure, including damages to the heart and arteries (eg, atherosclerosis) and increased incidence of stroke. A model was also used to estimate global IQ loss from lead exposure in the entire child population aged 0–4 years and to estimate the cost of cardiovascular disease deaths and IQ loss due to lead exposure.

The analysis estimates that lead exposure contributed to 5.5 million deaths from cardiovascular disease globally in 2019, or 30% of all cardiovascular disease deaths. This is more than six times higher than the GBD 2019 estimate of 850,000 CVD deaths from lead exposure. Of the 5.5 million deaths from lead exposure, 90% were in LMICs. As the analysis did not include deaths from high blood pressure — and because lead exposure also increases the risk of dying from causes other than cardiovascular disease — the true number of deaths linked to lead exposure may be substantially higher.

Lead exposure caused the loss of 765 million IQ points in children under five years old in 2019, with 95% of the losses among children in LMICs, the analysis suggests. During their first five years of life, children in LMICs on average each lose 5.9 IQ points from lead exposure. The authors estimate this can reduce these children’s total lifetime income by as much as 12%.

Economic impact

Analysis of the economic impact of lead exposure indicates it might have cost US$6 trillion worldwide in 2019, equivalent to 7% of global GDP. The cost was more than 10% in LMICs compared to 5% in HICs, due to higher BLLs in LMICs. The World Bank estimated that the combined cost of PM2.5 outdoor ambient and household air pollution in 2019 was equivalent to 6% of global GDP. ¹

More than three-quarters of the estimated economic cost (77%) of lead exposure was associated with cardiovascular disease deaths, with around a quarter (23%) due to predictions of lower future income caused by IQ loss.

The authors acknowledge some limitations to their study. These mainly revolve around the accuracy of global estimates of BLLs, as nationwide measurements are not available for many countries, particularly LMICs. The authors of the new study used BLL estimates from the Global Burden of Disease (GBD) 2019 study to estimate the global health impacts and costs of lead exposure.² The BLL estimates in the GBD 2019 study are based on a combination of 554 studies in 84 countries from 1970 to 2017 and modelling of BLLs.

1. https://openknowledge.worldbank.org/server/api/core/bitstreams/550b7a9b-4d1f-5d2f-a439-40692d4eedf3/content
2. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30925-9/fulltext

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