Lead exposure causes far more death, IQ loss than we thought

The detrimental impact of lead exposure could be far greater than previous estimates suggest, with lead causing 5.5 million adult deaths from cardiovascular disease and the loss of 765 million IQ points in children under the age of five in 2019.

That’s according to new analysis published in The Lancet Planetary Health, which states that the global health effects of lead exposure are on a par with PM_2.5 outdoor ambient and household air pollution combined, and three times greater than those posed by unsafe drinking water, sanitation and handwashing.

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. But 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 order to develop effective exposure mitigation plans.

No previous research had assessed the global health impacts and economic costs of IQ loss in young children and cardiovascular disease deaths in adults caused by exposure to lead: previous research on IQ loss was limited to LMICs and based on estimates of BLLs more than a decade old, while previous studies of cardiovascular disease deaths linked to lead exposure had looked only at those caused by increased blood pressure. The authors of the new research used BLL estimates from the Global Burden of Disease (GBD) 2019 study, which provides estimated average BLLs in 183 LMICs and high-income countries (HICs) — accounting for 99.9% of the world’s population.

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 damage 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 also 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%.

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; in comparison, the World Bank estimates that the combined cost of PM_2.5 outdoor ambient and household air pollution in 2019 was equivalent to 6% of global GDP. The cost of lead exposure was more than 10% of GDP in LMICs compared to 5% in HICs, due to higher BLLs in LMICs, and around three-quarters of this cost was associated with cardiovascular disease deaths (with one-quarter due to predictions of lower future income caused by IQ loss).

“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,” said lead author Bjorn Larsen. “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 PM_2.5 outdoor ambient and household air pollution.”

Image credit: iStock.com/RonBailey