THE LANCET PLANETARY HEALTH: Cardiovascular disease deaths and IQ loss caused by lead exposure far higher than previous estimates, global study indicates

Peer-reviewed / Modelling study / People

• New analysis indicates exposure to 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. Up to 95% of the effects were in low and middle-income countries (LMICs), with children in LMICs losing an average of 5.9 IQ points during their first five years of life.
• The findings indicate 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.
• IQ loss in LMICs due to lead exposure is nearly 80% higher than a previous estimate, while deaths from cardiovascular disease are six times higher.
• The global cost of lead exposure in 2019 was estimated to be US$6 trillion, equivalent to 7% of global GDP. In LMICs, it was equivalent to more than 10% of GDP, or twice as high as in High-Income Countries (HICs).
• The overwhelming majority of health impacts and economic costs from lead exposure are in LMICs, highlighting an urgent need for improved monitoring of exposure and exposure source identification, accompanied by relevant legislative responses and public health policies. 

The impact of lead exposure on cardiovascular disease deaths and IQ loss worldwide could be far greater than previous estimates suggest, according to analysis published in The Lancet Planetary Health journal.  

The new analysis indicates the global health effects of lead exposure are on a par with PM2.5 outdoor ambient and household air pollution combined, and three times greater than those posed by unsafe drinking water, sanitation, and handwashing. 

The study is the first to estimate lead exposure’s global health burden and cost in terms of IQ loss and deaths from cardiovascular disease in both LMICs and HICs. 

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.

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 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, 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 (BLLs) needs to be better understood in most LMICs in order 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.” [1]

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 in children was limited to LMICs and based on estimates of BLLs – the most common indicator of exposure – more than a decade old. Previous global studies of cardiovascular disease deaths linked to lead exposure had looked only at those caused by increased blood pressure. 

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] This provides estimated average BLLs in 183 LMICs and HICs, accounting for 99.9% of the world’s population. 

The average BLL in LMICs was 4.6 μg/dL, compared with 1.3 μg/dL in HICs. People in North America and in Europe and Central Asia had the lowest average BLLs, with the highest among people in South Asia, the Middle East and North Africa, and Sub-Saharan Africa.

They 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 (e.g., 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. 

The analysis also suggests that 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. 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. 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. [3]

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 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. 

NOTES TO EDITORS

This study was funded by the Korea Green Growth Trust Fund and the World Bank’s Pollution Management and Environmental Health Program. It was conducted by researchers from the World Bank.

[1] Quote direct from author and cannot be found in the text of the Article.
[2] https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30925-9/fulltext 
[3] https://openknowledge.worldbank.org/server/api/core/bitstreams/550b7a9b-4d1f-5d2f-a439-40692d4eedf3/content 

The labels have been added to this press release as part of a project run by the Academy of Medical Sciences seeking to improve the communication of evidence. For more information, please see: http://www.sciencemediacentre.org/wp-content/uploads/2018/01/AMS-press-release-labelling-system-GUIDANCE.pdf if you have any questions or feedback, please contact The Lancet press office pressoffice@lancet.com  

IF YOU WISH TO PROVIDE A LINK FOR YOUR READERS, PLEASE USE THE FOLLOWING, WHICH WILL GO LIVE AT THE TIME THE EMBARGO LIFTS: https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(23)00166-3/fulltext