Lead Exposure May Have Caused IQ Loss In Kids Under 5 Years, 5.5 Million Adult Cardiovascular Deaths: Study In Lancet

Lead exposure impact: About 95 per cent of the impacts of lead exposure were observed in people living in low- and middle-income countries, a new study published in The Lancet Planetary Health said.

Lead exposure may have resulted in the loss of 765 million IQ points in children under five years of age, and about 5.5 million cardiovascular disease deaths in adults globally in 2019, new analysis has suggested. About 95 per cent of these impacts of lead exposure were observed in people living in low- and middle-income countries, a new study published in The Lancet Planetary Health has said. Children living in low- and middle-income countries lost an average of 5.9 IQ points during their first five years of life. The way lead exposure affects one's health could be similar to the way particulate matter 2.5 (PM2.5), outdoor and indoor air pollution affect one's health. The effect of lead exposure on global health is three times greater than the health effects of unsafe drinking water, sanitation, and handwashing, the study said. 

Compared to a previous estimate, IQ loss in low- and middle-income countries due to lead exposure was found to be nearly 80 per cent higher, and cardiovascular disease deaths in adults were six times higher. 

What makes the study unique?

The study is unique because it is the first to estimate the global health burden and cost due to lead exposure, in terms of IQ loss and cardiovascular disease deaths in both low- and middle-income countries, and High-Income Countries. 

Another reason why this study is unique is that it looked at the health impacts and economic costs of IQ loss in children, and cardiovascular disease deaths in adults, as a result of lead exposure.

Previous studies only focused on IQ loss in children living in low- and middle-income countries, and analysed only those lead exposure-linked cardiovascular disease deaths that are caused by increased blood pressure. 

Global cost of lead exposure in 2019 equivalent to 7% of global GDP

In 2019, the global cost of lead exposure was around US$6 trillion, which is equivalent to seven per cent of the global Gross Domestic Product (GDP). The cost of lead exposure in 2019 in low- and middle-income countries was equivalent to more than 10 per cent of the global GDP. The cost of lead exposure in the low- and middle-income countries was twice as high as the cost of lead exposure in High-Income Countries (HICs). 

Low- and middle-income countries suffer the most from lead exposure

It is mostly the low- and middle-income countries that suffer from the health impacts and economic costs brought on by lead exposure. This highlights an urgent need to improve the monitoring of lead exposure, and the identification of exposure sources, especially in low- and middle-income countries. Also, public health policies must be implemented to ensure that the health impacts of lead exposure in people living in low- and middle-income countries are minimised. 

The study has indicated that the impact of lead exposure on cardiovascular disease deaths and IQ loss on a global level is far greater than what previous estimates suggest. 

Why are young children the worst affected by lead exposure?

Young children are the ones worst affected by lead exposure. This is because lead exposure damages their brain, slows brain development, and makes it difficult for them to learn things. 

How are adults affected by lead exposure?

Adults are at an increased risk of cardiovascular disease deaths due to lead exposure. Cardiovascular disease deaths account for almost 95 per cent of all deaths linked to lead exposure. Apart from cardiovascular disease deaths, adults are also at risk of chronic kidney disease and learning disabilities due to lead exposure. 

What are the major sources of lead exposure?

While lead-containing petrol has been phased out around the world, exposure to lead still elevates the risk of certain diseases on a global level, especially in low- and middle-income countries. Lead acid battery recycling, food, soil, dust, cookware from recycled materials, spices, cosmetics, fertilisers, metal mining, leaded paint, lead-glazed pottery and ceramics, toys, electronic waste, and cultured fish feed are the major sources of lead exposure. 

How the study was conducted

Different countries have varying levels of these sources of lead exposure. Also, different sources of lead exposure affect population blood lead levels (BLLs) differently. Therefore, a better understanding of how the different sources of lead exposure affect BLLs in low- and middle-income countries is important to devise effective exposure mitigation plans. 

As part of the new study, researchers used BLL estimates from the Global Burden of Disease (GBD) 2019 study. Using these estimates, they have tried to obtain insights into the global health impacts and costs of lead exposure. 

The authors obtained BLL estimates from 183 low- and middle-income countries and High-Income Countries, which account for 99.9 per cent of the world's population. 

What were the average blood lead levels in different countries?

In low- and middle-income countries, the average BLL was found to be 4.6 micrograms per decilitre, and that in High-Income Countries was found to be 1.3 micrograms per decilitre, in 2019. 

The lowest average BLLs were seen in people living in North America, Europe, and Central Asia, and the highest average BLLs were seen in people living in South Asia, Sub-Saharan Africa, the Middle East, and North Africa. 

The factors taken into consideration to analyse cardiovascular disease deaths linked to lead exposure were damages to the heart and arteries, and increased incidence of stroke. 

Lead exposure accounted for 30% of all cardiovascular disease deaths

The fact that lead exposure is likely to have caused 5.5 million cardiovascular disease deaths in adults in 2019, on a global level, means that lead exposure accounted for 30 per cent of all cardiovascular disease deaths. 

About 90 per cent of the 5.5 million cardiovascular disease deaths occurred in low- and middle-income countries.

An important point to note is that the analysis did not take into consideration high blood pressure as a factor involved in the cardiovascular disease deaths caused by lead exposure, and did not focus on how lead exposure is responsible for increased risk of deaths from causes other than cardiovascular diseases. This means that the actual number of deaths linked to lead exposure will be substantially higher than 5.5 million. 

95% IQ losses in children under five years of age due to lead exposure occurred in low- and middle-income countries

Of the 765 million IQ points lost in children under five years of age in 2019, 95 per cent losses occurred among children in low- and middle-income countries. 

Statistics of the estimated economic cost of lead exposure

About 77 per cent of the estimated economic cost of lead exposure was associated with cardiovascular disease deaths, and about 23 per cent was linked with predictions of lower future income caused by IQ loss, the study said.

Limitations to the study

Some of the limitations to the study include the fact that the authors relied on global estimates of BLLs because nationwide measurements were not available for many countries.