Informal lead-acid battery recycling and manufacturing remains a contributory factor for children’s elevated blood lead levels in emerging countries around the world.
The findings were published by Lancet Planet Health following an investigation into the leading sources of lead exposure to people living in 49 developing countries.
An estimated 632 million children in low-income and middle-income countries (LMIC) are estimated to have a blood lead level exceeding 5 μg/dL; and 413 million were estimated to exceed the previous reference value of 10 μg/dL.
Last October, the Centers for Disease Control and Prevention (CDC) updated its blood lead reference value (BLRV) from 5 µg/dL to 3.5 µg/dL in response to the Lead Exposure Prevention and Advisory Committee (LEPAC) recommendation made on May 14, 2021.
The Lancet report stated: “Given the toxicity of lead, even at low amounts of exposure, urgent attention is required to control exposures and to expand population-based sampling in countries with no or scant data.
“Major sources of lead exposure were informal lead acid battery recycling and manufacture, metal mining and processing, electronic waste, and the use of lead as a food adulterant, primarily in spices.”
In Mexico, lead-based ceramic glazes were a significant source of exposure, stated the report.
Lead exposure in LMICs
According to Lancet, reports have suggested that lead exposure remains substantial or is increasing in some LMICs but few studies have attempted to systematically assess blood lead levels over the full range.
Data on blood lead level were extracted and pooled, as appropriate, to make country-specific estimates of the distribution of background blood lead levels among children and adults, along with information on specific sources of exposure where available.
The researchers searched the PubMed database for the 137 countries in the World bank LMIC grouping.
The search yielded 12,695 studies (between 2010 and 2019). There were 520 unique studies included (1,100 sampled populations from 49 countries comprising more than 1 million individuals).
Pooled mean blood lead concentrations in children ranged from 1·66 μg/dL in Ethiopia to 9·30 μg/dL in Palestine; in adults the range went from 0·39 μg/dL in Sudan to 11·36 μg/dL in Pakistan.
Historical causes of exposure
The report noted the greatest historical source of lead exposure was the use of tetraethyl lead as an anti-knocking agent in petrol, which resulted in the dispersion of at least nine million tonnes of lead into the environment.
The global phase-out of leaded petrol began in the US during 1975, and was progressively adopted by high-income countries (HICs) in the 1980s and 1990s.
As a result, the average level of lead in the blood for people aged 1–74 years in the US decreased by 78%, from 12·8 μg/dL to 2·8 μg/dL; similar decreases were noted in other HICs such as Sweden and Germany between 1976 and 1991.
Phase-outs were slow to be adopted in LMICs, but by the end of 2005 nearly all had eliminated use of leaded petrol in automobiles.
Image: Pooled mean background blood lead levels in children in 34 low-income and middle-income countries with available data