Informal recycling of used lead-acid batteries accounts for roughly 33 percent of all lead exposure in low- and lower-middle-income countries, according to a new working paper from the Center for Global Development (CGD). That figure doubles the previous estimate of about 15 percent and reframes what policymakers had treated as a secondary exposure pathway as the single largest known driver of the global lead burden.

The uncertainty band is wide. Monte Carlo simulations across 50,000 runs place the 95 percent confidence interval between 20 percent and 90 percent of the burden, with the 80 percent interval spanning 26 percent to 71 percent. Every scenario, however, exceeds prior estimates. The direction of the finding is unambiguous even where the precision is not.

The numbers behind the burden

Translated into health outcomes using the Institute for Health Metrics and Evaluation's GBD 2023 lead exposure estimates, a 33 percent share equals eight million disability-adjusted life years, 800,000 deaths per year, and 180 million IQ points lost annually across low- and lower-middle-income countries.

Lead-acid batteries still start most vehicles on the road worldwide, and the value of the lead they contain drives extensive recycling activity. In many low- and middle-income countries, the breaking and smelting of these batteries occurs at facilities with no emission controls, contaminating soil around each site. Growing evidence links that contamination to severe health effects in nearby communities.

Model methodology

The CGD researchers adapted a model originally developed by Ericson et al. (2017), which focused on highly exposed populations within 300 metres of each recycling site. Soil lead in that zone typically runs orders of magnitude above safe levels, and children living there show symptoms of severe poisoning.

But several recent quasi-experimental studies have consistently connected lower-level exposure within two to ten kilometres of recycling sites to measurable damage to children's health and education. Atmospheric deposition can carry lead across entire oceans. The team therefore extended the model's outer boundary to 5,000 metres to capture dispersed, low-level contamination across much larger populations.

That adjustment changed the headline result. Mass low-level exposure spread over vast areas drives most of the total harm, not the acute hotspot exposure within a few hundred metres that earlier models counted.

The model rests on three inputs. First, site counts: the researchers estimated the number of recycling-polluted sites per country using two methods — one derived from vehicle counts and therefore used battery generation, the other extrapolated from an exhaustive census of polluted sites in Ghana — and took a midpoint between them. Second, exposure intensity: a global database of soil pollution around recycling sites models distance decay, which is then converted to blood lead levels using the All Ages Lead Model biokinetic framework. Third, exposed population: gridded population data counts people living within five kilometres of each site, with extrapolation to unmeasured countries based on population density.

The soil data underlying the distance-decay function covers 5,172 measurements from Pure Earth's toxic site identification program. The average fitted soil lead level across a five-kilometre disk around sites is 217 mg/kg — above the US EPA's 200 mg/kg soil lead concern threshold, even when averaged across the entire exposure area rather than measured at hotspots.

No blueprint for safe recycling

The policy problem the paper identifies has no proven solution at low-income settings. Extended producer responsibility schemes with mandatory buy-back obligations for battery sellers have worked in upper-middle-income countries such as Brazil and China. They remain untested in poorer countries with weaker enforcement capacity. Enforcement operations and closure of unsafe facilities may only hold where operators have a compliant alternative to move their material to.

That alternative barely exists in the worst-affected markets. Nigeria, one of Africa's largest vehicle fleets, has exactly one safe lead-acid battery recycler operating. The informal sector absorbs the remaining volume.

The authors concede they do not have all the answers. Their central claim is narrower: the scale of unsafe battery recycling as an exposure source is bigger than previously thought, and large enough to demand new regulatory instruments and delivery models rather than transfers of existing ones.

What happens next depends on whether low-income governments and donors can move from exposure quantification to facility-level substitution — building licensed capacity fast enough that enforcement against informal smelters does not simply displace the hazard.