Lead Poisoning must be Tackled, Worldwide
Lead poisoning hurts kids' cognitive development, yet remains pervasive across many low and middle income countries. This must be tackled.
Lead poisoning rots your brain. Babies exposed to lead are more likely to academically under-perform, get suspended, and become violent criminals.
In many low and middle-income countries, children have elevated levels of lead. Tackling the sources of contamination would deliver major dividends for education, social harmony, and gender equality.
Evidence from the US
In Rhode Island, economists Anna Aizer and Janet Currie shows that a one-unit increase in lead increased the probability of suspension from school by almost 10% and the probability of detention by between 27 to 74%.
Leaded gasoline was a major cause of poison in the US, but that varied with geography. Lead bioavailability is highest in areas with non-neutral pH, like the South-East and East. Exploiting this subnational variation, Federico Curci and Federico Masera show areas with more lead saw more violent crime. Scared city-dwellers then fled to the suburbs.
New research suggests that even mild lead exposure can cause IQ loss in the majority of children. Scientists have developed a way to estimate IQ loss based on blood lead levels in children under five. This ‘blood lead level-IQ loss function’ comes from analysing seven different studies across multiple countries.
Lead affects Everyone in the Classroom
A fascinating new paper by Ludovica Gazze, Claudia Persico and Sandra Spirovska examines how lead pollution affects not just the exposed children, but also their peers.
The economists used a novel dataset that links blood lead level tests for children in North Carolina to their education records. This allows them to track how lead exposure before age 6 affected children’s academic performance and behaviour throughout their school years.
Children with higher blood levels experience:
Higher rates of suspension
Lead-Exposed Children are Disruptive
Gazze et al also examine how lead-exposed classmates impacted other children, who were perfectly healthy.
To isolate the causal effects, the authors compared siblings whose grade cohorts happened to have different proportions of lead-exposed peers, while controlling for family background, school quality, and other factors. This allowed them to pinpoint the impacts of lead-exposed classmates, separate from other influences.
What did they find?
Having more lead-exposed peers in your grade significantly increased the likelihood of being suspended from school and decreased the chances of graduating high school or taking the SAT.
They state,
“Attending school with 10 percent more lead poisoned peers increases the suspension rate by 1.6 percent above the mean of 12.4 percent, and increases the suspension duration by one hour based on a 8-hour school day”
That makes sense. If some children are disruptive, others may emulate to look cool and make friends. Peers encourage disruptive behaviour. Everyone’s education suffers from some kids having lead poisoning.
Disruptive peers affect their same gender
Unsurprisingly, children are more negatively affected by peers of their same gender. Impacts also seemed to be driven primarily by exposure to disruptive students in middle school rather than elementary school.
Peer effects disproportionately harmed Black students and students from disadvantaged backgrounds.
Lead poisoning hurts kids’ education progress. This is now amply demonstrated.
Ludovica Gazze, Claudia Persico and Sandra Spirovska should be congratulated in documenting that lead poison also causes disruption, adversely affects peers. And that’s consistent with a larger body of research on lead poison and violence.
Tangentially, let me flag this fantastic new paper by Laura Kawano and colleagues, on how military families’ quasi-random assignment in ‘better’ neighbourhoods substantially improved their children’s subsequent education and earnings. Neighbourhoods matter!
While the Gazze et al. study focuses on North Carolina, lead pollution remains a global issue with particularly severe implications for developing countries.
Lead Pollution remains High, Globally
In countries with strong environmental mobilisation and strong state capacity, lead poisoning has been massively reduced. Even in Flint (Michigan), children’s blood lead levels reduced from 2.33 micrograms per deciliter in 2006 to 1.15 micrograms per deciliter in 2016. Early interventions can even reverse the effects of prior exposure.
In low and middle income countries (LMICs), regulation is typically far weaker. So when the USA toughened up regulation, lead-acid batteries were then exported to Mexico. Babies born near these recycling plants were more likely to be underweight.
In LMICs, children’s blood lead levels often exceed 5 μg/dL. It is dangerously high in Egypt (8.24), Palestine (9.3) and Pakistan (9.27). It’s over 10 in Telegana, Tamil Nadu and Rajasthan.
Here’s another estimate:
In a study of groundwater quality throughout Pakistan’s Sindh province, “54% of samples contained lead concentrations above 10 µg/L, and 23% of the samples contained more than 50 µg/L. The highest measured concentration was 111 µg”!!!!
Given the well-documented research on lead and violence, I wonder if poison has contributed to ongoing blasphemy mob attacks?
In Pakistan (2021), a young woman was making a Tiktok video for Independence Day, and was then viciously assaulted by a massive angry mob. Was this eruption of aggression exacerbated by Pakistan’s exceptionally high rates of lead poisoning?
We Must End Lead Poisoning, Worldwide
Gender interventions often target attitudes directly, raising awareness about equality and campaigning against intimate partner violence.
But this approach overlooks a crucial precursor: cognitive development. Critical reflection requires reason, logic and empiricism. Curious minds want to learn, read more, discuss alternatives and question tradition.
Psychologies also matter in how we handle stress and provocation. When neighbours seem rude, do we lash out or stay calm?
Cognitive capacities are malleable. That’s why we build schools - to support children’s educational development. But new research indicates major obstacles before kids even step into the classroom: lead poison.
Tackling these fundamentals could deliver major dividends - not just for human capital and economic productivity, but also for everyday conversations about culture, inequality, politics and religion.
We need are careful investigations into the causes of lead poison in each locality.
Adulterated turmeric was causing lead poisoning in Bangladesh, found Jenna Forsyth. An amazing national campaign then got lead out of spice, with huge implications for child health.
Afghan cookware also causes lead poisoning, yet remains widely used. This may be why Afghan refugee children register very high levels of lead poisoning (h/t Jeff Rigsby).
Further Reading
Another area would be revisiting Donohue–Levitt hypothesis using a gender based analysis. Donohue–Levitt hypothesis suggested the availability of abortion resulted in fewer births of children at the highest risk of committing crime. A research question could be Did abortion policy lead to a reduction in intimate partner violence? Could it be shown that women with access to abortion could at the margin leave partners committing violence and by having an abortion also reduce the number of births of males who would go own to commit intimate partner violence themselves or births of females who were more likely to be victims of intimate partner violence. Critics of Donohue-Levitt hypothesis have a problem with the twenty year time lag but the same time lag criticism seems to have been overcome in the lead research.
You may be wrong because the effects of lead could be overblown. There is publication bias in the field and a first meta-analysis of the literature suggested that lead exposure may not explain the majority of the large fall in crime observed in some countries. https://www.gla.ac.uk/media/Media_774797_smxx.pdf.