New research shows that lead poisoning is hindering children's mental development and dragging down their school marks in subjects like maths. The problem is overwhelmingly concentrated in poorer countries, including South Africa.

In 2019, only 14% of 10-year-olds in sub-Saharan Africa were able to read and understand a simple sentence. In high-income countries (including nations like the US and Japan) the figure was 92%. But what accounts for these huge educational disparities across different regions?

A new working paper by the Centre for Global Development (CGD) finds that the answer goes a lot deeper than just schooling quality - down to the toxins children in different countries consume and breathe in.

In particular, exposure to lead, a toxic heavy metal that can hinder brain development when consumed by children, is far more widespread in poor and middle-income countries than in wealthier nations, where anti-lead laws are strictly enforced and enormous amounts of money are spent on removing lead pipes and paint.

The CGD research estimates that more than half of all children in low-income countries have enough lead in their blood to meet the clinical threshold for lead poisoning.

When a child consumes lead, the metal is transported via the bloodstream to various organs, including the brain, where it can wreak havoc on mental development. As a result kids who are more exposed to lead often...