Might be able to confirm this by testing kids for lead poisoning in countries where leaded gas is still legal. There are children that lived in the country and

Might be able to confirm this by testing kids for lead poisoning in countries where leaded gas is still legal. There are children that lived in the country and later move to the city. How early their exposure began would be the variable being tested. You could treat all cases of lead poisoning you find and still be able to measure the impact of leaded gas on development. Of course, I think the jury has been in on lead gas and paint for decades. But I guess for a poor country, an economic case must be made.