Researchers calculate that exposure to car exhaust from leaded gas during childhood stole a collective 824 million IQ points from over 170 million Americans alive today, more than half of the population of the US. The findings from a study by Dr Aaron Reuben and his team from clinical psychology at Duke University, and published in the journal Proceedings of the National Academy of Sciences, suggest that Americans born before 1996 may now be at greater risk for lead-related health problems, such as faster ageing of the brain. Leaded gas for cars was banned in the US in 1996, but the researchers say that anyone born before the end of that era, and especially those at the peak of its use in the 1960s and 1970s, had concerningly high lead exposures as children. Lead, which is neurotoxic,  can erode brain cells after it enters the body.