STUDY: Past Lead Exposure Could Have Lowered the IQs of Americans

In the 1920s, lead was added to petrol as a cheap solution to engine knock. Little did we know until decades later that lead exposure caused a whole host of health issues. Although lead is no longer added to fuel today, the harm is done.

In the USA, lead was phased out from fuel and other products, starting from the seventies until the mid-nineties, which means many who are alive today were exposed. A recent study found that over 170 million Americans – that’s over half the population –  were likely to have been exposed to high levels of lead in their childhood and this could have had an effect on their IQ levels.

The study, published in the journal Proceedings of the National Academy of Sciences, estimated that Americans lost a total of 824,097,690 IQ points – an average of 2.6 IQ points per person – as of 2015 as a result of lead exposure. Those who were born between 1951 and 1980 were disproportionately affected.

While the number affecting the individual might sound small, even a small deficit in IQ could have a significant impact – one’s cognitive ability can determine a person’s level of education, career, health, wealth and happiness. On a population-wide scale, the study estimates a loss to the US economy of 165 to 319 billion dollars in wages, not to mention the increase in criminal and antisocial behaviour, which IQ levels have a correlation to, and healthcare costs related to lead exposure.

“Millions of us are walking around with a history of lead exposure,” said the author of the study, Aaron Reuben, a PhD candidate in clinical psychology at Duke University. “It’s not like you got into a car accident and had a rotator cuff tear that heals and then you’re fine. It appears to be an insult carried in the body in different ways that we’re still trying to understand but that can have implications for life.”