Half of American IQs lessened by lead in gasoline, study says

The IQ of more than half the United States population has been negatively affected by the presence of lead in gasoline, a new study estimates.

The peer-reviewed study published by the Proceedings of the National Academy of Sciences (PNAS) journal discovered childhood exposure to leaded gasoline cost the U.S. a deficit of at least 824 million IQ points, or approximately 2.6 points per American.

Researchers at Florida State University and Duke University focused on U.S. citizens born before 1996, as leaded gasoline was banned that year.

Though it was less known at the time, lead is a harmful neurotoxin. The Centers for Disease Control and Prevention (CDC) says lead is dangerous in most forms, especially when breathed in. For this reason, the study examined the consequences of inhaling automobile exhaust.

Using gas consumption data, calculations were made to estimate that as of 2015, more than 170 million Americans had blood-lead levels above five micrograms per decilitre as children.

Usage of leaded gasoline in the U.S. peaked from the late 1960s to early 1980s, the study claims. For this reason, certain cohorts were exposed to greater volumes of leaded gas than others.

Americans born in the 1960s and 1970s were estimated to have the greatest IQ deficits from leaded gas, sometimes more than seven points.

Black children were also exposed to leaded gas at higher rates than white children, the study claims. The same was found for Black adults under the age of 45, who were found to have higher blood-lead levels than white Americans in the same age demographic.

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“This is important because we often think about lead as an issue for children, and of course it is,” Michael McFarland, principal study author and Florida State University professor, told NBC. “But what we really wanted to know is what happens to those children who were exposed?”

McFarland told NBC the difference of two to three IQ points is not cause for concern, unless an individual is on the lower side of IQ distribution.

Lead was used in gasoline to make engines run more smoothly, and Canada was not exempt from this practice. On this side of the border, leaded gas was banned from use in passenger vehicles in 1990. Currently, the nation claims more than 99 per cent of gasoline in the country is lead-free.

Canada also has a Proposed Risk Management Strategy for Lead, which outlines actions to further reduce risks associated with exposure to lead that are underway or planned by the Government of Canada, with a particular focus on vulnerable populations.

There are also additional Canadian programs to monitor lead contamination and exposure, including the Food Directorate Updated Approach for Managing Dietary Exposure to Lead.

The directorate attempts to reduce dietary exposure to lead levels and ensure they are as low as reasonably achievable.

This includes annual surveillance of background concentrations of lead in prepared foods and annual monitoring for lead in specific items like baby formula and foods suspecting of contamination.