Half of U.S. Adults Have Low IQ Due To Leaded Gasoline Exposure as Children, Study Reveals

More than 170 million Americans or half of U.S. adults, born between the 1950s to the 1980s, likely experienced concerning amounts of leaded gasoline exposure as children, which has resulted in their low IQ, a new study has revealed.

Researchers from Duke University and Florida State University studied and compared data from the census, leaded gasoline consumption, and children's blood lead level from 1940 to 2015. The experts wanted to see how far-reaching leaded gasoline exposure impacted early childhood.

Their findings, published in the journal PNAS, showed that leaded gasoline exposure, through inhaling auto exhaust, resulted in a median drop of 2.6 IQ points per child. However, the impact was more widespread in some groups. For instance, those born between 1960 to 1970 had an estimated IQ drop of six to seven points. During this period, consumption of leaded gas was at its peak.

Blood Lead Levels Beyond CDC Threshold

The experts also estimated the blood lead levels of the adult population until 2015. Their calculations showed that exposure to this harmful substance was above 5 micrograms per decilite, which was beyond the threshold of the U.S. Centers for Disease Control and Prevention (CDC). The health agency said that blood lead levels higher than 3.5 micrograms per decilite should be a cause for concern, especially in kids.

Michael McFarland, the principal author of the study, said that their findings painted a "staggering" picture of what lead exposure can do to children's health and wellness when they become adults. He noted that the IQ drop of "a couple of points" will be significant for individuals already vulnerable to cognitive impairment.

After the 1970s, the U.S. started the phase-out of leaded gasoline or gasoline added with lead to help vehicles run smoother. The U.S. then altogether banned the substance in the 1990s. Tougher regulations against lead exposure and lead poisoning were also established for decades based on the recommendations of its public health officials.

Lead Exposure Will Have Lifelong Effects

Aside from cognitive impairment, lead exposure may also raise the risk of heart disease, kidney disease, and hypertension, which are the leading ailments of the adult population. Bruce Lanphear, who did a similar study on lead exposure and IQ in 2005, said that despite their findings, industries continue to make the same mistakes about harmful chemicals when the focus should be on "regulating chemicals differently."

McFarland said that their findings should be "infuriating" because the harmful effects of lead poisoning have been known for many years. Sung Kyun Park of the University of Michigan School of Public Health said that there is a "never-ending story" to lead exposure.

Additionally, lead exposure highlights racial and social disparities in minority and low-income neighborhoods. The latest study estimated that many Black adults below 45 years old had more exposure to toxic lead substances than white kids.