Tag Archives: lead exposure

Lead exposure from gasoline has affected the IQ of 1 in 2 Americans since the 1940s

In the 1920s, researchers realized that you can add lead to gasoline to help keep car engines healthy for longer. But while leaded gasoline was good for cars, it was bad for humans.

Leaded gasoline is highly toxic and in addition to causing a number of health problems, it can also cross the blood-brain barrier and accumulate in some parts of the brain, where it can cause a number of problems, including reducing intelligence. According to a new study, exposure to car exhaust from leaded gasoline affected the IQs of over 170 million Americans alive today, costing the country a collective 824 million IQ points.

Image credits: Joe Mabel.

The findings come from a new study published by Aaron Reuben, a PhD candidate in clinical psychology at Duke University, and Michael McFarland and Mathew Hauer, both professors of sociology at Florida State University. The researchers started from publicly available data on US childhood blood-lead levels and leaded-gasoline use. They then determined the likely lifelong burden of lead exposure of every American alive in 2015. From this, they calculated how much of an intelligence burden this exposure to lead proved to be. While IQ isn’t a perfect proxy to intelligence, it’s still a good population-level indicator.

Previous studies have suggested an association between lead exposure in childhood and a drop in IQ. But when the results came in, even the researchers were surprised.

“I frankly was shocked,” McFarland said. “And when I look at the numbers, I’m still shocked even though I’m prepared for it.”

The results show that over half of all Americans (170 million out of an entire population of 330 million) had clinically significant levels of lead in their blood, resulting in lower IQ levels as adults, as well as a number of potential health problems (such as reduced brain size, greater likelihood of mental illness, and increased cardiovascular disease). The people affected by lead exposure would have each lost, on average, 3 IQ points.

“Lead is able to reach the bloodstream once it’s inhaled as dust, or ingested, or consumed in water,” Reuben said. “In the bloodstream, it’s able to pass into the brain through the blood-brain barrier, which is quite good at keeping a lot of toxicants and pathogens out of the brain, but not all of them.”

Three IQ points may not seem like much, but keep in mind that this is an average for a whopping 170 million people. At its worst, people born in the mid-late 1960s may have lost 6 IQ points on average. At a population level, this is a considerable margin — and even though leaded gasoline was banned in the US in 1996, the effects of the problem are still visible today.

“Millions of us are walking around with a history of lead exposure,” Reuben said. “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.”

Thankfully, the era of leaded gasoline is finally over. Most countries banned it two decades ago, but only last year, in 2021, the era of leaded gasoline was finally over as the last stocks were used in Algeria (which had continued to produce leaded gasoline until July 2021).

Leaded gasoline is a good example of an exciting technology that turns out to be very bad for the environment and for human health. But while leaded gasoline has been phased out, there are plenty of other sources of pollution still affecting our brains, lungs, and hearts.

Journal Reference:  “Half of US Population Exposed to Adverse Lead Levels in Early Childhood,” Michael J. McFarland, Matt E. Hauer, Aaron Reuben. Proceedings of the National Academy of Sciences, March 7, 2022. DOI: 10.1073/pnas.2118631119

Lead exposure might be responsible for 10 times more premature deaths than previously thought

A new study suggests that lead exposure may be responsible for nearly 10 times more deaths in the United States than previously thought.

Credit: Wikipedia.

Scientists have discovered that nearly 412,000 deaths each year in the US can be attributed to lead contamination. That number is ten times higher than the Institute for Health Metrics and Evaluation at the University of Washington in Seattle had previously reported.

“Today, lead exposure is much lower because of regulations banning the use of lead in petrol, paints and other consumer products, so the number of deaths from lead exposure will be lower in younger generations. Still, lead represents a leading cause of disease and death, and it is important to continue our efforts to reduce environmental lead exposure,” explained Professor Bruce Lanphear, from Simon Fraser University in Canada.

Lanphear and colleagues estimated that 28.7% of heart disease-related premature deaths in the US could be caused by lead exposure, which comes to a total of 256,000 deaths annually. 

Researchers used data from the Third National Health and Nutrition Examination Survey, which monitored 14,289 US adults for 20 years. Of the 4,422 participants who died by 2011, approximately 18% of them could have been saved by reducing blood lead concentrations to 1.0 micrograms per deciliter.

Compared to those with low lead blood concentrations, people with high lead levels (over 6.7 micrograms) had the risk of premature death from any cause increased by 37%, the risk of cardiovascular death increased by 70%, and double the risk of death from ischemic heart disease.

“Our study calls into question the assumption that specific toxicants, like lead, have ‘safe levels’, and suggests that low-level environmental lead exposure is a leading risk factor for premature death in the USA, particularly from cardiovascular disease,” Professor Lanphear said in a statement.

Lead exposure can contribute to cardiovascular disease by various pathways. Lead affects the epithelial cells of the blood vessels, which increases the chances of developing plaques that can then cause a heart attack. Lead contamination also leads to kidney damage, which causes high blood pressure and probably acts synergistically with plaque formation.
Also, if you live near an airport, your blood lead levels will be a little higher than if you live farther away due to the lead found in the aviation gas used in single piston jets.

“Estimating the contribution of low-level lead exposure is essential to understanding trends in cardiovascular disease mortality and developing comprehensive strategies to prevent cardiovascular disease. Currently, low levels of lead exposure are an important, but largely ignored risk factor for deaths from cardiovascular disease,” said Professor Lanphear.

The team admits that the study’s principal limitation is that the research relied heavily on one blood concentration measurement taken at the beginning of the study period, almost 20 years ago.
“Our reliance on a single blood test as opposed to serial blood tests means that we have underestimated the impact of lead exposure on cardiovascular disease,” Lanphear said. “There are some things in the study design itself that we really couldn’t change.”

The team urges the retirement of lead-contaminated housing, lead-laden jet fuels, lead water pipes, and the reduction of emissions from smelters and lead battery facilities.

“We’ve made tremendous progress in reducing these exposures in the past four to five decades,” Lanphear added. “But our blood levels are still 10 to 100 times higher than our pre-industrial ancestors,” Lanphear concludes.

Scientific reference: Bruce Lanphear , Stephen Rauch, Peggy Auinger, Ryan W Allen , Richard W Hornung. Low-level lead exposure and mortality in US adults: a population-based cohort studyThe Lancet Public Health, 2018 DOI: 10.1016/S2468-2667(18)30025-2