Show 1432: Lead, Lies and Lasting Harm: The Chemical Roots of Chronic Disease

This week, the topic is lead. A hundred years ago, chemists discovered that adding lead to gasoline decreased engine knock and gave the cars of the day more power. It remained a popular additive for decades. At the same time, companies were adding lead to house paint to help it last longer. We know now that lead exposure harms children, but what about adults? Could lead in our environment have contributed to the horrific toll of heart disease over the past century? Find out about the chemical roots of chronic disease.

The Chemical Roots of Chronic Disease:

When the nascent automotive industry began adding tetraethyl lead to gasoline early in the 20th century, scientists did not fully understand the potential health impacts of this compound. They knew by 1889 that lead poisoning could result in saturnine (ie, lead-induced) gout, an inflammatory condition accompanied by atherosclerosis. And at first, public health officials worried that adding it to gasoline might not be safe, especially after large numbers of refinery workers suffered lead poisoning in 1924.

According to chemical warfare expert Yandell Henderson,

"The use of tetraethyl lead will cause vast numbers of the population to suffer from slow lead poisoning with hardening of the arteries.” (New England Journal of Medicine, Oct. 30, 2024).

Why didn’t regulators pay attention?

The Kehoe Problem:

One reason there wasn’t more regulatory attention is that the industry was new and the government hadn’t figured out how to regulate it to make it safer. Another reason is a persuasive individual named Robert Kehoe. As the chief medical officer of the Ethyl Corporation, he had a substantial conflict of interest. But he argued that no one had the right to ban the use of lead in gasoline until someone had proven that it was dangerous. Mind you, not whether lead was dangerous, which scientists knew, “but whether a certain concentration of lead is dangerous.” Unfortunately, the Kehoe rule held sway and has helped shape the American approach to chemical regulation ever since.

Lead was used very widely during the 20th century. People put it in insecticide and in jet fuel. We already mentioned its use in paint. The 21st-century water disaster in Flint, Michigan, reminded the country that many cities still contain lead pipes as part of their plumbing infrastructure. In the 1960s, lead levels in the most recent layers of glacial core samples were 1000 times higher than those in more ancient pre-industrial cores. Moreover, people were also carrying around 1000 times more lead in their bones than skeletons from pre-industrial times. Even now, the total amount of lead in our bodies is 10 to 100 times higher than that of pre-industrial people.

How Does Lead Affect Health?

We asked our guest, Dr. Bruce Lanphear, whether public health improved when we got lead out of gasoline late in the 20th century. The answer is yes; blood lead levels have dropped dramatically. Consequently, many fewer children are dying of acute lead poisoning. But we are still underestimating the overall health effects of chronic low-level lead exposure.

Lead exposure, even at low levels, is linked to hypertension and heart disease. People who are exposed to lead have higher blood pressure. In addition, they are more likely to have damage to the endothelium of the blood vessels. This can result in plaques that cause heart attacks. Scientific assessments show that people with blood level levels at the 90th percentile have double the risk of death from cardiovascular disease as those at the 10th percentile. The conclusion is that chronic low-level lead exposure is a leading cause of heart disease. Worldwide, there are about 5.5 million deaths a year due to low-level lead poisoning.

How Do We Learn About the Chemical Roots of Chronic Disease?

Some critics have objected that association is not causation. That is certainly true. When we have the opportunity to use randomized placebo-controlled trials, we can have more confidence in the conclusions. Yet when there is an overwhelming amount of evidence, we should pay attention. Just as no one now doubts that tobacco harms health, we do not need to doubt the lasting harm caused by lead exposure.

We can learn from the lead saga and apply those lessons to other toxic chemicals. First off, lead poisoning is preventable. Cutting lead exposure reduces the harms. In general, chronic disease risk rises with environmental exposure. To prevent disease, we need to clean up the environment. Just as Robert Kehoe objected to eliminating lead from gasoline, current manufacturers defend their own toxic chemicals, whether those are PFAS, cadmium, arsenic, phthalates or the herbicide glyphosate. If we want a cleaner environment, resulting in less chronic disease, we need to demand action.

This Week's Guest:

Bruce Lanphear, MD, MPH, is Professor of Health Sciences at Simon Fraser University in Burnaby, British Columbia. Professor Lanphear's research, at the intersection of preventive medicine, pediatrics, public health, toxicology, and infectious disease, is driven by a commitment to prevent death, disease, and disability. He has published over 350 peer-reviewed studies about the impact of toxic chemicals on intellectual deficits, behavioral problems, and brain structure in children. He is ranked among the top 1% of most-cited scientists globally. Bruce and his brother, Bob, co-founded Little Things Matter to make the science on toxic chemicals publicly accessible. They produce videos to show how human health is inextricably connected with exposures to toxic chemicals and to elevate efforts to prevent disease.

Professor Lanphear’s new video, Toxic Hearts, will soon be released. May 20th, 2025, was the 100th anniversary of the US Surgeon General's report on the safety of tetraethyl lead. Follow Dr. Lanphear on Substack at https://blanphear.substack.com/

[caption id="attachment_133997" align="alignnone" width="768"] Bruce Lanphear, a health sciences professor at Simon Fraser University and an expert on lead toxicity.[/caption]