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?

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.

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.

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.

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 radio show is a wake-up call to all those politicians calling for less regulation.