Bruce Lanphear: Chronic Lead Exposure, a Risk Factor for Heart Disease

This is a hybrid heart disease risk factor post of a podcast with Prof Bruce Lanphear on lead and a piece I was asked to write for the Washington Post on risk factors for heart disease.

First, the podcast. You may have thought the problem with lead exposure was circumscribed to children, but it’s a much bigger issue than that. I’ll concentrate on the exposure risk to adults in this interview, including the lead-estrogen hypothesis. Bruce has been working on the subject of lead exposure for more than 30 years.

Let me emphasize that the problem is not going away, as highlighted in a recent New England Journal of Medicine piece on lead contamination in Milwaukee schools, “The Latest Episode in an Ongoing Toxic Pandemic.”

Transcript with links to the audio and citations

Eric Topol (00:05):

Well, hello. This is Eric Topol with Ground Truths, and I'm very delighted to welcome Professor Bruce Lanphear from Simon Fraser University in British Columbia for a very interesting topic, and that's about lead exposure. We tend to think about lead poisoning with the Flint, Michigan, but there's a lot more to this story. So welcome, Bruce.

Bruce Lanphear (00:32):

Thank you, Eric. It's great to be here.

Eric Topol (00:33):

Yeah. So you had a New England Journal of Medicine (NEJM) Review in October last year, which was probably a wake up to me, and I'm sure to many others. We'll link to that, where you reviewed the whole topic, the title is called Lead Poisoning. But of course it's not just about a big dose, but rather chronic exposure. So maybe you could give us a bit of an overview of that review that you wrote for NEJM.

Bruce Lanphear (01:05):

Yeah, so we really focused on the things where we feel like there's a definitive link. Things like lead and diminished IQ in children, lead and coronary heart disease, lead and chronic renal disease. As you mentioned, we've typically thought of lead as sort of the overt lead poisoning where somebody becomes acutely ill. But over the past century what we've learned is that lead is one of those toxic chemicals where it's the chronic wear and tear on our bodies that catches up and it's at the root of many of these chronic diseases that are causing problems today.

Eric Topol (01:43):

Yeah, it's pretty striking. The one that grabbed me and kind of almost fell out of my chair was that in 2019 when I guess the most recent data there is 5.5 million cardiovascular deaths ascribed to relatively low levels, or I guess there is no safe level of lead exposure, that's really striking. That's a lot of people dying from something that cardiology and medical community is not really aware of. And there's a figure 3 [BELOW] that we will also show in the transcript, where you show the level where you start to see a takeoff. It starts very low and by 50 μg/liter, you're seeing a twofold risk and there's no threshold, it keeps going up. How many of us do you think are exposed to that type of level as adults, Bruce?

Bruce Lanphear (02:39):

Well, as adults, if we go back in time, all of us. If you go back to the 1970s when lead was still in gasoline, the median blood lead level of Americans was about 13 to 15 µg/dL. So we've all been exposed historically to those levels, and part of the reason we've begun to see a striking decline in coronary heart disease, which peaked in 1968. And by 1978, there was a 20% decline, 190,000 more people were alive than expected. So even in that first decade, there was this striking decline in coronary heart disease. And so, in addition to the prospective studies that have found this link between an increase in lead exposure and death from cardiovascular disease and more specifically coronary heart disease. We can look back in time and see how the decline in leaded gasoline led to a decline in heart disease and hypertension.

Eric Topol (03:41):

Yeah, but it looks like it's still a problem. And you have a phenomenal graph that's encouraging, where you see this 95% reduction in the lead exposure from the 1970s. And as you said, the factors that can be ascribed to like getting rid of lead from gasoline and others. But what is troubling is that we still have a lot of people that this could be a problem. Now, one of the things that was fascinating is that you get into that herbal supplements could be a risk factor. That we don't do screening, of course, should we do screening? And there's certain people that particularly that you consider at high risk that should get screened. So I wasn't aware, I mean the one type of supplements that you zoomed in on, how do you say it? Ayurvedic?

Supplements With Lead

Bruce Lanphear (04:39):

Oh yeah. So this is Ayurvedic medicine and in fact, I just was on a Zoom call three weeks ago with a husband and wife who live in India. The young woman had taken Ayurvedic medicine and because of that, her blood lead levels increased to 70 µg/dL, and several months later she was pregnant, and she was trying to figure out what to do with this. Ayurvedic medicine is not well regulated. And so, that's one of the most important sources when we think about India, for example. And I think you pointed out a really important thing is number one, we don't know that there's any safe level even though blood lead levels in the United States and Europe, for example, have come down by over 95%. The levels that we're exposed to and especially the levels in our bones are 10 to 100 times higher than our pre-industrial ancestors.

Bruce Lanphear (05:36):

So we haven't yet reached those levels that our ancestors were exposed to. Are there effects at even lower and lower levels? Everything would suggest, we should assume that there is, but we don't know down below, le