Show notes
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 citationsEric 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 LeadBruce 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, let's say one microgram per deciliter or that's the equivalent of 10 parts per billion of lead and blood. What we also know though is when leaded gasoline was restricted in the United States and Canada and elsewhere, the companies turned to the industrializing countries and started to market it there. And so, we saw first the epidemic of coronary heart disease in the United States, Canada, Europe. Then that's come down over the past 50 years. At the same time, it was rising in low to middle income countries. So today over 95% of the burden of disease from lead including heart disease is found in industrializing countries.Eric Topol (06:34):Right. Now, it's pretty striking, of course. Is it true that airlines fuel is still with lead today?Bruce Lanphear (06:45):Well, not commercial airlines. It's going to be a small single piston aircraft. So for example, when we did a study down around the Santa Clara County Airport, Reid-Hillview, and we can see that the children who live within a half mile of the airport had blood lead levels about 10% higher than children that live further away. And the children who live downwind, 25% higher still. Now, nobody's mapped out the health effects, but one of the things that's particularly troubling about emissions from small aircraft is that the particle size of lead is extraordinarily small, and we know how nanoparticles because they have larger surface area can be more problematic. They also can probably go straight up into the brain or across the pulmonary tissues, and so those small particles we should be particularly worried about. But it's been such a long journey to try to figure out how to get that out of aircraft. It's a problem. The EPA recognized it. They said it's an endangerment, but the industry is still pushing back.Eric Topol (07:55):Yeah, I mean, it's interesting that we still have these problems, and I am going to in a minute ask you what we can do to just eradicate lead as much as possible, but we're not there yet. But one study that seemed to be hard to believe that you cited in the review. A year after a ban leaded fuel in NASCAR races, mortality from coronary heart disease declined significantly in communities near racetracks. Can you talk about that one because it's a little bit like the one you just mentioned with the airports?Bruce Lanphear (08:30):Yeah. Now that study particularly, this was by Alex Hollingsworth, was particularly looking at people over 65. And we're working on a follow-up study that will look at people below 65, but it was quite striking. When NASCAR took lead out of their fuel, he compared the rates of coronary heart disease of people that live nearby compared to a control group populations that live further away. And he did see a pretty striking reduction. One of the things we also want to look at in our follow-up is how quickly does that risk begin to taper off? That's going to be really important in terms of trying to develop a strategy around preventing lead poisoning. How quickly do we expect to see it fall? I think it's probably going to be within 12 to 24 months that we'll see benefits.Eric Topol (09:20):That's interesting because as you show in a really nice graphic in adults, which are the people who would be listening to this podcast. Of course, they ought to be concerned too about children and all and reproductive health. But the point about the skeleton, 95% of the lead is there and the main organs, which we haven't mentioned the kidney and the kidney injury that occurs no less the cardiovascular, the blood pressure elevation. So these are really, and you mentioned not necessarily highlighted in that graphic, but potential cognitive hit as well. You also wrote about how people who have symptoms of abdominal pain, memory impairment, and high blood pressure that's unexplained, maybe they should get a blood level screening. I assume those are easy to get, right?Bruce Lanphear (10:17):Oh yeah, absolutely. You can get those in any hospital, any clinic across the country. We're still struggling with having those available where it's most needed in the industrializing countries, but certainly available here. Now, we don't expect that for most people who have those symptoms, lead poisoning is going to be the cause, right. It'd still be unusual unless you work in an industry, for example, smelting batteries to recycle them. We don't expect it to be real common, and we're not even sure, Eric, whether we should be doing widespread screening. If I looked at this as a population scientist, the real focus should be on identifying the sources. We mostly know where those are here and radically moving it down. Getting rid of the lead service lines, which was such a big part of what President Biden was doing, and it was perfect. For every dollar invested to reduce lead exposure from those lead service lines. Ronnie Levin at Harvard said there'd be a 35-fold return in cost, benefits really, and this has always been true, that reducing lead exposure throughout the past 40 years has always been shown to be amazingly cost beneficial. The problem is operating within a free market health system, even though there's tremendous social benefits, that benefit isn't going to be monetized or privatized. And so, who's going to make those decisions? We hope our government is, but that doesn't always play out.Eric Topol (11:52):Well. What's interesting is, as opposed to the problems we have today that are prominent such as the microplastic, nanoplastics, the air pollution, the forever chemicals, that just keep getting worse, I mean, they are just cumulative. This one, there was tremendous improvement, but it’s still not enough. And I guess you're zooming in on the lead lines. That'd be the most important thing to work on today. Another thing that has come up, there's been trials, as you may I'm sure, because all over this field of chelation, there's a trial that was run by the NIH, supported by NH that looked at chelation to prevent coronary disease. Is there any evidence that people who have a problem with lead would benefit from chelation therapy?Bruce Lanphear (12:44):Well, there's two major studies that have been done, and Tony Lamas was in charge of both of them. The first one Trial to Assess Chelation Therapy (TACT) study, it was a randomized controlled trial, not intended specifically to focus on lead, but rather it was to look at sort of this alternative therapy. They found significant benefits about an 18% reduction in subsequent cardiac events. That led to a second study that was just published last year, and it was focused on people who had diabetes. They saw some benefit, but it wasn't significant. So whether that's because there wasn't enough variability and exposure, it's not entirely clear, but we've seen this with lead in IQ deficits in kids where we can show that we can reduce blood lead levels. But ultimately what tends to happen is once you've taken lead out of the blood, some of it's released again from the bone, but you still have all that lead in the bone that's there. You get some of it out, but you're not going to get the bulk of it out.The Lead-Estrogen HypothesisEric Topol (13:47):Right. It's a reservoir that's hard to reckon with. Yeah. Now another thing, you have a Substack that is called Plagues, Pollution & Poverty, and you wrote a really provocative piece in that earlier and April called How Estrogen Keeps Lead - and Heart Attacks - in Check, and basically you got into the lead estrogen hypothesis.Eric Topol (14:10):Can you enlighten us about that?Bruce Lanphear (14:12):Yeah. A lot of the seminal work in this area was done by Ellen Silbergeld, who's a brilliant and somewhat peculiar toxicologist and Ellen for years, I focused on childhood lead exposure, and for years Ellen would tell me, almost demolish me for not studying adults. And because she had found back in 1988 that as women go into menopause, their blood lead levels spike increased by about 30%, and that's where most of our lead is stored is in our bone. And so, as I was thinking about this, it all became clear because blood lead levels in boys and girls is about the same. It's comparable up until menarche, and then girls young women's blood leads fall by about 20%. And they stay 20% lower throughout the reproductive years until menopause. And especially during those first few years around menopause, perimenopause, you see fairly striking increases in the weakening of the bone and blood lead levels.Bruce Lanphear (15:19):So that might very well help to explain why estrogen is protected, because what happens is throughout the reproductive life, women are losing a little bit of lead every month. And estrogen is at its lowest during that time, and that's going to be when blood lead is at its highest because estrogen pushes lead into the bone. Not only that, women lose lead into the developing fetus when they're pregnant. So what Ellen found is that there was less of a spike around menopause for the women that had three or four pregnancies because they had offloaded that into their babies. So all of this, if you put it together, and this is of course in a very short note of it, you can see that lead increases dyslipidemia, it leads to tears in the endothelium of the arterial wall, it's going to increase thrombosis. All of these things that we think of as the classic atherosclerosis. Well, what estrogen does is the opposite of those. It decreases dyslipidemia, it repairs the arterial endothelial wall. So how much of it is that estrogen is protective, and how much is it that it's moving lead out of the system, making it less biologically available?Eric Topol (16:46):Yeah, I know. It's really interesting. Quite provocative. Should be followed up on, for sure. Just getting to you, you're a physician and epidemiologist, MD MPH, and you have sp…
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