In part one of this two-part interview, Dr. Peter Thorne, University of Iowa Distinguished Chair and Professor of Occupational and Environmental Health and a leading expert in toxicology, provides an in-depth overview of how the federal government regulates chemicals in food, water, and air.

The views and opinions expressed in this podcast are solely those of the student hosts, guests, and contributors, and do not necessarily reflect the views or opinions of the University of Iowa or the College of Public Health.

Lauren Lavin:

Hello everybody, and welcome back to Plugged in to Public Health. I’m Lauren Lavin, I’m the producer. And today, Max and Caroline are going to be interviewing our guest, Dr. Thorne. If it’s your first time with us, welcome. We’re a student-run podcast that explores major issues in public health and how they connect to all of us both inside and outside the field.

So today, we’re kicking off the first of a two-part series with Dr. Peter Thorne, University of Iowa Distinguished Chair and Professor of Occupational and Environmental Health. Dr. Thorne has spent decades conducting research in toxicology and environmental health advising the EPA, including serving as chair of its science advisory board and shaping policy on chemical safety, environmental regulation, and climate-related health impacts.

In this first episode, we’ll unpack the science and policymaking behind chemical regulation in our air, water, and food. You’ll learn how agencies like the EPA and FDA use risk assessments, the role of precautionary principle, and why compounds like Red Dye No. 3 are being banned after decades on the market. Dr. Thorne also shares examples from his own work, including policy decisions on arsenic, lead, and other persistent pollutants, and what that means for protecting the public health for all of us. So, let’s get plugged into public health.

Plugged in to Public Health is produced and edited by the students with the University of Iowa College of Public Health, and the views and opinions expressed in this podcast are solely those of the student hosts, guests, and contributors. They do not necessarily reflect the views or opinions of the University of Iowa or the College of Public Health.

Max Hansen:

Hello, everybody. Welcome to Plugged in to Public Health. Today we’re joined by Dr. Peter Thorne. Dr. Thorne, I got the pleasure of being in your Climageddon class my junior year. However, I’m sure that many of our listeners are not graced by that class in their course schedule, unfortunately. But if you could just give us a brief introduction of your background and your research focus, as if I’m a new student.

Peter Thorne:

Okay, sure, happy to do it. And I just came from teaching Climageddon a few minutes ago, so I’m very much enthusiastic about that course.

Yeah, so I am a Professor in the Department of Occupational and Environmental Health, and I hold the University of Iowa Distinguished Chair, and I’m primarily a toxicologist, environmental health scientist by training. I did my training at the University of Wisconsin through my PhD and at the University of Pittsburgh for postdoctoral and faculty after that. And then I came to the University of Iowa way back in 1988, and I stayed here and have had a number of roles in the university over time. But I’ve had the pleasure of having a large number of masters and PhD students doing research in lung disease and climate change and many things in between, water contaminants, and so that’s really my bread and butter. And it’s been a wonderful area to work over the years because I think our research has really made a difference, in terms of trying to provide the best science possible to inform policymaking and decision-making. And so, that’s what I get up to do every day.

Caroline Powell:

Related to policymaking, you’ve spent decades advising the Environmental Protection Agency or EPA, including serving as Chair of the Science Advisory Board during the Obama Administration. Could you give us an overview of how the federal government regulates chemicals in food, water, and air?

Peter Thorne:

Yeah, that’s a large question, and I can put it fairly succinctly, I think. For many people, they see the Environmental Protection Agency or EPA as a regulatory agency and think of it as going out and slapping industry on the hand for doing the wrong thing, but they’re much, much more than that.

First and foremost, the EPA is a science-based organization. They apply the very best science to all the decision-making that they do to enforce laws that are enacted by Congress. So the EPA and the FDA, the Federal Drug Administration similarly, don’t make laws. The Congress makes the laws and they’re signed into law by the president, and then these agencies of government have to interpret the laws, apply the best science to making decisions, and then help industry comply with those. And in some cases, that’s incentives, and in some cases it is a regulatory decision that might require litigation or Department of Justice referral. And the whole goal of these organizations, FDA, EPA, and also I would say Center for Disease Control and Prevention, are to protect human health. And in the case of EPA, human health and the environment, they’re charged with both of those.

And so, part of EPA’s role as a science organization is to ensure that they use the best science to inform all their regulatory decisions. And so in order to do that, they have internal scientists who are dedicated civil servants, most of whom have PhDs and decades of experience. But then just to make sure everything’s above board, they have outside oversight. And so the Science Advisory Board of the EPA, as an example, and the Science Board of the FDA, were created by acts of Congress that require that these organizations get outside scientific advice and expertise, and so that’s where the board comes in.

So, I’ve served four terms on the Science Advisory Board for the EPA, and I served as Chair, as you mentioned. It’s a body that has about 45 members. And over the decades, this has been a nonpolitical entity that draws expertise from people in academia, people in industry, and people in non-governmental organizations, such as Environmental Defense Fund and Breast Cancer Alliance, and groups like that. And then also, state and tribal governments are represented among those 45 people. And so, we meet regularly and we review every regulatory decision that the EPA makes and decide whether we need to weigh in on the science or not. So, that’s the role of that and it’s really served, I think, the public extremely well as a safeguard to make sure EPA is making good decisions and to really make sure that we’re using all the great science that we have to make us safe.

Max Hansen:

It sounds like that those regulations and just the policy in regards to those chemicals, it’s really rather dynamic in the way that it develops itself.

Peter Thorne:

Yeah. I mean, things come and go. I know later we’re going to want to talk about Red Dye No. 3 as an example of a food additive that has been around forever and now suddenly it’s banned now.

Similarly, in the environmental arena, last year I completed a evaluation of the EPA’s risk assessment for inorganic arsenic. Inorganic arsenic is a toxic chemical, has been known for thousands of years. It’s been used as a weapon, it’s been used as a medication, it’s been an environmental toxicant. There’s at least 25,000 peer-reviewed publications about the toxicity of inorganic arsenic. And yet, it came up again last year as something to take another look at because there is new data, very nice large epidemiologic studies, some more mechanistic animal studies that have added new information that allowed us to take another look at it and say, are we doing enough to protect the health of the public from inorganic arsenic contamination in drinking water? And the answer was largely, no, we’re not doing enough. The maximum contaminant level that we now allow is higher than it should be, and it should be lowered so that we provide more protection against diabetes, cancer, and ischemic heart disease and neurodevelopmental outcomes. So, that’s an example of a compound, keeps coming around.

And it’s important to the public health but it’s also important to industry, because a number of industries that have a responsibility for hazardous waste sites and have to clean those up, if the safe level is judged to be much lower, then they have to clean those up that much more, and that’s a tremendous amount of money that it costs to clean up these hazardous waste sites. So oftentimes, the decisions for industry can be very expensive, but then again on the other side, if we aren’t protecting the public, the loss of life and the healthcare costs associated with excessive exposures is huge.

Max Hansen:

You touched on Red Dye No. 3 for a second there, and it’s been in the news recently. It’s been, the regulations on it are changing, it’s starting to be banned from those food products. I’m curious if you could just walk through briefly the regulatory history and why now it’s being targeted.

Peter Thorne:

Yeah. Well, I can walk you through that. I’m not sure I can answer the why now part so much.

Max Hansen:

Yeah, no worries, no worries.

Peter Thorne:

I mean, I can at one level, but another level, it’s ambiguous and I’ll tell you why. But as a toxicology student, I first learned about butter yellow. Butter yellow was a food additive, it was invented in Germany. It was added to butter to make it yellow, obviously, in the 1920s and 1930s. And then it was discovered to be a fairly potent liver carcinogen because it resembled many other, what we call aniline dyes that were at that time being found to be carcinogenic. Initially, among dye workers and chemical workers they found cancer, and then they said, “Hey, we’re adding nearly the same compound to food. That must be dangerous too.” They did studies and concluded, yes, indeed it is causing cancer. So, that was banned in 1930.

And so around that time, we started to see that there were things that our food systems were not being regulated at all. And so there started to be more attention to trying to protect the public from dangerous chemicals being added to food. And so that gave rise to the Food, Drug, and Cosmetics Act, which then started to regulate these in the 1950s. And so actually, it started in the 1930s, but then picked up much more so in the 1950s. And then the 1958, there was an amendment added to the Food, Drug, and Cosmetics Act called the Delaney Clause. And that, basically the Delaney Clause said that a compound cannot be added to food if it’s been shown to cause cancer in any animal species. It didn’t have to be shown to be human carcinogen, it was judged that if it’s a carcinogen and an animal model, then we’re going to assume it’s carcinogenic and dangerous for people. And so that also meant it couldn’t be added at any level.

With regard to Red Dye No. 3, which is also known as erythrosine, in Europe, it’s called E127, and it’s a compound that is added to candy and cupcake frostings and things like that, it gives a bright watermelon red color. It makes it look more appetizing, makes it look more fresh to people. Maraschino cherries, that’s the color that we’re talking about if you’ve ever seen those. And so, also ice cream bars, it was phased out as for some uses in the 1990s. In fact, in the year 1990, it was banned from cosmetics and it was banned from externally applied drugs, so skin creams that had a therapeutic value. So, the strange thing was that it was banned from those uses, but it wasn’t banned from food. And you’d think, well, why is that? We should be banning it from food. And the FDA, the Food and Drug Administration said that they would ban its use in foods and ingested drugs soon, and they said that in 1992, and soon just didn’t happen.

And so in 2023, amidst a growing concern about food additives, we have a lot of food additives. Some are in the class, it’s grass generally regarded as safe. We call it grass, and these are things that have been in food forever and we basically have no reason to think that they cause problem. But some of these color additives and pesticides are things that we worry about more now. And so in 2023, a consortium of public interest groups basically petitioned the FDA to now go ahead and ban the use of Red Dye No. 3, and they were actually interested in other chemicals as well from our food. So the main groups were, these might be familiar, Center for Science and the Public Interest, Consumer Reports, Breast Cancer Prevention Partners, Environmental Defense Fund, and there were several others. So a group of these advocacy groups, you could call them, public interest groups to compel the FDA.

So the FDA looked at this and they said, “Yeah, we said we’d do this in 1992. Yes, we did say that it causes thyroid cancers in male rats,” based on a 1987 study that was quite definitive. It was done by the National Toxicology Program, so it was a very authoritative study. And although we don’t have any strong evidence to cause cancer in humans, we’re going to apply what we call a precautionary principle and say, “Yep, it makes sense to ban this,” and it isn’t needed nutritionally or medically, it doesn’t offer any health benefit per se, other than making the food look more appealing to some. And so they then banned it January 16th, 2025. Notice came in the Federal Register, and this was also discussed among their science board to make sure that they were looking at the best science. And so there was a comment period, they received one comment from a cake baker. Otherwise, there was very little opposition to this, which was somewhat surprising. And so now, Red Dye No. 3, people who use it have two years to phase it out and then no more. So, that’s the long story.

There’s more to it than that about what this compound does and its mechanism of action that gets a little complicated, but I would just say that it contains iodine, and iodine is active with the thyroid, and so the fact that it caused thyroid follicular tumors in rats makes sense, in terms of its mode of action. So yeah, it’s probably as deep as we go in the toxicology.

Caroline Powell:

You mentioned the precautionary principle.

Peter Thorne:

Yes.

Caroline Powell:

Could you explain what that is for folks who might not know?

Peter Thorne:

Yeah.

Caroline Powell:

And maybe, I’ve always heard precaution versus reactionary policies. So if you could maybe talk about where the United States stands when it comes to the precautionary principle.

Peter Thorne:

Well, so 20 years ago we used to teach that in the US, we don’t follow the precautionary principle and Europe does. And in Europe, the burden was on industry or those who, in this case, the food chemical people to prove that their product is safe. Whereas in the US, it was the burden of the government to prove it was unsafe. That’s what we used to say.

Now, we’ve kind of come to a middle ground where all the data are used. Data from in vitro studies, cell culture studies mostly, data from computer simulations that compare this compound to other chemicals that we know about, animal data in some cases. And then human epidemiologic data when the chemical has already seen exposure to people, or I should say people have seen exposure to the chemical. Precautionary principle just means that we take the evidence we have and we look at it with an eye towards protecting the health. And if there’s a question about whether something is truly a carcinogen in people or likely to be a carcinogen in people, we’re going to weigh on the side of safety and take that precaution to say yes.

And indeed, almost every compound that’s been shown to be a carcinogen in an animal, a mammalian model is also carcinogenic in humans, because mammals have very similar physiology across a wide range of species. And so there’s every reason to make the leap that if it’s carcinogen and rats or mice, it’s very highly likely to be a carcinogen in humans, and therefore, we shouldn’t be exposing people to it if we don’t have to. Is that a good explanation?

Caroline Powell:

Yes, yes.

Peter Thorne:

Okay.

Caroline Powell:

I’m in human toxicology and risk assessment right now.

Peter Thorne:

Oh, perfect.

Caroline Powell:

So all the words are coming to my head about just the process of risk assessment. And so I’m curious, after the risk assessment is done and we’ve decided if this substance is safe or not, what does communicating that look like to the public?

Peter Thorne:

Yeah, so there, it depends a lot on who’s doing the communication and what is the hazard that we’re trying to communicate about and to whom. So in the case of Red Dye No. 3, I think it’s pretty easy because we can say okay, this is the stuff in your cakes and cookies and ice cream bars and gummies that makes it look red. You could use beet juice or other things to make it look red that aren’t cancerous, cancer-causing, and so let’s do it that way and we don’t need this. And there is every reason to think that it could be causing adverse health effects. So not needed, unnecessary risk, there are substitutes available, expense is not an issue because the other things that we can use to make stuff red don’t cost any more than this.

Some people in their communications about it have said, well, this comes from petrochemicals, and use that as a way to make it sound like it’s dangerous. A lot of stuff we use comes from petrochemicals. So to me, that’s not as compelling but I think with the public, that resonates quite a bit. So you can say oh, this has been used for decades and it hasn’t caused an epidemic of cancer. Or you can say, well, we don’t need it, there’s evidence that it is hazardous. Let’s just take it out of the food supply. And as the FDA would say, de-list it. So they have a list of allowable compounds. Now it’s going to be de-listed, so it’ll no longer be allowed.

And with some other things, I earlier talked about inorganic arsenic. There, we regulate it. Every public water supply has to measure how much inorganic arsenic is in the drinking water that they deliver to the distribution system, and they’re allowed to have 10 parts per million. And we now think that that should be something like three or two in order to provide more safety. Or with lead, we recognize that there’s no safe level of lead exposure for children, and so we’re trying to get rid of lead pipes nationwide in the water system to reduce the burden of lead exposed children. And we’ve also taken actions to remove lead from gasoline, to remove lead solder from cans that hold food, and to take lead out of paints that are used in homes. So when there’s a determination that something is hazardous to health and poses an undue risk, we have a number of things we can do from banning a product or its use, to regulating the amount that can be consumed, or putting other safeguards in place.

Caroline Powell:

You mentioned having substitutes for Red Dye No. 3, like beet juice. I’m curious for other substances, does having a readily available substitute make it more likely to be banned because they know what they can replace that substance with?

Peter Thorne:

That’s a great question.

Caroline Powell:

Or does it depend?

Peter Thorne:

The answer is, it shouldn’t be yes, but it is yes, is what I would say. So it makes it easier for an organization like FDA to say, “Well, we’re going to ban this but there are alternatives. So, it isn’t going to harm the industry.” In this case, the food industry. It might harm the people who manufacture that food dye, but they presumably have other chemicals that they produce as well, and they do. But really, it should be the science and the risk assessment that drives the decision, not whether there are alternatives.

But to give an example with the EPA, every time they make a regulation, they have to do a cost-benefit analysis. So they have to say, “How much will it cost industry to comply with this regulation and what are the health benefits that we’ll see?” And they monetize those health benefits by looking at disability, life years loss. They look at loss of income from missing work, and they look at deaths and put a monetary value on each death that’s prevented. And so, it is imperative that there be this comparison to make sure that that there’s a payback, a benefit to these regulations that because we do recognize that it does cost industry money to comply with regulatory decisions that are made by EPA and FDA.

To your other question with regarding Red Dye No. 3, there’s also Red Dye No. 40, which has been suggested that it could be a replacement. There’s no evidence that it causes cancer. There’s some suggestion it might cause neurodevelopmental effects, but there has to be more research on that. We haven’t had the definitive studies, as I understand it, for Red Dye 40 as we have for Red Dye No. 3.

And then others would point to if you’ve ever cooked with a turmeric or saffron, different color, mind you, but they’re an intense color, and you can take a little bit of saffron and put it in white rice and make that have that beautiful saffron color that we associate. And so similarly with carrot oil and beta-carotene it gives the orange color, and with beet juice, it gives a purplish red color. So, there are some. Another one I remember was butterfly pea flowers produce a lovely color. So some of these kind of naturally occurring intense colorizers could be a potential substitute and they could be mixed and blended to give the color palette that the manufacturers are looking for.

Caroline Powell:

Yeah, it’s great to hear about the different alternatives as they navigate the ban.

Peter Thorne:

Now, I should say, someone whose expertise is color blending for food additives could well say, “Well, yeah, but those are harder to use or they cost more, or the beauty of Red Dye No. 3 is it’s so intense and has this exact color that we’re looking for.” But I think that the safety part of the issue to me is a lot more compelling.

Caroline Powell:

Thank you. And I know we’ve mentioned arsenic, lead, Red Dye No. 3, now Red Dye No. 40 it sounds like. And those are just a handful of the hundreds of thousands?

Peter Thorne:

40,000.

Caroline Powell:

40,000 chemicals.

Peter Thorne:

40,000 chemicals in common use.

Caroline Powell:

And so, I know your current research focuses on persistent organic pollutants in air, water, and food. Could you talk about what these pollutants are and why they pose a risk?

Peter Thorne:

Yeah, I’d be happy to. I would say that I work in a number of different areas, that’s one that you just mentioned. I also do research on the impacts of climate change on health, wildfires, and especially ever of interest to me as a pulmonary toxicologist I also have done a lot of work with indoor air quality and asthma, particularly in children.

But on the persistent organic pollutants, we sometimes call those POPs, P-O-P. And among those are things that lately, instead of calling them POPs, people are calling them forever chemicals. And the one that’s getting the most attention or the class of those right now is PFAS chemicals, the per-fluoroalkyl compounds that are extremely persistent in the environment. I’ve been studying PCBs, polychlorinated biphenyls, which are a class of chemicals that were widely used, millions of tons in the 1920s to 1970s. In 1978 in the US they were banned from production, but they continue to exist and in large number, and we’ve been measuring school children and their exposures to PCBs. And they are neurotoxic, they’re immunotoxic, they’re carcinogenic. They cause learning disabilities, developmental disabilities. It’s a class of 209 different compounds that have a structural similarity. And so they’re, I think, a classic case of something that was widely used and then banned, but continues to exist for decades and decades with exposures that are significant.

And the thing that I think is interesting about this is that from an epidemiologic standpoint, we look at the burden, global and US burden of health, and we see that some things like cancer is increasing in Iowa. We’re number two in the nation for cancers, but the causal nature of that is not understood. And when we talk about, why are cancer rates so much higher in Iowa? We can look at things that are decidedly Iowa and think about, well, okay, we have more nitrates in our drinking water from runoff from agriculture, and to a lesser extent, golf courses and lawns. We have a lot of animal manure going into the surface water. We have pesticides that we use intensely in our agricultural operations. We have naturally high inorganic arsenic in our drinking water. In some places we are high for radon, which causes lung cancer. And then there’s the behavioral risk factors that we’ve talked about. Obesity, which is some part is behavioral, some is not. But then drinking and binge-drinking in particular is the one I’m really thinking about, and then cigarette smoking in the past especially.

So, all of these things contribute to that burden of cancer and I think the public often wants to know, what is the thing that’s causing us to be number two, and the cancer rates to be going up? And from an epidemiologic standpoint and a toxicologic standpoint, there isn’t a simple answer to that. And I think that frustrates the public a little bit because they’d like to think, well, okay, there is a cause. We reduce exposure to that cause and the problem will resolve, and it’s just not that simple. And so, that is what we try to help understand. And so in the case of the PCBs, if we can reduce exposures to those and the PFAS compounds, reduce exposures to those, that should help with the burden of cancer and other chronic diseases that we see.

Lauren Lavin:

That’s it for our episode this week and the first half of our conversation with Dr. Peter Thorne. A big thank you to Dr. Thorne for sharing his expertise in breaking down complex issues like chemical regulation, risk assessment, and the science policy connection. Today we learned how agencies like the EPA and FDA interpret laws, gather and evaluate scientific evidence, and make decisions to protect human health and the environment. We also explored the concept of the precautionary principle, the history and ban of Red Dye No. 3, and how policy evolves as new science emerges.

This episode was hosted and written by Maxwell Hansen and Caroline Powell, and edited and produced by Lauren Lavin. You can learn more about the University of Iowa College of Public Health on Facebook. Our podcast is available on Spotify, Apple Podcasts and SoundCloud. If you enjoyed this episode, please share it with your colleagues, friends, or anyone interested in public health. Have a suggestion for our team? You can reach us at cph-gradambassador@UIowa.edu. This episode is brought to you by the University of Iowa College of Public Health. Until next week, stay healthy, stay curious, and take care.