Picture a coal power plant: a building with tall smoke stacks with big plumes of gasses coming out of them. By now, we know that those gasses aren’t great for our health or the environment. But how bad are they? That’s where Professor Cory Zigler comes in. He worked with a team of researchers to figure out where those gasses go and who they affect. Their approach was so specific, the team could point to a single power plant and say how many people it killed.

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Science: Mortality risk from United States coal electricity generation

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Welcome to Humans in Public Health. I'm Megan Hall.

In the past few years, the field of public health has become more visible than ever before, but it's always played a crucial role in our daily lives. Each month, we talk to someone who makes this work possible. Today, Cory Zigler

Picture a coal power plant. They’ve got those tall smoke stacks with big plumes of gasses coming out of them. By now, we know that those gasses aren’t great for our health or the environment. But how bad are they?

That’s where Cory Zigler comes in. He worked with a team of researchers to figure out where those gasses go and who they affect. Their approach was so specific, the team could point to a single powerplant and say how many people it killed. We wondered how they managed to do this, so we invited Cory Zigler to the studio.

He started by explaining the basics of how coal plants affect our health

When coal is burned, lots of things go out into the air. Where my research sits is mostly focused on the emissions of sulfur dioxide – SO2 and when sulfur dioxide goes into the atmosphere, it's bad for us. But what happens, in addition to just the sulfur dioxide being in the air, is it starts to react with other chemicals in the air, starts to blow around with the wind, and it turns into particulate pollution, or fine particulate matter. These are tiny particles, small enough to penetrate our lungs and make us sick.

And what are some of the major health effects of those little particles?

The main one that is, is all cause mortality,

What does that mean?

That means mortality from anything except an accident is usually how these large epidemiological studies are done.

So breathing this stuff in can kill you.

Over a long period of time, people die sooner than they would have otherwise died. But the list of other health outcomes that this has been shown to influence is pretty long, respiratory health, cardiovascular health, neurological health, things like Alzheimer's disease, they find these particles crossing the placental barrier in pregnant women. So there are lots of different mechanisms through which these particles can make people sick.

But not all of those particles are the same thing. They can be made up of different chemicals. And there's some evidence, mounting evidence, that the chemicals that make up the particle can be better or worse for health. And there was even some emerging evidence that the types of particles that come from coal plants specifically were among the most harmful types of particles. And so what that meant is that it was possible that we were not quantifying the health implications of coal accurately.

Got it so there was an understanding that what's coming out of these coal plants is bad for people's health. But there was an assumption that the health effects were similar to breathing in any other small particles.

Right. That may have come from traffic or a barbecue restaurant or anything. The way most of the research worked was kind of treated all those things equally. And so where we entered this problem was can we isolate the particles that are specifically coming from the coal plants, and not just isolate the particles that came from any coal plant. We really tried to isolate which coal plants were sending their particles to which parts of the country. That way if you live in Rhode Island, you could say it's actually this power plant, that power plant and that power plant in Ohio, Indiana, Pennsylvania, that are sending most of their pollution to Providence. That type of information was not really available when we started this.

And so Cory, and some other researchers, set out to answer this question. They had a few pieces of data to work with.

What we had at our disposal was every power plant in the United States, there's very good data, this is public data from the EPA, on essentially real time emissions. We know very well what exactly is coming out of the smokestacks for power plants in the US. So how SO2 in this case, sulfur dioxide in this case. So that's kind of step one. We know what's coming out of the smokestacks. At the other end of the equation, so to speak, is we had data on Medicare beneficiaries in the US. So this is almost everybody over age 65 we know what zip code they live in, and we know when they died.

Do we know how they died, or just that they died?

Just that they died.

Okay.

And then maybe we knew things about, you know, the city they lived in, the demographics of their neighborhood, the weather around where they live, and stuff like that. And so the main trick here is, how do we reliably link what we know is coming out of the smokestacks of the power plants to characterize the exposure of the people in a given zip code? That was the big analytical challenge of all of this.

And that is a huge challenge. To start, they had to figure out where this pollution went, once it left the power plants.

And you basically did that by understanding, sort of the way the wind was blowing?

It's mostly wind. It's an old tool. It's called HYSPLIT. It takes as its inputs mostly, mostly just the wind directions, and then simulates where, if a mass of air started at a power plant, where it went. And we do that millions of times, for every few hours, for every power plant over 20 years, so that we can isolate in this year or in this month, this is the amount of pollution at this location that came from that power plant over there. And do that for every location and every power plant. The way in which we were able to do this took some old tools from atmospheric science, but could repurpose them with high performance computing, basically, and do lots and lots of calculations over and over and over again to establish these individual links between every power plant and every zip code in the United States.

By combining that information with the data about when and where people died, Cory and the other researchers could figure out how many people had been killed because of coal plants.

How many deaths did you associate with exposure to coal power plant emissions?

So these are just among Medicare beneficiaries, but it's about 460,000 excess deaths in the United States over this time period, over this that's over about 20 years.

And how do you know that they died because of breathing in these small particles and not because of something else?

That's the million dollar question. The large question with that is, well, maybe there's some other reason why the pollution goes into places where people are generally less healthy or older, or something like that. And so what this study did, and what most large scale epidemiology studies do, is they get as much information as they can about the people who live in different parts of the country, and there are models at large scale, epidemiological models that adjust for this type of thing. And so what this is trying to get is to say, if we have places in the country where the population demographics are sort of the same and the weather is sort of the same, and everything we can think of is sort of the same between these locations. If the one with more of this coal pollution saw people die sooner, then we can attribute those deaths to the excess coal pollution.

And they could also attribute those deaths to specific coal plants. Some caused much more harm than others.

This is a story about where there are dense populations in the United States, where the power plants are located, and mostly where the wind blows. And so the power plants that tended to be associated with the most deaths were large coal power plants. They tended to be in that kind of mid Atlantic or Ohio River region, that are blowing their pollution to large population centers, so the Northeast, or there are some in Georgia where the wind goes to Atlanta. These are the power plants that were associated with the most mortality.

But there’s good news in all of this. Their research, which looked at 1999 to 2020 showed that as the US has burned less coal, deaths have gone down.

What's true across the board, even these power plants that historically are associated with a lot of mortality, even they have gone way down over time, even if they're still operating, Some of them install these scrubbers. Scrubbers being something that you can think of it as, like literally scrubbing the sulfur dioxide out of the smoke before it comes into the atmosphere. It prevents more of these particles from being formed. Across the board, the deaths attributable to coal have been going down over time.

This research came out a little while ago. What has been the impact since it came out?

That's a good question. I've been on a couple of podcasts

So John Kerry mentioned this paper at the COP climate meetings shortly after it came out. That's a big meeting about all kinds of climate change related things. And he mentioned this paper specifically. Part of what the US was there to do was offer their positions on coal power plants for things like climate change, but also health benefits of climate related regulations and policies. So if the papers like this are informing decisions at that level, that's where the potential for impact comes.

In a way it seems like a success story. But what’s the point if the US is already moving in this direction? It seems like we already know that these coal power plants are no good? Why quantify it?

That's basically what John Kerry said on this stage – he said something to the effect of, this important study came out. We didn't actually need another study to tell us these things were bad. But that's a very US centric view of this. There are other parts of the world where coal is very much a part of their energy mix,

Megan Hall: While coal power is on the decline in the US and Europe, for a handful of countries, including China, coal power is actually increasing.

Cory Zigler

and they do not have regulatory environments like we've had in the US. And China, India, lots of South America, Africa, coal is still a cheap fuel source, so it's a big part of the energy mix. And so scientific knowledge like this can also help to inform decisions made in places where coal still is more of a problem.

What do you hope are the long-term effects or implications of this research. What do you hope it does moving forward?

I hope that it helps people who have to make decisions about where power plants are going, or where they should be regulated, or what type of fuel to use in a new power plant. You know, the part that we have to add, is it will help people understand, if I'm going to put a new power plant in this location, where is that? Where do we think that pollution is likely to go and who's going to be exposed, and might that inform where we're going to put a power plant, or in parts of the world where there are lots of power plants in place burning coal, and maybe there's questions about, Well, which one should we try and regulate next?

I think one of your co authors said it sort of attacks the fable or the myth about coal in our country, or sort of quantifies that it, you know, the harms that it has done?

Yeah, Coal does even still have sort of a mythical role in the US. And, you know, I feel like when I see that on TV or wherever, it's only focusing on part of the story with power generation and coal and the jobs it provides in the parts of the country where this has been a big part of life, and this is a little bit the other side of the coin.

That all those years When coal was providing jobs, it was also killing people,

Yeah, and it's tricky. We have to generate electricity. So, you know, it's not necessarily relevant to think about United States in the year 2000 with no coal. We needed it. But the world is complicated, and this is, this is part of those complications.

Well. Cory, thank you so much for joining us today. This was really interesting. I learned a lot

My pleasure. Thanks.

Cory Zigler is a professor of Biostatistics at the Brown University School of Public Health. You can find A link to Cory’s research, and an interactive map that shows the impact of individual coal power plants, in our show notes.

Humans in Public Health is a monthly podcast brought to you by Brown University School of Public Health. This episode was produced by Nat Hardy and recorded at the podcast studio at CIC Providence.

I'm Megan Hall. Talk to you next month!