When you check the weather on your phone, you're getting a "best guess" based on the nearest airport—but your actual neighborhood could be much hotter. And in high-risk communities, this invisible temperature spike or major air quality issue transforms a daily forecast into a serious medical emergency.

In this special episode in honor of Brown’s first-ever Climate Week, environmental epidemiologist Allan Just explains how his team uses NASA satellite data to measure hyper-local temperatures and air pollution. Discover why these precise measurements are vital for public health, especially for those on common medications that can unexpectedly increase vulnerability to extreme heat.

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, on a special episode celebrating Brown's Climate Week, Professor Allan Just.

What you're seeing is a computer algorithm basically taking a pretty good guess. It's using data from thermometers somewhere nearby, often at the closest airport.

That's fine for figuring out if you need to wear a coat that day, but for researchers who are studying how temperature affects our health, it can be a problem.

[00:01:07] Megan Hall: This is Allan Just, he is an environmental epidemiologist -- meaning he studies how the environment, mostly temperature and air pollution, affects people's health. He's been working to develop a more accurate way for researchers to measure a place's temperature. Not just a whole city, but down to the buildings.

[00:01:40] Megan Hall: Using satellite data, and some complicated math, Allan and his team have developed a model that can create much more accurate estimates of a place's temperature. And that lets their research get really specific.

[00:02:15] Megan Hall: But let's back up a bit. Why is Allan interested in finding exact temperatures in the first place? For Allan, it goes back to an interest in the environment

As a student in college, Allan used to think that -- nature, and the places where people live, were pretty separate things. He was actually studying at Brown.

It was so eye-opening because I had previously really thought about pristine wilderness areas without a connection to humans. And I had had this frankly naive concept that nature was something else. It was something far away that it was distinct. And you know, I wasn't thinking about the ways in which we are all experiencing the temperature in the neighborhoods that we walk around in and the air that we're breathing continuously.

[00:03:26] Allan Just: It was a real aha moment. And then I took epidemiology at Brown and I thought, this is such a really interesting nuanced and challenging field to try to link things and understand the causes, the, the determinants of disease. It, it just, it hooked me.

[00:03:57] Allan Just: And it's sometimes easy to forget that, particularly for people who are very vulnerable to it. Warm weather can come with really severe health consequences, and when we have extreme heat events, the consequences can be quite profound, one of the impacts of extreme heat is it can increase. Things like heart attacks and strokes and other sorts of common conditions that can be very severe but aren't specific. And so when we talk a lot about heat-related illnesses, we think that that might only apply to something like a…you know, a heat stress, but in fact, you can also have these increases in common conditions that are, that are very serious.

And so the burden of extreme heat has probably been undercounted.

[00:05:02] Allan Just: We have used kind of a broad brush to assign what we think people are exposed to and have not always tracked that different neighborhoods are experiencing different temperatures.

[00:05:17] Allan Just: We think that when we get more specific, we've been underestimating the burden.

[00:05:39] Allan Just: By bringing in data from NASA satellites.

And those satellites are telling us things like the temperature of the surface of the earth, and we're also bringing in information about. land cover, how much vegetation there is, the amount of people nearby.

We're bringing together lots of different kinds of information. and we're training up a model so that we can have a better reconstruction where we don't have those direct measurements.

[00:06:18] Allan Just: With air pollution, there's even fewer of those regulatory grade, the high quality monitors that are measuring air pollution.

Many US counties don't even have a single measurement, and when we just use the nearest monitor, you know, we're accepting quite a bit of error in the measurement that we're assigning. And then that error means that if we try to relate what someone is being exposed to what they're actually breathing, we get the answer slightly wrong.

And so there's particular value in reconstructing what people breathe or what they're feeling, where they live, where they work and play.

[00:07:03] Allan Just: So we see, for example, that people that live in a valley are experiencing worse air pollution on average than people who live up on a hill. And it sort of makes sense when you think about it because the air gets trapped and it can stay there. So when you have some sort of local emission source or you have long range transport of air pollutants that are coming down, they can settle close to the surface, and then that's what you're breathing and it may not get moved out by, by wind or other patterns.

Megan Hall: Can you explain how you use these satellites to capture information about air pollution?

[00:08:55] Megan Hall: Wow, that's so cool. So the satellites can see something that we can't, the

[00:09:46] Megan Hall: Let's make it practical. What do we do with this data? How does it help people who are experiencing extreme heat, or how does that help us improve public health?

And the goal of that project is so that we know what are the levels at which we need to take public health actions. Who needs that intervention? If there is a heat wave coming, who do we need to reach out to? When we see that the air quality is starting to degrade and we're working towards analyses to better understand how people who are using particular medications might be left more vulnerable to heat because those medications impact the body's ability to regulate its own temperature, and we're trying to set up

comparisons. So we're looking at sets of medications that are used to treat common conditions and evaluating whether you're better off on drug A or drug B, if there's a heat wave coming from the perspective of the risks related to heat.

[00:11:20] Allan Just: Yeah. I think that we're often trying to treat, you know, one symptom at a time, and the drugs that we are handing out the side effects, the literature that goes with it often gets buried and, and kind of put behind us, but there are quite a few medications that, through different mechanisms, they can alter our ability to feel thirst. They can change the ways in which we retain body fluids. They can impair our ability to sweat.

I mean, there are just several really important mechanisms at play when we think about the ways in which people end up vulnerable to extreme heat. And, particularly when we think about older adults, the use of medications just goes up and up. And so the likelihood that someone is taking, you know, a common medication that could have this sort of side effect, it does increase with age.

[00:12:25] Allan Just: So the project is called CHAIRS-C. It's the Center for Heat Health Aging Innovation Research Solutions for Communities. We love a good acronym.

[00:12:50] Allan Just: Yeah, that's right. So social vulnerability can have many different dimensions, but what we see in both heat and in air pollution is that overburdened communities, underserved communities, they are systematically hotter, and that's driven by land use decisions and structural racism.

That's led to differences in where we've kept vegetation and where we've put pavement and roadways and those subtle differences are lost when we assume that everyone is living at the airport because, we know that urban core areas often have heat island impacts where the density of pavement and dark impervious surfaces really holds onto that heat, particularly in the nighttime. And so people in communities that stay hotter at night, they don't get that physiologic relief and they're experiencing more intense heat stress than people who are living in cooler vegetated suburbs.

[00:14:04] Allan Just: And so one of our goals is to. Broaden the ways in which we're examining the relation between climate and health at Brown and we're looking at these relations between heat and air pollution.

By linking these state-of-the-art models that have reconstructed temperature and humidity and air pollution with these very large data sets, we're hoping we can do a better job of quantifying how much air pollution and heat matters for human health focused on this Medicare population that that could drive.

Better policy, better investment, and bring about just a greater attention to how big a risk this is. And we're hoping that we come out with some practical solutions, the. Idea that you might work with your clinician and consider the risks that are related to the medications that you take. It makes a lot of sense to me in a warming world, that we do need to look for things that are potentially modifiable and we do need to take actions to protect people.

It's gonna get hot this summer and we keep using this phrase, “the hottest year yet.” And I think it's something that part of being forward looking is planning for that, that these risks are going to recur and we need to find, actions, policies, interventions, things that we can do to help protect people.

[00:15:39] Allan Just: Thanks for having me.

Humans in Public Health is a monthly podcast brought to you by Brown University School of Public Health. This episode was a collaboration with Possibly, a weekly climate science podcast produced by The Institute at Brown for Environment and Society, Ocean State Media, and WBRU.

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!