Heat and health risks:

a multifaceted human problem

To one Valley resident, rising temperatures signify the beginning of the summer season. To another, the pounding of the desert sun ushers in severe health threats. The dangers of heat exposure are not a result of rising temperatures alone. Our experts discuss the interwoven nature of heat, housing, climate change and other “threat multipliers” in our desert state.

David Hondula is an associate professor in the School of Geographical Sciences and Urban Planning. He works closely with local, regional and state authorities on the development and implementation of plans and programs to make communities safer and more resilient to extreme events.

Jennifer Vanos is an associate professor in the School of Sustainability. She focuses on extreme heat and air pollution and related health impacts on vulnerable populations, such as children and athletes. She is currently running numerous field projects in Arizona and collaborates with schools, government and nonprofits in community-based research.

Patricia Solís is the executive director of the Knowledge Exchange for Resilience, a campus-wide effort to link multi-sector community needs with research innovations in building community resilience. She is also the co-founder and director of YouthMappers, a consortium of student-led chapters on more than 208 university campuses in 48 countries who create and use open spatial data for humanitarian and development needs.

David Hondula: Phoenix, like most other cities around the world, has gotten hotter over the past several decades. However, the specific way that Phoenix has gotten hotter might be a little different than other locations. What we see in records and what we hear talking to people is that the summers are generally getting hotter and are getting longer, but it’s really a shift in our typical summer days that’s been more noticeable. We haven’t pushed toward new all-time record highs — the all-time record for “hottest day” was set in 1990 and has stood for more than 30 years. But that doesn’t mean that the increase in heat isn’t associated with increased danger for public health and increased stress on households. The days that used to be 108 degrees are now 111 and the days that used to be 111 are now 114. Those are all certainly meaningfully more impactful on the population.

These changes, just like everywhere else around the world, are happening for two reasons. The first is what’s happening on the global scale of climate change and the concentration of certain gasses in the atmosphere. But also what’s happening locally on the ground and how we’re building and designing our cities. Both of those factors have contributed to a general increase in how hot it is for people in our city over the past few decades. Understanding what is happening with changes in the physical and built environment, and how we might be able to impact the outcomes is really important knowledge to build. The story of heat is certainly about more than just the air temperature.

Zachary Van Tol is a sustainability Ph.D. student in the College of Global Futures. As an interdisciplinary scholar, his research explores how access to space impacts climate risk among vulnerable communities.

Jennifer Vanos: ASU and the Urban Climate Research Center have really emphasized the fact that it’s a lot more than just the air temperature value that is going to indicate if someone is experiencing heat stress or heat strain or heat death. Especially in the Valley, incorporating metrics of radiation and understanding how much radiation the human body is receiving from the sky and the ground is extremely vital. That’s why we see shade being so important as an urban design feature to keep populations who don’t have access to cooled, indoor areas as safe as possible. We can measure how well various types of shade do to keep people safe. Those measurements help us understand patterns of where unsheltered individuals are seeking shaded areas for cooling. So it makes sense why there’s an attraction to these cooler places, and we do need more of these spaces to provide refuge from the heat and decrease the overall heat load on the human body from the sun, not just from high air temperatures.

ASU has really been pushing forward in the last five or so years on understanding what heat exposure means in someone’s daily life. That is going to look different for someone who is unsheltered compared to someone with consistent access to cooling and shelter. Weather conditions are one piece of that, and some people may not be able to escape extreme weather conditions. If a person doesn’t have the ability to get those coping resources like water, cooling and food, then they might enter into heat strain. This is where they start to see rising core temperatures, which can result in hyperthermia and potentially death. We can also see that an elevated heart rate from the body trying to cool itself can cause cardiovascular collapse.

There are a lot of nuances to what heat exposure means for individuals. We often just assume everyone experiences heat in the exact same way, but for somebody who already has preexisting conditions, who is dehydrated, who is using drugs or alcohol, that pathway in the body may look completely different and that means the solution is going to look completely different. So this isn’t really just a climate change problem, it’s even more so a vulnerability problem. Climate change can exacerbate this problem, but the amount of vulnerable people being exposed to these extreme conditions is going up.

Patricia Solís: Just as Dr. Hondula and Dr. Vanos explained, the intersection of climate change and heat is indeed an interesting one. I would add that the impacts of climate change that we have to address are not some far distant future — they’re with us right here, right now. There are people and institutions trying to address that of course. But as Dr. Vanos noted, not everyone experiences things the same way. One of the main factors on how you might be exposed to heat has a lot to do with how you can shelter yourself from heat. People who are experiencing homelessness make up about 50% of outdoor, heat-related deaths. They certainly don’t make up half of our residents. Importantly, it’s not just people who don’t have any housing that are represented in numbers on heat-related deaths. Indoor heat-related deaths can happen when a person has inadequate housing or cannot keep their own housing cool. They may not have the economic resources, they might be economically insecure or energy insecure.

With indoor heat-associated deaths, we found that people who live in older mobile homes, which were produced in an earlier era of manufactured housing, are also very disproportionately over-represented in heat-related deaths. In Maricopa County, 5% of our housing is mobile and manufactured housing, but anywhere between 25-40% of indoor heat-related deaths in the last 10 years occur among people who are residing in older mobile homes. Inefficient shelter combines with an energy problem when you cannot pay to cool with AC. Furthermore, a large number of people in manufactured housing tend to be older adults who might have other health conditions, so they’re disproportionately at risk to heat for that reason as well.

Looking towards the future, we know we’re going to see high temperature patterns increase exposure to heat and that is in part due to global climate change, yes. But also, our city is growing at an extremely fast rate and our housing situation is not keeping up with that. At the same time, we’ve got another worrisome trend just beginning, where evictions this past July, hit the highest numbers since the 2008 housing crisis right here in our county. All these systems are really interconnected to create a threat multiplier to heat.

Zachary Van Tol: I would just echo the fact that climate change and social issues are inextricably linked with one another. I think the biggest issue that we will see over the next few decades here in Phoenix is that we are not only the hottest city in the country, but we’re also simultaneously located in the fastest growing county population-wise in the entire country. Even if temperatures were not to increase at all, how do you account for the influx of people moving to our area? We see eviction rates and housing prices increasing, so more and more people are finding themselves in precarious housing situations or even experiencing homelessness. When you consider inflation and other economic phenomena that are ongoing and overlapping with the issue of extreme temperatures here in the Valley, we have to start thinking about how we can change the narrative or change social behaviors around heat. An example is making mediary factors like public transportation more easily accessible for those who find themselves homeless, or strategically placing cooling shelters to maximize effectiveness.

Not only do we need people to be able to seek medical attention so they don’t find themselves in a really dangerous situation with the heat, but we also need to provide services or an avenue for them to actually make it to the medical services. Having hospitals is great — having readily available practitioners is awesome — but if you don’t have a way to actually get to these facilities to receive the care that you need, then we’re only doing half of the job. So I think the climate change aspect is a really important point to touch on, but it’s equally as important to understand that even without any increase or change in temperatures from a sustainability perspective, we really have to think about how we change the housing, financial and economic situations of our county. This makes it so that we can actually accommodate the influx of people because I think that’s a more important aspect: city growth here in Phoenix.

Solís: And the fortunate thing is, if you solve the housing problem you’ve taken a bite out of the heat problem.

Hondula: It’s just as important to think about the non-climate factors, and I would argue if preventing heat deaths is the goal, it’s actually much more important to think about those non-climate factors. As we look at the past 10 years of data here in Maricopa County, we see heat associated deaths rising tremendously. It can be argued that there’s been a temperature increase over that time but nowhere near what we’ve seen in those outcomes statistics. That is because of all the factors that I and my colleagues have mentioned with housing and access to other services. So while I agree that climate is a part of the story here, we think there are other parts of the story that are much more influential in shaping our trends and year-to-year variability and outcome data.

Vanos: You can think about it this way: the housing crisis here is increasing the number of exposure hours to the population. So if we put a thousand more people on the streets, that means that we have a thousand more people who potentially have 24 hours of exposure to heat every day. And that means that hospitals have to respond even quicker and have more room for them and so forth. So the connection to health is obviously there. Not just health, but the health system as well. If we want to be supportive of increasing our population in Maricopa County, the health system also has to be able to respond, and the housing system, and I’m really hopeful we can get to that point.

Hondula: This may be a bit overgeneralized, but I don’t think the solutions to the unsheltered heat death problem are going to come exclusively from biometeorologists. That’s not to say that biometeorology research isn’t important. As a member of that community, I believe it is very important. However, I think we have a pretty good understanding by now that a body outside, all day, in Phoenix in the summer is at risk. The research has already told us that, and we need action elsewhere to support solutions to the problem.

I think the solutions to unsheltered heat deaths are coming from housing policy experts and their adjacent communities. We need to make sure the biometeorologists and the housing policy experts are talking to one another and can have some literacy in each other’s domains so we can speak effectively to each other and a larger audience. That’s part of the reason why university initiatives that connect people working on these topics are so important.

Solís: Like you said, we need to have a multidisciplinary and multi-sector group connected to break down silos. Many of the solutions to these issues are already known solutions, but it’s really hard to move those systems in tandem with each other. It takes a lot of conversations, like the ones we’re having right now, to get everyone on the same page so we can promote and implement solutions once the resources become available, and the willingness of decision-makers to act. At this point there are still barriers. I would love to see more effort from the developer community and the private sector. Right now, if you can’t make money on a solution it’s off the table. But, I’ll say that the public sector has been tremendously responsive to our work, as has the nonprofit sector. From where I’ve been sitting, there has been a great amount of growth in awareness and mobilization and I do think there will be a time that we can fill in all of these gaps. I’m hopeful that in five to 10 years, we can look back and know that we made the future better because of the conversations and growth we had today. We need a few key actors to join us, in order to get there.

Van Tol: Something that I always like to bring up is that Arizona is one of seven states in the country that prohibits local jurisdictions from mandating inclusionary zoning, which is one of the largest issues I think when it comes to creating affordable housing. For example, we have the Valley Metro light rail going across the Valley and there’s a lot of development occurring along the rail line, which is awesome for those communities. But, a lot of it is luxury apartments, upscale dining and coffee shops. From a local level perspective, we can’t do a lot of things that we would like to do to make our communities more inviting, more affordable, because state law would have to change in order for us to be able to make such changes. So I think that is a complex portion of the puzzle: there are multiple layers of policies that have to change in order for local governments – who are doing a great job within the confines of the rules they are playing under – to make changes. There are other things that need to change on higher levels in order for Maricopa County, for example, to make the kinds of progressive jump that I think a lot of local policymakers want to make.

It’s important to note that the solution to preventing outdoor heat deaths doesn’t just end with housing. We’re looking for solutions to set people up for improving both their physical and economic well-being. That doesn’t mean just putting someone into a house where they can’t afford the utility bills, and patting ourselves on the back. At a national scale, there is a narrative of “housing first, but not only.” What’s the easiest way to prevent people from falling victim to a lot of the dangers that come with being homeless? Get them into a house, and that’s the first step but that’s not the only step. They may need mental support, career support and other resources in order to actually maintain and pay to cool their home. There are resources that exist to help people who need it, but they’re often underfunded. It takes more than just a house to keep people from being unsheltered, and those resources need more support.

Solís: At the end of the day, there is no money left on the table when it comes to funding for resources aimed at helping the unsheltered population everything allocated is being spent and the needs are too great. The main problem isn’t that people in need don’t know about programs that could help them. From my experience, the main problem is there’s not enough resources being put at the right kinds of things. There is a severe shortage of resources.

Vanos: Another barrier we haven’t really talked about is the importance of social cohesion. In just looking at the 2021 heat deaths report by the county, 50% of the heat deaths were in a house, but 80% of those were people living alone. Very few of those deaths were associated with illicit drug use. The indoor heat deaths often pose such a different problem than those experiencing homelessness or who are unsheltered on the street. There’s no one-size-fits-all solution when it comes to understanding and solving the problem and this is a really good example of that.

Bringing social cohesion into it, especially as we consider those indoor heat deaths, what would have happened if there was a better buddy system for those living alone? Social cohesion goes a long way, and that’s something that was directly impacted by the pandemic. Social cohesion and the use of cooling centers was definitely disrupted by COVID-19 and we can especially see that in the indoor heat deaths. It’s especially notable when you consider that older adults who often live alone are particularly at risk for both COVID-19 and heat complications, so during the pandemic we’re looking at a threat multiplier for older adults in particular.

Hondula: We see another potential multiplier in substance use as well, whether those substances be prescriptions or illicit substance use. Some prescriptions will impact how the body regulates temperature, and adding on to the issue of population and housing we have another connected issue to heat deaths in methamphetamine and fentanyl use.

Solís: Speaking to the human perception of heat as well, research has shown that the longer that you live here the less you perceive yourself to be at risk from heat exposure. An older adult might have lived here for 20 years, and then their heat risk is elevated due to their age. But they perceive themselves to be less at risk, just because over so many years they’ve survived it. It’s sort of a psychological attitude around heat. So not only do we see issues from our society that play into heat vulnerability, but personal attitudes as well. And the attitude of the existing solutions is that individuals are responsible to address their own vulnerability, so the prescription is limited to just outreach and awareness. We need to change these perceptions so that we redesign our cities and rethink our relationship to climate.

Vanos: I think this is a good time to note that the people experiencing heat vulnerability are just that: human. These are people, and regardless of how multifaceted an issue of heat is, it remains crucial to treat people with the dignity and respect that they deserve. That should be reflected in our research and our policy going forward, and I hope that continues to be at the forefront of conversations as we move into the future.