How does extreme weather affect community health? A University of Michigan researcher explains
Environmental epidemiologist Carina Gronlund on the surprising links between housing, heat and health equity—and what can be done about it
On a sunbaked summer afternoon in Detroit, the difference between cool shade and hot asphalt pavement is more serious than you might think.
Carina Gronlund knows this better than most. As an environmental epidemiologist at the University of Michigan School of Public Health and Institute for Social Research's Survey Research Center, she’s spent years unraveling how the weather, air quality and housing shape the daily lives—and risks—of people across Michigan.
Gronlund started her career managing cancer data in Detroit, where she witnessed how disease often arrived after years of harmful exposures—long after prevention was possible.
“I was very interested in this push and pull between the economic growth and jobs for the middle class that the auto industry has traditionally provided, and then the environmental consequences of that industry and its industrial emissions,” she said. “And, I would also say the environmental justice issues, around industrial practices in the United States and globally. Then, I discovered that there was this discipline called environmental health that perfectly captured those instances.”
Gronlund looks at neighborhoods, policies and weather patterns alongside patient data. Guided by environmental epidemiologist Marie O’Neill, professor of Environmental Health Sciences and Epidemiology, Gronlund began focusing on how extreme heat threatens vulnerable communities—a challenge that’s growing as environmental conditions shift.
With support from the National Institutes of Health (NIH), the National Science Foundation and the Graham Sustainability Institute, Gronlund leads a portfolio of projects that combine boots-on-the-ground fieldwork with innovative data analysis.
She collaborates with Detroit community groups and state officials to study how social, economic, health and built environment factors—like poor housing or high utility costs—can multiply the risks posed by extreme heat, precipitation, pollen and wildfire smoke. Her research ranges from evaluating how energy-efficient home improvements boost sleep and cognitive health for older adults, to mapping the patterns of allergy and asthma attacks as pollen levels rise across the Midwest.
“One way I describe public health is figuring out how to keep people out of emergency rooms,” Gronlund said. “We want to prevent you from getting that health problem in the first place. Or at least minimize it so that you can live a full life, and, for all that life, do the things that you feel are productive and meaningful to you.”
For Gronlund, it’s about helping cities adapt, closing gaps in health equity, and empowering people to thrive, no matter what the forecast brings.
Weather affects us every day—what we wear, how we act, and how much money we spend on heating or cooling our homes. A really important way to help people cope with extreme weather is through housing. Our homes are meant to protect us from the weather, and if housing quality is poor, people suffer more during heat waves or cold spells.”
— Carina Gronlund
What are some surprising findings from your work connecting environmental factors to health in communities?
One major surprise was how much the built environment can impact temperature, even within one city. For example, on a hot day in Detroit, if you’re in a leafy suburb, it can be up to seven degrees cooler than in a downtown area surrounded by pavement and brick buildings. This “urban heat island” effect makes some neighborhoods much more vulnerable during extreme heat.
It’s not just an urban problem. We now study extreme weather effects in rural areas, too, where people are more spread out but face their own kinds of challenges, such as less reliable electricity delivery.
In our research, we found that hospitalizations for kidney disease go up during extreme heat, but there isn’t as strong a connection for cardiovascular-related hospitalizations—though there is for heart-related deaths. That tells us that perhaps some people don’t make it to the hospital when extreme heat hits, which is a stark reminder of the risks involved.
Adaptation also plays a big role. People in northern cities, like Detroit, experience more health impacts from extreme heat than those in the South, where air conditioning is common and homes are built for hotter weather. In colder cities or cities with old homes originally designed to trap the heat inside, we see uncomfortably high temperatures indoors in the summer. Air conditioning is especially expensive to run in these older homes, leaving fewer options for low- and middle-income families to escape the summer heat.
How do you measure the health benefits of weatherization and energy improvements in Detroit homes?
In one project, we ask participants to put a temperature monitor in their home for a whole year. We also have them wear a device on their wrist that tracks their sleep, kind of like a Fitbit but more accurate. Some families receive weatherization services—like better insulation and energy-efficient appliances—and some don’t, so we compare differences in sleep and home temperature.
We also measure cognitive effects, because everyone knows your brain isn’t at its best if you’re too hot, or cold, or didn’t sleep well. We ask questions about mental sharpness, as well as about household finances, since expensive utility bills can be a huge stress.
Why do rising pollen levels matter for public health, and how does your team’s new model help?
My collaborator Allison Steiner, professor of Climate and Space Sciences and Engineering, developed a model that predicts pollen levels for different species, like ragweed, grasses, and trees, at a very local level each day. This is more detailed than typical weather forecasts, which just give a general pollen count and might not be specific for your area.
By linking these predictions to health data—like deaths or emergency room visits—we can see when allergies or asthma cases spike. Having more specific information helps us plan better public health responses and can help people with allergies and asthma understand and prepare for those days.
What do people often overlook about how extreme weather affects daily life, and how can we help communities adapt?
Weather affects us every day—what we wear, how we act, and how much money we spend on heating or cooling our homes. A really important way to help people cope with extreme weather is through housing. Our homes are meant to protect us from the weather, and if housing quality is poor, people suffer more during heat waves or cold spells.
That’s why we focus on improving homes, especially during a housing crisis, to help prevent disease and emergencies. It’s key in making communities more resilient.
What else would you like people to understand about your research or public health in general?
Our field isn’t just about finding risks—it’s about fixing them. Interventions like weatherization and improving housing quality aren’t just technical fixes to reduce utility costs; they might help people live healthier lives and reduce inequalities across neighborhoods.
Written by Bob Cunningham
Media Contact
Destiny Cook
PR and Communications ManagerUniversity of Michigan School of Public Health734-647-8650
