When researching the effects of extreme weather and climate change, it’s common for research to focus on outdoor/environmental exposure or population-level health outcomes. These areas are well worth investigating, yet specific environments where people spend much of their day—particularly inside homes and workplaces— are an understudied area in the field, comparatively.
Faculty Member with the Urban Health Collaborative and Arthur L. and Joanne B. Frank Associate Professor of Environmental and Occupational Health at the Dornsife School of Public Health, Leah Schinasi, PhD, MSPH, has spent much of the last ten years exploring the ways by which heat exposures contribute to health inequities, and identifying the upstream and structural drivers of these disparities. We spoke with her about the need for solution-oriented research that identifies modifiable and actionable evidence for protecting health in the places where people live and work.
How Is Extreme Heat Studied, and Where Are the Gaps?
Epidemiological research on extreme heat has evolved over time. Some of the first large-scale studies of heat and mortality outcomes (I’m thinking, for example, of studies that were published in the mid-1990s) used a simple but powerful approach. In essence, researchers counted the number of deaths that occurred during a heat wave event and then compared this to the number of deaths that occurred in times immediately before and after the heat event. These studies were important: they demonstrated, very clearly, that excess deaths occurred during waves of extreme heat. They were valuable in other ways. For example, they provided information about the types of deaths we saw in excess during heat events (e.g., cardiovascular-related); they showed us what demographic groups were dying in excess during these events (e.g., older adults, minoritized groups), and in some cases, showed us the neighborhoods where more of these excess deaths were occurring.
Later, researchers started to use more advanced statistical approaches to study heat-mortality or heat-health relationships, and to explore impacts of daily spikes in heat (in addition to the multiple-day waves of hot temperature): they linked daily outdoor temperature measurements with daily counts of deaths (or other health outcomes of interest). These studies provided additional, valuable information: they demonstrated the shape of the dose-response relationship between temperature exposure and deaths (showing that rates of death tend to be higher when temperatures are highest or lowest); they showed that the definition of what a "dangerous" or "risky" temperature is varies from place to place; and they provided information about the number of days following a spike that exceptionally high or low temperatures remain dangerous. Researchers are still doing this type of work today.
The temperatures assigned to these deaths are usually based on outdoor measurements and linked to deaths based on where a person was living. These studies do not account for what was going on indoors (were they using air conditioning, for example?), the ways people are behaving or responding to heat, or exposures experienced in other places (such as the workplace).
These are important gaps. When temperatures soar, some people have the luxury of staying indoors, at home all day in well-air-conditioned spaces. Others may be forced to relocate, but only from their air-conditioned homes to their air-conditioned cars to their air-conditioned work offices—barely experiencing the heat. Those who are less fortunate, though, might have to endure heat exposure while staying in their un-air-conditioned and, at times, poorly ventilated homes. Others might have to leave their air-conditioned homes to labor in a grueling outdoor work environment. Others might work in stifling un-air-conditioned hot indoor settings, only to then return to a similarly hot and un-air-conditioned home (thus never having the opportunity to recover from the heat—which may be especially dangerous). A lot of epidemiology research ignores these differences in exposure, which may be important determinants of the differences that we see in terms of who bears the adverse consequences of heat exposure.
How Do You Think the Field Should Evolve?
I would love to see greater emphasis on capturing and representing exposures and experiences in hard-to-study or overlooked settings—the residential indoor environment, the workplace, or the school environment, to name a few. Leveraging interdisciplinary approaches and collaborations may be key.
For example, for an NHLBI-funded R01 study that I am leading, which aims to better capture differences in indoor environmental exposures and the housing factors that contribute to these differences, I am collaborating with Dr. Simi Hoque and her PhD student, Chima Hampo, both from Drexel’s College of Engineering. These engineering colleagues are applying physics-based models, used in the field of Building Science, to simulate indoor temperature (and humidity) measures. We can then apply these simulated temperature (and humidity) estimates in our epidemiological models, in order to hopefully better represent people’s true experiences.
In addition to the residential environment, I believe it is important to capture and represent exposures and experiences in other spaces and places where people spend a lot of time, like workplace environments for working-age adults, and schools for children. Historically, and even now, we do not have very strong data on environmental conditions and exposures in these settings. This makes it challenging to quantify impacts in these environments, and among particularly vulnerable subpopulations (like some worker groups) who experienced particularly pronounced exposure levels because of the nature of their work. The downstream result of this lack of data is less research, less evidence, and potentially, less intervention design, implementation, and protection.
I also think that, given that we now know a lot about how dangerous heat is, the field of heat-health research can evolve to have a greater focus on identifying structural interventions to prevent adverse health outcomes. For example, colleagues (including Dr. Alina Schnake-Mahl, also a member of the UHC and Dornsife faculty) and I have written about the potential importance of social and labor policies as interventions that might support resilience in the face of high ambient exposures. Little attention has been given to the role of such structural interventions in supporting resilience to extreme weather exposures.
What Research Do You Have on the Horizon?
I am very excited about a just-launched NIMHD-funded five-year study. We will quantify associations between heat exposure and workplace morbidity and mortality outcomes. We will also use state-level heat safety policies as a natural experiment. The staggered timing and partial adoption of these policies in U.S. states allow us to evaluate whether and to what extent they reduce heat-related harms. By doing this work, I’m hopeful that we can inform the design of effective interventions and maybe even inspire future research on the health effects of extreme weather in important but difficult-to-study settings or populations.