Working in the heat is deadlier than we thought

Abas Shkembi, MS ’23

Environmental Health Sciences PhD student

April 20, 2026

By Bob Cunningham

For millions of American workers—the people building our roads, hauling our freight, mowing our lawns and fixing our pipes—the heat is not just an uncomfortable part of the job.

According to ongoing research from the University of Michigan School of Public Health, it may be deadly on a scale that has gone almost entirely unnoticed.

Abas Shkembi, MS ’23, a PhD student in Environmental Health Sciences, has spent years trying to put a real number on how many workers die each year because of occupational heat exposure. What he’s found is both striking and troubling: The true death toll may be hundreds of times higher than what official records show.

A hidden crisis in plain sight

The federal government currently tracks deaths caused by occupational heat—meaning deaths that happen on the job, on a hot day, where heat is clearly the cause. Those official numbers put the annual death toll somewhere between 30 and 60 people per year.

Shkembi's research suggests the real number is something else entirely.

Using a statistical modeling approach, Shkembi linked detailed data on heat exposure across the United States with mortality records from 2010 to 2019. What made his approach unique was the occupational exposure data itself—estimates that varied across both location and time, something rarely available for workplace exposures. What he found was startling: Somewhere between 3,000 and 17,000 deaths per year among working-age Americans may be linked to occupational heat exposure.

That is a gap of potentially hundreds-fold.

When looking for a reason for the massive difference, he said the answer comes down to how we define and count an “occupational” death and the limitations built into the way the system works.

“Those 30 to 60 deaths are those that likely occurred on the job on very high heat days,” said Shkembi, who has a master’s degree in Industrial Hygiene from Michigan Public Health. “The death followed shortly after symptoms were observed. But we know that occupational disease—health conditions caused by long-term exposure to hazardous agents, particularly in the case of occupational heat—can take days, weeks, to months for the effects of exposure to lead to premature mortality.”

In other words, heat does not always kill quickly or cleanly. It can worsen existing respiratory conditions. It can accelerate chronic kidney disease. It can quietly wear down the body over time. When someone dies weeks after a stretch of dangerous working conditions, heat is rarely listed as a contributing cause on a death certificate. The connection simply does not get made.

“Heat can contribute through many different pathways,” Shkembi said, “but these estimates don’t capture that. That’s why we see this large gap between what’s reported and what is potentially the true burden.”

PROSPECTIVE STUDENT? Learn more about Michigan Public Health.

Mapping who gets hurt most

A second paper—still under peer review—builds on the groundwork laid by an earlier study Shkembi published in the Journal of Exposure Science and Environmental Epidemiology. That first paper tackled a different but equally important question: Who, exactly, is exposed to dangerous levels of heat at work, and where are they?

At the time the research began, existing data on occupational heat exposure was thin. Most of it was outdated, not detailed enough, and tended to focus on a narrow slice of workers—often farmworkers and construction crews.

Shkembi set out to change that. He built a model capable of estimating likely heat exposure for workers across every census tract in the United States, for every day between 2010 and 2019. Then, he connected that exposure data with demographic information: race and ethnicity, income level, education and immigration status.

The results confirmed what many researchers in the field of environmental justice have long suspected: The burden of occupational heat is not shared equally.

Workers with lower incomes, workers with less formal education, workers from racial and ethnic minority groups, and immigrants were all disproportionately exposed to dangerous heat on the job. These are, not coincidentally, often the same workers doing the physical, outdoor, or poorly climate-controlled jobs that keep our daily lives running.

“We saw very starkly that each of those groups are disproportionately burdened by occupational heat exposure,” Shkembi said.

“Most people understand that some of the most vulnerable populations to extreme weather are children and the elderly and pregnant women,” he said. “But we sort of have a preconceived notion that workers are healthy—middle-aged, doing jobs where physical activity is part of the routine—so they can’t be as vulnerable. This work is important to highlight that yes, even ‘healthy people’ are impacted by heat, whether we like it or not.”

READ MORE about faculty, students, alumni and staff.

A path that was never planned

None of this was the career Shkembi expected to have.

Growing up in Macomb, Michigan, about 30 minutes north of Detroit, Shkembi was a numbers person. He earned his bachelor’s degree in Statistics from the University of Michigan in 2020 with a minor in Environmental Science. 

Public health was not on his radar. He barely knew it existed as a field.

That changed in 2019, when Shkembi traveled to Thailand as part of an undergraduate research project studying electronic waste—the mountains of discarded phones, computers, and appliances that pile up across the developing world. He came to the project thinking about sustainability, about waste streams and environmental impact. He was not thinking about people.

“I came into that project fully from a sustainability, sort of waste generation perspective, not even thinking about how that waste generation impacts human health,” he said. “Even the first year I worked on that project, I really wasn’t interested in the human health aspect.”

That began to change through his exposure to the researchers around him, especially one in particular.

Rick Neitzel, professor of Environmental Health Sciences and Global Public Health is the director of the Industrial Hygiene program at Michigan Public Health. He also has been Shkembi’s advisor, collaborator and mentor since 2018—a working relationship that has stretched across eight years and multiple research projects.

“Dr. Neitzel is the best mentor I ever could have asked for because I truly feel that,” Shkembi said. “He has a real knack for understanding what people’s interests are and creating an environment where they can explore those interests.”

For Shkembi, that freedom has been essential. He wants to connect ideas across different fields and try things that have not been tried before. In many research labs, that kind of wandering curiosity gets reined in. In Neitzel’s lab, it’s encouraged.

“I feel like I’m an inventor in a way; I get to invent new ideas and connect one idea to another,” Shkembi said. “In Dr. Neitzel’s lab, that is definitely allowed to flourish because he gives you the space for that.

“I just love the environment he’s created.”

That space led Shkembi to apply econometrics—a branch of statistics common in economics and occupational safety research—to questions rooted in traditional industrial hygiene and public health. It is not an entirely new combination, but one that remains relatively uncommon in industrial hygiene studies with a public health focus. It is also, he said, exactly the kind of methodological bridge-building that Neitzel’s lab made possible.

Neitzel said it’s been a privilege serving as Shkembi’s mentor in his doctoral and master’s programs.

“Abas has been incredibly productive, and has done some remarkable research examining exposures to, and impacts from, a range of health hazards in communities and workplaces in Michigan and across the US,” Neitzel said. “He has been particularly focused on assessing disparities in exposures and health outcomes from environmental exposures among minority and marginalized populations. 

“As a result of his work, we have a better understanding of how a number of harmful exposures—including noise, heat, air pollution and psychosocial stress—are inequitably distributed in US communities and workplaces.”

Shkembi is now in the final stretch of his doctoral work. His research sits at a crossroads that he sees as deeply meaningful: The place where the environment, the workplace and human justice all collide.

He grew up in a family of immigrants who understood work as something you did to survive—whatever it took, wherever it was. The idea of fighting for fairness in the workplace felt foreign to him for a long time. But years of studying who bears the heaviest burdens of environmental harm—and why—changed his thinking.

"As I leaned further into studying environmental justice,” Shkembi said, “I started to realize how occupational justice is just as important.”

SUPPORT research and engaged learning at Michigan Public Health.

---