In the dozens of Texas prisons that don’t have air conditioning, new research shows that 13 percent of deaths during the six hottest months every year from 2001 through 2019 were likely due to extreme heat. The study, which was published last week in the academic journal JAMA Network Open, is the first epidemiological evidence that the lack of air conditioning in a large proportion of U.S. prisons is substantially increasing the risk of death for those incarcerated. It also suggests that over 250 Texans lost their lives over the past two decades because of the state’s failure to mitigate indoor heat.

In Texas, where two-thirds of the state’s nearly 100 prisons lack air conditioning, temperatures inside facilities have risen to as high as 149 degrees Fahrenheit. Climate change will only increase the number of dangerously hot days: Historically no Texas county typically saw more than 25 days annually where the heat index rose above 105 degrees F. By midcentury, however, more than a third of counties in the Lone Star State will likely be subject to more than 50 days with heat that high, according to data from the nonprofit Union of Concerned Scientists.

Nevertheless, Texas lawmakers have repeatedly failed to advance bills that would fund prison air conditioning, and prison officials have suggested that heat deaths are not a problem. At a July hearing before the Texas House of Representatives’ Appropriations Committee, Texas Department of Criminal Justice executive director Bryan Collier claimed that that there have been zero heat-related deaths since 2012.

“Their numbers are wrong,” said Amite Dominick, one of the new report’s coauthors and the president and founder of Texas Prisons Community Advocates, an organization that is pushing Texas policymakers to fund prison air conditioning.

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“I hope it adds further credence to what we’ve been saying all along — that these individuals are dying because the Texas Department of Criminal Justice is refusing to put AC in prisons,”she added. “Our legislators aren’t getting the job done.”

The 271 deaths in facilities without air conditioning — an average of 14 per year — occurred on days that were unusually hot for the region, when the heat index rose above the 90th percentile for the location. On such days, the risk of death rose 15 percent. The study also found that each 1-degree increase in temperature over 85 degrees increased risk of death by 0.7 percent.

These deadly effects were not observed in air-conditioned facilities: The researchers, led by Brown University Ph.D. Julianne Skarha, found no correlation between heat and mortality in the latter. This is not surprising, given that heat-related death is uncommon among the general population — accounting for less than half a percent of U.S. deaths.

While Texas jails are required to maintain temperatures between 65 and 85 degrees F, state prisons have no such regulations. “There is life-saving potential if the Texas Department of Criminal Justice applies a similar temperature regulation policy to its prison facilities as it does to its jail facilities,” the researchers wrote.

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The Texas Department of Criminal Justice declined to comment on the report. “The agency takes numerous precautions to lessen the effects of hot temperatures for those incarcerated within our facilities. These efforts work,” Communications Director Amanda Hernandez said by email. “In 2022, there have been thirteen inmates who required medical care beyond first aid for heat related injuries and none were fatal.”

Skarha chose to focus her research in Texas in part because it has the highest state prison population in the U.S., incarcerating around 118,000 people. However, the JAMA study has implications far beyond the state.

“We know there are many states in the U.S., especially in the South, that don’t have AC in the majority of their prisons,” Skarha said. “There’s no reason to assume that it’s not a similar story there.”

Heat deaths are difficult to track, and the cause of a heat-induced death isn’t always listed as hyperthermia. Researchers have found that heat increases the risk of cardiovascular- and diabetes-related deaths as well as the risk of death for people over age 75. U.S. prison populations are aging, and prisoners are more likely to have both heart conditions and diabetes. People taking psychotropic medications, used to treat a range of mental health issues, are also particularly heat-sensitive and are also over-represented among those incarcerated.

Hernandez, the corrections department communications director, told Grist that prisoners have access to fans and ice water. Additionally, in 2018 a lawsuit forced Texas to implement a system for protecting prisoners in unairconditioned prisons on hot days, including by offering access to cooled respite areas and by moving heat-sensitive individuals to air-conditioned housing. Although the JAMA study period overlaps with the new measures, it provides minimal insights into the effectiveness of that program.

Separate survey results published this summer by Texas A&M University suggest the new measures have fallen short. Close to a third of incarcerated survey participants said they were aware of at least one heat-related death in prison. Many described near-death experiences or a fear that the heat would kill them. That research was also a collaboration between scholars and grassroots organizers with Texas Prisons Community Advocates.

To Dominick, it’s long past time for policymakers to act. “This problem has been happening for decades and they want reports and testimonies and articles,” said Dominick. “It is hot in Texas and they know it. They are choosing not to get this done quickly.”