The researchers analyzed 7,500 suicide cases across Utah from 2000 to 2016, comparing each death with local temperature and air quality data in the days leading up to it.
The findings point to a particularly dangerous combination: heat and nitrogen dioxide — a pollutant largely produced by cars, trucks and power plants.
On days when both temperatures and nitrogen dioxide levels were high, suicide risk increased by nearly 50%.
Lead author Amanda Bakian, a psychiatric epidemiologist at the University of Utah, said the timing of those exposures is key.
“It is a critical period for intervention, the two weeks just before a suicide death,” Bakian said. “So, if we can better understand what might be happening in that time period, the better we might be positioned to intervene.”
Nitrogen dioxide can build up in the air during certain weather conditions. In the summer, heat and stagnant air can trap pollution near the ground. In winter, similar buildups can happen during inversion events, when cold air holds pollutants in place.
Bakian said the study highlights how environmental conditions can shape short-term mental health risks, not just long-term trends.And that could have real-world implications for public health.
The research comes as the Mountain West experiences hotter summers and, increasingly, more days with unhealthy air, which are trends driven in part by climate change and shifting pollution patterns.
The region is currently seeing an unusual early-season heat wave, with temperatures climbing well above normal in several states.
Measures like opening cooling centers, issuing extreme heat warnings and alerting people to poor air quality could help reduce risk during vulnerable periods, said Bakian.
Researchers say understanding how heat and pollution interact could help communities better prepare for those kinds of conditions, and potentially save lives.
This story was produced by the Mountain West News Bureau, a collaboration between KUNR, Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNC in Northern Colorado, KANW in New Mexico, Colorado Public Radio, KJZZ in Arizona and NPR, with additional support from affiliate newsrooms across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting and Eric and Wendy Schmidt.
