Researchers have found an association between air pollution exposure and a rare type of bleeding within the brain.
An aneurysmal subarachnoid hemorrhage, or aSAH, can damage brain tissue enough to leave patients paralyzed or in a coma or cause death.
Neurosurgeon Robert Rennert led a retrospective study of 70 patients treated at the University of Utah Hospital for aSAH over a 5-year period. Utah’s Wasatch Front is often beset with high levels of fine particulate pollution (PM2.5) during wintertime inversions.
Rennert’s team, which included neurosurgeons from the University of California, San Diego, reviewed nearly 13,000 data points to determine PM2.5 levels on the Wasatch Front in the days, weeks and months leading up to the admissions of local patients. The goal was to determine whether PM2.5 levels affected each patient’s risk of hemorrhage.
“After controlling for other variables, we expected to find that patients were more likely to be admitted for aSAH within a week of exposure to high PM2.5 levels,” Rennert says.
“Instead, we found that these patients were experiencing higher rates of aneurysmal rupture three to six months after peaks in air pollution levels.”
This gap in time between when PM2.5 levels were highest and when a brain hemorrhage actually occurs makes studying the association between these events challenging.
Nonetheless, “aSAH has a high risk of death and disability, so understanding the risk factors for rupture in patients with brain aneurysms is critically important from a public health perspective.”
The air quality along Utah’s Wasatch Front has long been considered poor, especially during the winter when inversions trap polluted air in the valleys, but researchers are still learning exactly how our health is affected by poor air quality.
The American Lung Association’s 2024 list of most polluted cities in the U.S. ranked the Salt Lake City-Provo-Orem area 25th for short-term PM2.5 pollution. PM2.5 consists of tiny particles or droplets (30 times finer than human hair) that are easily inhaled and can be harmful, damaging lungs and increasing the risk of ischemic strokes and other maladies.
Rennert says this study is the beginning of the team’s efforts to understand the effects of PM2.5 on brain health, with additional studies planned to determine more definitively whether PM2.5 pollution can cause aSAH, including in regions beyond the Wasatch Front, as well as further assess the mechanisms and risks of air pollution on cerebrovascular disease more broadly.
“We’re hoping that our research helps alert people to the public health risks of air pollution and encourages changes,” Rennert says.
“Incentivizing public transportation use, applying stricter daily pollution quota regulations, and broadening research funding for environmental studies will all help to lessen our exposure and have long-term benefits for collective health.”
The research appears in the journal npj Clean Air.
Source: University of Utah
