Cities across the western United States are grappling with a dual threat: extreme heat coupled with rising levels of air pollution. A recent study by Jessica Leffel, a master’s student in the University of Oklahoma’s School of Meteorology and SURF Lab, reveals that these two environmental hazards are on the rise. Together, this potent cocktail creates grave health dangers to city dwellers. These studies were led by Chenghao Wang, an assistant professor in the School of Meteorology and the Department of Geography and Environmental Sustainability at OU. Their findings show some pretty shocking trends when it comes to compound weather events.
Research indicates that cities are experiencing longer and more intense stretches of compound heat days. At the same time, particulate matter (PM2.5) pollution is increasing. These trends have been accelerated in recent years, largely driven by the impact of wildfire smoke on air quality. The public health and urban planning implications are deep and complicated, raising immediate questions about what should be done to reduce that risk.
Understanding Compound Weather Events
Chenghao Wang, Bert Huang, and their colleagues published two groundbreaking studies. These studies illustrate the interplay between extreme heat and air pollution. The first, published recently in the journal Urban Climate, explores the connection between these compound heat events and ozone pollution. The second, titled “Cities as hotspots of compound heat and fine particulate matter pollution,” appears in Environmental Research. The new study provides a detailed look at the differences between U.S. cities and towns for the last 23 years. It further demonstrates the enormous disparities between urban and rural responses to environmental stressors.
The research shows that cities can be significantly hotter after the sun goes down, as our buildings and roads send the day’s stored heat back into the air. Rural areas cool down significantly faster during the night. Cities are frequently caught in a feedback loop of increased heat. This can compound the impacts of air pollution even further. This dangerous phenomenon has a huge effect on residents. It raises specific dangers to at-risk groups, such as the elderly and those with pre-existing medical conditions.
Rising Pollution Levels
As a result, research points to increases in PM2.5 pollution as the concentration of compound event days increases in metropolitan areas. Additionally, when heat waves do occur, they frequently coincide with PM2.5 episodes. Therefore, almost all (nearly 98%) of the surveyed cities are increasingly experiencing more frequent and intense compounding events. This shocking data point drives home the urgency to take action now to tackle extreme heat and worsening air quality at the same time.
Over half of the cities analyzed reported increased lengths of overlapping events. This trend was pronounced when heat waves overlapped with PM2.5 events. This kind of exposure can have life-threatening effects on your health. It contributes to respiratory disease, cardiovascular disease, and heat-related illness. The data shows how badly we need public health interventions. To address these effects, we need to more aggressively reduce emissions and introduce urban green infrastructure to fight against these impacts.
Urban vs. Rural Disparities
Wang’s research uncovers a shocking truth—when a heat and ozone event co-occur, 88.8% of cities experience a more intense cumulative heat and ozone effect. This is stark contrast to the levels in their rural counterparts. This disparity raises concerns about environmental justice, as urban residents may face greater health risks due to systemic inequalities in exposure to pollution.
This new research sheds light on the fact that most cities are double trouble areas for extreme heat and PM2.5 pollution. This combo puts them at greater risk of the health impacts of these environmental stressors. In this context, planning strategies that promote compact, transit-oriented urban development may be key in tackling these issues. These takeaways fuel the need for more integrated approaches. To truly protect public health, these approaches must prioritize climate change adaptation needs and simultaneously improve air quality.
