By Sam Roherty & Paul Mathewson, Ph.D.
Summary
Ground-level ozone (“bad ozone”) is an air pollutant formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in sunlight and warm temperatures. Unlike the protective ozone layer high in the atmosphere, ground-level ozone damages the lungs and respiratory system, increasing the risk of asthma attacks, respiratory illness, hospitalization, and premature death. Although ozone levels have declined across Wisconsin since the 1990s due to cleaner vehicles and stronger air pollution regulations, unhealthy ozone pollution remains a significant public health concern, particularly along the Lake Michigan shoreline. Warmer temperatures driven by climate change are also expected to increase ozone formation, while wildfire smoke can further elevate ozone levels by transporting ozone-forming pollutants into the state.
Key takeaways:
- Ozone pollution is estimated to be responsible for 100-400 premature deaths per year in Wisconsin, along with 1,000 hospital and emergency room visits for respiratory issues, 396,000 cases of asthma symptoms, and 240,000 lost school days each year.
- The public health burden of ozone pollution is approximately $6 billion per year in Wisconsin.
- Fossil fuel combustion from vehicles and power plants are the primary sources of ozone precursors.
- In Wisconsin, 2.5 million residents (44% of the population) live in areas seeing at least one day with ozone concentrations above the current health-based air quality standard of 70 parts per billion (ppb), and 214,000 residents (4%) live in areas seeing at least five days with ozone concentrations above 70 ppb.
- Evidence suggests that there are significant public health risks at ozone concentrations below the current health-based air quality standard of 70 ppb, meaning that the harmful impacts of ozone in Wisconsin are significantly underestimated by only considering areas that exceed 70 ppb.
- Limiting climate change to 2.5°C warming by 2050 would have a co-benefit of 135-360 fewer ozone-related premature mortalities per year in Wisconsin.
