August 03, 2026

Heavy-Duty Harms: Fighting EPA’s Truck Rule Rollback

Despite making up only a small fraction of vehicles on the road, heavy-duty diesel vehicles are among the top sources of health-harming NOx pollution.

By Susan Mudd, Senior Policy Advocate

Common-sense emissions controls are critical to helping protect our air and reduce the pollution responsible for smog, acid rain, and other hazards. A new EPA proposal would gut these NOx provisions for heavy-duty vehicles and exacerbate air pollution in the Midwest. I testified to the EPA last week against the proposal, here are some highlights:

Read Full Testimony

The Science is Clear: NOx Harms Health

NOx is a short-hand term for nitric oxide (NO) and nitrogen dioxide (NO2) gases, which contribute to the formation of smog, acid rain, and other hazards, poisoning communities, especially those in areas of high motor vehicle traffic. Despite making up only a small fraction of vehicles on the road, heavy-duty diesel vehicles are among the top sources of health-harming NOx pollution.

EPA staff scientists released a new draft report this month, Integrated Science Assessment of Oxides of Nitrogen. It reflects advances in atmospheric chemistry, pollutant transport research, satellite measurements, modeling capabilities, and health effects studies since 2014. The report found conclusive evidence of the harms of NOx pollution, including a causal relationship between both short- and long-term exposure and respiratory effects. It also concluded that NOx exposure likely contributes to numerous other adverse health effects.

Scientists at EPA and elsewhere must wonder, when EPA clearly finds that NOx harms public health in many ways, why are diesel trucks being given a pass on reducing this harmful pollution?

What’s in this proposed rollback?

Critical provisions of the rule included in this proposed gutting would ensure truck emissions are reduced throughout their time on our roads:

• Reducing the required useful life of emission control devices, meaning more emissions allowed over a truck’s time on the road; and
• Shortening the warranty period for emission controls, so individual truckers, not manufacturers, will be responsible for compliance costs, and reducing the chances of emission controls being properly maintained and functioning over a truck’s lifetime.

What the heck are EPA policy makers thinking?

What does this mean for the Midwest?

Chicago is at the crossroads of numerous interstate highways, and the largest concentration of intermodal facilities. In Cook County and the surrounding collar counties, emissions from medium- and heavy-duty trucks account for 22% of nitrogen dioxide pollution and contribute to more than 1,300 premature deaths each year, according to a 2025 Northwestern University study.

According to the American Lung Association’s 2026 State of the Air Report, Chicago, southeast and eastern Wisconsin and St Louis areas have among the top 25 most unhealthy days due to ozone pollution.

Every summer EPA ozone standards are exceeded in these cities and residents are advised against working, exercising, or spending time outdoors. This occurred this summer, even before the climate change caused wildfire smoke. Outdoor workers are exposed to unhealthy levels of smog, and hundreds of thousands of children can’t play outdoors. In some Chicago neighborhoods, 1/3 of children already have asthma. More NOx in the air would worsen their lives.

EPA’s decision now will have decades-long impacts. A typical diesel semi-truck, if allowed to get away with weaker tailpipe controls will emit massive quantities of unnecessary health-harming, asthma and lung-cancer causing pollution during its 750,000-mile lifespan.

EPA — please withdraw this proposal and focus on protecting Americans’ freedom to breathe clean air.