Office of the
Illinois Attorney General
Kwame Raoul

Chicago – Attorney General Kwame Raoul, as part of a coalition of 19 attorneys general and five cities, submitted a comment letter to the U.S. Environmental Protection Agency (EPA) opposing its proposed rule to delay implementation of the Tier 4 emissions standards for light- and medium-duty vehicles. The proposed rule would give manufacturers two additional years before implementing these health-protective standards that ensure vehicles emit fewer harmful pollutants, including nitrogen oxides, particulate matter, hydrocarbons and carbon monoxide. 

In the comment letter, Raoul and the coalition assert that the EPA’s proposal to delay this compliance schedule, such that manufacturers are not required to take any action until they begin producing model year 2029 vehicles, would harm public health and welfare by delaying the benefits of stricter air pollutant emissions standards.  

“Failing to implement EPA’s Tier 4 emissions standards by delaying compliance undercuts progress we have made to reduce harmful pollutants from vehicles, including air toxins and pollutants that cause smog,” Raoul said. “I stand with my colleagues against the EPA’s failure to enforce timely standards that protect the environment and our health.”   

Under the current, state-of-the-art “Tier 4” standards adopted by the EPA in 2024, manufacturers must ensure vehicles emit fewer harmful pollutants, including nitrogen oxides, particulate matter, hydrocarbons and carbon monoxide. When the EPA adopted these standards, manufacturers had sufficient lead time before the standards would begin to be phased in and several additional years before full implementation of the standards is required. 

Following that schedule, manufacturers are required to start implementing the standards with their model year 2027 vehicles and will have to obtain Tier 4 certification for all light-duty vehicles by 2030 and for all medium-duty vehicles by 2033. However, the EPA has now proposed to delay the start of this phase-in schedule for two years, which will delay the health protections the standards provide. 

Raoul and the coalition explain in their letter that air pollution from motor vehicles continues to impact public health, welfare and the environment. Motor vehicle emissions contribute to ozone, increased levels of particulate matter and air toxics, which are linked to premature deaths and other serious health impacts, including respiratory illness, cardiovascular problems and cancer. 

In their letter, Raoul and the attorneys general and cities assert that: 

• The EPA has failed to support with any evidence its claims that compliance with the Tier 4 standards is not feasible. In fact, the Tier 4 standards are still feasible and cost-effective based on the lengthy phase-in schedule and the flexible compliance pathways outlined in the 2024 rule, including low-cost, off-the-shelf controls for internal combustion engines. 
• The EPA failed to conduct any air quality modeling; nor did EPA make any attempts to consider the economic value of the harm of delaying the Tier 4 standards on air quality, and, by extension, public health and welfare. 
• The Clean Air Act does not allow the EPA to reverse course and weaken criteria and toxic air pollutant standards. It also does not authorize the EPA to make it harder for states to meet federal air quality standards, making this proposal, if finalized, unlawful.  

Under the Trump Administration, the EPA has already repealed federal greenhouse gas standards for vehicles, which Raoul and a coalition are currently challenging in court. Now the EPA seeks to delay the implementation of their criteria and toxic pollutant standards, which would similarly erase important health and welfare benefits from the 2024 rulemaking. 

Joining Raoul in sending the letters were the attorneys general of California, Colorado, Connecticut, Delaware, the District of Columbia, Hawaii, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New York, North Carolina, Oregon, Rhode Island, Washington and Wisconsin. Also joining the letter were the cities of Chicago, New York, Denver and San Francisco.