In 2024, EPA updated its emissions standards for light- and medium-duty vehicles. These included more protective standards for smog- and soot-forming pollutants. EPA now seeks to weaken these life-saving limits on smog- and soot-forming emissions for two model years of covered vehicles, while noting that amendments to standards for future model years “will be proposed separately.” This weakening would increase emissions of soot-forming pollutants such as particulate matter (PM), as well as smog-forming pollutants, also called ozone precursors, for decades to come, causing billions of dollars in harms to human health. Yet in the Proposed Rule, EPA spurns decades of agency practice and an enormous scientific record by declining to incorporate in its analysis any estimates of the impact of PM and ozone on human health. EPA’s decision to abandon its well-established estimates quantifying and monetizing these impacts is contrary to the best available science: EPA’s own Science Advisory Board (SAB) reviewed and affirmed these “essential tools” just two years ago.
We submitted comments, along with our partners at Clean Air Task Force, Environmental Defense Fund, Montana Environmental Information Center, Natural Resources Defense Council, Sierra Club, and Union of Concerned Scientists, explaining that EPA’s new claim that these estimates are too uncertain is flawed for numerous reasons. By failing to incorporate these estimates, EPA has arbitrarily failed to consider an important aspect of decisionmaking in the Proposed Rule. EPA should reverse this irrational about-face and implement the 2024 Rule on schedule.