A distant view of a smoggy city

Particulate Matter

Particulate matter (PM) pollution is a mixture of solid particles and liquid droplets found in the air that vary in size. PM comes from construction sites, unpaved roads, fields, smokestacks or fires and has been associated with a wide range of health problems, including cardiovascular disease, respiratory impacts and cancer. PM pollution is regulated under the Clean Air Act’s National Ambient Air Quality Standards (NAAQS) program as a criteria air pollutant.

NAAQS Policy Assessment

2017-2020

  • September 2019

    In September 2019, the Environmental Protection Agency (EPA) released its draft Policy Assessment regarding NAAQS for PM. The study is supposed to help the agency develop conclusions about the adequacy of existing PM standards and potential alternatives under the NAAQS. The EPA made a number of changes to the process for developing the draft Policy Assessment that have reduced the transparency of the agency’s PM NAAQS review.

  • November 2019

    In November 2019, California Attorney General Xavier Becerra led a coalition of six attorneys general in submitting comments on the draft Policy Assessment. The comments highlighted several problems with the draft Policy Assessment’s development process, including the EPA’s consolidation of key components of the review process and elimination of opportunities for public comment on multiple interim drafts of critical documents produced as part of the review. Further, the attorneys general criticized discontinuation of the long-standing practice that the Clean Air Scientific Advisory Committee PM Review Panel provide analysis and feedback on the agency’s review of the PM NAAQS. Addressing the shortcomings in the draft Policy Assessment’s development process would help ensure that the final PM NAAQS standard protects public health and welfare with an adequate margin of safety as required by the Clean Air Act.

Strengthening NAAQS

2021-2024

  • January 2021

    In January 2021, California Attorney General Becerra led a coalition of 17 attorneys general in filing a petition for review in the Court of Appeals for the D.C. Circuit challenging the December 2020 rule leaving the current NAAQS for PM unchanged.

  • January 2023

    On January 27, 2023, EPA released a proposed rule, which would revise the NAAQS for PM. Reconsideration of the National Ambient Air Quality Standards for Particulate Matter.

  • February 2023

    EPA held a public hearing on EPA’s proposed decisions for the Reconsideration of the NAAQS for PM on February 21-23, 2023.

    This case has been held in abeyance since February 2021. Motions to govern are due May 30, 2024.

  • February 2024

    On February 7, 2024, EPA issued its final rule.

2017-2020

  • April 2020

    In April 2020, the EPA released a proposed decision not to strengthen the NAAQS for PM. The EPA is required under the Clean Air Act to review the NAAQS for PM every five years and last revised the standards in 2012.

  • June 2020

    On June 29, 2020, New York Attorney General Letitia James led a coalition of 17 AGs in filing comments in “strong opposition” to EPA’s proposed decision to not amend the NAAQS for PM. The comments emphasized that the “weight of new scientific evidence and other analyses regarding harm to health from particulate matter since the last review . . . demonstrates the need to strengthen those standards in order to meet the [Clean Air] Act’s requirement to protect public health and welfare.” The comments also warned that EPA’s assertion that its proposed decision will not cause disproportionate harm to environmental justice communities is “egregious and wholly contradicted by the record.” The comments noted that, contrary to EPA’s assertion that “uncertainty in the evidence supports leaving the current standards unchanged,” the Clean Air Act requires EPA to “establish more protective standards in the presence of uncertainty in order to provide the requisite margin of safety against harmful effects.”

  • November 2020

    On November 20, 2020, New York Attorney General Letitia James led a coalition of 16 AGs in filing comments urging EPA to change course on its decision to leave the existing NAAQS for PM in place despite a significant and growing body of scientific evidence that they are failing to protect public health. The AGs highlighted three recently published scientific studies that provide further evidence of “both the immediate harms of exposure to particulate matter during a respiratory disease pandemic and the long-term cognitive impacts” of exposure to fine particulate matter. One of the studies found a statistically significant connection between particulate matter exposure and an elevated risk of death in COVID-19 patients; another study found that older people exposed to PM2.5—which are fine, inhalable particles that have diameters of 2.5 micrometers and smaller—faced “an increased risk of Parkinson’s disease, Alzheimer’s disease, and related dementias.”

  • December 2020

    In December 2020, disregarding the concerns of the attorneys general, the EPA published its final rule leaving the current NAAQS for PM unchanged. California Attorney General Becerra condemned the Trump administration’s decision as “despicable” and highlighted the disproportionate impact the decision will have on low-income communities, “particularly when coupled with a deadly respiratory pandemic.”