Quick turnaround on air-quality standards

In June 2021, the US Environmental Protection Agency (EPA) announced that it will reexamine the National Ambient Air Quality Standards (NAAQS) for particulate matter (PM), even though the current standard was finalized in Dec 2020, about 2 years ahead of schedule. Such a rapid reexamination is unusual. In the announcement, EPA cited available scientific and technical information indicating that the current standards may not adequately protect public health and welfare. The review will be conducted by the Clean Air Scientific Advisory Committee (CASAC), composed of seven members and chartered under the Clean Air Act to review the NAAQS of six criteria pollutants every 5 years and provide science-based recommendations--protecting human health and the environment--to the EPA administrator. The work of the seven-member "charter" CASAC is typically supported by expert panels. However, the Trump administration disbanded the particulate and ozone panels while the standards were under review, causing great outcry.