US HB4218

Extends the EPA's review cycle for national ambient air quality standards from 5 years to 10 years, and allows the Administrator to consider "likely attainability" as a secondary factor when setting primary air quality standards

Requires EPA to give states at least 1 year to correct deficiencies before imposing a federal implementation plan, and extends the federal plan deadline from 2 to 3 years if states submit corrections

Exempts ozone nonattainment areas classified as "Extreme" from contingency measure requirements, and adds "economic feasibility" as a consideration alongside technological achievability for emission reduction plans

Expands the definition of "exceptional events" to include prescribed fires and wildfire mitigation activities, allowing states to exclude related air quality monitoring data from compliance determinations; requires EPA to create a public website tracking petition statuses within 12 months

Increases state representation on the Clean Air Scientific Advisory Committee from 1 to 3 members with geographic diversity requirements, and mandates assessment of adverse public health, welfare, social, economic, and energy effects before setting air quality standards