The U.S. Environmental Protection Agency (EPA) issued rules that it says strengthened the National Ambient Air Quality Standards (NAAQS) for ground-level ozone to 70 parts per billion (ppb). The EPA says the updated standards will improve public health protection, particularly for at-risk groups including children, older adults, people of all ages who have lung diseases such as asthma, and people who are active outdoors, especially outdoor workers.

(More information from EPA, including the final rule, is available here.)

Nonattainment areas will have until 2020 to late 2037 to meet the health standard, with attainment dates varying based on the ozone level in the area. EPA says that most states can build off work they are already doing to reduce pollution to help them meet the standards. EPA Administrator Gina McCarthy, in issuing the rule, concluded that a standard of 70 ppb also will provide the adequate margin of safety the law requires. EPA says the updated standard will protect more than 98% of school-age children from repeated exposures to ozone concentrations as low as 60 ppb – a 60% improvement over the current standard.

In issuing the rule, EPA says that California has unique air quality challenges due to the combination of meteorology and topography, population growth, and the pollution burden associated with mobile sources. EPA says it will work with stakeholders to "explore strategies and technologies to reduce pollution and improve public health protection for California residents." EPA says that a number of California counties likely will have attainment dates ranging from 2032 to late 2037.

EPA says that existing and proposed federal rules will help states meet the standards by reducing ozoneforming pollution. These rules include: requirements to reduce the interstate transport of air pollution, Regional Haze regulations, the Mercury and Air Toxics Standards, the Clean Power Plan, the Tier 3 Vehicle Emissions and Fuels Standards, the Light-Duty Vehicle Tier 2 Rule, the Mobile Source Air Toxics Rule, the Light-Duty Greenhouse Gas/Corporate Average Fuel Efficiency Standards, the Heavy-Duty Vehicle Greenhouse Gas Rule, the Reciprocating Internal Combustion Engines (RICE) NESHAP, and the Industrial/Commercial/Institutional Boilers and Process Heaters MACT and amendments.