US EPA tightens federal ozone standard to 70 ppb

2 October 2015

The US Environmental Protection Agency (EPA) has finalized new National Ambient Air Quality Standards (NAAQS) for ground-level ozone. The agency has tightened the primary (health based) ozone standard to 70 ppb, from the current limit if 75 ppb.

The adopted 70 ppb standard is on the least restrictive end of the considered range. In the proposal released in November 2014, the EPA considered a standard between 65 and 70 ppb, while the EPA scientific advisory board recommended a standard between 60 and 70 ppb.

The EPA has also strengthened the secondary ozone standard to 70 ppb, and extended the ozone monitoring season for 32 states and the District of Columbia.

Public health groups, including the American Lung Association, have criticized the new standard as too lenient. Both supporters and opponents of tougher ozone standards are likely to file lawsuits against the EPA.

The Clean Air Act requires EPA to review the ozone standards every five years. In this review, the EPA examined nearly 2,300 studies, including more than 1,000 new studies published since the last review of the standards in 2008. Scientific evidence shows that ozone can cause a number of harmful effects on the respiratory system, including difficulty breathing and inflammation of the airways. The revised standards will significantly improve public health protection, resulting in fewer premature deaths, and thousands fewer missed school and work days and asthma attacks, said the agency.

From 1980 to 2014, average US ozone levels have fallen 33%, while the economy has continued to grow. By 2025, the EPA projects that existing rules and programs will bring the vast majority of the remaining counties into compliance.

The Clean Air Act provides states with time to meet the standards. Depending on the severity of their ozone problem, areas would have until between 2020 and 2037 to meet the standards.

Source: US EPA