8 January 2010

The US Environmental Protection Agency (EPA) proposed to strengthen the national ambient air quality standards for ground-level ozone (O3). The new standards will replace the standards set in 2008 by the previous administration, which “many believe were not protective enough of human health”, said the EPA.

The EPA is proposing to set the “primary” ozone standard, which protects public health, at a level between 0.060 and 0.070 ppm measured over 8 hours.

In September 2009 the EPA announced that it would reconsider the existing ozone standards, set at 0.075 ppm in March 2008. The ozone standards adopted in 2008 were not as protective as recommended by the EPA’s panel of science advisors, the Clean Air Scientific Advisory Committee (CASAC). The reconsideration will be based on the scientific and technical record used in the March 2008 review, which included more than 1,700 scientific studies.

EPA is also proposing to set a separate “secondary” standard to protect the environment, especially plants and trees. The EPA proposes that the secondary O3 standard—which was set identical to the primary standard in 2008—should instead be a new cumulative, seasonal standard expressed using weighted hourly concentrations cumulated during the O3 season, set at a level within the range of 7-15 ppm-hours.

Costs of implementing the proposal are estimated between $19 billion and $90 billion. The EPA estimates that the new standards would yield health benefits between $13 billion and $100 billion, depending on the level of the final standard.

EPA will take public comment for 60 days after the proposed rule is published in the Federal Register. The agency will hold three public hearings on the proposal: on February 2, 2010 in Arlington, VA and in Houston, TX; and February 4, 2010 in Sacramento, CA. The new standards are expected to be finalized in August 2010. Final designations of nonattainment areas are to be published in August 2011.

Source: US EPA