On 1 October, the US Environmental Protection Agency (EPA) set a new national ambient air quality standard of 70 parts per billion (ppb) for ground-level ozone, down from the current level of 75 ppb set in 2008.
But the new limit is the least restrictive that the agency had been considering, and health experts complained it does not go far enough. The EPA had been considering a range of 60 to 70 ppb before settling on a level at the top end of this range.
Harold P. Wimmer of the American Lung Association, said: “Given the health threats from ozone, greater health protections are clearly needed. The level chosen of 70 ppb simply does not reflect what the science shows is necessary to truly protect public health. Protecting the public health is the fundamental requirement of the national standard under the Clean Air Act. An ozone limit of 60 ppb would have given Americans much greater health protections. According to EPA’s proposal, a 60 ppb standard would have prevented up to 1.8 million asthma attacks in children, 1.9 million school days missed, and 7,900 premature deaths nationwide.”
The public health benefits of the 70 ppb standard are estimated at US$2.9 to 5.9 billion annually in 2025, outweighing the estimated annual costs of US$1.4 billion.
Depending on the severity of their ozone problem, states would have until between 2020 and 2025 to meet the standards. But California has been given until 2037, 12 years longer than the rest of the country, to meet the standard.
The Clean Air Act requires EPA to review the ozone standards every five years to determine whether they should be revised in light of the latest science.