The Environmental Protection Agency (EPA) is reconsidering the 2015 ozone standards that set the limit for ozone pollution in the air at 0.070 ppm. The EPA has released a draft policy assessment that evaluates whether the current standards are adequate or need to be changed, based on a draft integrated science assessment that reviews the latest scientific evidence on ozone and its effects. The draft documents are open for public comment and peer review by an independent panel of experts. The EPA plans to make a final decision by October 2024.
Ozone is a gas that forms when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. Ozone can have both beneficial and harmful effects, depending on where it is in the atmosphere. In the upper layer of the atmosphere, called the stratosphere, ozone protects life on Earth from harmful ultraviolet (UV) radiation. However, in the lower layer of the atmosphere, called the troposphere, ozone is a pollutant that can harm human health and the environment.
The Environmental Protection Agency (EPA) is required by the Clean Air Act to set National Ambient Air Quality Standards (NAAQS) for six criteria pollutants, including ozone. The NAAQS are based on scientific evidence and are intended to protect public health and welfare with an adequate margin of safety. The EPA must review and revise the NAAQS every five years, as appropriate.
In 2015, the EPA revised the primary (health-based) and secondary (welfare-based) ozone standards from 0.075 parts per million (ppm) to 0.070 ppm, based on a comprehensive review of the scientific literature and input from independent experts and stakeholders. However, in 2017, under a different administration, the EPA announced its intention to reconsider the 2015 ozone standards and initiated a new review process.
In March 2023, the EPA released a draft policy assessment (PA) document that summarizes the scientific and policy information relevant to reconsidering the 2015 ozone standards. The draft PA evaluates whether the current standards are adequate to protect public health and welfare, or whether they should be retained, revised, or revoked. The draft PA also considers potential alternative levels, forms, and averaging times for the ozone standards.
The draft PA is based on a draft integrated science assessment (ISA) document that was released in December 2022. The draft ISA provides a comprehensive evaluation of the current state of the science on ozone and its effects on human health and welfare. The draft ISA updates and expands on the previous ISA that was published in 2013 and formed the basis for the 2015 ozone standards.
The draft PA and ISA are currently undergoing public comment and peer review by the Clean Air Scientific Advisory Committee (CASAC), an independent panel of experts that provides advice to the EPA on NAAQS-related issues. The EPA will consider the comments and recommendations from CASAC and the public before finalizing the PA and ISA documents. The EPA will then propose a decision on whether to retain or revise the 2015 ozone standards, followed by another opportunity for public comment and CASAC review. The EPA expects to complete this process by October 2024.
The EPA encourages interested parties to review and comment on the draft PA and ISA documents, by April 14, 2023.