US EPA

This draft document provides EPA’s evaluation and synthesis of the most policy-relevant science related to the health effects of sulfur oxides. When final, it will provide a critical part of the scientific foundation for EPA’s decision regarding the adequacy of the current primary (health-based) National Ambient Air Quality Standard (NAAQS) for sulfur dioxide.

The references considered for inclusion in or cited in the external review draft ISA are available at https://hero.epa.gov/hero/sulfur-oxides.

Sulfur oxides are one of six principal (or criteria) pollutants for which EPA has established NAAQS. For sulfur oxides, the indicator for the NAAQS is sulfur dioxide (SO2). The Clean Air Act requires EPA to periodically review the scientific basis for these standards by preparing an Integrated Science Assessment (ISA). These reviews play a significant role in EPA’s commitment to ensuring a clean and healthy environment for the public.

The draft ISA is part of the Agency’s periodic review of the primary (health-based) NAAQS for SO2. Overall, findings from recent studies strengthen the conclusions from the previous NAAQS review, which was completed in 2010. Results from recent studies strengthen the body of evidence indicating that short-term exposure to SO2 can cause respiratory effects, in particular, effects related to asthma exacerbation. There remains uncertainty regarding the potential for SO2 effects outside the respiratory system.

The intent of the ISA, according to the CAA, is to “accurately reflect the latest scientific knowledge expected from the presence of [a] pollutant in ambient air” (U.S. Code, 1970a, 1970b). It includes an assessment of scientific research from atmospheric sciences, exposure sciences, dosimetry, mode of action, animal and human toxicology, and epidemiology. Key information and judgments formerly found in the Air Quality Criteria Documents (AQCDs) for sulfur oxides (SOx) are included; Annexes provide additional details supporting the ISA. Together, the ISA and Annexes serve to update and revise the last SOx ISA which was published in 2008.

This draft will be reviewed by the Clean Air Scientific Advisory Committee (CASAC) at a public meeting announced in the Federal Register. A future Federal Register notice will inform the public of the exact date and time of that CASAC meeting. In revising and finalizing the ISA, EPA will take into account CASAC advice and recommendations as well as public comments. The final assessment, will be posted on EPA’s website, and will provide a critical part of the scientific foundation for the primary NAAQS for sulfur dioxide.

U.S. EPA. Integrated Science Assessment (ISA) for Sulfur Oxides – Health Criteria (Second External Review Draft, Dec 2016). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-16/351, 2016.