Integrated Science Assessment (ISA) for Sulfur Oxides - Health Criteria

The Integrated Science Assessment for Sulfur Oxides – Health Criteria provides the U.S. EPA’s evaluation and synthesis of the most policy-relevant science related to the health effects of sulfur oxides (SO_x). Integrated Science Assessments (ISAs) are evaluations of the scientific information related to the human health and welfare effects of criteria pollutants. The ISAs provide a comprehensive evaluation and synthesis of the policy-relevant scientific literature, including that published since the last assessment, and serve as the scientific foundation for establishing and reviewing the national ambient air quality standards (NAAQS) under the Clean Air Act. In 2017, EPA released the Integrated Science Assessment for Sulfur Oxides - Health Criteria (Final).  

Sulfur oxides are a group of closely related sulfur-containing gas-phase compounds [e.g., sulfur dioxide (SO₂), sulfur monoxide (SO), disulfur monoxide (S₂O), and sulfur trioxide (SO₃)]. Sulfur oxides also appear in the particle phase, as components of particulate matter (PM), and particle phase sulfur compounds are discussed separately as part of the Integrated Science Assessment for PM. Among the SO_X, SO₂ is the most abundant in the atmosphere, the most important in atmospheric chemistry, the one most clearly linked to human health effects. Short-term exposure to SO₂ can cause respiratory effects, in particular, effects related to asthma exacerbation. The indicator for the NAAQS for SOx is SO₂. 

Integrated Science Assessment for Sulfur Oxides – Health Criteria (PDF) (12.26 MB, December 2017, EPA/600/R-17/451)

Scientific Studies Considered in the ISA 

The published studies cited and considered in ISAs are identified in the Health and Environmental Research Online (HERO) database. HERO is a searchable database of more than 1.6 million scientific studies and other references used to develop EPA assessments for understanding the health and environmental effects of pollutants and chemicals. For the most recent final ISA for SOx, these are identified on the ISA-Sulfur Oxides-Health Criteria (2017 Final Project Page)