Evaluation of adverse human lung function effects in controlled ozone exposure studies

Area of Science:

• Environmental Health
• Pulmonary Toxicology
• Air Quality Standards

Background:

• The U.S. Environmental Protection Agency (EPA) is assessing controlled human ozone exposure studies.
• Current ozone National Ambient Air Quality Standards (NAAQS) are set at 75 ppb.
• Previous studies indicate lung function decrements at ozone exposures of 80 ppb and higher.

Purpose of the Study:

• To critically review studies with ozone exposures below 80 ppb.
• To determine the lowest ozone concentration causally associated with adverse lung function decrements.
• To evaluate findings using the Adverse Effects/Causation Framework.

Main Methods:

• Review of controlled human ozone exposure studies.
• Application of the Adverse Effects/Causation Framework to assess causation and adversity.
• Analysis of lung function effects at ozone concentrations below 80 ppb.

Main Results:

• Lung function effects below 72 ppb ozone were primary but isolated, independent, and not statistically significant compared to filtered air.
• These effects are transient, reversible, of low severity, and do not interfere with normal activity.
• No evidence of permanent respiratory injury or progressive dysfunction was observed up to 72 ppb.

Conclusions:

• Studies up to 72 ppb ozone do not demonstrate a causal association with adverse lung function effects.
• Lung function changes below 72 ppb are not considered adverse as they are not severe or persistent.
• The current ozone NAAQS of 75 ppb is not demonstrated to be inadequate based on the reviewed studies.