Air pollution success stories in the United States: The value of long-term observations

We summarize past examples of the use of science to document the effectiveness of policy in air quality management. Our goal is to inform public discourse amidst attempts to negate the relevance and value of scientific data and fact-based analysis in favor of partisan opinion and ideology. Although air quality is fundamental to environmental and human health, air pollution has degraded natural systems and reduced economic and cultural benefits and services. The quality of air and fresh water across much of the United States vastly improved in recent decades in response to the Clean Air and Clean Water Acts and other rules and policies. We point to recently observed decreases in air pollution and its effects attributable to policy that have been informed by environmental monitoring and research. Examples include decreased environmental lead contamination due to the elimination of tetraethyl lead from gasoline, decreases in tropospheric ozone, improved visibility from reduced airborne particulate matter, declines in atmospheric sulfur and nitrogen deposition that acidify the environment and declines in atmospheric mercury and subsequent bioaccumulation of toxic methyl mercury. Pollutant reductions have provided environmental, social, and economic benefits, highlighting the urgency to apply these lessons to address current critical environmental issues such as emissions of greenhouse gases. These examples underscore the important role of data from long-term research and monitoring as part of fact-based decision-making in environmental policy.