In addition, the US NAAQS are periodically reviewed, frequently strengthened, commonly enforced and allow serious legal penalties if the standards are not met.
The NAAQOs are set by the federal government based on recommendations from a National Advisory Committee and Working Group on Air Quality Objectives and Guidelines.
The NAQOs were made with the intention to protect the general population as well as the environment from the harm of bad air quality.
The executive summary of the National Ambient Air Quality Objectives states the effect of air pollutants on the environment include less than desired growth conditions for vegetation and the adverse health effects on people include an increased risk of death and lung disease.
Furthermore, in an archived report some considerations offered were to focus on a 24 hour range rather than the peak exposure times as some of the data suggests.