• List potentially dangerous but unregulated air pollutants for regulatory attention. Determine whether there are sufficient data on adverse impacts, chemical structure, and potential for population exposure and identify whether some level of regulatory response would be prudent and appropriate.

  • Address multiple pollutants in the NAAQS review and standard-setting process by beginning to review and develop NAAQS for related pollutants simultaneously.

  • Enhance assessment of residual risk by performing an increased number of assessments in the years to come and by attempting to include in the assessments other major sources of the same chemicals.

Recommendation Five

Enhance protection of ecosystems and other aspects of public welfare.

Many of the programs and actions undertaken in response to the CAA have focused almost entirely on the protection of human health. Further efforts are needed to protect ecosystems and other aspects of public welfare. The critical actions include

  • Completion of a comprehensive review of standards to protect public welfare.

  • Develop and implement networks for comprehensive ecosystem monitoring to quantify the exposure of natural and managed resources to air pollution and the effects of air pollutants on ecosystems.

  • Establish acceptable exposure levels for natural and managed ecosystems by evaluating data on the effects of air pollutants on ecosystems at least every 10 years.

  • Promulgate secondary standards where needed that take the appropriate form. For example, in some cases a standard based on the amount of a pollutant that is deposited on the earth’s surface over a particular area may be more appropriate than a standard based on the atmospheric concentration of that pollutant. Allow for consideration of regionally distinct standards.

  • Track progress toward attainment of secondary standards by using the aforementioned monitoring of ecosystem exposure and response.


Because the nation’s AQM system has been effective in many aspects over the past three decades, much of the system is good and warrants retaining. Thus, the recommendations proposed here are intended to evolve

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