Findings and Recommendations
Climate change and intercontinental transport of air pollutants have the potential to significantly affect global air quality in the coming decades. Establishing a suitable infrastructure for reliable, long-term observations of the chemical state of the atmosphere is a critical component of the research framework needed to characterize global air quality and to help develop and evaluate the models used for projecting future changes. The following is a summary of the committee's priority finding and recommendations for addressing these issues:
Current observational systems are not adequate for characterizing many important medium- and long-term global air quality changes. Some particularly notable weaknesses in our current observational capabilities include the lack of (i) long-term measurements of reactive compounds and PM, (ii) methods for obtaining vertical profile data, and (iii) measurement sites that allow for a meaningful examination of long range transport and trends in background concentrations.
The global air quality issues discussed in this report intersect with the concerns of several federal agencies, yet none of these agencies have a clear mandate to lead U.S. research efforts or maintain the long-term observational programs that are needed to address these issues.
Maintain and strengthen the existing measurement programs that are essential for detecting and understanding global air quality changes. High
priority should be given to programs which aid in assessing long-term trends of background ozone and PM.
Establish new capabilities to provide long-term measurements and vertical profiles of reactive compounds and PM that will allow meaningful examination of long-range transport and trends in background concentrations.
These two recommendations will require providing support to:
develop uniform and traceable standards on a global basis for calibration of both gas-phase and aerosol measurements;
improve measurement technologies for use in current observational platforms (such as ground-based air quality monitoring networks, commercial aircraft, and balloons/sondes), and in new potential platforms such as “supersites” for measuring a comprehensive suite of compounds in remote locations, and unmanned aerial vehicles for long-duration sampling of the atmosphere over a wide range of altitudes;
integrate measurements obtained from different observational programs and platforms with a particular focus on integrating remotely sensed satellite observations with in situ aircraft and ground-based measurements;
promote observational programs specifically designed to address chemical and meteorological data requirements for the improvement and validation of models.
Responsibility for carrying out this work should be clearly assigned to a U.S. federal agency (or interagency) research program, and the U.S. should play a leadership role in fostering international cooperative research and observational activities to enhance our understanding of global air quality changes.
In conclusion, the committee wishes to emphasize that developing global-scale research and observational programs inherently requires substantial international cooperation. In recent years, the atmospheric chemistry research community has successfully coordinated multinational programs to study issues such as stratospheric ozone depletion and the atmospheric effects of aviation. Studies of global air quality change should build upon these successes, and yet will likely require even deeper levels of international cooperation. For instance, quantifying long-range transport of air pollutants would be greatly aided by an
Implications for U.S. Air Quality Management
To what extent will the United States be in control of its own air quality in the coming decades? It is not possible to provide a simple answer to this question given the vast uncertainties about future global economic development, technological advances, and policy choices. As discussed in this report, however, evidence does point to the plausibility of a scenario in which non-U.S. emissions and changing climatic conditions could significantly affect the air quality in some regions of the United States.
This concern will become even more pressing with the application of the national ambient air quality standards (NAAQS) that were issued by EPA in 1997. The ozone NAAQS was changed from a 1-hour, 0.12 parts per million (ppm) ambient concentration to an 8-hour, 0.08 ppm concentration. 1 The longer averaging time and lower concentration of the new standard means that background ozone will play an increasingly important role in determining whether or not an area is in compliance with the NAAQS. As background levels rise, local emission control strategies would become less effective at maintaining compliance with mandated standards. Because the observational record for PM is much less extensive than that for ozone, it is more difficult to assess likely future changes. There are similar concerns, though, that increases in background PM levels could greatly hinder the ability of some areas to comply with the PM NAAQS. 2
Currently, air quality management plans focus primarily on controlling emissions at state and local levels. In recent years, the EPA has begun considering regional air quality management strategies, and an assessment of the North American Research Strategy for Tropospheric Ozone program (NARSTO, 2000) emphasized the importance of viewing ozone pollution from a continental perspective. It seems likely that this consideration will ultimately need to be broadened even further, to encompass a hemispheric-scale perspective. Likewise, current studies of the meteorological impacts on air quality will likely need to be expanded to include studies of how air quality is affected by long-term climatic changes. Meeting these new air quality management challenges requires a stronger scientific base which, in turn, will require strengthening the observational infrastructure for tropospheric chemistry.
1 The 0.08 ppm ozone NAAQS is defined as the 3-year average of the annual 4th-highest daily maximum 8-hour ozone concentrations.
2 In 1997 EPA revised the PM NAAQS by adding a new annual PM2.5 standard set at 15 micrograms pre cubic meter (ug/m3), and a new 24-hour PM2.5 standard set at 65 ug/m3. EPA retained the current annual PM10 24-hour standard (150 ug/m3 by replacing the 1-expected-exceedance form with a 99th percentile form, averaged over 3 years.
open exchange among countries of data from national emission inventories and air quality monitoring networks.
Programs such as the World Meteorological Organization's Global Atmosphere Watch have made substantial efforts to establish data centers and quality control programs to enhance integration of air quality measurements from different national and regional networks, and to establish observational sites in undersampled, remote regions around the world. Similarly, the International Global Atmospheric Chemistry project (of the International Geosphere-Biosphere Programme) has strongly endorsed the need for international exchange of calibration standards and has helped coordinate multinational field campaigns to address a variety of important issues related to global air quality. Maintaining these worthwhile activities depends upon continued support from the United States and other countries. The committee urges the U.S. federal agencies (working, where appropriate, with interested and qualified parties in academia, the private sector, etc.) to play a leadership role in fostering these types of cooperative efforts and developing new research and observational activities that will enhance our understanding of global air quality change.