NRC: SMOG CONTROL EFFORTS OFF MARK

The National Research Council says U.S. regulatory programs to control smog may have been misdirected the past 20 years, and more emphasis needs to be placed on limiting nitrogen oxide emissions.

An NRC study said ozone control efforts have focused mainly on controlling volatile organic compounds (VOC) emissions.

"However, in many parts of the country controlling emissions of nitrogen oxides would be more effective," it said, noting VOCs and nitrogen oxides are precursors of ozone.

The study found the main statistical method used to assess ozone trends is unreliable, VOC emissions have been seriously underestimated, and ozone regulatory programs are badly flawed due to unverified emissions estimates.

It said although switching to alternative motor vehicle fuels and reformulated gasoline has the potential to improve air quality in some urban areas, the amount of improvement is uncertain and will vary depending on the location and the fuels used. Alternative fuel use alone will not solve ozone problems nationwide.

It said use of reformulated gasoline and alternative fuels such as natural gas, methanol, ethanol, hydrogen, and electricity may provide little benefit to urban air quality because motor vehicle emissions are only a part of total VOC emissions.

For example, using methanol instead of gasoline in automobiles in the Los Angeles area is predicted to result in little decrease in peak ozone levels.

MONITORING PROBLEM

John Seinfield, a California Institute of Technology professor who headed the NRC study, said, "'Despite more than two decades of massive, costly efforts to bring ambient ozone levels under control, there has been a lack of progress in many areas of the country that's disappointing and perplexing.

"One of the most important findings of this committee is that ozone problems persist in part because regulatory agencies have not been monitoring the precursors of ozone adequately to establish the validity of their own emissions inventories."

The study noted lower atmosphere ozone pollution is produced in the presence of sunlight when nitrogen oxides react with VOCs. Nitrogen oxides come mainly from fossil fuel combustion, and VOCs from cars, evaporating solvents, the chemical and petroleum industries, and natural vegetation.

It said most ozone abatement strategies have focused on VOCs, "but state of the art air quality models and improved knowledge of atmospheric chemistry indicate that control of nitrogen oxides is necessary for effective reduction of ozone in many areas of the U.S."

In areas where VOCs mainly determine the amount of ozone formed, efforts to control them are the most effective. "But new data show that VOC emissions may be significantly undercounted in many regions. In such regions, it is likely that VOCs are not determining factors in the amount of ozone formed.

"In these cases, nitrogen oxides are more important in determining ozone formation, and a shift is needed toward greater consideration of nitrogen oxide controls."

BETTER METHOD NEEDED

The study said the main statistical method used for assessing ozone trends is faulty. Trends are judged on the basis of the second highest daily 1 hr ozone level measured during a year for a given urban, suburban, or rural area. It said that technique is not reliable because it is highly sensitive to fluctuation in weather patterns.

VOC emissions have been underestimated to such a degree that regulatory strategies may have been seriously misdirected during the past two decades. VOC emissions have been estimated instead of monitored, and the estimates are much smaller than the true emissions from motor vehicles, industry, and other sources.

Methods used to develop "emissions inventories," data bases of estimated amounts of pollutants believed to be emitted in a given geographical area must be reviewed and revised, NRC said. It recommended that regulatory agencies use ambient air measurements to determine whether the inventories give an accurate picture of ozone pollution sources.

The report said regulators rely on unverified estimates of reductions in precursor emissions, and verification programs should be included in emission control strategies. VOCs emitted by vegetation in the presence of nitrogen oxides emitted from human activity can contribute to high summertime ozone concentrations.

"These naturally produced VOCs must be taken more carefully into consideration to provide a baseline for evaluating ozone control strategies.

"In cities such as Atlanta, where more VOCs are emitted by natural vegetation than by human sources, strategies to bring ambient ozone levels into compliance with the air quality standard probably will need to include previously unattempted reductions in nitrogen oxides."