Your editorial "Clean Air and Cars" {Nov. 27} again states The Post's opposition to additional controls on sources of air pollution.

It is astonishing that The Post would suggest loosening the health-based air-quality standards for areas that have the highest levels of pollution. The issue is not whether the standards are met but whether the public health is being protected. Research by the Environmental Protection Agency and testimony before the Senate subcommittee on environmental protection justify the conclusion that while public health may be protected with the current standards, there are strong arguments for more, not less, stringent standards.

Presumably support for nonprotective standards is justified by The Post's unsubstantiated conclusion that cities such as Los Angeles and Houston will never meet the existing standards. These cities present the highest health threat to area residents. Attainment for these areas should therefore be our highest, not our lowest, priority. These areas can meet existing standards and public opinion surveys show people are willing to pay for such efforts.

The Post also oversimplifies the air pollution control problem by attributing it all to mobile sources. It is true that most of the carbon monoxide pollution is due to mobile sources. Ozone, however, is formed from nitrogen oxides and hydrocarbons. There are stationary and mobile sources of these pollutants. Stationary sources are often 50 percent of the ozone pollution problem. The share of mobile sources varies with the location.

In Houston, for example, the dominance of the petrochemical industry and associated emissions is a major factor in its air pollution. If the problems were solely attributable to mobile sources, the logical first step would be to require tighter tailpipe standards, as legislation recently reported by the Senate Environment and Public Works Committee requires. Requiring vehicles to meet the applicable standards for a longer period of time and requiring regular and improved emissions testing of vehicles in more areas would also dramatically reduce mobile source emissions. The Post fails to recognize that these options are available.

The Post does a disservice to those supporting reasonable control measures by suggesting the only solution to our air pollution problem is to restrict driving. Limits on access to congested downtown areas may be needed in some cities, but there is nothing inherent in the air pollution control problem that dictates such restrictions must be the first and only control strategy. In some areas, driving restrictions alone would not be sufficient to control pollution.

This editorial and previous editorials on clean air assume that the benefits of control are outweighed by the costs. The Post's insistence that we cannot afford clean air ignores the fact that Americans pay for dirty air every day in the form of higher medical bills (which the urban poor and the elderly are most likely to incur and least able to afford), crop and forest damage, etc.

In the words of the American Forestry Association, which is concerned primarily with forest damage and not public health, "the risks and costs associated with further delaying additional pollution controls now seem to outweigh the risks and costs associated with action."

The only air pollution problem for which The Post apparently finds the benefits worth the costs is that of radon. I agree that radon contamination of homes and other buildings poses a serious health threat.

I worked with my colleagues to develop legislation addressing the radon problem earlier this year. The bill, which is supported by the administration, was passed by the Senate in July and is now under consideration in the House.

While I am determined to develop the best possible response to the radon problem, I reject The Post's suggestion that we should reduce our efforts to protect outdoor air quality as we identify and address new problems such as radon and other contaminants found in air indoors.

The American people do not want us to trade protection of health outdoors for protection of health indoors. We do not save money by postponing air quality controls. In every environmental area, the risks to the public health and the environment are more substantial, and more costly to address, than previously believed. Twenty years hence we may find that the price of controlling air pollution today was a bargain. -- George J. Mitchell The writer, a Democratic senator from Maine, is chairman of the subcommittee on environmental protection.