On Dec. 16 The Post's readers were treated to the latest installment in the Mobil Corp.'s series of attacks on the Clean Air Act Amendments of 1990. In its advertisement in Outlook titled "Cows, bulls and clean air," Mobil bemoaned the fact that Congress "hastily" passed a clean air bill that could cut into its profit margin and would not improve air quality. The corporation advertisement seems to credit Congress with good intentions but suggests that intent led to a precipitous and imprudent result.

Mobil's answer to this dilemma is, predictably, more study and further delay. Before working up too much sympathy for Mobil, let's examine the facts.

The Clean Air Act Amendments of 1990 were the first revision of the act since 1977 and only the second in its 20-year history. The bill was the most extensively debated piece of legislation considered by the 101st Congress. It was the primary subject of Senate floor debate from January until April. The conference between the House and Senate lasted almost five months. The final conference bill received overwhelming bipartisan support in both houses.

Mobil suggests that Congress and the president should have waited longer until the petroleum industry could come up with its own answers to our nation's air quality problems. As early as 1977 the Environmental Protection Agency pointed out the staggering rise in the level of benzene and other toxic chemicals in gasoline as lead was replaced as an octane-enhancer by the aromatic compound known as BTX -- the collective name for benzene, toluene and xylene, all of which are EPA-listed toxic chemicals. During the past decade, these toxic components in gasoline increased by more than 50 percent.

EPA says that more than 50 percent of the cancer deaths attributed to air pollution come from automobile exhaust. Gasoline has become so toxic today that it can cripple a car's catalytic converter. Since 1970, cars have become as much as 96 percent cleaner. Yet gasoline has become much more toxic.

How long does Mobil suggest the American people wait for the toxicity level of motor vehicle emissions to be reduced?

Mobil contends that the requirements of the Clean Air Act cannot be met. This argument conveniently ignores the fact that there is high-octane "oxygen" in one quarter of our nation's gasoline today, either in the form of ethanol or MTBE, a methanol derivative. If this oxygen were simply redirected to the markets that have air quality problems, the supply demands would be met.

Moreover, there is idle and oncoming capacity in the U.S. ethanol industry, and MTBE is the world's fastest growing chemical. According to Tenneco, a major methanol producer, a large-scale MTBE plant can be built in two years. World-scale facilities are already under construction in the United States, Canada and abroad, and analysts predict that the global MTBE supply will double within four years.

Mobil questions whether the Clean Air Act will improve air quality. The EPA and almost every reputable scientist that has looked into this issue acknowledge that the oxygenated fuels provisions of the Clean Air Act will have an immediate and significant impact on air quality. By cleaning up gasoline, we don't have to wait for fleet turnover to breathe cleaner air.

So what exactly is Mobil's problem? Maybe it's that it has invested a lot of money in making highly toxic gasoline. Or maybe it's that it doesn't like the EPA estimate that the fuel provisions of the Clean Air Act will displace more than 500,000 barrels of imported crude oil every day.

I suggest that Mobil join Amoco, ARCO, Marathon and other petroleum companies that have already started selling clean gasoline and contribute to the solution to our air quality problem instead of its cause. TOM DASCHLE U.S. Senator (D-S.D.) Washington