In offering to spend $200 million to reduce sulfur dioxide emissions at its Magna smelter by more than two-thirds, Kennecott is making a significant move in the right direction. Whether that will be enough to satisfy subsequent state and federal air quality demands remains to be seen.

The Kennecott plan calls for construction of a "double contact acid plant" to scrub more sulfur dioxide from the gases emitted by smelter smokestacks. When finished in 1994, the new acid plant and other steps would capture 96 percent of the sulfur released in the smelter process.The improvement is significant. Kennecott currently is allowed to release a peak of 17,500 pounds of sulfur dioxide per hour. The new equipment would slash that amount to 5,700 pounds per hour.

Unfortunately, that reduction might not be enough. The Bureau of Air Quality wanted to reduce Kennecott's emissions to 3,240 pounds per hour, a level the company seems to think is not attainable.

Despite the difference, Kenneth L. Alkema, director of the Utah Division of Environmental Health, is pleased with the Kennecott offer. The decision on the proposed acid plant had been a sticking point in negotiations between state and Kennecott officials and now the company appears to have adopted largely what the state wanted.

However, Kennecott says the basic State Implementation Plan (SIP) limiting PM10 pollution by certain industries is flawed. The PM10 designation describes very tiny particles that can cause respiratory problems. Part of the PM10 problem is caused by sulfur dioxide gas, the kind coming from the smelter smokestacks, which subsequently undergoes a chemical change in the atmosphere.

Kennecott says the plan makes the company responsible for more PM10 pollution than it really produces and cites studies by a consultant that produced different figures. Alkema acknowledges that Kennecott and others have raised good points and the SIP is going to have to be rewritten.

But it would be unfortunate if the rewritten version simply touched off a battle between different industries over who is responsible for what measure of PM10 pollution. Nobody wins that kind of dispute.

It should not be forgotten that behind the Utah SIP lies the federal version, the potential FIP or Federal Implementation Plan. Utah must meet general federal air quality standards and if the state plan does not do the job, the Environmental Protection Agency will step in and start issuing orders to Kennecott and others - with a lot less sympathy.

Kennecott's willingness to invest heavily in cleaner air is to be commended. The task now is to get the Utah SIP rewritten and get everyone involved in similar cleanups - with little or no delay - so that the job doesn't get preempted by the EPA.