AS MANY CLEAN-AIR ADVOCATES see it, Environmental Protection Agency administrator Douglas Costle changed the nation's smog standard the other day for the wrong reasons -- but came out in the right place. They charge his action was impelled by intense pressure from White House inflation-fighters and from industries and communities that don't want to change their smog-producing ways. Yet they commend him for easing the standard less than the economists and industries had urged. Our view is just the opposite: Mr. Costle acted for the right reasons but did not go far enough.

The crucial question is how much smog creates dangers to health. Until you have a good assessment of the hazards, it's impossible even to debate intelligently how much smog-plagued communities should be required to change the ways they work, live, travel and grow. Arguments about costs and benefits are hopeless unless you know what the health costs and benefits may be.

Obviously a lot of smog causes lots of people problems -- itching eyes and sore throats -- and makes breathing harder for people who have chronic respiratory ailments or are generally infirm. Early on, most pollution-fighters suspected that air so foul probably caused permanent or long-run health damage too. Thus EPA originally called for reducing ozone, one key element in smog, to a very low level,.08 parts per million (ppm).

In many areas of pollution control, more study has produced more evidence of danger, showing that early standards were not strict enough. But that is not the case with smog. On the contrary, re-assessments of the research show that even temporary ill effects from ozone are elusive below ozone concentrations of.15 or even.20 ppm.

Future studies may identify more subtle problems, and indeed may show that ozone is not the most threatening element in the photochemical stew called smog. But national standards ought to evolve as scientific research and understanding do. Given the current state of smog research, Mr. Costle moved super-cautiously in easing the ozone standard only to.12 ppm. A shift to.15 or even a somewhat higher level could have been justified as the point at which even temporary health problems seem to start.

Of course health is not the only element in the political atmosphere. The smog debate does involve billions of dollars and potentially great disruption of people's habits in many metropolitan areas, including ours. Each easing of the standard exempts more communities and allows those with larger air-quality problems, such as Washington, to impose less wrenching controls. Thus the pressures on EPA to back off are immense. Moreover, with many air-quality standards up for review right now, the smog decision had become a major early skirmish in the general battle over future pollution-control policies.

That's why environmental groups are so relieved that Mr. Costle did not, by their lights, sell out. And that's another reason why we think a higher ozone standard would have been a wiser move. In order to avoid being routed in even rougher fights ahead, EPA is going to have to be able to show the public, Congress and the White House that its requirements are solidly grounded in concerns for public health. Experience does show that the vast majority of this country's citizens and companies will accept strict clean-up requirements, even at a high price, when the alternatives are genuinely poisonous.