IN DECIDING to leave most decisions about the control of airborne toxic chemicals to state and local governments, the Environmental Protection Agency has directly addressed a tricky question: whether the degree of environmental protection afforded citizens can be allowed to vary according to where they live. Given current resources and information, EPA's decision may well be the best compromise. But the concerns that it has raised deserve full and continuing public attention.

Environmental activists, worried that EPA's decision may foreshadow further retrenchment from national environmental standards, naturally focus on hazards that may not be prevented if left to state and local concern. EPA, on the other hand, points out that the general air pollution controls already in place have eliminated half of toxic emissions. Stricter controls required for new plants should eliminate another quarter.

Since the Bhopal calamity the mere mention of airborne chemicals arouses public concern. But EPA's review indicates that even judged by strict standards -- and, conscious of its credibility gap in the first years of the Reagan administration, the agency has, if anything, exaggerated likely hazards -- the general health effects of most toxic air pollutants is minuscule. What sense, the agency argues, can it make to spend large sums to eliminate a pollutant that is causing less than one cancer death a year? How much better to spend that money on reducing risks, such as careless driving, smoking and bad eating habits that kill thousands.

EPA does plan to add one or two chemicals to the list of those already regulated, to consider stronger regulation of gasoline emissions at pumps and to strengthen procedures for dealing with chemical disasters like Bhopal. But it plans to leave control of unusual toxic hazards -- caused, for example, by multiple sources of pollution, localized weather conditions or especially hazardous plants -- to state and local agencies.

Already burdened by lost federal aid, those agencies are understandably reluctant to take on this new responsibility. And communities in certain areas -- especially those with substantial concentrations of petrochemical producers -- clearly suffer substantial health risks that local politicians have not been willing to address. Still, local leaders already have much discretion in deciding how rigorously to enforce national pollution controls. And local control over truly local problems really does make good sense -- if localities really have both the resources and the power to make it effective. Congress probably ought to give the EPA plan a try -- but with a sharp eye out to see that EPA is really prepared, as it says it is, to provide local agencies with the technical help they need and to make sure that local citizens are well-informed about real hazards.