THE RESULTS of a study of crop losses from airpollution were announced last week. The National Crop Loss Assessment Network, a federally funded research program, covered only four crops and only one form of pollution--ozone--yet it concluded that the annual losses amount to $3 billion yearly. (If you thought the problem was too little ozone, rather than too much, you were thinking about ozone in the stratosphere, which protects the earth from harmful radiation; down in the atmosphere, ozone is a pollutant.)

Though much larger than earlier cost estimates, the $3 billion figure represents only a fraction of the actual costs of air pollution. It does not include losses of crops other than the four that were studied or indirect losses to pests and disease of crops initially weakened by exposure to the pollutant. Nor did the study cover other kinds of air pollution known to have substantial impacts on farm and forest production. Acid rain, for example, is believed to be costing the timber industry $1 billion annually. Considering the potential of all the still unmeasured effects, many researchers believe agricultural losses due to air pollution could be around $10 billion a year.

In releasing the crop loss figures, Rep. George Brown (D-Calif.) called ozone a "quiet thief." The phrase is a useful reminder that although the losses from air pollution do not show up on anyone's balance sheet, they do impose a substantial dollars- and-cents cost. Yet, because so much is still uncertain, current comparisons of the costs and benefits of air pollution control must weigh known costs against largely unknown benefits.

>There are comparable uncertainties about the costs of other forms of pollution. Generally speaking, as more is learned about its extent and effects, more detrimental effects of pollution become evident. There are exceptions to this. For example, in some areas, controlling nitrogen emissions may make smog worse, rather than better. Still, it is a good guess that today's lack of knowledge about pollution means that its effects are underestimated.

That may have something to do with the cuts the Reagan administration has proposed in the Environmental Protection Agency's research budget. While most federal research programs have sustained only modest cuts, the president's 1983 budget proposes that EPA's research program be cut by $127 million, almost half--in real terms--of its 1981 level. Air pollution research, including the study that uncovered the ozone losses, would be cut by $23 million, more than one-third its 1981 level.

The Crop Loss Assessment's findings are just one illustration of why we need better to understand the extent and sources of pollution, its effects and the different methods of controlling it. Some past EPA research programs left a lot to be desired. But if better, not less, environmental regulation is what the administration is after, slashing the research budget is not the way to proceed.