RONALD REAGAN came out against Mount St. Helens on Wednesday. Even allowing for the extravagance of campaign rhetoric, this, along with other of his recent comments on environmental pollution, was about as wrong as you can get. If not, in fact, a little wronger.

Speaking to representatives of Ohio's coal and steel industries, the Republican candidate said he suspected that Mount. St. Helens had released more sulfur dioxiode into the air "than has been released in the last 10 years of automobile driving or things of that kind that people are so concerned about." As it happens, automobiles produce nitric oxide, carbon monoxide and other types of pollutants, but negligible amounts of sulfur dioxide. If Mr. Reagan was referring to power plant emissions, he was also wrong. The volcano has emitted an average of 1,500 tons of SO2 per day for the past 100 or so days. Daily man-made production of this pollutant in the United States is 81,000 tons.

Mr. Reagan then went on to assert that air pollution has been "substantially controlled" and that millions of dollars are being wasted on auto emissions controls and other devices to control nitrogen oxide pollution. It takes a special gift to have made remarks like these on a day when the largest city in Mr. Reagan's home state was more or less closed down largely because of automobile-caused air pollution.By way of explanation, Mr. Reagan defended his earlier comments attributing 93 percent of all nitrogen oxide pollution to vegetation. What he did not mention was that the 93 percent is a benign, non-toxic, naturally occurring gas called nitrous oxide, whereas the remaining 7 percent is composed of nitric oxide and nitrogen dioxide, both the products of burning fossil fuels and both harmful in a variety of wasy to health and air quality.

Mr. Reagan also told his audience that despite all the opposition to oil drilling off the coast of Santa Barbara, there have been "16 permanent oil slicks in the Santa Barbara Channel as long as the memory of man" and that "around the turn of the century when we did know something about oil, Santa Barbara was a great health spa for the country," which advertised that winds blowing across the natural slicks "purified the air and prevented the spread of infectious diseases." There are slicks in the Santa Barbara Channel caused by natural seepage of oil from the ocean floor. But what was Mr. Reagan's message? Was it that the natural pollution nullifies or is in some way comparable to the disastrous 1969 Santa Barbara oilwell blowout that produced a slick covering 800 square miles of water and blackened miles of beach with oil and dead and dying birds? The former governor's professed belief that more atmospheric contamination is caused by Mother Nature than by man-made pollution is spectacular in its misinformation, yet Mr. Reagan stubbornly persists in it.