COAL-BURNING power plants represent a greater danger to public health than nuclear reactors, as we observed a couple of weeks ago. In response, Carl E. Bagge, the president of the National Coal Association, sends a letter that we print on this page today. Mr. Bagge cites a report issued last July by the Office of Technology Assessment, a nonpartisan congressional agency. Let's see what the OTA report actually said.

The discussion begins with sulfur dioxide in the atmosphere, most of it coming from coal burned under boilers to generate electricity. As Mr. Bagge notes, the OTA report says that sulfur dioxide poses no threat to health at normal concentrations. The following sentence, which Mr. Bagge does not quote, points out that as the relatively harmless sulfur dioxide blows around in the air, it forms other compounds, notably sulfate particles, that raise greater concern.

Similarly, there is no evidence that sulfate particles alone harm people. Instead, the report continues, recent evidence suggests that the damage is done by a combination of pollutants associated with coal -- sulfates, fine particles of soot and perhaps other chemical elements in the smoke.

Although the OTA report doesn't use this analogy, the medical evidence on coal smoke is much like the evidence on cigarette smoking. As the tobacco lobby has endlessly repeated, nobody knows exactly which chemical agent in tobacco smoke causes cancer, or how. The proof of the connection is statistical, in the distribution of lung cancers. Similarly, nobody knows exactly which components of coal smoke are harmful. The evidence of damage is statistical.

Mr. Bagge quotes the OTA about "uncertainties" among scientists. The full passage says: "Reseachers at Brookhaven National Laboratory (under contract to OTA) have estimated that about 2 percent (a range of 0-5 percent) of the deaths per year in the U.S. and Canada might be attributable to atmospheric sulfur-particulate pollution. The range reflects uncertainties within the scientific community about the causal relationship between air pollution and mortality." Two percent means something over 40,000 deaths a year. Elsewhere, the same OTA report estimates, more precisely, that at 1978 pollution levels there would be about 51,000 premature deaths per year caused by it in the United States and Canada.

That estimate is higher than many, and most epidemiologists prefer to report a range rather than a precise number. But there is a large scientific literature on the subject, and nearly all investigators have found a high probability of a significant death rate associated with coal-fired power plants. Electricity is, of course, not only a convenience but a necessity that prolongs lives in far greater numbers. But the deaths caused by coal-fired pollution, running to many thousands of deaths a year, are a reminder of the importance of the Clean Air Act. Beyond that, these numbers bring into further question the wisdom of public policies that would discourage nuclear power to replace it with coal.