THE DEATH RATES for young Americans between the ages of 15 and 24 continue to rise while the rates for all other groups are falling. That somber report from the Public Health Service's statisticians reflects a silent epidemic running through this country -- one that has nothing to do with viruses or bacteria. The causes of those deaths are predominantly homicides, suicides and accidents -- above all, automobile accidents. They are the result of a national tradition in which alcohol, cars and firearms have always been too important for anybody's health. For young Americans, the figures ominously show that this self-destructive tendency is becoming more pronounced.

It confirms a point that Victor R. Fuchs of Stanford University has been making for some years. Medical care in this country is already good, and at this point further improvement in clinical care -- more doctors, newer drugs, bigger hospitals -- can no longer do much for the health and life expectancy of the average American. The far greater influences on American death rates now are people's habits and ways of life.

Perhaps you are suspicious of cultural explanations of morality rates. But how do you otherwise explain a rate for young men three times as high as for young women? There is a prevalent style of North American macho that underlies this epidemic. The number of fatalities is rising because, evidently, alcohol is back in fashion among the young.

The death rates for young Americans are half again as high as for their counterparts in northern Europe. Americans often dismiss foreign comparisons as irrelevant. But Mr. Fuchs answered that evasion with an example closer to home, the comparison of health data from Utah and Nevada. On one side of the border there's the stern Mormon disapproval of smoking, drinking and irregular bedtimes; on the other side, there are the round-the-clock casinos. Except among the very young and elderly, death rates in Nevada ran about 40 percent higher than in Utah. Nevada's death rates for cirrhosis of the liver and lung cancer were, for people in their 30s, five times as high. The inclination to self-destructiveness in American life does not end at the age of 24. The habits that bring some Americans to violent deaths early will bring others to clearly preventable diseases later.

Americans have joined, over the past decade, in a laudable, vigorous and expensive campaign to protect the environment. But there's an ironic disparity between the national determination to control some kinds of health danger while studiously ignoring others. Scientists cannot agree how many dozen or hundred people may die every year from automobile emissions. But no one disputes the hard truth that some 25,000 people die every year in accidents involving automobiles and alcohol. Americans like the idea of environmental standards. But they don't apply those standards to the health risks in a social environment for young people that is marked by a resurgence of heavy drinking, plus fast driving, plus easy access to firearms.