In the Dec. 28 editorial "250 Million Americans," a cursory effort was made to address the broader implications of this nation's rapid population growth on "American national life."

To argue that with 310 million people, we would still be "one of the least densely settled" of the "world's developed democracies" skirts the enormous cultural and other substantive issues that our nation neglects. We remain caught in the grip of the frontier myth of individualism. No wonder so many of us are overwhelmed by a "sense of crowding." Nor can the substantive issues be denied: from urban haze in the Grand Canyon to the recent succession of bankruptcies of our major cities.

Unless we slow down our rapid rate of growth, our political and organizational mechanisms will continue to be outpaced. Our children shall witness the unrelenting deterioration of our vast natural resources and our social fabric.

In 1972, after two years of congressionally authorized research, the Commission on Population Growth and the American Future, chaired by John D. Rockefeller III, concluded: "In the long run, no substantive benefits will result from further growth of the nation's population, rather the gradual stabilization of our population through voluntary means would contribute significantly to the nation's ability to solve its problems. We have looked for, and have not found, any convincing economic argument for continued population growth. The health of our country does not depend on it, nor does the vitality of business nor the welfare of the average person."

MARTIN ZIMMERMAN Silver Spring

The editorial "250 Million Americans" states that the United States is "still far from a crowded country," which, even with a population of 310 million, "would remain, among the world's highly developed democracies, one of the least densely settled." Perhaps inside-the-Beltway editorial writers are unaware that this country, unlike most highly developed democracies, contains huge areas of desert, wetlands, mountains and Arctic tundra unsuitable for permanent human habitation.

In population biology, what counts is not how many individuals an area contains but how many it can support. In a geographically heterogeneous and urbanized land like ours, indexes such as price of real estate, average commuting time, availability of parking, size of the international trade deficit and decline in standard of living among the poor are much more meaningful measures of crowding than a crude ratio of people per square mile.

By those measures, this country, with its quarter of a billion people, is already overcrowded.

DARYL P. DOMNING Associate Professor of Anatomy Howard University Washington