CANCER, Dr. Samuel S. Epstein tells us, is a preventable diesease. "Environmental factors cause from 70 percent to 90 percent of all cancers," he writes in the opening pages of this book. "While much is known about the science of cancer, its prevention depends largely, if not exclusively, on political action."

What prevents cancer from being abolishedx

"A combination of powerful and well-fucused pressures by special industrial interests, together with public inattention and the indifference of the scientific community, has created a major imbalance in decision-making and public policies." The soultion, Dr. Epstein writes, lies in pressuring federal agencies to enforce regulations already on the books in pursuit of zero-exposure-levels to industrial and chemical carcinogens, since, as he states over and over again, there is "no safe dose" of a carinogenic substance. The task of applying pressure has fallen, by default, to "labor unions and public-interest groups," meaning environmental organizations, according to the author.

Dr. Epstein has probably been the most active scientist in the country in espousing the view that cancer is an "environmental" disease, and that whathe terms the current "epidemic" of cancer is due largely to "the dangers of synthetic petrochemical carcinogens . . . which have been introduced into the workplace and environment in growing numbers over the last few dcades." He was the major medical spokesman for the Enviromental Defense Fund's successful effort to ben DDT 10 years ago, and it sometimes seems from the footnotes of this book as if almost every major policy statement, committee report, and significant piece of legislation in the area of environmental carcinogens in the past 10 years has had Dr. Epstein, in part at least, as its author. Now Dr. Epstein, with the help of the Sierra Club, has pulled together a compendium of all the information on the "environmental" causes of cancer that is probably going to serve as a Bible for the forthcomingeffort by the President's Council on Enviromental Quality to drive all carcinogenic materials from the marketplace and from the world.

But there is a significant omission in the book. It is that, although Dr. Epstein says that "85 percent of all cancers" are due to "environmental" causes, nowhere in the text do we find the word "environment" defined. The reader is thus invited to infer that Dr. Epstein is talking about " the environment" of the environmentalists-the fouled air, the polluted waters, and the contaminated working places where traces of many carcinogenic materials are frequently found. In fact Dr. Epstein's implied definition of "the environment" actually includes anthing that is outside our bodies. The tobacco in cigarettes, which is probably responsible for 80 percent of all lung cancers (the only form of cancer that is rising darmatically in the general population) is part of "the environment." Common foods such as spinach and other leafy vegetables which contain nitrates, the precursors of highly carcinogenic nitrosamines, are part of "the environment" (whereas the same nitrates which exist in human saliva, it would appear, are not). The betel nuts which are chewed widely in Asia and are, along with chewing tobacco, probably responsible for the high rates of mouth cancer in this area are also part of "the environment."

This distinction between "environmental" and "non-environmental" cancers is important since it tells us that the other 15 percent of cancers-the non-preventable cancers-probably come form sources within our own bodies.But Dr. Epstein seems to ignore this by dwelling on what are actually slight increases in cancers noted among women who have taken excess female hormones. He also does not mention that the same natural hormonrd in female bodies are suspected as one of the reasons why women of breast cancer, while the disease is almost unknown among men. (Breast cancer is one of the cancers in which genetic links have definitely been observed.)

What is missing entirely from this book is all the recent work which seems to show that the human body does have defenses in its immune system which can deal with a limited number of cancer "incidents," where the genetic material is disrupted by a carcinogenic agent.

Dr. Epstein has done his major work in helping to identify occupational cancers and protect working people from exposure to known and suspected carinogens, and here he has compiled an admirable record of service. The stories are true tales of horror-industrial manufacturers destroying records to prevent epidemiological studies, company doctors neglecting to tell workers that they were already suffering from precancerous conditions, and industrial executives dismissing the whole issue as the result of their workers' peculiar "susceptiblities" and "personal habits."

Yet it should be remembered that all these well-documented incidents of job-related cancers still form only a small fraction of the 350,000 cancer deaths each year, and that the total rate of cancer incidence among nearly all section of the population has been steadily decreasing since 1947. (Cancer incidence is decreasing among all women.When the smoking-related lung-cancer figures are disregarded, it is also decreasing among white men. Cancer incidence is increasing among black men but only now reaching the rate among white men, and an improvement in diagnosis is believed at least partially responsible.)

Dr. Epstein's book will undoubtedly add fuel to the controversy over cleaning up the use of specific varcinogens in the workplace. But to make the extrapolation to the idea that the "majority" of cancers in the society at large can be "prevented" through similar "political" tactics of environmental improvement is a leap of faith that few scientists other than Dr. Epstein would be willing to amke at this time. It is easy to forget in reading this book that no one-including Dr. Epstein-is yet ready to claim they understand the mechanism that is behind the development of cancer. The tragedy that this book invites is that we will make the extraordinarily heroic effort to scrub the environment clean of carcinogenic materials, only to find that cancer-as it has always been-is still with us.