The greatest battle, by Dr. Ronald J. Glasser, Random House, 180 pages, $6.95.: A frightening account of how human actions may account for more than 75 percent of the cancers present in humans today.

Cancer is no mystery. It is something 75 to 85 percent of the time, that we inflict on ourselves of that someone else inflicts on us. It is, then, potentially preventable 75 to 85 percent of the time. Not necessarily for those of us who have reached adulthood and have litter cancer time bombs already ticking within us, but for our descendants. That’s the terrible message Dr. Ronald J. Glasser, the author of two previous best-sellers and currently an instructor and researcher in pediatric nephrology (kidney) disease at the University of Minnesota, has for us in this lucid volume.

Glasser has collected assorted facts and theories, put them in coherent form and rejected the objections put up by those with a financial interest in carcinogenic (cancer-causing) agents or those who insist that nothing be done until guilt of a cancer-causing pollutant has been proven beyond any statistical doubt whatsoever. If you read this and you’re a parent, you’ll want to ask questions the next time your child’s doctor suggests x-rays. Is the x-ray necessary for the diagnosis, or may ask, or is it to protect the doctor against a malpractice suit? No one really knows, Glasser says, what the absolutely safe levels of radiation are. Glasser has a chapter, “A Tragic Medical Error,” about the innocent but careless misuse of x-ray equipment in the useless treatment of infants and children that is brining cancer to many of them. It began after World War II. Doctors bought office x-ray machines by the ten of thousands from a war industry looking for peacetime markets and used the machines for treatment at well as diagnosis. What did they treat?

Well, a lot of them used the x-rays to shrink the thymus glands in the upper chests of infants. There was a theory that an infant would have fewer colds if the thymus gland were made smaller. There wasn’t, says Glasser, “the slightest biological or medical reason to think there was a connection between thymus size (it is fairly large in infancy while it helps build a new immunity system, then shrinks gradually till the end of the first year of life) and the incidence of colds.” In 1950 in the Journal of Clinical Endocrinology, two doctors reported that of 28 children with thyroid cancer they had seen, nine had had their thymus glands irradiated in infancy. That should have served as a red flag. The article was criticized because the sampling was too small to show that irradiating a thymus would cause cancer in the nearby thyroid gland.

Two years later two other scientists reported they could use radiation to produce thyroid cancer in rats. Rats, the counterargument went, aren’t people. So the radiation went on. Evidence kept pilling up. In 1955 in the widely read Journal of the American Medical Association a doctor said that all 15 children he’d seen recently with thyroid cancer had, early in life, received radiation to the thymus, tonsils, or other parts of the head and neck. Glasser argues that at this point all further such treatment should have stopped. It didn’t. Not ill the late 1960s. More cancers will be coming in, Glasser explained, because it usually takes about a third of a life span, whether of humans or rats, for a cancer-causing chemical to bring out overt, diagnosable cancer. Between the time of exposure and the outward appearance of cancer, a period that may run 20 or 30 years, even the victims are likely to ignore all warning as in the case of cigarettes, Glasser says.

The cigarette-lung cancer connection is well established. The most likely chemical culprit is benzopyrine, known since the late 1940s to be a component of cigarette smoke. Benzopyrene is one of the most potent cancer-causing chemicals known. Why so many delays? Why are millions still hooked on tobacco? Glasser blames the tobacco industry and the media, the latter largely because of its openness to tobacco industry advertising. The tobacco interests, he points out, over and over have raised objections to every bit of evidence even after the case was proven beyond a reasonable doubt thus giving smokers a slight hope of escaping the odds against them. Glasser also warns about the “hidden poisons,” such as Red Dye No. 2, suspected since 1950s of being cancer-causing and still present in some foods we eat and Red Dye No. 40, which industry may substitute for No. 2 but which has been banned in some countries. His most valuable contributions, I think, comes in his reasonable explanation of why we should accept research done on animals as strongly indicative of whether a chemical can cause cancer in man. Cancer occurs at the sub-cellular level, he explains. At that level man and animals are very similar. Because it is impractical to wait for a third of man’s 70-year life span to see if something is going to kill us, it’s far better to do the experiments on animals, which may have a one-third life span of a matter of months of a year at most. It’s a frightening book.