Up to a million Americans will die in the next twenty years from a cancer-like malignant tumor that they will contract from constant exposure to asbestos, exposure that as urban dwellers they cannot now avoid. This fatal growth, called mesothelioma, can develop twenty to forty years after its victims begin to inhale the asbestos fiber. The tumor attacks the pleura and peritonium--the membrane sacks that surround the lung and abdominal cavities--and can grow whether or not the exposure continues. Most alarming of all, the number of asbestos fibers in the air around us increases every year.

Asbestos is used in thousands of everyday products, and roughly a hundred new ones appear on the market each year. Pot holders, ironing board covers, draperies, rugs, movie screens, electrical tape, automobile brake linings, vinyl floor tiles and metal alloys contain asbestos, as do a whole host of plastic articles ranging from frying pan handles to playdough. The asbestos-cement industry is a principal user, employing asbestos in the fabrication of shingles, insulation and plastic board, pipes, roadways, sidewalks, asphalt and almost every other fireproof or high-friction cement product. No satisfactory substitute has yet been discovered.

It is precisely because of this accelerating use that the fiber's threat to health has become apparent. Twenty years ago, mesothelioma was a disease so extremely rare that it was thought to be a freakish although invariably malignant chance happening. Until recently, most medical books did not include it in their descriptions of tumors, and the World Health Organization's Classification of Diseases omitted it altogether. It is now found in only one of every 10,000 autopsies performed in the United States. But because of the increasing presence of the mineral fiber in the air we breathe, the incidence of the tumor may increase dramatically in the near future.

The disease was so uncommon that when between 1957 and 1961 eighty-seven cases suddenly appeared in Johannesburg, South Africa, the medical world signalled a mysterious epidemic of major proportions. Physicians in the area were dumbfounded. Pathologists and epidemiologists began an extensive investigation into the factors that might be common to each case. When all the data had been gathered, a startling conclusion became evident: that each of the eighty-seven rare tumors had grown in people who had been exposed to South African asbestos.

Case histories of the victims revealed that they had all lived in the wind-swept region that contained Cape Horn's asbestos fields. A few actually had worked in the mines for a short time. But most had simply lived in communities in which the prevailing winds and daily travel past asbestos slag piles had brought them into contact with the small, easily respirable asbestos fibers.

The fibers, intermeshing with the tissue of the lung, had condensed to form small asbestos bodies that were visible upon autopsy. They had passed from the lungs into the pleural and peritonial sacks, and over a 20- to 40-year period had caused the malignant growths.

No sooner had the history of the South African epidemic been reported in the medical literature than new outbreaks of mesothelioma began to crop up all over the world, wherever asbestos was mined or used in manufacture. It became evident that the onset of exposure to the mineral fiber among those who had died in Johannesburg had coincided with the beginning of asbestos mining operations, the first in the world, in South Africa. As the industry had grown, spreading into different geographical areas, successive generations were becoming increasingly affected. It was clear that the problem was proliferating like a juggernaut. Since the industry showed no capacity to control community exposure to its operations, scientists and health professionals banded together in attempts at preventive medicine and physiological research.

Exposure is not by any means limited to those who frequent asbestos factories. The combined effects of day-to-day wear and tear on asbestos-containing products, as well as a certain degree of industrial planned obsolescence, insure that varying amounts of the fiber will be continuously liberated into the consumer's air. Floor tiles scuff, ironing boards rip and fray, clutch and brake linings are slowly ground down, asbestos cement dust is kicked into the air when buildings are destroyed by demolition companies. Up to a microgram of asbestos is now found in singlevial doses of injectable drugs. This feeds directly into the bloodstream, the equivalent of a week's exposure to asbestos at an area of high industrial exposure. Injections are a frightening form for the exposure to take, in light of the fact that mesothelioma and other miscellaneous tumors, or neoplasms, have been induced in rats by arterial injection of asbestos fibers.

Critics of nuclear power plants have long warned of the danger of contamination from Plutonium 239, a highly dangerous byproduct of nuclear fission that has a half-life of a quarter million years. But asbestos has a nearly infinite half-life and unlike Plutonium 239, the air-borne fibers cannot be buried in salt mines far below the earth's surface to remove them from populated areas. The danger is ubiquitous, increasing and well-nigh invisible.

It has occurred to several research groups that much of what doctors have in the past decade assumed was general "mutagenic" cancer, cancer of unknown cause, may actually have been asbestos-induced. Recent studies have indicated that smoking may greatly increase the neoplastic effects of asbestos, suggesting that the fibers are absorbing large amounts of benzo(a)pyrene, the primary carcinogenic component of tobacco. Water commissions are beginning to have problems with asbestos contamination of their supplies. The prognosis for future urban communities is disquieting. As long as there are no substitutes to stem the increasing use of asbestos, nothing short of a ban on the industrial use of the fiber will be able to deal effectively with the problem.

Even if such a ban were issued, we would have to contend with at least another century of asbestos-induced diseases, as products now on the market gradually decay and release fibers into the surrounding environment.

Attempts to investigate asbestos-induced cancer have led doctors to look more closely at exposure, where contamination is most prevalent. It has long been known that industrial exposure may result in a different asbestos-caused disease, severe scarring of the lungs that causes a pulmonary fibrosis called, appropriately enough, asbestosis. This disease ultimately kills eight of every 100 asbestos workers, an incidence so high that almost all states have made it legally compensible under their workmen's compensation programs.

Investigation has shown that the same qualities that make asbestos a prime ingredient in all forms of industrial fireproofing and insulation are those that make it a deadly irritant once inhaled. A crystalline mineral extracted from a host rock, asbestos is incombustible, and is impervious to bacterial, organic or almost any other type of corrosion or decay. Endowed with the tensile strength of piano wire, the fiber is extremely flexible, spinnable and absorbant. It is so fine--about 2000 times finer than human hair--that once imbedded in the lung tissue, a fiber of asbestos will remain there indefinitely, unless it happened to have settled high enough in the respiratory tract so that it could be removed via the mucous. If it is imbedded below this point, the body can neither remove asbestos fiber nor destroy it.

Dr. Irving J. Selikoff of the Mount Sinai School of Environmental Health has suggested that the persistence of the fiber once it comes into contact with lung tissue may result not only in asbestosis but in other sarcomas and cancers besides mesothelioma. Selikoff, the leading authority in this area of asbestos research, subsequently examined mortality figures for 18,000 American and Canadian asbestos workers. He found that the death rate among them from lung cancer was six times that found in the general population. Deaths from gastro-intestinal cancer or cancer of the esophagus were respectively four and six times more prevalent than normal. Worst of all, the death ratio for mesothelioma indicated that it occurred 100 times more frequently among asbestos workers than in the general population, or in one of every 100 workers.

Selikoff's work has attracted the interest of labor unions, which have begun to demand large-scale control of asbestos contamination. At the same time a federal agency, the Occupational Safety and Health Administration, has set a limit of five fibers per cubic centimeter of air that will be reduced further to two fibers in 1976. The regulation is forcing some smaller industries to close down their asbestos-incorporating operations, while others are coming slowly into compliance with federal and state regulations. But control is no easy matter. More than one million tons of the mineral are imported into the United States annually, affecting hundreds of thousands of workers.