Like asbestosis and lung cancer, mesothelioma is thought to follow a dose-response model -- the bigger the dose, the more likely the disease. But no reputable scientist has ever arrived at a threshold for safe exposure to asbestos. On the one hand, the risk posed by relatively few fibers would seem to be very low: city dwellers, for example, breathe in thousands of fibers from shedding car brakes. On the other hand, in approximately one-third of the known cases, mesothelioma patients could recall no industrial exposure to asbestos.
Why they should have contracted the disease remains a mystery. However, since asbestos exposure is the only significant cause of mesothelioma, American society had to face the possibility that everyday exposure to an everyday material could kill. In 1960, mesothelioma was killing an estimated two dozen Americans every year; by the 80's, the figure was 1,000 to 3,000 (the estimates vary, because the disease is difficult to diagnose). Some experts were predicting that mesothelioma would overtake lung cancer as a mass killer by the end of the century.
But so far, it hasn't happened. Rates have risen almost exclusively among older men who suffered occupational exposure to asbestos in the days before regulation. But among women, whose asbestos exposure has primarily been environmental, the mesothelioma rate has been flat for the last 20 years. The cancer remains, relatively speaking, rare.
Mossman and her colleagues say they think they know why: recent European studies have convinced them that chrysotile is not very good at causing mesothelioma, even at the highest industrial concentrations. The lungs wash the fibers out before they can cause serious harm. Only the amphiboles, they say, have been shown to be so highly carcinogenic that we need to worry about them at low-level, environmental concentrations. With the exception of the United States and South Africa, the industrial nations have accepted this so-called "amphibole hypothesis" and regulate chrysotile less stringently.
American public-health scientists usually insist that the jury is still out on chrysotile's ability to cause mesothelioma. Dr. Stephen Levin, a Mount Sinai researcher, points out that the asbestos installed in schools in the 50's and 60's did not begin to deteriorate until a decade later. Since mesothelioma has a 40-year latency period, the epidemiological bad news could still be on its way. "It's like the joke about the man falling out the building," Levin says. "He passes the 15th floor and says, 'So far, so good.' "
But it is unlikely that the near future will bring a dramatic increase in environmental mesotheliomas -- otherwise, epidemiologists would already have seen an increase in mesotheliomas with a shorter-than-average latency period. Most public-health advocates object to the Mossman articles not because they find the arguments unreasonable, but out of fear that they will be used as an excuse to ignore completely the problem of in-place asbestos. They often use the term "human experimentation" to describe a policy of doing nothing.
In truth, there are several choices that fall between doing nothing and decreeing a national emergency. Ten months before Congress passed Ahera, New York City enacted the nation's most stringent asbestos regulation, Local Law 76, which mandated removal of asbestos from buildings facing renovation or demolition. Most experts would agree that these abatements are justified -- releasing great clouds of asbestos dust during a demolition is no one's idea of public health.
Currently, the city is considering further legislation that would require an asbestos inspection for every building in the five boroughs. This is a dicier proposition, since it envisions more inspections, which critics assume will trigger a host of removals, rarely the safest course. The majority of industrial hygienists now believe that most in-place asbestos can be maintained or encapsulated in a bonding material or enclosed in an airtight chamber, so that fibers do not reach the air. Even the much-castigated E.P.A. has come out with a new manual for building owners entitled "Managing Asbestos in Place." But building owners generally opt for removal anyway, to defend themselves from lawsuits or to shore up the market value of their property. Even so, Dr. Morton Corn, one of Mossman's co-authors and a former head of OSHA, says he believes that the inspection approach is worth trying -- in-place management can't work without inspections to locate the asbestos.
In her two articles, Mossman was less interested in sorting out the policy options than in exposing the absurdity of spending billions on removal. She argues that the nation would get more bang for its public-health buck if it concentrated on such health risks as the passive inhalation of cigarette smoke, which by some estimates is 200 to 400 times more lethal than low-level asbestos exposure.
IF THE MOSSMAN articles enraged the scientists at Mount Sinai, they did not go down too well, either, with the people and companies who make their living from asbestos. The abatement companies felt threatened, but no more so than the plaintiff attorneys who represent injured workers and building owners in lawsuits against former asbestos manufacturers. They worried that the Mossman pieces would provide legal ammunition for their adversaries in court.