Media and Science: Harmless Dioxin, Benign CFCs, and Good Asbestos

Environmental Health Perspectives V.102, N.1, Jan94

If good government ultimately follows the will of the people, then good government requires a well-informed public. When the public is misled, seeds of bad government are sown. This is happening now in regard to three serious environmental concerns: dioxin, chlorofluorocarbons (CFCs), and asbestos.

In the last few years, the public in effect has been told through mass media not to worry about the toxicity of tetrachlorodibenzodioxin (dioxin), the destruction of the ozone layer (resulting in increased UV exposure) by CFCs, or the carcinogenicity of the chrysotile form of asbestos (which makes up 95% of asbestos in place in the United States). Overwhelming evidence from current research strongly suggests that, in all three cases, what the public is being told is wrong.

Recent popular press reports encourage the public to believe that dioxin, the inadvertent by-product of the chemical synthesis of certain chlorine-containing compounds or the incineration of some chlorine compounds, may not be so dangerous after all.

Dioxin first became famous as the contaminant of the herbicide 2,4,5-T in Agent Orange used in the Vietnam conflict. It was also found in chemically contaminated soil at Times Beach, Missouri, and deposited around the Italian town of Seveso as a result of a chemical plant explosion in 1976.

In the late 1970s, dioxin was shown to be a highly potent carcinogen in test animals. It also can affect the immune system, alter hormone actions, and cause a specific skin lesion (chloracne) in humans. Rodents and other test animals die weeks after a single dose, experiencing decreased food intake and weight loss. A mechanism to explain the great variability in the doses that are toxic among species appears to have been found: a mediating receptor in the cytoplasm.

By the mid-1980s, 2,4,5-T had been banned, other dioxin-generating chemical processes had been controlled, and Times Beach had been evacuated. However, in the late 1980s dioxin was found in effluents of paper mills using chlorine bleach. Some scientists and others associated with the chlorine and paper industries suggested that the receptor theory of dioxin's mechanism of action implied a threshold concentration below which dioxin would pose no hazard. Other scientists, including some from EPA, were considering the same possibility.

Based on these views, on 15 August 1991, the New York Times reported that exposure to dioxin "is now considered by some experts to be no more risky than spending a week sunbathing" in a story with the headline "U.S. Officials Say Dangers of Dioxin Were Exaggerated." Other major newspapers followed suit with news stories and editorials.

The New York Times story ignored a January 1991 report from Fingerhut et al. of the National Institute of Occupational Safety and Health that workers exposed to dioxin for more than 2 years and observed for at least 20 years had a 46% greater cancer death rate than expected. Little effect was seen after shorter observation periods, which explains earlier studies finding no effects. Confirming observations were published in the Lancet by Mantz et al. in the fall of 1991. A 10-year follow-up of those exposed to dioxin after the chemical explosion at Seveso in 1976, published in Epidemiology this summer, showed an increase in some cancers. Laboratory scientists continued to develop still more data suggesting that dioxin is very toxic.

The story of the widely publicized challenge to the role of chlorofluorocarbons in the thinning of the stratospheric ozone layer, and the resultant increase in UV irradiation on earth, is neatly told in the 11 June 1993 issue of Science. Critics--including Dixie Lee Ray, Maduro and Schauerhammer, and Rush Limbaugh--claim that CFC molecules are too heavy to diffuse up into the stratosphere (where they destroy ozone) and that volcanic eruptions inject into the atmosphere many times the amount of chlorine found in CFCs (thus the increase in chlorine from CFCs must be trivial).

Sherwood Rowland, current president of the American Association for the Advancement of Science and proponent of the view that CFCs are a major factor in the destruction of the ozone layer, refutes these claims with hard data. These data indicate vigorous mixing of CFCs in the atmosphere far above the stratosphere and rapid washing by rain of most chlorine from volcanic eruptions. Measured stratospheric increases of chlorine after two recent major eruptions have been small.

The 19 January 1990 issue of Science carried a well-publicized report that asbestos exposure in public buildings is being over-regulated. The argument is made by Mossman and others (most associated with the asbestos industry) that chrysotile fibers are less toxic than other forms and pose minimal risk at low doses.

Ignored in the Mossman account are countervailing human data on the carcinogenic effects of chrysotile asbestos (including large numbers of mesotheliomas among Canadians) and the finding of mesothelioma, largely from chrysotile asbestos exposure, among family members of workers who are exposed to low doses. Moreover, asbestos seldom appears in a pure form, and a threshold of effect has never been found.

There was little, if any, press coverage of the refutation of the Mossman article in letters to the editor of Science. With the New York Times accounts, it seems that not enough knowledgeable scientists were interviewed to get the whole story. Certainly, few were named. Ties to industry were not explored. Few of the many letters to the editor challenging the factual basis for much of the material were printed.

The coverage in Science is somewhat more complicated. Too few scientists with special expertise on key issues were given the opportunity to express their views at the same time and in the same issue with equal prominence and space. After-the-fact letters to the editor have less likelihood of coverage in the popular press. More careful peer review would have helped.

How do we correct these mistakes in editorial policy and reporting? Most of the public does not read Science, the Journal of the American Medical Association, or any other professional journal. But journalists and publicists who specialize in these issues do. The first line of defense against bad science and medical reporting is, then, an internal review of editorial policies and practices of professional journals with a better focus on the fact that part of the readership is the lay press. A renewed effort to balance controversial views in the same issue and to invite letters and commentary for publication in the same issue is a necessity. The presentation of views by scientists requires vigilance not only on what is said, but on how and when opposite views are published. These actions could assist in ensuring that the public is well and accurately informed.

David P. Rall
Founder, EHP
Former Director, NIEHS

Last Update: August 18, 1998