The 1985 Vienna Convention provided the framework for international restrictions on the production of ozone depleting substances.
To evaluate the consequences of these restrictions, Slaper et al. projected skin cancer incidence under three scenarios: (1) n o restrictions; (2) reduced production of five ozone-depleting chemicals by 50 percent by 1999 (under the "Montreal protocol"); and (3) eliminated production of 21 ozone depleting chemicals by 1996 (under the "Copenhagen Amendments").
Assuming full global compliance with the restrictions and no change in human behavior with regard to sun exposure, the researchers estimated that (1) without restrictions, skin cancer incidence would quadruple by the year 2100; (2) under the Montreal protocol, skin ca ncer incidence would (only) double by the year 2100; and (3) under the Copenhagen Amendments, skin cancer incidence would increase by only 10 percent in the next 60 years.
Don't you just love fortunetellers? Can't you just imagine someone trying to predict in 1896 what public health conditions would be like in the year 2000?
So what's holding this house of cards up?
First, the researchers assumed various rates of ozone depletion for the three scenarios. This assumption enabled them to estimate levels of ultraviolet radiation (UV) reaching earth over the next 100 years. Keep in mind that this is such an exact science that ground-based UV detectors have yet to agree with satellite measurements.
Next, they assumed a dose-response relationship for skin cancer from UV. Oh... and did I mention that this was based on a dose-response relationship for skin cancer in mice exposed to UV?
The folly of this is best illustrated by a recently published study [Am J Epidemiol, 199 6;144:1034-1040] in which Australian scientists stated that
In any white-skinned populations, routine monitoring of the most common [skin] cancers... is difficult; and this is particularly so in high-risk populations...
Although it is accepted that solar radiation causes skin cancer, there is a paucity of quantitative evidence regarding this relation in humans. Indeed, in epidemiologic studies, characteristics associated with a sun-sensitive complexion appear to be more strongly linked to the occurrence of skin cancer than sun exposure itself. This is partly due to the difficulty in measuring the received dose of solar ultraviolet radiation, the salient component of sunlight. Even for chronic sun exposure, which traditi onally has been linked with skin cancer since the nineteenth century, epidemiologic studies show no greater than a doubling of risk relative to minimal levels of sun exposure.
The bottom line here is that Slaper et al. have simply guessed their way to their conclusions. Not great science. But, if skin cancer predicting doesn't work out, maybe they've got a future guessing bodyweight at carnivals.
Material presented on this home page constitutes opinion of the author.
Copyright © 1996 Steven J. Milloy. All rights reserved. Site developed and hosted by WestLake Solutions, Inc.