In 1954, Richard Doll and Bradford Hill published their famous investigation into the smoking habits of British doctors which clearly revealed that the chances of developing lung cancer increased with the number of cigarettes smoked.(1) More than a dozen similar (human) studies had already been published but some scientists still argued that the link between smoking and lung cancer was unwarranted since no-one had produced the disease in laboratory animals.(2)
Two years after publication of Doll and Hillís findings, the British Empire Cancer Campaign - the forerunner of today's Cancer Research Campaign - reported nearly two years of experiments during which mice, rabbits and other animals were exposed to tobacco derivatives by direct inhalation, feeding, injection into the lungs, and skin painting. None developed cancer.(3) And in 1957, American pathologist Eric Northrup concluded in his book Science Looks at Smoking that the "....inability to induce experimental cancers, except in a handful of cases, during 50 years of trying, casts serious doubt on the validity of the cigarette-lung cancer theory."
Health warnings were delayed for years and Northrup describes how "it is reassuring...that public health agencies have rejected the demand for a mass lay educational programme against the alleged dangers of smoking. Not one of the leading insurance companies, who consider health hazards in terms of monetary risk, has raised the life insurance rates for heavy smokers."
Despite years of further experimentation, it has proved "difficult or impossible" to induce lung cancer in animals using the method (inhalation) by which people are exposed to the smoke.(4)
1) R.Doll and A.B.Hill, British Medical Journal, 1954,June 26, 1451-1455.
2) Reported in S.Peller, Quantitative Research in Human Biology (J.Wright & Sons, 1967).
3) Reported in E.Northrup, Science Looks at Smoking (Conard-McCann, 1957).
4) Lancet, 1977, June 25, 1348-1349. See also F.T.Gross et al, Health Physics, 1989, vol.56, 256.
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