Hirayama's work has stood the test of time.

In January 1981, Takeshi Hirayama published his epidemiological study demonstrating that second-hand smoke increased the risk of lung cancer in non-smoking Japanese women married to men who smoked compared with non-smoking women married to non-smoking men (1). Hirayama is generally credited with publishing the first evidence linking passive smoking and lung cancer, though there were two other studies published at about the same time, by Trichopoulos et. al (2) from Greece and Garfinkel (3) from the USA. While both studies showed an elevation in the point estimate of lung cancer risk associated with passive smoking, Garfinkel's study did not reach statistical significance. Moving well beyond its usual efforts to create controversy about scientific studies that reach bothersome conclusions, the tobacco industry responded with a multimillion-dollar advertising campaign designed specifically to discredit Hirayama's paper (4). The industry commissioned epidemiologist Nathan Mantel to write a critique and used it, together with a cleverly worded description of the Garfinkel study, to suggest that it disputed the passive smoking-lung cancer connection, in advertisements that reached an estimated 80% of the American population (5). This campaign was particularly cynical since it was run despite the fact that the industry's own scientists, after reviewing Hirayama's work, concluded "Hirayama is a good scientist and his non-smoking wives publication was correct" and "that Hirayama was correct, that TI [Tobacco Institute] knew it, and that TI published its statement about Hirayama knowing that the work was correct" (6, 7). The British Medical Journal took note of these public attacks and re-opened correspondence about Hirayama's paper to provide him with an opportunity to respond in a scientific forum. The editors took the exceptional step of publishing Mantel's criticisms, which had been addressed to the Tobacco Institute and not the British Medical Journal, nine months after Hirayama's paper was originally published (9, 10). Hirayama and others demolished the criticisms (9, 10). The campaign against Hirayama's findings was not limited to the United States. The tobacco industry ran similar advertisements worldwide. In Australia, the Australian Federation of Consumer Organizations took the Australian Tobacco Institute to court for misleading advertising over these claims, and won on the grounds that the advertisement was false and misleading (11). The controversy generated by the tobacco industry attracted the attention of other epidemiologists who sought to see who was right. As a result, by 1986, 13 studies had been done on passive smoking and lung cancer, and the evidence was strong and consistent enough for the US Surgeon General to issue the first report dealing entirely with the effects of passive smoking (12), which concluded that "involuntary smoking causes disease, including lung cancer, in healthy nonsmokers". A few weeks later, the US National Academy of Sciences issued a similar report reaching the same conclusion (13). Concerning anything other than tobacco, the issue would have been considered closed at that point. As time passed, several independent scientific bodies around the world reviewed the evidence that passive smoking causes lung cancer (and a wide variety of other diseases) and reached similar conclusions (Table 1). These reports helped stimulate the passage of clean indoor air ordinances, which not only protect non-smokers from second-hand smoke but also create an environment that makes it easier for smokers to stop (14, 15). Table 1. Risk of lung cancer in passive smokers: results of study by Hirayama (1) confirmed by major international consensus reports Report Year Country Hirayama (1, 9, 10) 1981 Japan 1-19 cigarettes a day 20 cigarettes a day or more US Environmental Protection 1992 USA Agency (20) National Research Council(13) 1986 USA Surgeon General (12) 1986 USA California Environmental 1997 USA Protection Agency (21) National Health and Medical 1997 Australia Research Council (22) Scientific Committee on 1998 UK Tobacco and Health (23) Relative Confidence Report risk interval(a) Hirayama (1, 9, 10) 1-19 cigarettes a day 1. …