Commentary: John Snow's 'On the Supposed Influence of Offensive Trades on Mortality': the 'Snow paradigm'

In 1855, the renowned anaesthesiologist-epidemiologist John Snow, President of the Medical Society of London, physician to the royal family, irritant of the British sanitarians, then at the height of his prestige, appeared before the British Parliament’s Select Committee on Public Health on the Nuisances Removal and Disease Prevention regarding the need to ‘‘tackle the problems of accumulations of excrement and street refuse, industrial waste and smoke, polluted rivers, slaughterhouses, and filth’’. As one who considered the mouth as the portal for the entry of all pathogens into the body, Snow had little concern regarding the potential adverse health effects of the merchants and factory owners in Southwark whose cause he was championing. Were Parliament to enact any legislation restricting the disgorgement of such ‘pathogens’ into the environment, particularly near residential housing, those merchants and factory owners may no longer have had their businesses. It was on behalf of those merchants and factory owners (those with involvement with the ‘offensive trades’ including gasworks, bone boilers, soap manufacturers, tallow melters, dye makers, leather tanners and the like) that Snow’s name as an expert on such health matters had been put forward as one whose testimony might inform the Committee in its consideration of the proposed law. Snow appeared before the Committee on 5 March 1855. He made clear his view that these ‘offensive trades’ presented no health risk to those residing near them; that the increased mortality from cholera in South London resulted from the use of cholera-infested water supplied by the Southwark and Vauxhall Water Company; and that he believed that ‘epidemic diseases are propagated by special animal poisons coming from diseased persons and causing the same diseases to others’. This testimony was not well received in all quarters of the Victorian London medical community. The Lancet published an editorial condemning that testimony. The editorial left little doubt in its stinging criticism, noting that Snow: