The first provincial laws mandating pasteurization (Ontario, 1930s) were introduced not in response to food safety concerns but as a marketplace strategy to eliminate competition from farmers who were selling milk direct to consumers: see pp 26-27 of “1932 – 1966 the Ontario Whole Milk Producers’ League” (by E. H. Brethour and C. L. Clarke, 1966) below:
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Page 27: