[Study of a cancer aggregate in a metallurgy plant: practical implications for public health]

We present the strategy used to determine whether there was an excess of laryngeal cancer at a primary metal factory in Montreal. The study period extended from 1968 to 1987. Standardized mortality ratios (SMR) and standardized incidence ratios (SIR) were computed for different cancer sites. The number of person-years at risk was estimated (N = 10,860 person-years). This method permitted a summary evaluation of the situation. Statistically significant excesses were not observed for laryngeal cancer or any other site of cancer: SMRs and SIRs were elevated for certain cancers, particularly cancers of the larynx and cancers of the central nervous system (CNS). No association was observed with potential carcinogens in the workplace. However, all three CNS cancer cases were crane operators. Following this investigation, we recommended an industrial hygiene evaluation of the workplace.