Bladder Cancer as an Occupational Disease in the British Rubber Industry: An In-Depth Factory Study to Show the past Extent of the Risk and Confirmation of its Subsequent Disappearance *

Abstract

A hazard and risk of occupationally-induced bladder cancer (papilloma) existed in the British Rubber Industry up to the end of 1949.

To explore this in more detail, an in-depth factory study was undertaken between 1946 and 1985 to define the incidence of bladder tumours in male rubber workers employed there up to 1949, and who were inadvertently exposed to a human bladder carcinogen in a compounding ingredient. The objective was to follow them up for the next 35 years. This carcinogen was betanaphthylamine which contaminated certain antioxidants being used by the rubber industry at that time. A comparison with the incidence of bladder tumours in new employees who started work only after January 1950 when the dangerous chemicals had been withdrawn was also made. A clear statistically significant excess incidence of bladder cancer was shown for the ‘at risk’ men working at the factory before December 1949; whereas tumour incidence was generally less than expectation for those employed after the discontinuance date. The evidence that the hazard had ceased when the dangerous products were removed was thus purposely sought out and not just presumed.

An analysis of the occupationally-induced bladder tumours themselves indicated a marked shift in incidence to younger age groups, which pattern is consistent with that predicted for a work-related cause. The data also support the premise that epidemiologists should now consider conducting morbidity (incidence) rather than mortality studies for the future, because of the steadily improving prognosis and more prolonged survival currently associated with bladder cancer. Both have influenced the usual parameters (mortality data) previously used to measure outcome in long term studies.