O6B.2 Cancer risk by ore type in a mixed miners cohort

Demers PA, Berriault C, Ramkissoon A, Do MT, Lightfoot N, Zeng X, Arrandale VH. Occupational & Environmental Medicine 2019;76(Suppl 1):A1–A109. (Presentation abstract).

Background and objectives Mining may involve exposure to many carcinogens, including respirable crystalline silica (RSC), diesel engine exhaust (DEE), nickel (Ni), chromium (Cr), radon (Rn), and arsenic (As), which vary by ore being mined. The province of Ontario, Canada has a diverse mining sector with associated exposures including gold (RSC/DEE/As/Cr), uranium (RSC/DEE/Rn), and nickel-copper (DEE/Ni), and other ores (RSC/DEE). The study aim was to examine the risk of cancer by ore type in a mixed mining cohort.

Methods From 1928–1987 workers in the Ontario minerals industry were required to undergo an annual physical examination and chest x-ray, as well as record their mining work history in order to receive certification. Data from these exams was used to create the Mining Master File (MMF) cohort. Cancers were identified through linkage of the MMF with the Ontario Cancer Registry (1964–2017). Cancer risk among miners was compared to provincial rates using Standardized Incidence Ratios (SIR); internal analyses were conducted using Poisson regression.

Results Individuals who died or were lost before 1964, had missing or invalid data, or employment of less than two weeks were excluded. Too few women (n=161) were available for analysis. In total, 61 397 men were included in the analysis. Gold miners had excesses of lung (SIR=1.30, 95%CI=1.23–1.38) and nasopharyngeal cancer (SIR=2.34, 95%CI=1.39–3.70). Uranium miners had excesses of lung (SIR=1.57, 95%CI=1.45–1.70), bladder (SIR=1.20, 95%CI=1.02–1.40), and bone (SIR=2.45, 95%CI=1.30–4.19) cancers. Nickel-copper miners had excesses of lung (SIR=1.13, 95%CI=1.08–1.19), bone (SIR=2.02, 95%CI=1.32–2.96), and sinonasal cancer (SIR=1.73, 95%CI=1.12–2.56).

Conclusions Increased risks for specific cancers were observed among people who mined many different ore types. Most of the associations were as expected, but several (e.g., bone cancers) will undergo further investigation. Future analyses will examine the impact of combined exposures among miners of multiple ore types.