Bladder cancer risk in aluminum production workers: A systematic review

To summarize the key findings of occupational exposures during aluminum production in cohort studies on bladder cancer published between 1979 and 2023.

This systematic review was conducted in accordance with PRISMA guidelines and registered in PROSPERO. Study quality was evaluated using the Newcastle-Ottawa scale.

The literature search identified 24 cohort studies examining the standardized incidence (SIR) and mortality ratios (SMR) of bladder cancer among aluminum production workers. Five of the 13 studies examined SIR (95% CI) and three of the 16 studies that examined SMR (95% CI) reported a statistically significant increased risk of bladder cancer among aluminum production workers. The highest SIR was recorded in the secondary aluminum smelter (2.85; 95% CI: 1.23-5.62), suggesting a significantly elevated risk. In aluminum reduction plants, the SIR was 1.82 (95% CI: 1.59-2.07), while in Söderberg plants, it was 1.69 (95% CI: 1.06-2.57) and 1.4 (95% CI: 1.0-1.9), respectively. For aluminum plants overall, the SIR was 1.30 (95% CI: 1.10-1.50). The results indicate an increased risk, with the highest SMR of 5.90 (95% CI: 1.58-15.1), suggesting a significantly elevated hazard in the secondary aluminum smelter. The other values-3.47 (95% CI: 1.25-9.62) for the aluminum smelter and 2.24 (95% CI: 1.77-2.79) for the aluminum reduction plant-also indicate an increased risk, albeit with varying degrees of statistical certainty.

The International Agency for Research on Cancer has classified aluminum production as a Group 1 carcinogenic activity, providing strong evidence of its association with bladder cancer. The studies primarily included workers from Prebake, Söderberg, and aluminum reduction plants. Some findings indicate a significant yet variable risk across different segments of aluminum production. However, the review did not clearly confirm an increased risk of bladder cancer in specific aluminum-related occupations. Aluminum exposure may influence the lifetime risk of bladder cancer among these workers.