8249601 Benzene exposure and risk of colorectal cancer in the Norwegian offshore petroleum workers cohort

<h3>Objective</h3> To investigate the association between low levels of benzene exposure (average intensity&lt;0.05 parts per million [ppm]) and risk of colorectal cancer (CRC) including its anatomical subsites. <h3>Material and Methods</h3> Among the 25,347 men in the NOPW cohort with offshore work history between 1965 and 1998, we prospectively identified 469 CRC cases 1999–2021 and compared them with 2031 non-cases drawn from the cohort in case-cohort analyses. Work histories were linked to job-exposure matrices for benzene and other occupational exposures. Weighted Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for overall CRC and anatomical subtypes (right- and left-sided colon cancer [RCC and LCC] and rectal), adjusted for age, body mass index, smoking, alcohol intake, red/processed meat intake, and physical activity. <h3>Results</h3> Risks of CRC increased with increasing benzene exposure. For all CRC, the HRs (95% CI) for the most exposed [quartile 4] vs the unexposed were 1.32 (0.96 to 1.81, [0.177–0.879 ppm-years]; p-trend=0.085) for cumulative, 1.52 (1.11 to 2.07, [17–34 years]; p-trend=0.032) for the duration, and 1.56 (1.15 to 2.12, [0.015–0.046 ppm]; p-trend=0.005) for average intensity of benzene exposure. For right-sided colon cancer, the association was most evident for exposure duration (HR=2.25, 1.33 to 3.80, quartile 4 [17–34 years] vs. unexposed; p-trend=0.007). Sensitivity analyses showed consistent associations. <h3>Conclusion</h3> Our results suggest that risks of CRC, and particularly RCC, increased with increasing duration of rollover shift work and benzene exposure in male offshore workers.