Metalworking Fluids and Colon Cancer Risk: Longitudinal Targeted Minimum Loss-based Estimation

Area of Science:

• Occupational health
• Epidemiology
• Toxicology

Background:

• Metalworking fluids (MWFs) are complex mixtures containing carcinogens, potentially increasing cancer risk for millions of workers.
• Previous studies on MWFs and colon cancer incidence have yielded inconclusive results.

Purpose of the Study:

• To investigate the association between exposure to straight, soluble, and synthetic MWFs and colon cancer incidence in automobile manufacturing workers.
• To address healthy worker survivor bias using time-varying confounding adjustment.

Main Methods:

• A cohort study of automobile manufacturing workers was conducted.
• Longitudinal targeted minimum loss-based estimation (TMLE) was employed to estimate causal effects.
• Exposure cutoffs were defined at the 90th percentile for total particulate matter for each MWF type.

Main Results:

• A significant 25-year risk difference of 3.8% for colon cancer was associated with straight MWF exposure.
• Risk ratios indicated a higher risk with straight MWFs (2.39) compared to soluble (1.43) and synthetic (1.08) MWFs.
• While soluble and synthetic MWFs showed increased risk, the associations were not statistically significant.

Conclusions:

• This study provides evidence for a causal effect of straight MWF exposure on colon cancer risk.
• Controlling for time-varying confounding improved the ability to detect causal associations.
• Findings highlight the need for stricter occupational safety measures regarding straight MWF use.