Rectal cancer and exposure to metalworking fluids in the automobile manufacturing industry

Abstract

Background: Rectal cancer has been previously associated with exposure to metalworking fluids in a cohort mortality study of autoworkers. Objective: To better specify the exposure-response relationship with straight metalworking fluids (mineral oils) by applying non-parametric regression methods that avoid linearity constraints and arbitrary exposure cut points and by lagging exposure to account for cancer latency, in a nested case-control analysis. Methods: In addition to the classical Poisson regression with categorical exposure, survival models with penalised splines were used to estimate the exposure-response relationship between cumulative exposure to straight metalworking fluid and mortality from rectal cancer. Exposures to water-based metalworking fluids were treated as potential confounders, and all exposures were lagged by 5, 10, 15 and 20 years to account for cancer latency. The influence of the highest exposures was dealt with by a log transformation and outlier removal. The sensitivity of the penalised splines to alternative criteria for model selection and to the placement of knots was also examined. Results: The hazard ratio for mortality from rectal cancer increased essentially linearly with cumulative exposure to straight metalworking fluid (with narrow confidence bands) up to a maximum of 2.2 at the 99th centile of exposure and then decreased (with wide confidence bands). Lagging exposure up to 15 years increased the initial steepness of the curve and raised the maximum hazard ratio to 3.2. Conclusions: Non-parametric smoothing of lagged exposures has shown stronger evidence for a causal association between straight metalworking fluid and rectal cancer than was previously described using standard analytical methods. This analysis suggests an exposure-response trend that is close to linear and statistically significant over most of the exposure range and that increases further with lagged exposures. Smoothing should be regularly applied to environmental studies with quantitative exposure estimates to refine characterisation of the dose-response relationship.

Occurrence and characterization of culturable bacteria and fungi in metalworking environments

“…Water-based MWFs, especially, are used in industrial environments, and the use of these MWFs during mechanical operations often results in the formation of aerosols that are associated with adverse health effects. These effects can include respiratory illnesses such as hypersensitivity pneumonitis (HP) (Hodgson et al 2001) as well as rectal cancer (Malloy et al 2007), rhinitis-related symptoms (Park et al 2008), and dermatitis (Ueno et al 2002).…”

“…Targeted groups include automobile-manufacturing workers (Malloy et al 2007), automotive ring-manufacturing workers (Park et al 2008), and machine operators (Lillienberg et al 2008).…”

Case–control study of male germ cell tumors nested in a cohort of car‐manufacturing workers: Findings from the occupational history

“…Several publications confirmed a possible carcinogenic potential of metalworking fluids (MWF) [Mirer et al, 1988;Park, 2001;Savitz, 2003;Agalliu et al, 2005;Bardin et al, 2005;Malloy et al, 2007], but an explicit association with testicular cancer has never been described before. MWF are a complex mixture of chemicals and toxic microbial agents [Gordon, 2004].…”

Burying the Evidence: How Great Britain is Prolonging the Occupational Cancer Epidemic

“…A Harvard University report noted that existing studies substantially under-estimate the metalworkingfluids cancer risk. 22 When medium-density fiberboard (MDF)-a composite creating potential for exposures to two recognized carcinogens during manufacture or machiningbecame the subject of a recent safety controversy, HSE backed entirely the industry line on potential health problems, failing to acknowledge the cancer risk. 23 It did not modify this position when formaldehyde was upgraded in 2004 24 to the International Agency for Research on Cancer's (IARC's) top cancer-risk category, Group 1.…”