Are occupational, hobby, or lifestyle exposures associated with Philadelphia chromosome positive chronic myeloid leukaemia?

Objectives-To investigate a broad range of occupational, hobby, and lifesty le exposures, suggested as risk factors for Philadelphia chromosome positiv e (Ph+) chronic myeloid leukaemia (CML). Methods-A case-control study, comprising 255 Ph+CML patients from southern Sweden and matched controls, was conducted. Individual data on work tasks, hobbies, and lifestyle exposures were obtained by telephone interviews. Occ upational hygienists assessed occupational and hobby exposures for each sub ject individually. Also, occupational titles were obtained from national re gistries, and group level exposure-that is, the exposure proportion for eac h occupational title-was assessed with a job exposure matrix. The effects o f 11 exposures using individual data and two exposures using group data (or ganic solvents and animal dust) were estimated. Results-For the individual data on organic solvents, an effect was found fo r moderate or high intensity of exposure (odds ratio (OR) 3.4, 95% confiden ce interval (95% CI) 1.1 to 11) and for long duration (15-20 years) of expo sure (OR 2.1, 95% CI 1.1 to 4.0). By contrast, the group data showed no ass ociation (OR 0.69, 95% CI 0.27 to 1.8; moderate or high intensity versus no exposure). For extremely low frequency electromagnetic fields (EMFs), only individual data were available. An association with long occupational expo sure to EMFs was found (OR 2.3, 95% Cl 1.2 to 4.5). However, no effect of E MF intensity was indicated. No significant effects of benzene, gasoline or diesel, or tobacco smoking were found. OR estimates below unity were sugges ted for personal use of hair dye and for agricultural exposures. Conclusions-Associations between exposure to organic solvents and EMFs, and Ph+CML were indicated but were not entirely consistent.