Objectives Since there are few data on the effects of metalworking in populations representing a variety of metal companies or on dose–response relationships concerning metalworking, this study investigated the relationship between occupational exposures in machine shops and the occurrence of upper and lower respiratory symptoms, asthma, and chronic bronchitis.

Methods A cross-sectional study of 726 male machine workers and 84 male office workers from 64 companies was conducted in southern Finland. All of the participants filled out a questionnaire, and aerosol measurements were performed in 57 companies.

Results Exposure to metalworking fluids (MWF) showed a greater risk [odds ratio (OR) ≥2) for upper-airway symptoms, cough, breathlessness, and current asthma than exposures in office work did. Exposure to aerosol levels above the median (≥0.17mg/m³ in the general workshop air) was related to an increased risk (OR ≥2) of nasal and throat symptoms, cough, wheezing, breathlessness, chronic bronchitis, and current asthma. Machine workers with a job history of ≥15 years experienced increased throat symptoms, cough, and chronic bronchitis.

Conclusions This large study representing machine shops in southern Finland showed that machine workers experience increased nasal and throat symptoms, cough, wheezing, breathlessness, and asthma even in environments with exposure levels below the current occupational exposure limit for oil mists. The study suggests that improving machine shop environments could benefit the health of this workforce. It also suggests that it is time to consider reducing the current Finnish occupational exposure limit for oil mist or introducing the use of other health-relevant indicators of exposure.

Key terms asthma; chronic bronchitis; machine shop; machinist; metal-working fluid; occupational exposure; respiratory condition; respiratory symptom