Fractional exhaled NO in a metalworking occupational cohort

Abstract

Purpose: Secondary metalworking carries exposure to relatively heavy levels of respirable particulate. We investigated the extent to which metalworking is associated with increased exhaled nitric oxide (FeNO), an established inflammatory biomarker.

Methods: We studied 80 metalworking factory employees in Kazakhstan. Informed by industrial hygiene data, we categorized them into three groups: (1) machine operators (41%); (2) welders or assemblers (33%); and (3) all others, including administrative and ancillary staff (26%). Participants completed questionnaires covering occupational history, smoking, home particulate sources, respiratory symptoms, and comorbidities. We measured exhaled carbon monoxide (CO), exhaled fractional nitric oxide (FeNO), and spirometric function. We used mixed-effects modeling to test the associations of occupational group with FeNO, adjusted for covariates.

Results: The median age was 51.5 (interquartile range 20.5) years; 7% were women. Occupational group (p < 0.01), daily current cigarette smoking intensity (p < 0.05), and age (p < 0.05), each was statistically associated with FeNO. Welders, or assemblers (Group 2), who had intermediate particulate exposure, manifested significantly higher exhaled FeNO compared to machinists (Group 1, with the highest particulate exposure) and all others (Groups 3, the lowest particulate): adjusted Group 2 mean 44.8 ppb (95% confidence interval (CI) 33.8-55.9) vs. Group 1 24.6 ppb (95% 20.5-28.7) and Group 3, 24.3 ppb (95% CI 17.7-30.9). Secondhand smoking and height were not associated with FeNO.

Conclusion: In a metalworking industrial cohort, welders/assemblers manifested significantly higher levels of FeNO. This may reflect respiratory tract inflammation associated with airborne exposures specific to this group.

Keywords: Assembling; Exhaled nitric oxide; Inflammation; Mixed-effects model; Occupational; Welding.