Fractional Exhaled Nitric Oxide Levels in Metalworkers

Welder working in steel manufacturing facility
To what extent is the metalworking occupation associated with increased levels of fractional exhaled nitric oxide, an established inflammatory biomarker?

Welders/assemblers in a metalworking industrial cohort presented significantly higher fractional exhaled nitric oxide (FeNO) levels than machine operators or administrative and ancillary staff, according to results published recently in the International Archives of Occupational and Environmental Health. Researchers surmise that respiratory tract inflammation associated with airborne exposures specific to the welders/assemblers may explain this finding.

In this cross-sectional cohort study, researchers investigated the extent to which metalworking is associated with increased FeNO, an established inflammatory biomarker. Participants included 80 employees of a metalworking plant in Almaty, Kazakhstan (median age, 51.5 years [IQR 20.5]; 61% smokers; 6 females).  Participants were categorized into 3 groups: machine operators (41%); welders/assemblers (33%); and administrative and ancillary staff (26%). All answered questionnaires and underwent testing for levels of carbon monoxide (CO) and fractional nitric oxide (FeNO) and for lung function.

The investigators found that the machinists group (group 1) had the highest particulate exposure; however, the welders/assemblers group (group 2) showed significantly higher FeNO than group 1 or group 3 (other employees). The adjusted group 2 FeNO mean was 44.8 ppb (95% CI, 33.8–55.9) vs group 1 mean, 24.6 ppb (95% CI 20.5–28.7) and group 3 mean, 24.3 ppb (95% CI 17.7–30.9). Secondhand smoking and height were not associated with FeNO.

Although researchers found the highest FeNO values in welders/assemblers, even after adjusting for age and smoking, they also found no statistical difference in respiratory symptoms or comorbidities among the 3 occupational groups. However, particulate matter was highest among machinists, which suggested to researchers that either the chemical specificity of the particulate (rather than its bulk) or gaseous pollutants may be the determining factor driving inflammation.

Researchers concluded, “Further research is needed to shed light to the etiology of this inflammatory biomarker elevation in welders/assemblers, in particular more detailed industrial hygiene characterization of their working environment and additional characterization of biomarkers in addition to FeNO, such as induced sputum or exhaled particles.”

Researchers noted numerous limitations of the study, including the inability to exclude a contribution of other exposures or long-term smoking to altered FeNO values.


Vinnikov D, Tulekov Z, Blanc PD. Fractional exhaled NO in a metalworking occupational cohort. Int Arch Occup Environ Health. Published online October 9, 2021. doi:10.1007/s00420-021-01801-z