Association of expired nitric oxide with occupational particulate exposure

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Journal Article
Environmental Health Perspectives, 2003, 111 (5), pp. 676 - 680
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Particulate air pollution has been associated with adverse respiratory health effects. This study assessed the utility of expired nitric oxide to detect acute airway responses to metal-containing fine particulates. Using a repeated-measures study design, we investigated the association between the fractional concentration of expired nitric oxide (FENO) and exposure to particulate matter with an aerodynamic mass median diameter of ≤ 2.5 μm (PM2.5) in boilermakers exposed to residual oil fly ash and metal fumes. Subjects were monitored for 5 days during boiler repair overhauls in 1999 (n = 20 or 2000 (n = 14). The Wilcoxon median baseline FENO was 10.6 ppb [95% confidence interval (CI): 9.1, 12.7] in 1999 and 7.4 ppb (95% CI: 6.7, 8.0) in 2000. The Wilcoxon median PM2.5 8-hr time-weighted average was 0.56 mg/m3 (95% CI: 0.37, 0.93) in 1999 and 0.86 mg/m3 (95% CI: 0.65, 1.07) in 2000. FENO levels during the work week were significantly lower than baseline FENO in 1999 (p < 0.001). A significant inverse exposure-response relationship between log-transformed FENO and the previous workday's PM2.5 concentration was found in 1999, after adjusting for smoking status, age, and sampling year. With each 1 mg/m3 incremental increase in PM2.5 exposure, log FENO decreased by 0.24 (95% CI: -0.38, -0.10) in 1999. The lack of an exposure-response relationship between PM2.5 exposure and FENO in 2000 could be attributable to exposure misclassification resulting from the use of respirators. In conclusion, occupational exposure to metal-containing fine particulates was associated with significant decreases in FENO in a survey of workers with limited respirator usage.
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