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Jee Young Kim,¹ Matthew P. Wand,² Russ Hauser,¹ Sutapa Mukherjee,¹ Robert F. Herrick,^1,3 and David C. Christiani^1,4

¹Department of Environmental Health, Occupational Health Program, ²Department of Biostatistics, and ³Department of Environmental Health, Environmental Science and Engineering Program, Harvard School of Public Health, Boston, Massachusetts, USA; ⁴Pulmonary and Critical Care Unit, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA

Abstract

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 (F_ENO) and exposure to particulate matter with an aerodynamic mass median diameter of 2.5 µm (PM_2.5) 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 F_ENO 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 PM_2.5 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. F_ENO levels during the work week were significantly lower than baseline F_ENO in 1999 (p < 0.001) . A significant inverse exposure-response relationship between log-transformed F_ENO and the previous workday's PM_2.5 concentration was found in 1999, after adjusting for smoking status, age, and sampling year. With each 1 mg/m³ incremental increase in PM_2.5 exposure, log F_ENO decreased by 0.24 (95% CI: -0.38, -0.10) in 1999. The lack of an exposure-response relationship between PM_2.5 exposure and F_ENO 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 F_ENO in a survey of workers with limited respirator usage. Key words: air pollutants, epidemiology, nitric oxide, occupational, particulate matter. Environ Health Perspect 111:676-680 (2003) .