Association of expired nitric oxide with urinary metal concentrations in boilermakers exposed to residual oil fly ash

BACKGROUND: Exposure to metal-containing particulate matter has been associated with adverse pulmonary responses. Metals in particulate matter are soluble, hence are readily recovered in urine of exposed individuals. This study investigated the association between urinary metal concentrations and the fractional concentration of expired nitric oxide (F(E)NO) in boilermakers (N = 32) exposed to residual oil fly ash (ROFA). METHODS: Subjects were monitored at a boiler overhaul site located in the New England area, USA. F(E)NO and urine samples were collected pre- and post-workshift for 5 consecutive workdays. Metals investigated included vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), and lead (Pb). RESULTS: The median F(E)NO was 7.5 ppb (95% CI: 7.4-8.0), and the median creatinine-adjusted urinary metal concentrations (mug/g creatinine) were: vanadium, 1.37; chromium, 0.48; manganese, 0.30; nickel, 1.52; copper, 3.70; and lead, 2.32. Linear mixed-effects models indicated significant inverse exposure-response relationships between log F(E)NO and the log-transformed urinary concentrations of vanadium, manganese, nickel, copper, and lead at several lag times, after adjusting for smoking status. CONCLUSIONS: Urine samples may be utilized as a biomarker of occupational metal exposure. The inverse association between F(E)NO and urinary metal concentrations suggests that exposure to metals in particulate matter may have an adverse effect on respiratory health.