Serum pneumoproteins: A cross-sectional comparison of firefighters and police

Background: Serum pneumoproteins provide a measure of the permeability of the lower respiratory tract, and have shown promise as a biomarker of acute and chronic exposure to respiratory toxicants. Methods: To evaluate the effects of chronic occupational smoke exposure, 105 firefighters were compared with 44 police controls in a cross-sectional study using spirometry, diffusing capacity of the lung, serum Clara cell protein (CC16), and serum surfactant-associated protein A (SP-A) measurements. Results: There were no significant differences in age, gender, height, spirometry (FVC and FEV₁), and diffusing capacity between the two groups. Serum SP-A was lower in firefighters (260.1±121.2 μ/L) than police (316.0±151.4 μg/L, P = 0.019). Serum CC16 was also lower in firefighters (8.39±3.11 μg/l) than police (10.56±4.20 μg/L, P<0.001), although this difference lost statistical significance when adjusted for confounders. Conclusions: Firefighters have lower serum concentrations of SP-A than do police. Although the clinical significance of this finding is presently unknown, SP-A deserves further study as a biomarker of toxic exposure to the lower respiratory tract.