Reduced serum club cell protein as a pulmonary damage marker for chronic fine particulate matter exposure in Chinese population

Abstract Background Exposure to fine particulate matter (PM 2.5 ) pollution is associated with increased morbidity and mortality from respiratory diseases. However, few population-based studies have been conducted to assess the alterations in circulating pulmonary proteins due to long-term PM 2.5 exposure. Methods We designed a two-stage study. In the first stage (training set), we assessed the associations between PM 2.5 exposure and levels of pulmonary damage markers (CC16, SP-A and SP-D) and lung function in a coke oven emission (COE) cohort with 558 coke plant workers and 210 controls. In the second stage (validation set), significant initial findings were validated by an independent diesel engine exhaust (DEE) cohort with 50 DEE exposed workers and 50 controls. Results Serum CC16 levels decreased in a dose response manner in association with both external and internal PM 2.5 exposures in the two cohorts. In the training set, serum CC16 levels decreased with increasing duration of occupational PM 2.5 exposure history. An interquartile range (IQR) (122.0 μg/m 3 ) increase in PM 2.5 was associated with a 5.76% decrease in serum CC16 levels, whereas an IQR (1.06 μmol/mol creatinine) increase in urinary 1-hydroxypyrene (1-OHP) concentration was associated with a 5.36% decrease in serum CC16 levels in the COE cohort. In the validation set, the concentration of serum CC16 in the PM 2.5 exposed group was 22.42% lower than that of the controls and an IQR (1.24 μmol/mol creatinine) increase in urinary 1-OHP concentration was associated with a 12.24% decrease in serum CC16 levels in the DEE cohort. Conclusions Serum CC16 levels may be a sensitive marker for pulmonary damage in populations with high PM 2.5 exposure.