Personal exposure to fine particulate matter, lung function and serum club cell secretory protein (Clara)

The underlying mechanisms about the association between ambient fine particulate matter (PM_2.5) and lung function were unclear. Few epidemiological studies have evaluated the potential mediating effects of serum club cell secretory protein (Clara) (CC16), a biomarker of pulmonary epithelium integrity.

To evaluate the short-term effect of personal PM_2.5 exposure on lung function and to explore the potential mediating role of CC16 in this effect.

We enrolled 36 healthy, nonsmoking college students for a panel study in Shanghai, China from December 17, 2014 to July 11, 2015. We measured personal and real-time exposure to PM_2.5 for 72 h preceding each of four rounds of health examinations, including lung function test and serum CC16 measurement. We used linear mixed-effect models to examine the effects of PM_2.5 on lung function and CC16 over various lag times. Furthermore, we analyzed the mediating effect of CC16 in the association between PM_2.5 and lung function.

Average PM_2.5 exposure ranged from 36 to 52 μg/m3 across different lag periods. PM_2.5 exposure was negatively associated with lung function and positively associated with serum CC16 concentration. The effect of PM_2.5 on CC16 occurred earlier than that on lung function. For instance, an interquartile range (IQR) increase in 0-2 h average exposure to PM_2.5 was significantly associated with a 4.84% increase in serum CC16; and an IQR increase in 3-6 h average exposure to PM_2.5 was significantly associated with a 1.08% decrease in 1-sec forced expiratory volume. These effects lasted up to 24 h after exposure. Increased serum CC16 contributed 3.9%-36.3% of the association between PM_2.5 and impaired lung function.

Acute exposure to PM_2.5 might induce an immediate decrease in lung function by virtue of the loss of pulmonary epithelium integrity.