Objective To describe the distribution and influencing factors of serum Clara cell 16 (CC16) and surfactant protein-D (SP-D) among greenhouse workers.
Methods A total of 782 greenhouse workers in a village of Gansu Province, China were enrolled to fill a questionnaire and their fasting venous blood samples were collected. ELISA was used to detect the concentrations of serum CC16 and SP-D. The effects of gender, age, body mass index (BMI), greenhouse working years, number of greenhouses owned, smoking, drinking, and individual protection equipment usage on serum CC16, SP-D, and CC16/SP-D were also analyzed.
Results The P5, P25, M, P75, and P95 levels of serum CC16 were 22.94, 51.04, 81.81, 139.74, and 394.60 μg/L, respectively. The levels of CC16 in subjects of different subgroups of age were significantly different (P < 0.05) and decreased with increasing age (r=-0.145, P < 0.01). Age was an influencing factor of serum CC16 level according to the result of multiple linear regression analysis (b'=-0.183, P < 0.001). The P5, P25, M, P75, and P95 levels of serum SP-D were 1.54, 2.37, 3.24, 4.37, and 7.32 μg/L, respectively. The levels of SP-D in subjects of different subgroups of age were significantly different (P < 0.05), and the level was highest in the 46-60 years old subgroup. The level of SP-D in current or former smokers was significantly higher than that in nonsmokers (P < 0.05). The levels of SP-D were also different among the subgroups with different numbers of greenhouses owned (P < 0.05), and the subgroup owing two greenhouses showed the highest level of SP-D. Smoking (b'=0.121, P=0.001), greenhouse working years (b'=0.087, P=0.015), and drinking (b'=-0.081, P=0.026) were influencing factors of serum SP-D level according to the results of multiple linear regression analysis. The P5, P25, M, P75, and P95 levels of serum CC16/SP-D were 6.73, 14.95, 24.89, 44.11, and 150.30, respectively. The CC16/SP-D in subjects of different subgroups of age were significantly different (P < 0.05) and decreased with increasing age (r=-0.179, P < 0.01). The ratios among subgroups of different greenhouse working years were statistically different (P < 0.05), and the 6-10 years subgroup showed the highest ratio. The ratio in non-smokers was significantly higher than that in current or former smokers (P < 0.05). Age (b'=-0.216, P < 0.001) and smoking (b'=-0.076, P=0.031) were influencing factors of CC16/SP-D ratio according to the results of multiple linear regression analysis.
Conclusion Greenhouse working might influence the levels of serum CC16 and SP-D and the ratio of CC16/SP-D in greenhouse workers. Possible influencing factors are age, greenhouse working years, smoking, and drinking. The findings indicate that serum CC16, SP-D, and CC16/SP-D may serve as biomarkers of respiratory injury in greenhouse workers.
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