**5. Conclusions**

Though air pollution exposure levels were higher in spring than in summer, measured biomarkers levels were higher during summer than in spring. The results showed that cytokine expression (biomarker levels) did not show dependency only with personal PM2.5 exposure levels among traffic police and there may be other unmeasured factors such as genetics and stress. In general, short-term daily PM2.5 exposure levels solely affected half of measured biomarker concentrations in a highly polluted environment in the Kathmandu Valley. Particularly, PM2.5 had a mixed effect on these measured biomarker concentrations (positive association with 3 biomarkers and negative association with 4 biomarkers). Among the six variables tested for the statistical effect on individual biomarkers, season and gender were the most important variables affecting biomarker concentrations among traffic volunteers. This study has several limitations and further study is recommended to continue the investigation on potential factors that impact inflammation biomarkers.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1660-4601/16/3/377/s1. The strategy diagrams for building linear mixed models and variation of air pollution among six sites are given in supplementary information. Figure S1. Strategy diagram for building linear mixed models. Table S1. Variation of personal air pollution exposure at six sites between two seasons.

**Author Contributions:** Conceptualization, K.M.S. and R.E.P.; data collection and analysis, K.M.S.; Statistical analysis and software, Y.Z.; resources, K.M.S., R.E.P., and B.D.P.; writing—original draft preparation, K.M.S.; writing—review and editing, Y.Z. and R.E.P.

**Funding:** This study was supported by IASS in Potsdam, Germany, and the International Centre for Integrated Mountain Development (ICIMOD), Lalitpur, Nepal.

**Acknowledgments:** We acknowledge the Ministry of Home Affairs, the Metropolitan Traffic Police Division, and the traffic police volunteers for their cooperation in this research. We appreciate the help from the Nepal Health Research Council (NHRC) for the permission to conduct this study, and K. Aryal from NHRC for his cooperation and support on coordination with various governmen<sup>t</sup> agencies. We thank the excellent support from our field research assistants A. Shahi, B. Gaire and J. Balami, and a local phelobotomist B. Ghimire. We also thank the help from B. Khadayat and R. R. Pokhrel. We also appreciate the help from M. Rupakheti at the Institute for Advanced Sustainability Studies (IASS) in Potsdam and R. Maskey at Tribhuvan University, Nepal.

**Conflicts of Interest:** The authors declare no conflicts of interest.
