Association Between Seasonal PM2.5 Exposure and Immune Response in Residents Living in Chiang Mai Province, Thailand

Fine particulate matter (PM2.5) is an air pollutant that significantly impacts environmental and health outcomes. In Chiang Mai province, Thailand, residents face recurring PM2.5 pollution from November to May each year, primarily due to open biomass burning and transboundary emissions. The long-term health impacts of PM2.5 in Chiang Mai remain inadequately documented. This study aims to investigate leukocyte distribution and IgE level in response to long-term PM2.5 exposure. Participants residing in San Patong district, Chiang Mai, were recruited. Leukocyte distribution was investigated by the complete blood count and flow cytometry. IgE levels were measured by sandwich enzyme-linked immunosorbent assay. Long-term PM2.5 exposure is associated with significant changes in leukocyte distribution, including WBC count, neutrophil, monocyte, and basophil absolute count, while lymphocyte and eosinophil counts were not significantly affected. In the present study, flow cytometric immunophenotyping was performed during the late PM2.5 season to evaluate the distributions of major leukocyte populations and the expression of activation and inhibitory markers on lymphocyte subsets. Interestingly, IgE levels showed a decreasing trend. These findings highlight the immunological effects of repeated PM2.5 exposure and underscore the need for further research to clarify its mechanisms and health implications.