Environmental impacts on childhood rhinitis: The role of green spaces, air pollutants, and indoor microbial communities in Taiyuan, a city in Northern China.

Rhinitis is one of the most common respiratory diseases, influenced by various environmental factors such as green space, air pollution and indoor microbiomes. However, their interactions and combined effects have not been reported. We recruited 1121 preschool children from day care centers in a northern city of China. Health and demographic data were collected through questionnaires answered by the children's parents. Surrounding green space was assessed by Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and land cover data of grassland proportion within 1500/3000 m. Ambient air pollution was estimated using the inverse distance weighted (IDW), and the indoor microbiome in classroom vacuum dust was profiled by bacterial 16S rRNA and fungal ITS amplicon sequencing. Mixed-effect logistic regression revealed the proportion of natural grassland, grassland leaf-off and total grassland was negatively associated with current rhinitis. Stratified analysis indicated that greater green space exposure was associated with a reduced current rhinitis in children at high levels of air pollution. Additionally, grassland also protects children against environmental tobacco smoke at home. Indoor microbiome analysis showed Haemophilus and Dolosigranulum were enriched in low-rhinitis day care centers, while Amaricoccus, Blautia and Mycosphaerella were enriched in high-rhinitis day care centers. Mediation analysis indicated that the indoor microbiome did not have significant mediating effects on the relationship between green space and children's current rhinitis. This is the first study to reveal interactions of green space, air pollution and indoor microbiome on rhinitis, providing new insights into how environmental factors collectively influence respiratory health in children.