2018 Yes https://pmc.ncbi.nlm.nih.gov/articles/PMC5994187/ Lai, Peggy S. North America Experimental Observational Students Elementary (K-5) Dust Pests/Pesticides Bacteria Fungi Respiratory symptoms Asthma Schools Environment microbiome Shotgun metagenomics sequencing Pilot randomized trial in 25 children compared school vs home microbiomes; classroom diversity linked to asthma symptoms, supporting microbial-focused environmental health interventions.