Altered Microbiomes in Thirdhand Smoke-Exposed Children and their Home Environments

INTRODUCTION. Tobacco smoke contains numerous toxic chemicals that accumulate in indoor environments creating thirdhand smoke (THS). We investigated if THS-polluted homes differed in children’s human and built environment microbiomes as compared to THS-free homes. METHODS. Participants were N=19 THS exposed children and N=10 unexposed children (≤ 5 years) and their parents. Environmental and biological samples were analyzed for THS pollutants and exposure. Swab samples were collected from the built environment (floor, table, armrest, bedframe) and child (finger, nose, mouth, and ear canal) and 16S ribosomal RNA genes were analyzed for bacterial taxa using high-throughput DNA sequencing. RESULTS. Phylogenetic α-diversity was significantly higher for the built environmental microbiomes in THS-polluted homes compared to THS-free homes (p<0.014). Log2 fold comparison found differences between THS-polluted and THS-free homes for specific genera at built environment (e.g., Acinetobacter, Bradyrhizobium, Corynebacterium, Gemella, Neisseria, Staphylococcus, Streptococcus, Veillonella) and in samples from children s (esp. Corynebacterium, Gemella, Lautropia, Neisseria, Rothia, Staphylococcus, and Veillonella). CONCLUSION. When exposed to THS, indoor and children microbiomes are altered in an environment-specific manner. Changes are similar to those reported in previous studies for smokers and secondhand smoke-exposed persons. THS-induced changes in child and environmental microbiome may play a role in clinical outcomes in children.