study summary / 009

Can forest microbes enter our homes?

A small Finnish experiment tracks soil-associated microbes after forest soil is added to entrance rugs.

Buildings mediate contact between outdoor and indoor environments. Täubel and colleagues tested whether a small soil intervention could alter household dust microbiota.

The study

Six Finnish homes took part: five received 15 g of forest soil on entrance rugs at weeks 0, 4 and 8; one served as a control. Researchers analyzed bacteria and fungi in dust using molecular methods.

The findings

Soil-associated bacterial signals were strongest near the rug at infant breathing height during the first two weeks and weakened with distance and time. Changes in diversity and a farm-like microbiota index were localized. The soil-specific fungal index showed no significant effect.

Architectural interpretation

The study illustrates a possible route for microbial transfer into interiors. Location and sampling height matter when studying contact between buildings and outdoor biodiversity.

Limits and conclusion

Five intervention homes and one control cannot establish general health benefits. These semiurban or semirural Finnish homes do not represent every dwelling. No clinical or brain outcome was measured, and adding soil to homes was not established as a health recommendation.