# Our Best Friends: How Dogs Alter Indoor Air Quality

## TL;DR

Dogs significantly affect indoor air quality by emitting pollutants like CO2, bacteria, and VOCs, with bigger dogs having a stronger impact.

## Contribution

This study quantifies and compares pollutant emissions from small and big dogs, revealing their role in indoor air chemistry and microbial transport.

## Key findings

- Big dogs emit higher levels of CO2, NH3, fungi, and bacteria compared to small dogs.
- Dogs contribute to the formation of nanocluster aerosols and ozonized VOCs, likely from human skin oils transferred to their fur.
- Big dogs emit more coarse particles and microbes than humans but fewer medium-sized particles.

## Abstract

Dogs are dynamic contributors to the indoor environment,
yet their
impact on air quality remains largely unexplored, warranting a comprehensive
assessment of their pollutant emissions. This study characterized
chemical, particulate, and microbial emissions from small and big
dogs. Big dogs emitted CO2, NH3, fungi, and
bacteria at considerably higher rates than small dogs, whereas their
emissions of 1–10 μm particles were similar. With ozone
present, all dogs contributed to the formation of nanocluster aerosols
(1–3 nm) and ozonized volatile organic compound (VOC) products,
likely from human skin oil transfer through petting. With ozone present,
nanocluster aerosols (1–3 nm) were observed during dog experiments,
likely reflecting ozone reactions with human-derived skin lipids transferred
onto dog fur. Relative to a seated adult, big dogs emitted less ozonized
products, comparable CO2 and NH3, more >5
μm
coarse particles (fewer 2–5 μm particles), 2–4×
more bacteria and fungi, and showed compound-specific differences
in VOCs: while some species exhibited a strongly elevated dog-to-human
ratio (with one up to 15×), others were not pronounced when dogs
were present. Our findings highlight dogs as significant indoor emission
sources and contributors to indoor air chemistry and microbial transport,
with implications for air quality and exposure assessment.