Dogs do more than share living space with their owners — they also influence the air inside homes. Researchers in Lausanne have, for the first time, measured the gases, particles and microbes that dogs introduce into indoor environments.
The findings provide data that could help improve models used to understand indoor air quality, according to the Swiss Federal Institute of Technology Lausanne (EPFL). While the effect of human activity on indoor air has been studied extensively, the role of pets has received little attention.
The study found that a large dog at rest produces roughly the same amount of carbon dioxide as an adult person. Emissions of ammonia — a gas formed during protein breakdown and released through skin and breathing — were also similar.
Dogs had the strongest effect on airborne particles. Activities such as shaking, scratching or being stroked release dust, pollen, plant material and microbes into the air. Large dogs were found to release two to four times more microorganisms than a person in the same space.
Researchers describe dogs as mobile carriers that bring biological material indoors and redistribute it throughout the room. A higher diversity of particles is not necessarily harmful, they note. Some research suggests that exposure to a wider range of microbes may support immune system development, particularly in children.
Chemical reactions indoors
The study also examined chemical reactions that occur inside homes. Ozone entering from outdoors reacts with skin lipids and produces new compounds such as aldehydes and ketones. In humans, these reactions involve squalene, a substance found in skin oils.
Dogs do not produce squalene themselves, but it can be transferred to their fur through contact with people. These residues can then also react with ozone. Overall, however, dogs generated about 40% fewer ozone reaction products than humans.
Measurements were carried out in a controlled environmental chamber at EPFL in Fribourg. Researchers studied two groups of animals: three large dogs — a Mastiff, a Tibetan Mastiff and a Newfoundland — and four small dogs, all Chihuahuas.
