I live in a somewhat smoggy/polluted city, where the air pollution level regularly varies from totally clean to fairly dirty (3 mile visibility).

When I'm exercising (cycling) and the air is on the dirtyish side, I try to only inhale air through my nose, because it filters out the particles... right?

Is there any scientific data on this? How effective is nose-breathing at filtering contaminants?

1 Answer 1


I don't have any empirical data, but my thought is "not much".

The natural way for breathing at rest is to have the mouth closed and breathe through the nose.

I've seen no information at all to suggest that people who might be breathing through their mouths (while exercising) are warned against an increased risk of pollution. If there was any significant risk of open-mouth breathing leading to pollution-related illnesses, I'm sure we would have heard about it by now.

The nose does contain sticky mucous and hairs, but not enough to screen every particle coming in (and smoke particles are small).

This hasn't stopped various manufacturers from inventing "nose filters" to cash in on people's paranoia though.

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