It is unfortunate true the fact that I have encountered a lot of people who think that nasal hair will stop all air pollutants from being inhaled and reach the lungs, or as we now know, the heart and brain. They feel completely sure that they are safe irrelevant the concentration of the pollution.
The human nose is an extraordinary human organ that offers us so much, many times we don’t even appreciate its function until we lose it. It can warn us that something isn’t right, for example, food has gone bad, or the presence of toxic gases in a close/open environment but it can also offer us a pleasant sensation when we smell a rose or lavender flowers.
The human odor threshold is almost perfect, below you can see the odor threshold determinations of 53 odorant chemicals in parts per million (ppm).
Fun fact: Did you know that when we lose the scene of smell we lose part of our taste abilities too.
But enough with our smelling abilities. Let’s address the filtration capabilities of the nasal hair.
Does nasal hair offer a filtration function?
Yes, but it is complicated, theoretically, it’s a filter for dust, pollen, viruses, and bacteria. Particles adhere to the wet surface of your nose hairs, which prevents them from reaching your lungs and causing infection. In real human experiments, scientists applied aerosols during single or multiple respiratory cycles that have shown that particles larger than 3 μm in diameter have a maximum deposition in the anterior part of the nose. Particles smaller than 3 μm and larger than 0.5 μm are filtered too. The filtration for particles smaller than 0.5 μm is low. They seem to pass easily into the lower respiratory tract, so size does matter.
In another study, researchers found that increased nasal hair density decreases the development of asthma in those who have seasonal rhinitis, possibly due to an increased capacity of the hair in the nose to filter out pollen and other allergens. It’s a combination of a lot of mechanisms that keep out larger particles. The shape of the particle also matters. More research is needed.
Keep in mind that the concentrations of the pollutants are very important too as high concentrations of air pollutants can saturate the filtration mechanisms nature has given us and then the pollutants continue their journey inside us.
Particulate matter of 10 μm in diameter can reach the bronchial tree and particulate matter of less than 10μm in diameter (PM2.5) can reach lower airways. In another study pollen of 20 μm has been found in the lung periphery.
Although nasal hair offers some level of filtration with the combination of other mechanisms, a lot of parameters can affect its capabilities like size, shape, and concentration of the pollutants. The smaller the pollutant, the easier it passes. Remember, trim nose hair if they get too long, but don’t remove them completely.