The Scientific American September 2001 has an article by Joan Raymond The Shape of a Nose that has implications for inhalation toxicology. [The original article is
Noback, M. L., K. Harvati, et al. (2011). “Climate-related variation of the human nasal cavity.” American Journal of Physical Anthropology 145(4): 599-614]
“Scientists have long been interested in the relation between a nose’s form and its function. New research is showing that climate may have played an important role in how the nose’s internal structure evolved.
Researchers in Germany recently showed that individuals from cold, dry climates, such as Greenland or Siberia, had higher and narrower nasal cavities than those from hot, humid climates, such as Papua New Guinea or Gabon. The German team, led by Marlijn Noback of Eberhard Karls University of Tübingen, took computer-aided measurements of the nasal cavities of 100 skulls representing 10 human groups living in five different climates. They found that the nasal cavities of cold, dry climate populations are relatively high and show a larger and more abrupt change in diameter in the upper part of the cavity than those of hot, humid climate populations. Her research was published online in the American Journal of Physical Anthropology this past June.
This narrowing of the nasal passage enhances contact between the air and the mucosal tissue, which helps to warm and humidify that air, Noback notes. Cold, dry climate populations also show a relatively longer nasal cavity, giving this population more space in which to bring incoming air in line with body temperature. Microscopic hairs called cilia, which line the nasal passage, help to keep out pathogens and dust that may infect or irritate the lungs, and the cilia work more efficiently when incoming air is moist. “Proper heating and humidification of air in colder climates are important for respiratory health,” says paleoanthropologist Nathan Holton of the University of Iowa. In warm-climate-adapted populations, inhalations are not directed toward the narrow upper part of the nasal cavity for warming. So “people from warm climates, moving into cold climates, could be more susceptible [to] colds and related diseases,” Noback says.
Which sort of nose do you have? Although you can’t tell much about the external shape of the nose when looking at its internal structure, a narrow, longer internal cavity is generally linked to a relatively narrower and more projecting nose, Holton says”
It is not clear from this excerpt what the implications are for Eskimos and other Asiatic people with flatter noses who live in cold climates. I must read the article.
The velocity of air in the nose and the sharpness of changes in direction have great effects on particle deposition. If “nasal cavities of cold, dry climate populations are relatively high and show a larger and more abrupt change in diameter in the upper part of the cavity than those of hot, humid climate populations”, then for people with high nasal velocities and sharp changes in the direction of air:
- fewer respirable particles should deposit in the respiratory tract and the incidence of some lung diseases should be lower
- the incidence of neoplasms in the nasal cavity should be higher.
In a paper I presented in 1988 (Bromwich, D. W. The Nose, Can you trust it? Melbourne, Australian Institute of Occupational Hygienists) I referred to an article that suggested nasal hairs had a significant influence on silicosis. I’ll have to chase that up and re-examine the data.
