THE ANTERIOR HUMAN NASAL PASSAGE AS A FIBROUS FILTER FOR PARTICLES

The anterior adult human nasal passage contains hairs which act as a f ibrous filter for inhaled particles. Particles which are collected by these hairs are likely removed by physical means and are unable to pro duce toxic effects in the respiratory tract. Measurements have been ma de of the anterior nasal passage and nasal hair of an adult caucasian subject, and calculations have been carried out using fibrous filter t heory to determine the deposition efficiency for unit density spherica l particles of diameter ranging from 1 nm-40 mu m at three steady insp iratory flow rates. For particles > 5 mu m, inertial and interception deposition on the nasal hairs was predicted to account for a measurabl e fraction of the experimentally measured nasal deposition, becoming s ignificant for particles > 20 mu m. Diffusion of ultrafine particles t o the nasal hair was predicted to be appreciable for particles < 5 nm. These results have important implications for nasal dose and transpor t of certain size inhaled particles.