Nasal Toxicity: End Points of Concern in Humans

Abstract

The nose is perhaps the most used portal of the human body, with gases, particles, and aerosols flowing in and out of it many times each minute of life. It should be no surprise that some of these inhaled materials are chemically and biologically active and that their effects may be either beneficial or harmful. Gaseous oxygen is certainly needed to sustain life, while cyanide can quickly end it. Similarly, while pure water aerosols can moisten and help heal the nasal mucosa, viral and bacterial particles in the aerosol can infect that same mucosa. The anatomy of the nasal cavities and the path of airflow through them determine many of the characteristics of the nasal response to inhaled xenobiotics. For example, carcinomas caused by the inhalation of wood dust often form on the anterior head of the middle turbinate, where one of the main air streams in the nasal cavity hits it. It is at the level of the nasal mucosa, however, where inhaled xenobiotics interact with the cells of the nasal lining, whether they be squamous, respiratory, transitional, or olfactory. This interaction can have local effects in the nasal cavity, such as mucosal inflammation or crusting caused by cilia dysfunction. There can also be distant or systemic effects, such as decreased athletic performance, when inhaled ozone is not detoxified by the metabolically active nasal mucosa. There are many ways to evaluate the effects of inhaled materials on the nose. These can be used in response to individual complaints after a particular exposure, or as part of a testing protocol. Direct visual examination of the nasal cavities, especially with endoscopy, can reveal changes in the nasal epithelium. Other studies can assess airflow resistance, nasal cavity shape, and nasal mucosal thickness while nasal lavage assesses the mucosal secretions. Neural function can be evaluated with tests of olfactory and trigeminal ability. If the nose has been damaged by inhaled xenobiotics, the traditional medical techniques of humidification, antibiotics, steroids, and surgery can sometimes restore health. More importantly, in specific areas of high pollution, prevention and avoidance programs have been successful in decreasing the levels of morbidity.