The Oronasal Airways: The Definer and Ignored Respiratory Zone of the PM-10 Regulatory Convention

Abstract

The particle penetration properties of the nasal and oral airways are the defining feature of the PM-10 convention. This definition implicitly assumes that only particles able to penetrate these airways can produce particle-associated health effects. Though not stated explicitly, this definition implies that no health effects resulting from exposure to particles are associated with these airways. Some particles within the PM-10 envelope are deposited in the nasal and oral airways, as well as particles outside of the envelope (except for noninhalable particles). Evidence for health effects of particles deposited in the oronasal (ON) airways is scant, primarily because most epidemiological and clinical studies have focused on the intrathoracic airways. With improved techniques for detecting physiological changes andlor acutelchronic health effects in the ON airways, the role of these airways in providing data for regulation and control of particle exposure needs further examination. Surveys of the incidence of nasal diseases indicate evidence for increasing occurrence of allergy, rhinitis, and sinus infection in urban dwellers; these studies suggest that further investigation of the factors relating particle exposure to nasal disease is needed. There is evidence for variability of ON particle deposition efficiency whose relationship to health effects has not been studied.