Acute Effects of Sulfur Dioxide Exposure on the Middle Ear Mucosa

Abstract

A variety of atmospheric pollutants are known to depress mucociliary function in the respiratory system. Since the mucociliary function in the middle ear is similar, and the middle ear may be invaded by atmospheric pollutants, we decided to investigate the possible contribution of sulfur dioxide to middle ear effusion. Guinea pigs were exposed for 24 hours to 300 ppm of sulfur dioxide or air. Immediately after exposure, ciliary activity and epithelial structure were examined close to the tympanic orifice (proximal site) and more distal to it (distal site). In the animals exposed to sulfur dioxide, no effusion was found in the tympanic cavity. Ciliary activity was reduced only in the distal site. Electron microscopy demonstrated hypersecretion in the proximal site and severe pathologic changes in the distal site. Although the normally functioning cilia in the proximal site may prevent retention of surplus secretions in the ear, sulfur dioxide may promote middle ear effusion when combined with other detrimental factors, because it stimulates mucus secretion in the proximal site and impairs ciliary function in the distal site.

Air Pollution and Emergency Department Visits for Otitis Media: A Case-Crossover Study in Edmonton, Canada

“…Third, pollutants may result in adenoidal hyperplasia, resulting in narrowing of the Eustachian tubes. Lastly, pollutants might directly cause mucosal swelling of the Eustachian tube (Ohashi et al 1989a, 1989b). Whatever the mechanism, it is certainly plausible that that these same mechanisms could be attributed to traffic-related pollutants as well.…”

“…A growing body of evidence links OM to ambient air pollutants. Animal studies have demonstrated impairment of ciliary function and increased middle ear mucus secretion after sulfur dioxide (SO 2 ) exposure (Ohashi et al 1989b). Consequently, the possible link between air pollution and OM is important to understand.…”

Air pollution and Otitis media: A review of evidence from epidemiologic studies

“…Considering insufficient evidence at the moment on the role of ETS on OM: lack of consistent and strong impact of ETS on otitis; convincing biologically plausible mechanisms for the associations between ETS and OM; positive support from animal experiments on guinea pigs showing impaired ciliary function and increased mucus secretion in the middle ear following SO 2 exposure [30]; and an increasing body of evidence on positive associations between ambient air pollution and OM from epidemiologic studies, we consider a potential triggering effect of ambient air pollution exposure on OM as a reasonable hypothesis. The data at the moment are so sparse that we are not in a position to provide any far-reaching conclusion yet.…”

Air Pollution and Otitis Media in Children: A Systematic Review of Literature

“…Air pollutants such as particulate matter (PM), trigger oxidative responses and inflammation in lung epithelium leading to asthma and allergies. Animal studies provide evidence that air pollutants, such as sulphur dioxide (SO 2 ), impair the mucociliary function of the Eustachian tube and increase middle ear mucus secretion [ 18 ]. Similarly, evidence from epidemiological studies supports a link between air pollution and OM; however, there has been no recent comprehensive systematic review of these investigations in children.…”