Chemicalinduced changes

Many chemicals including nickel, chromium and aromatic hydrocarbons, have been implicated in the causation of cancer of the nose and sinuses30. These materials poison the nasal cilia. Occupational settings that carry an increased risk of cancer of the nose are woodworking in the furniture industry, the use of cutting oils, and employment in the shoe and leather industry. The wood dust impedes the normal mucociliary function allowing accumulation and retention of inhaled substances in the nasal cavity. The mucus transport rate decreases to less than 1 mm.min-1 (mucostasis). This increases the risk of developing adenocarcinoma of the nasal cavity and sinuses, especially the ethmoid31 32. Formaldehyde vapour also causes a slowing of clearance in the anterior nose, and exposure has been shown to precede nasal cancer in rodents29.

Studies in rats have shown that inhalation of sulphur dioxide (SO2) increases the thickness of the mucus blanket, and exposure to ammonia, formaldehyde and sulphur dioxide results in the cessation of ciliary movement to varying degrees33. Volunteers subjected to 1 ppm, 5 ppm and 25 ppm SO2 concentrations in inspired air showed a significant decrease in mucus flow rate with the higher concentrations, the effect being greatest in the anterior part of the nose. The subjects reported discomfort proportional to the SO2 concentration. There was also a marked decrease in cross section of the nasal airways, even at 1 ppm25. However, these levels are significantly higher than those normally present in the air.

Other factors which affect mucociliary clearance

An increase of mucociliary transport rate has been shown during the periovulatory phase of the menstrual cycle18. The mucociliary transport rate shows a diurnal cyclic pattern which is out of phase with the levels of serum IgA concentrations. The phase shift is such that the

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