Air humidification is sometimes used to reduce dryness symptoms in temperate climates, but the biological mechanism behind this effect is not well understood. We have investigated the effect of air humidification on physiological signs from the eyes and nose, other medical symptoms and on perceived air quality. An experimental study was performed in two units of a well-ventilated geriatric hospital in southern Sweden. Blinded central steam air humidification in one of the units during 6 weeks raised the relative air humidity to 43% RH (January–March 1997), while the other unit with 35% RH served as control. All staff (N = 32) working the day shift were invited to undergo a medical investigation performed in the hospital units. It included measurement of tear film stability, acoustic rhinometry, nasal lavage and completing a medical questionnaire. The investigation was repeated at both units after 6 weeks and 26 subjects participated on both occasions (81%). The technical measurements were room temperature, relative air humidity and the levels of nitrogen dioxide (NO2), moulds, bacteria, formaldehyde, and total as well as specific volatile organic compounds in the air. The mean room temperature (22.5°C), and indoor concentrations of pollutants were similar in both units, before and after humidification. Air humidification decreased the sensation of air dryness and reduced the number of dermal symptoms. No effect on other symptoms, i.e. tear film stability (breakup time), nasal patency, or biomarkers in nasal lavage, was observed. In conclusion, increasing air humidity from 35 to 43% RH with central steam humidification was found to reduce dermal symptoms and perception of air dryness, but there was no evidence of an effect on tear film stability, nasal patency, or nasal mucosal inflammation or secretion.

Keywords:
Acoustic rhinometry, Air humidification, Albumin, Eosinophilic cationic protein, Hospital workers, Lysozyme, Myeloperoxidase, Nasal lavage, Tear film stability
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© 2000 S. Karger AG, Basel
2000
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