Clinical and allergological findings of workers in a printing office with humidifier system - 10 years of follow-up

Exposure to humidifier systems leads to inhalation of aerosols by humidifier water contaminated with microorganisms and may induce allergic reactions and work-related illness. In this study we investigated humeral immunological response to work-specific and ubiquitous antigens and respiratory function of 191 workers of a printing office up to a period of 10 years. More than 50% of persons developed specific IgG but not IgE antibodies against humidifier water. Independent of exposure intensity, antibody levels may persist over years. No decrease in respiratory function or increase in unspecific bronchial hyperreactivity was observed. Better water quality by periodical cleaning of the humidifier caused a remarkable reduction of work-related symptoms. Ln context to these findings IgG antibodies are mainly a marker of exposure and not a sure sign of illness. A total of 10% of workers developed sensitisation to smoothing powder with specific IgE antibodies, and partly rhinitis and bronchial irritation. Our investigations show that maize flour is an important allergen in printing offices.