Assessment of health risks by air conditioning systems in a printing office.

Repeated measurements were taken in a printers' office where one case of humidifier lung disease had occurred. In water supplies of the office's air conditioning systems, the number of moulds was mainly below 50 colony-forming units (CFU)/mL, the quantity of anaerobic bacteria mostly below 10,000 CFU/mL. Twenty-nine out of the 120 participating employees complained of symptoms such as dyspnea, cough, malaise whose majority was not associated with the workplace. Twenty-eight had IgG antibodies to humidifier antigens prepared from water supplies of the air conditioning systems. 17 employees had at least one pathological lung function parameter. There was no significant correlation between complaints, antibody levels and lung function finding. Repeated measurements within two years did not show significant changes in complaints, lung function parameters and antibody concentrations. We conclude that the described amount of moulds and bacteria in the air conditioning systems did not cause new cases of humidifiers lung. IgG antibodies indicate exposure to antigens which are obviously of no clinical relevance.