Are air-conditioning maintenance personnel at increased risk of Legionellosis?

We surveyed by use of medical questionnaires and blood tests 21 maintenance workers involved with cleaning and servicing cooling towers and evaporative condensers at a large company to determine the frequency of pneumonia and antibody levels against Legionella pneumophila serogroup 1. The 21 high-risk workers were compared with 27 low-risk workers, persons who were not directly involved in service or maintenance for the company. The overall prevalence of titers greater than or equal to 128 for the 21 high-risk workers was 19.0% compared with 22.2% for the low-risk group. There were no significant differences in the history of pneumonia between these groups. Possible explanations for these findings are discussed.