Prevalence of antibodies to Legionella pneumophila among workers exposed to a contaminated cooling tower.

A serosurvey for antibodies to Legionella pneumophila was conducted among 206 employees of a power-generating plant. L. pneumophila serotype 6 and a non-typable L. pneumophila organism were isolated from cooling-tower water specimens at the plant, and antibody titers in workers were measured using homologous antigens prepared from these isolates. For the serotype 6 water isolate, none of workers with low cooling tower exposure, 4.6% with intermediate exposure, and 7.6% with high exposure levels had titers equal to or greater than 1:128 (P less than .05, Kruskal-Wallis test). For the non-typable L. pneumophila isolate, a similar trend was observed, but differences among workers in the three exposure groups were not statistically significant. No association was observed between antibodies to L. pneumophila serotypes isolated from cooling water and workers' age, race, smoking status, or duration of job assignment. None of the study employees had findings suggesting the occurrence of L. pneumophila pneumonia since the plant had been in operation. Use of respiratory protection devices by workers exposed to aerosols from cooling towers was not recommended.