Abstract:

Objective To investigate health risk of Legionnaires' disease from cooling towers of central air conditioning ventilation systems in star-rated hotels and secondary and tertiary hospitals in a certain District of Beijing from 2018 to 2024. Methods From May to September each year from 2018 to 2024，on-site inspections were conducted on the operational cooling towers within central air conditioning systems of 20 star-rated hotels and 26 secondary and tertiary hospitals，a questionnaire survey about usage status and management practices was conducted at the same time.The cooling water were collected from on single or group of cooling towers at each facility and analyzed for Legionella pneumophila，turbidity，and free chlorine residual. The health risk assessment of Legionnaires' disease in each unit's cooling tower was evaluated by using a cooling tower Legionnaires' disease health risk index model to calculate the cooling tower Legionnaires' disease health risk index. Results The detection rates of Legionella pneumophila in cooling water from hotels and hospitals were 26.32% and 9.09%，respectively，with a statistically significant difference（χ²=4.273，P<0.05）.The cooling tower water condition was primarily assessed as low risk，accounting for 70.0% of cases in star-rated hotels and assessed as medium risk，accounting for 53.8% of cases in hospitals.95.0% of hotel cooling towers and 61.5% of hospital cooling towers were assessed as high risk，due to absence of drift eliminators of cooling tower.There was no statistically significant difference in the average risk index for Legionella proliferation between hotels（15.96） and hospitals（16.14）（t=-0.105，P>0.05）. Legionella-containing aerosol transmission risk indexs and population infection risk indexs of cooling towers were statistically significant differences between hotels and hospitals（t=2.126，Z=-5.923，both P<0.05）. The average health risk index of Legionnaires' disease in hotels and hospitals were 50.52 and 60.84，respectively，with a statistically significant difference （t=-3.204，P<0.05）. Conclusion Both star-rated hotels and secondary and tertiary hospitals face certain health risks of Legionnaires' disease associated with their cooling towers.Engineering managers for hotels and hospitals need to conduct regular maintenance，cleaning，disinfection，and testing of the cooling towers.Additionally，drift eliminators should be installed to reduce the diffusion of aerosols into the environment，in order to effectively control the proliferation of Legionella bacteria in the cooling water of the central air conditioning cooling tower and reduce the risk of transmission via bacteria-containing aerosols.

Key words: Cooling tower, Legionella pneumophila, Risk assessment, Hotel, Hospital, Legionnaires' disease