Impact of air-conditioning system disinfection on microbial contamination of passenger cars

An automobile air-conditioning (AC) system can be a source of microbiological contamination in a driver's car. The aim of this study was to assess the level of microbial contamination before and after servicing of the automobile AC system, based on qualitative and quantitative analyses of bacteria and fungi isolated from the air, and to check the efficiency of different AC system cleaning methods in the removal of microbial contaminants. The study was carried out in 35 randomly selected cars, equipped with AC systems. In each car tested, viable bioaerosol samples were taken using a single-stage MAS impactor before and after servicing the AC systems. Four methods were used to disinfect the air-conditioning installations in the vehicles examined: ozonisation, application of chemical disinfectant using ultrasounds, manual application of chemical disinfectant foam and simultaneous ozonisation and application of chemical disinfectant foam. The bacterial and fungal concentrations in air samples before AC servicing in cars were between 7.5 x 10(1) cfu/m(3) and 2.0 x 10(3) cfu/m(3) and 4.0 x 10(1) cfu/m(3) and 5.0 x 10(2) cfu/m(3), respectively. Regardless of the disinfection method, after the AC service, a decrease in microbial concentrations was observed. The highest disinfection efficiency was observed for two methods: ozonisation combined with manual application of the chemical disinfectant into the air-conditioning system and spraying of the chemical disinfectant using ultrasounds. On the basis of the results obtained, it can be concluded that air-conditioning systems in cars should be regularly disinfected to eliminate microbiological contaminants, which may be the cause of adverse health effects on humans.