London - Motorists are being urged to clean the air conditioning units in their cars after researchers found potentially dangerous bacteria living and breeding in systems.
With the weather warming up in the northern hemisphere, the study shows drivers may be putting their health at risk when they reach for the cool switch. Bacteria associated with meningitis, urinary tract infections and septic arthritis were among the many types discovered in air conditioning filters.
Swabs of 15 air conditioning filters were taken from cars across the UK and sent for laboratory analysis. Micro-organisms were detected in all of the filters tested at London Metropolitan University.
The most common was Bacillus licheniformis, a bacteria most commonly associated with birds and soil. Eight out of 15 of the filters tested positive for this micro-organism, which is among a type of bacteria known to cause food poisoning.
Bacillus subtillis and Bacillus were the second most common micro-organisms found. Bactillus subtillis are normally found in the gastrointestinal tract of humans and some mammals. They generally do not cause disease but have been known to cause septicaemia in a patient with leukaemia.
Bacillus is more dangerous and has links with a wide range of infections including meningitis, abscesses and septicaemia.
Perfect conditions for bacteria
A car’s air con works by mixing fresh air from outside with a refrigerant and the mixture turns into liquid as it is cooled. It is then turned into vapour as it travels through evaporation coils and blown into the cabin as cool air. It is the evaporator in the system that provides perfect conditions for bacteria, mould and fungi to build up and thrive. Although the car filter will prevent many pollutants entering the passenger compartment, it will not stop all micro-organisms.
The research was commissioned by Kwik Fit, which urged drivers to clean their cars' air conditioning systems at least once every two years. On average, the test found 1.6 different strains of mico-organisms within the filters.
Dr Paul Matewele, a senior lecturer specialising in microbiology at London Metropolitan, said: "Some of the bacteria found have links to animals, the gastrointestinal tract of humans and some infections that could cause a lot of harm to individuals, especially those with a compromised immune system.
"The study highlights that air conditioning systems are suitable breeding grounds for bacteria and therefore underlines the importance of cleaning and replacing filters.
"I’m sure if car owners knew what they were blowing out of their air conditioning vents they would think twice before switching them on this summer."