Recent research, published by the International Journal of Hospital Infection and collected by experts in the Microbiology Department at Leeds General Infirmary in the UK, examined the amount of Clostridium difficile (C. diff) that becomes airborne and contaminates surrounding surfaces when flushing a lidless toilet. Using fecal suspensions of C. diff, the researchers measured airborne suspension of the bacteria, in addition to surface contamination by the bacteria after flushing both lidless and lidded toilets.

Air samples 25 cm above the toilet, which is about the height of the handle, contained C. diff, with the highest numbers coming from samples taken immediately after flushing. The number of viable bacteria declined 8-fold within an hour, from 36 colony-forming units (cfu) collected at seat height to 8 cfu, and by 90 minutes, the number fell to 3 cfu. Surrounding surfaces were contaminated within 90 minutes of flushing, with relatively large droplets released in the immediate environment. According to the reports, the mean number of droplets was between 15 and 47, depending on toilet design.

Researchers also found the number of viable bacteria to be 12-fold higher from open toilets compared with the same toilet when the lid was closed. They collected 35 cfu at seat height within 30 minutes of flushing an open toilet, but only 3 cfu at seat height within 30 minutes of flushing a lidded toilet.

This bacteria can settle on any surface in the vicinity, including sinks, towels and toiletries. Experts conclude that even with strict disinfecting processes in place, C. diff clusters continue to appear in healthcare settings, prompting a search for unaddressed contamination sources.

"Lidless conventional toilets increase the risk of C.difficile environmental contamination, and thus we suggest their use is discouraged, particularly in settings where infection is common," the researchers conclude.