Swarms of diarrhea-causing bacteria may be sprayed into the air every time you flush the toilet with the lid up, researchers have found.

In a study of lidless hospital toilets in the United Kingdom, the air up to 10 inches above the toilet seat was found to be seething with the bacterium C. difficile, which causes an intestinal infection resulting in diarrhea and a potentially lethal inflammation of the colon. C. difficile is common in hospital settings where prolonged antibiotic use is common.

“The highest numbers of C. difficile were recovered from air sampled immediately following flushing,” researchers at Leeds Teaching Hospitals reported in the Journal of Hospital Infection.

After one hour, the number of C. difficile in the air above the toilet declined eightfold, and then declined an additional three times after an hour and a half, they noted. Even so, C. difficile was found on surrounding surfaces 90 minutes after flushing.

Up to 50 contaminated toilet water droplets were sprayed into the air with each flush, said study author Mark Wilcox, clinical director of microbiology at Leeds.

Experts say simply putting the lid down when flushing the toilet can prevent this type of environmental contamination.