Is it important to shut the toilet lid before flushing? Yes

I just pooped.


And I shut the toilet lid before I flushed.

The question came up internally – no pun intended – a few months ago and the barfblog braintrust saw evidence that closing the seat before flushing played a role in reducing the dispersal of microorganisms.

A pilot study by researchers with the University of Iowa has found that bioaerosols from flushed toilets in the rooms of patients with Clostridioides difficile infection (CDI) may contribute to the spread of healthcare-associated bacteria in hospitals. The research was published today in Infection Control and Hospital Epidemiology.

In the study, which was conducted at the University of Iowa Hospitals and Clinics, researchers collected bioaerosols on plates placed 0.15 meters (m), 0.5 m, and 1.0 m from the rims of toilets in 24 rooms of patients hospitalized with CDI and collected bathroom air continuously with a bioaerosol sampler before and after toilet flushing. They then cultured and identified bacteria on the plates (focusing on C difficile), measured bacterial density, and calculated the difference in bioaerosol production before and after flushing.

Bacteria were positively cultured from 8 of 24 rooms (33%). In total, 72 preflush and 72 postflush samples were collected, with healthcare-associated bacteria found in 9 of the preflush samples (12.5%) and 19 of the postflush samples (26.4%); postflush plates had a significantly higher probability of culturing positive than preflush plates (P = .0309). The predominant species cultured were Enterococcus faecalis, E faecium, and C difficile. Compared with the preflush air samples, the postflush samples showed significant increases in the concentrations of the two large particle-size categories: 5.0 micrometers (P = .0095) and 10.0 micrometers (P = .0082).

The authors conclude, “This study potentially supports the hypothesis that toilet flushing may lead to the spread of clinically significant pathogens in healthcare settings. More information is needed to determine the risk factors associated with toilet flushing and environmental contamination by pathogens.”