The Plume: Controlling Bacteria Growth on Bathroom Surfaces


You may have heard that when you flush a toilet with the lid up, microbes entrained in the air can travel up to 6 feet, landing on all of the surrounding bathroom surfaces within this space. This “plume” phenomenon was first described in the early 1900s by Sir William Horrocks1, and has been elaborated on by multiple labs including that of Dr. Charles Gerba, an American microbiologist. As described in an Applied Microbiology publication in 1975,2 Dr. Gerba and his team added bacteria or viruses to toilet water and then assessed the level remaining in and around the toilet after flushing. The study indicated that after 1 flush, the majority of added microorganisms were removed but that the level remained at 104 bacteria/viruses in the toilet bowl even after multiple flushes. The evidence suggested that bacteria/viruses were being retained by the porcelain surface and only released during flushes. Scrubbing or adding detergent to the bowl was able to remove all adherent bacteria but viruses were never entirely eradicated from the surface with simple cleaning.

Dr. Gerba’s lab also discovered that bacteria/viruses were not only retained in the toilet bowl, but that these microorganisms were also aerosolized throughout the bathroom as a consequence of toilet flushing. The study found that 1,000-10,000 bacteria would be ejected from the bowl with every flush. After the flush, these bacteria are encased in droplets of varying sizes. The larger droplets settled around the toilet within 2 hours after the flush (i.e. rim, seat, and handle). However, bacteria and viruses also remained suspended in the air in smaller droplets for longer periods of time. The study found that bacteria could be recovered up to 4 hours after the flush from airborne droplets and the authors speculated that the time frame could be even longer for viruses.

The Plume Split Screen

In order to understand the distance that these plume droplets can travel, Microban evaluated the ability of a fluorescent dye to be dispersed by the toilet flushing.3 Pictures were taken before and after the toilet was flushed and then the distance that droplets traveled was measured. In agreement with prior work, the largest and most numerous droplets were identified at the back of the toilet seat and around the rim. Droplets traveled slightly more than 2 feet and were found on the floor, wall, handrail and countertop. Taken in conjunction with Gerba’s work that indicated bacteria can absorbed by the porcelain surface, this suggests that bacteria/viruses that are aerosolized after flushing and can travel considerable distances.

Numerous technologies exist to help inhibit the growth of bacteria on the surface of your bathroom products. Proper cleaning and disinfectants can remove or eliminate bacteria and other microbes on surfaces, but provide no residual protection against subsequent recontamination. Built-in antimicrobial preservatives have also been shown to effectively inhibit the growth of microorganisms on the protected surfaces. By using a toilet containing an antimicrobial preservative technology to provide built-in antimicrobial product protection, along with a consistent cleaning regimen, you can help to inhibit the growth of microbes that can be released in the air during a flush, keeping your bathroom surfaces cleaner in between cleanings.4


1. Horrocks, W. H., Experiments Made to Determine the Conditions under which "Specific" Bacteria Derived from Sewage may be Present in the Air of Ventilating Pipes, Drains, Inspection Chambers and Sewers. Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character 1907, 79 (531), 255-266.

2. Charles Gerba, C. W., Joseph Melnick, Microbiological Hazards of Household Toilets: Droplet Production and the Fate of Residual Organisms. Applied Microbiology 1975, 30 (2).

3. Microban Products Company, unpublished data. 

4. Microban antimicrobial product protection is limited to the product itself and is not designed to protect the users of these products from disease causing microorganisms or as a substitute for normal cleaning and hygiene practices.  Microban International, Ltd. makes neither direct nor implied public health claims for the products containing Microban® antimicrobial product protection.