Twenty percent of mugs at work may contain fecal bacteria.

Here’s an unsettling thought: the coffee mug you drink out of every day at work could be harboring a colony of germs.

Charles Gerba, a professor of environmental microbiology at the University of Arizona, tells Men’s Health Magazine that his research discovered that 90 percent of workplace mugs carry some sort of germs.

He says 20 percent of mugs at work contain fecal bacteria.

Why so gross?

Gerba says the germs are being spread by the sponge in the work-place kitchen, which everyone uses.

He says bacteria from the sponge can live in mugs for up to three days.

Gerba suggests bringing home the mug each day and cleaning it thoroughly in your dishwasher.

If you forget, make sure to clean the mug with hot water and use a clean paper towel while at work, rather than the filthy office sponge.