A: coffee mug

If you’re being “green” and bring your own coffee mug to work rather than use disposable cups, put that mug down before you read any further. If you don’t wash your coffee mug daily, reusing it could be putting your health at risk. “Colonies of germs are living in your favorite cup,” Dr. Charles Gerba, a professor of environmental microbiology at the University of Arizona, told Men’s Health. According to his research, 20 percent of office coffee mugs contain fecal bacteria and fully 90 percent are covered in other types of germs. Why? Unlike at home where you put a used coffee mug in the dishwasher after you use it, people typically clean their office coffee mugs with a sponge or scrub brush found in the office kitchenette. The bacteria found on the sponge is then transferred to your coffee mug where those germs can live for up to three days. What can you do? Dr. Gerba, who is also known as “Dr. Germ,” offers the following suggestions:

• Don’t nurse a cup of coffee longer than an hour or so.
• Take your coffee mug home every evening to be washed in the dishwasher.
• When cleaning your dishes in the dishwasher, always use the dry cycle. This exposes the dishes to the highest temperatures and kills all the germs.
• If you can’t take your mug home every evening, be sure to wash it thoroughly in hot water and soap and dry it with a paper towel. Do not use the icky sponge in the office kitchenette.
• If you leave your coffee mug on your desk without washing it, bacterial colonies will begin reproducing immediately–even if the mug only contains a coffee ring.