TAMPA, Fla. (WFLA) — Some may find comfort in knowing their reusable water bottle is saving the ecosystem one sip at a time, but fewer may know it could be at the expense of their own health.

A study from U.S.-based WaterFilterGuru.com found on average, reusable water bottles can hold up to 40,000 times more bacteria than a toilet seat.

For the study, researchers swabbed multiple household items including toilets, dog bowls, computer mice, kitchen sinks, and, of course, reusable water bottles. Each item was swabbed three times before samples were sent for testing and analysis.

Researchers found two main types of bacteria present in the samples: Gram-negative rods and Bacillus.

The Centers for Disease Control and Prevention (CDC) says Gram-negative bacteria can cause infections including pneumonia and meningitis, and are increasingly resistant to most available antibiotics. The CDC also says Bacillus is a leading cause of Anthrax, which can cause severe illness in both humans and animals.

On average, the study found that straw-top reusable water bottles faired better than screw-top water bottles. However, straw-top bottles still had 14 times the amount of bacteria found inside a pet bowl.

“More surprisingly, the average reusable water bottle was 40,000 times dirtier than a toilet seat,” researchers said in their findings.

So what should you do to avoid these bacteria?

Researchers said it’s important to wash your reusable water bottles regularly.

A survey of 1,000 Americans regarding their water bottle preferences and habits found that 88% of people cared deeply about the quality of their drinking water, but only 42% said they washed their reusable bottles every day.

The survey also found that Gen Zers cleaned their bottles the least often, with 16% cleaning theirs only a few times per month.

“The same vessel that brings healthy hydration to your daily routine could make you sick if not cared for properly,” researchers said. “If you’ve been feeling unwell, check in with your water bottle cleaning habits to see if bacteria and mold might be the culprit.”

Experts recommend washing your water bottle once per day and sanitizing it at least once per week. Users should also wash their bottles more often if they have been sick or filling it with something other than water — especially if it has sugar.