This may be a sign for you to finally clean your reusable water bottle.

Reusable water bottles have become an essential item that we carry around and use everyday—as with toilet seats.

However, your reusable water bottle might contain 40,000 times more bacteria than an average toilet seat, as per new findings by United States-based waterfilterguru.com.

In the new study, researchers found that spout-top and screw-top lids contain the most bacteria of all water bottles, containing 30 million colony-forming units (CFUs). The study is exploratory and does not involve statistical testing.

A squeeze-top water bottle also had 6,000 times more bacteria than a toilet seat, though they are the cleanest in comparison to others.

The findings came after researchers swabbed the water bottles and toilet seats three times each, where they found two types of bacteria—gram-negative rods and bacillus.

The first type of bacteria, the study said, can cause infections as bacillus is known to contribute to gastrointestinal issues.

The research found that water bottles have an average of 20.8 million CFUs of bacteria.

“Bacteria are known as biological drinking water contaminants. They’re just one of four types of pollutants that might be present in the water coming out of your taps and into your reusable bottles,” the researchers said.

In another comparison, researchers found that water bottles contain about twice the amount of germs in kitchen sinks, which it described as “one of the most germ-filled spots in a home”.

The study noted that moist environments serve as “breeding grounds for germs”, stressing the importance of cleaning reusable water bottles on a daily basis and sanitising it at least once a week.

Reusable water bottles have become more commonly used as countries have moved to ditch single-use plastic water bottles in an effort to protect the environment.

In 2019, the Washington Post spoke to experts on the safest types of reusable water bottles, with the market offering a variety of ones made from glass, steel and plastic.

Experts stated that glass bottles are the safest to use, due to being made from natural materials.