How harmful is it to reuse a plastic water bottle?

ahsan65@gmail.comOctober 31, 2025

0 0 6 minutes read

How harmful is it to reuse a plastic water bottle?

After emptying a water bottle, it can be tempting to fill it from the tap without hesitation. But can you really reuse plastic water bottles?

Plastic bottles don’t seem to be disappearing quickly. Americans drink about 15.9 billion gallons of bottled water each year – almost 48 gallons per person – according to a report from Research and Markets.

But you might want to reconsider reusing plastic water bottles. Read on to learn how sipping from single-use containers for days can lead to bacterial growth, chemical leaching, and preventable waste.

Types of plastic water bottles

Not all plastic bottled water is the same: different brands and containers may be made from different materials.

You can tell what type of plastic a product is made from by checking the triangular recycling code printed on the bottle, which can also help you determine if the bottle is recyclable through your local program, according to the Environmental Protection Agency (EPA).

Many water bottles are made from polyethylene terephthalate, according to the National Institutes of Health (NIH) and the EPA. Here is the breakdown of this and other common plastics:

Types of plastic

Name	Recycling code	Examples
Polyethylene terephthalate (PET or PETE)	1PETE or 01PET	Plastic pots and drinks bottles
High density polyethylene (HDPE)	2HDPE or 02PE-HE	Drinking bottles and carafes
Polyvinyl chloride (PVC)	3V or 03PVC	Produce egg containers and cartons
Low density polyethylene (LDPE)	4LDPE or 04PE-LD	Food films and bags
Polypropylene (PP)	5PP or 05PP	Produce egg containers and cartons
Polystyrene (PS)	6PS or 06PS	Produce egg containers and cartons
Other	7OTHER or 07O

Source: Environmental Protection Agency. “How to recycle? : common recyclable products »

Plastic bottles may contain potentially harmful bacteria

So, is it safe to reuse plastic water bottles? It turns out that a days-old bottle is the perfect breeding ground for bacteria.

“After about two days, the colonies of microorganisms will form a biofilm, similar to the way barnacles adhere to a boat,” says Philip Tierno, PhD, director of microbiology and immunology at NYU Langone Medical Center and author of First, wear a face mask: a doctor’s guide to reducing infections during the pandemic and beyond.

This slimy layer is made up mostly of oral bacteria, but it can also contain waterborne pathogens as well as germs from your hands that contaminate the water when you unscrew the cap. And when you take a drink, your mouth may come into contact with the germy outer surface of the bottle.

It’s okay to reuse plastic water bottles, but only up to a certain point. “You can refill the bottle as often as you like for 24 hours and then throw it away,” says Dr. Tierno.

In one study, researchers compared bacterial growth in 15 stainless steel water bottles and 15 PET plastic water bottles. They found that plastic bottles contained significantly higher levels of bacteria and that most bottles contained more bacteria than toilet seats.

Reusable water bottles can contain disease-causing bacteria like E. coli and salmonella if you don’t clean them regularly, according to The Water Project.

But can you get sick from reusing plastic water bottles? “E. coli indicates that there is fecal transmission in the water, and where you find fecal matter, you can also find other organisms like salmonella and norovirus,” Tierno says. Although these infections don’t always cause infection, the potential is there, he adds.

Whether you put your water bottle on a bacteria-filled public surface, carry it in front of someone who is talking or coughing, or hold it with unwashed hands while you’re out and about, you’re exposing it to contamination.

“Use a wipe to periodically disinfect the exterior of your bottle, the same way you would your cell phone,” suggests Tierno. You can also save an extra day of using your bottle by washing it with warm, soapy water, he says.

And most importantly, don’t sip it for more than 48 hours without cleaning it.

“The thin plastic that disposable bottles are made of has grooves, nooks and crannies that make it impossible to remove the biofilm,” says Tierno. “In fact, most bottles have labels saying ‘do not reuse.’ »

In comparison, reusable metal or glass bottles are much easier to clean thanks to their smooth, flat surface.

Harmful chemicals can leach into water

When reusing a plastic water bottle, another concern is that it will increase the amount of toxic compounds leaching from the plastic into your water. According to research, PET plastic water bottles in particular can leach potentially harmful substances into your water over time.

“PET contains suspected carcinogens, including the compounds antimony trioxide and acetaldehyde,” says Marta Guron, PhD, environmental health and radiation protection project manager at the University of Pennsylvania.

Some PET also contains bisphenol A (BPA) and similar chemicals, although these are more often found in bottles with the number 7 in the recycling symbol. Research suggests that BPA is an endocrine disruptor, meaning it can interfere with the body’s hormones.

“In 2011, the Food and Drug Administration (FDA) banned it in bottles and cans intended for children,” says Dr. Guron. “Unfortunately, the general population is still exposed to BPA in their consumable water bottles.”

But whether filling a bottle with water amplifies the rate and degree of chemical leaching remains a matter of debate.

Using a water bottle for the first time would release the greatest amount of chemicals, Guron says. “The concentration of these additives would decrease over time as the chemicals are carried away or ingested.” The exception is acetaldehyde, which leaches out in greater quantities as the bottle degrades, according to some research.

Chemicals can also leach from scratched or rough plastic, notes the National Poison Control Center. And the longer your bottle has been around, the dirtier it will be.

Guron says that creating space between plastic particles — such as by scraping or stretching it if the bottle freezes and expands — makes it easier for additives to leak.

Even a little damage increases the risk of microplastics entering the water, says Jabraan Pasha, MD, an internal medicine physician and community health advocate in Tulsa, Oklahoma. “These microdoses aren’t enough to make you sick, but you still want to minimize your exposure.”

Additionally, research suggests that the alteration caused by UV light accelerates the release of chemicals.

Since heating a disposable bottle speeds up the oxidation reaction that breaks down plastic over time, you may notice the funny taste of acetaldehyde when a bottle is left in a hot car for a day, Guron says.

Guron adds that warmer temperatures can also cause more antimony trioxide and BPA to leach from the surface, because the solubility of a solid increases slightly with temperature.

So do not wash it in the dishwasher or in hot water before filling it. Research on PET bottles has found that temperatures of 95 degrees Fahrenheit and above increase the release of BPA, while temperatures of 77 degrees and below do not cause detectable BPA release.

The bottom line: Reusing your bottle increases the likelihood that it will be exposed to damage, light and heat – and, therefore, chemical leaching.

It’s not ideal for the environment

Reusing a water bottle may seem like an eco-friendly alternative to using a new disposable container every time you get thirsty. But given the potential harmful effects of plastic water bottles, it might be better for your health and the environment to ditch single-use plastic altogether.

Here’s how plastic water bottles affect the environment right off the bat: Plastic production requires fossil fuels and emits greenhouse gases, both of which threaten environmental health, according to the NIH.

And after all that, according to the EPA, only about 29% of disposable PET and HDPE bottles are recycled. The rest is sent to landfills, or 27 million tonnes of plastic in 2018, according to the most recent data available.

The environmental impact of plastic water bottles thrown into landfills can be immense. According to research, some potential side effects of plastic water bottles in landfills – and as waste – include:

Chemicals that can leach into soil or groundwater
Aging plastic waste, as well as burning it, can release toxic chemicals into the air.
Damage to ecosystems, for example plastic in the ocean, which damages marine environments and animals.

Alternatives to Reusing Plastic Water Bottles

While you can safely reuse plastic water bottles for about 24 to 48 hours, here are some alternatives to try to minimize any negative effects on your health or the environment:

Buy a reusable water bottle.
Switch to tap water.
Purchase a water filter to further clean tap water intended for drinking.
If you must use plastic water bottles, be sure to recycle them.

How to clean a water bottle

To avoid excess bacteria, it is important to clean your reusable water bottle regularly, at least once a week. Here’s how to do it:

Use a bottle brush to scrub the inside of the bottle with soap and water. Rinse until the water runs clear.
For a deeper clean, soak it overnight in a solution of half vinegar, half water, then rinse and wash it in the morning.

Takeaways

It’s probably no problem to fill your bottle for a few days. “Any longer than that, a biofilm can form inside. It’s not a guarantee that you’ll get sick, but you start to increase the risk,” says Tierno.

In addition to these health effects, reusing plastic water bottles can also create potentially unnecessary waste. It’s best to invest in a reusable bottle for safe and sustainable sipping.

ahsan65@gmail.comOctober 31, 2025

0 0 6 minutes read