After draining a water bottle, it might be tempting to fill it back up from the tap without a second thought. But can you really reuse plastic water bottles?
Plastic bottles don’t seem to be going anywhere fast. Americans are drinking somewhere in the neighborhood of 15.9 billion gallons of bottled water each year — nearly 48 gallons per person — according to a Research and Markets report.
But you might want to reconsider reusing plastic water bottles. Read on to learn how sipping from single-use containers for multiple days can lead to bacterial growth, chemical leach, and avoidable waste.
Types of Plastic Water Bottles
Not all plastic-bottled water is the same — different brands and containers can be made from different materials.
You can tell what type of plastic a product is made of by checking the triangular recycling code stamped on the bottle, which can also help you determine if the bottle is recyclable by your local program, according to the Environmental Protection Agency (EPA).
Many water bottles are made from the plastic polyethylene terephthalate, according to the National Institutes of Health (NIH) and EPA. Here’s the breakdown of this and other common plastics:
Types of Plastic
| Name | Recycling Code | Examples |
|---|---|---|
| Polyethylene terephthalate (PET or PETE) | 1PETE or 01PET | Plastic jars and drink bottles |
| High-density polyethylene (HDPE) | 2HDPE or 02PE-HE | Drink bottles and jugs |
| Polyvinyl chloride (PVC) | 3V or 03PVC | Produce containers and egg cartons |
| Low-density polyethylene (LDPE) | 4LDPE or 04PE-LD | Cling wrap and bags |
| Polypropylene (PP) | 5PP or 05PP | Produce containers and egg cartons |
| Polystyrene (PS) | 6PS or 06PS | Produce containers and egg cartons |
| Other | 7OTHER or 07O |
Source: Environmental Protection Agency. “How Do I Recycle?: Common Recyclables”
Plastic Bottles May Harbor Potentially Harmful Bacteria
So, is it safe to reuse plastic water bottles? As it turns out, a days-old bottle is the ideal breeding ground for bacteria.
“After two days or so, 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 Infection During the Pandemic and Beyond.
This slimy coating is made up primarily of your mouth 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 to a point. “You can refill the bottle as often as you like for 24 hours, but then discard it,” Dr. Tierno says.
In one study, researchers compared the bacterial growth in 15 stainless steel and 15 plastic PET water bottles. They found that the plastic bottles harbored significantly higher levels of bacteria, and most of the bottles had 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 you have transmission from feces into the water, and where you find fecal matter you can also find other organisms like salmonella and norovirus,” Tierno says. While these won’t always cause infection, the potential is there, he adds.
Whether you put your water bottle down on a bacteria-filled public surface, carry it past someone who’s talking or coughing, or hold it with unwashed hands when you’re on the go, you’re exposing it to contamination.
“Use a wipe to periodically sanitize the outside of your bottle, the same way you would your cell phone,” Tierno suggests. You can also get around a day’s extra use out of your bottle by washing it with warm, soapy water, he says.
And definitely don’t sip from it for longer than 48 hours without cleaning.
“The thin plastic that disposable bottles are made of has grooves, nooks, and crannies that make it impossible to get rid of the biofilm,” Tierno says. “In fact, most bottles have labels that say, ‘do not reuse.'”
In comparison, reusable metal or glass bottles are much easier to clean thanks to their smooth, flat surface.
Health-Disrupting Chemicals Can Leach Into the Water
When you reuse a plastic water bottle, another concern is that it will increase the amount of toxic compounds seeping from the plastic into your water. Plastic PET water bottles in particular may release potentially harmful substances into your water over time, according to research.
“PET contains suspected carcinogens, including the compounds antimony trioxide and acetaldehyde,” says Marta Guron, PhD, environmental health and radiation safety project manager at University of Pennsylvania.
Some PET also contains bisphenol A (BPA) and similar chemicals, although these more often occur in bottles with the number 7 in the recycling symbol. Research suggests that BPA is an endocrine disruptor, meaning it may interfere with the body’s hormones.
“In 2011, the Food and Drug Administration (FDA) banned it in bottles and cans intended for children,” Dr. Guron says. “Unfortunately, the general population is still exposed to BPA in their consumable water bottles.”
But whether refilling a water bottle amplifies the rate and degree of chemical leach is up for debate.
Using a water bottle for the first time would release the highest amount of chemicals, says Guron. “The concentration of those additives would decrease over time as the chemicals get washed away or ingested.” The exception is acetaldehyde, which seeps out in greater quantities as the bottle degrades, according to some research.
Chemicals can also seep out of scratched or rough plastic, notes the National Poison Control Center. And the longer your bottle has been around, the more dinged up it will be.
Guron says creating space between the particles of plastic — such as through a scratch or stretching if the bottle freezes and expands — makes it easier for additives to escape.
Even a little damage increases the chance that microplastics will enter the water, says Jabraan Pasha, MD, 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.”
What’s more, research suggests that weathering from UV light speeds up chemical release.
Since heating a disposable bottle speeds up the oxidation reaction that breaks down the plastic over time, you might notice the funny taste of acetaldehyde when a bottle has been left in a hot car for a day, Guron says.
Guron adds that warmer temperatures may also cause more antimony trioxide and BPA to leach from the surface since the solubility of a solid slightly increases with temperature.
So don’t wash it in the dishwasher or with hot water before refilling. Research on PET drinking bottles found that temperatures of 95 degrees Fahrenheit and above increase the release of BPA, while temperatures of 77 degrees and below didn’t cause a detectable release of BPA.
The bottom line: Reusing your bottle increases the likelihood it will be exposed to damage, light, and heat — and as a result, chemical leach.
It’s Not Ideal for the Environment
Reusing a water bottle might feel like an environmentally friendly alternative to using a new disposable container every time you’re thirsty. But given the potential harmful effects of plastic water bottles, it may be best for your health and the environment to skip single-use plastic altogether.
Here’s how plastic water bottles affect the environment from the get-go: Producing the plastic requires fossil fuels and emits greenhouse gases, both of which threaten the health of the environment, according to the NIH.
And after all that, only about 29 percent of PET and HDPE disposable bottles are recycled, according to the EPA. The rest go into landfills, amounting to 27 million tons of plastic in 2018, the most recent available data.
The environmental impact of plastic water bottles in landfills can be immense. According to research, some potential side effects of plastic water bottles in landfills — and as litter — include:
- Chemicals that can leach into the soil or groundwater
- Aging of plastic waste, as well as burning, can release toxic chemicals into the air
- Harm to ecosystems, for instance plastic in the ocean damaging marine environments and animals
Alternatives to Reusing Plastic Water Bottles
While you can reuse plastic water bottles safely for about 24 to 48 hours, here are some alternatives to try instead to minimize any negative effects on your health or the environment:
- Buy a reusable water bottle.
- Switch to drinking tap water.
- Purchase a water filter to further clean tap water 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’s 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.
The Takeaway
It’s probably not an issue to refill your bottle for a couple of days. “Any longer than that and a biofilm may form inside. That’s not a guarantee you’re going to get sick, but you start to increase the risk,” Tierno says.
Besides these health effects, reusing plastic water bottles can also create potentially unnecessary waste. Your best bet is to invest in a reusable bottle to sip safely and sustainably.
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