Plastic water bottles are popular for their convenience, and their use keeps rising worldwide. But there are also potential harms from plastic.

When you drink out of plastic water bottles, you may ingest microplastics and nanoplastics. Research has linked these tiny plastic particles to many chronic health conditions. Water bottles and other plastic containers may also leach harmful chemicals, such as bisphenol-A (BPA).

It's important to know the facts about microplastics, nanoplastics, and chemicals leaching into water. Read on for tips for water bottle safety.

What Are Microplastics and Nanoplastics?

Microplastics and nanoplastics are tiny fragments of plastic.

Microplastics range from 1 nanometer to 5 millimeters in size. Nanoplastics are even smaller — under 1 nanometer — and occur when microplastics break down.

There are two types of microplastics:

  • Primary — Microplastics and nanoplastics that manufacturers intentionally add to a product, such as microbeads and nanobeads in personal care products.
  • Secondary — Microplastics and nanoplastics that form as plastic degrades over time or when exposed to the environment.

You can likely find microplastics and nanoplastics everywhere in the environment — groundwater, soil, even the air. An estimated 2.7 million tons of microplastics seeped into the environment in 2020, according to the United Nations Environment Programme (UNEP). That total could double by 2040, the UNEP says.

What's the Danger of Microplastics and Nanoplastics in Bottled Water?

The breakdown of plastic bottles can lead to nanoplastics and microplastics in water. Experts are still studying the health risks of nanoplastics and microplastics. But studies have linked them to chronic health problems.

A 2024 study in Proceedings of the National Academy of Sciences reported an average of 240,000 tiny plastic particles per liter of bottled water. Nanoplastics made up 90% of the total.

Opening and closing the cap and squeezing a bottle can release microplastics and nanoplastics into water, according to a 2025 Journal of Hazardous Materials review. Sunlight and heat can cause shedding, too.

The 2025 review also reported that bottled water drinkers ingest up to 90,000 more micro- and nanoplastics each year than tap water drinkers.

What are the health risks of drinking from plastic bottles?

Your body can absorb microplastics and nanoplastics, depending on their size. They can enter your bloodstream and reach major organs.

Nanoplastics are especially worrisome because they're small enough to reach any organ. They can even cross the blood-brain and placental barriers. Nanoplastics and smaller microplastics may disrupt normal cellular processes and cause cell damage.

Chemicals used in plastic manufacturing are also a health concern.

Although research is still ongoing, scientists have linked microplastic and nanoplastic exposure with health conditions like:

  • Cancer (gastrointestinal and lung).
  • Cardiovascular disease.
  • Chronic obstructive pulmonary disease (COPD).
  • Diabetes.
  • High blood pressure.
  • Infertility.
  • Inflammatory bowel disease (IBD).
  • Kidney stones.
  • Metabolic dysfunction-associated steatotic liver disease (MASLD).
  • Neurological and cognitive effects.
  • Obesity.
  • Stroke.

Because nanoplastics can cross the placental barrier, researchers are also looking into their effect on fetal development.

BPA and Chemical Leaching in Bottled Water

Another concern for bottled water drinkers is chemicals leaching from the bottle into the water. Chemicals help make plastic more durable, flexible, or heat-resistant. But they may also pose a risk to your health if they leach into food or drink.

As for contact with bottled water, commonly talked about chemicals include:

  • Bisphenols, especially bisphenol-A (BPA).
  • Per-and polyfluoroalkyl substances (PFAS).
  • Phthalates.

These chemicals are endocrine disruptors, meaning they can affect your body's hormones. This may cause issues with metabolism, fertility, and other functions.

Researchers are still studying the effects of these and other chemicals on human health. But potential health issues associated with BPA, PFAs, and phthalates include:

  • Cardiovascular disease.
  • Certain cancers.
  • Early menopause.
  • Fertility problems.
  • High blood pressure.
  • High cholesterol.
  • Obesity.
  • Premature births.
  • Type 2 diabetes.
  • Uterine fibroids.

Children may be at greater risk of some of these effects because they're still developing.

It's also important to note that other chemicals beyond BPA, PFAS, and phthalates may occur in plastic water bottles.

How do plastic bottles release chemicals?

Exposure to sunlight or heat and reusing single-use bottles can raise the risk of BPA, phthalates, and other chemicals leaching into drinking water.

How can I choose a BPA-free water bottle?

You can often tell the type of plastic used in a water bottle by looking at the recycling code on the bottle.

Containers marked with recycling code 7 (other) are the most likely to include BPA. But not all bottles with that code have BPA.

Some products marketed as "BPA-free" may include other potentially harmful bisphenols. You should also avoid containers marked with:

  • Recycling code 3 — Can leach phthalates.
  • Recycling code 6 — Can leach the carcinogen styrene.

Generally, single-use water bottles made with the plastic polyethylene terephthalate (PET) and marked with the recycling code 1 are safe for single use. But you shouldn't reuse them.

Tips for Water Bottle Safety

Even if you like the convenience of plastic water bottles, you can still reduce your risk from chemicals, microplastics, and nanoplastics.

Choose safer water bottles

Stainless steel and glass bottles are eco-friendly alternatives to plastic bottles and the best water bottles to avoid microplastics. They're also less likely to leach chemicals. Plus, stainless steel bottles are often insulated, keeping drinks hot or cold for longer periods.

When choosing reusable plastic bottles, the safest options are generally:

  • High-density polyethylene (HDPE) — Marked with recycling code 2.
  • Polypropylene (PP) — Marked with recycling code 5.

With any reusable water bottle, you should make sure to:

Do not reuse single-use bottles

Most single-use plastic bottles made with PET, which is BPA-free, are generally safe for one use. But repeated use of single-use plastic raises the risk of microplastic and nanoplastic shedding.

Avoid exposing water bottles to heat or sunlight

Environmental effects like ultraviolet light or heat can raise the risk of micro- and nanoplastics shedding into water or chemicals leaching. You should avoid:

  • Leaving plastic water bottles in a hot car or in direct sunlight.
  • Microwaving anything in a plastic container.
  • Putting hot liquids in a plastic container.