Written by Rachel Gladstone

An estimated 583 billion single-use plastic bottles were produced globally in 2021.With every sip, gulp, and slurp from one of these disposable bottles, there is a handy little tool that tops off even the drippiest of drinks. Of course, we are talking about bottle caps. Although these tiny tops are extremely useful, they are very problematic for the environment.

Marine Debris Tracker listed bottle caps as its fifth most tracked item in 2021. In fact, bottle caps are among the top 10 items found during beach clean-ups around the world. 

So why are bottle caps littered so frequently, and how can we put a cap on this type of plastic pollution?

To answer this question, it's important to separate the cap from the bottle and explain why this distinction can lead to so much pollution. 

Single-use plastic bottles are typically made from a polymer called polyethylene terephthalate (PET). PET has one of the highest recycling rates of all types of plastic: 29.1% in 2018. However, bottle caps are not typically made of PET; instead, they are made of high density polyethylene (HDPE) or polypropylene (PP). The recycling processes of HDPE and PP are more complicated and therefore less profitable than PET, so not all recycling plants recycle these types of plastic. In countries like Bangladesh and India, which have robust informal recycling sectors, plastic bottles are more likely to be collected and recycled because PET is a more valuable polymer. 

In fact, in one study that used Marine Debris Tracker to characterize plastic litter along the Ganges River Basin, researchers found that bottle caps were more likely to be littered in comparison to their plastic bottle counterpart. 

It is theorized that the small size, low value, and therefore low recyclability of bottle caps make them more susceptible to improper disposal, leading bottle caps to be one of the most littered items around the world. 

We know it is happening, so what does that mean for our ocean’s health? 

Marine life can mistake brightly colored plastics like bottle caps for food. Caps can be ingested and pose a major choking and toxicity hazard to marine life. This problem is so severe that plastic bottle caps are classified among the top 5 most deadly marine debris items for sea life. 

Putting a cap on plastic bottle cap pollution: so, what can we do? 

To cut down on caps, consider reducing your waste by using alternative items to bottle caps such as reusable bottles or items without caps like metal cans. If you plan on recycling your caps, check with your local recycling center to see if they accept bottle caps and prefer them on or off the bottle. If your local recycling facility does not accept caps, you can dispose of bottle caps in an enclosed bag such as a trash bag to minimize improper disposal.