The Truth About the Plastic Bags Given out in Changing Rooms

It’s standard in so many gyms, after finishing a workout or class you grab a plastic bag labelled ‘biodegradable’ and stuff your sweaty kit into it.

In fact, those bags which are presented as a greener alternative are still releasing microplastics into the environment. Sometimes they release more than regular plastic bags, and there's a growing base of evidence to show that microplastics are harmful, not just to the environment, but also to your health.

Microplastics: No Longer Just an Ocean Problem

Microplastics are everywhere, including inside us.

Recent research has detected microscopic plastic particles in blood, lung tissue, breast milk and even in placentas. While long term implications are still being studied, early findings have raised questions around the effects of cumulative exposure.

A study published in The New England Journal of Medicine looked at people having surgery to clear blocked arteries. The patients who had microplastics in their arterial plaque had significantly higher risk of heart attack, stroke and death compared to those who didn't.

With research until this point focusing more on environmental impact and marine life, it’s hard to know the extent of the problem but the list of potential health effects is growing, with links to inflammation, hormone disruption, cardiovascular problems and potentially greater chronic inflammation linked to cancer.

Degradable, Biodegradable, Recyclable – What Does It All Actually Mean?

There is no denying that plastic is a fantastically useful material but it’s not the best choice for products which are used only once. As consumers, we are presented with alternatives to single use plastic but the labelling can be confusing.

Degradable

This simply means a material will break down into smaller pieces over time. That process can result in fragmentation into microplastics.

Biodegradable

This suggests that microorganisms can break the material down into water, carbon dioxide and methane. However, this usually requires specific industrial composting conditions involving controlled heat, moisture and microbial activity. In a gym bin, hotel changing room or general landfill, those conditions rarely exist. As a result, ‘biodegradable’ bags may still fragment or persist far longer than consumers expect.

A 2021 study compared biodegradable PBAT plastic with regular plastic in water. The biodegradable version generated more microplastic fragments, especially when sunlight was recreated. A 2024 reviewconcluded that degradation rates often fall below 50-60%, leading to the formation of micro-biodegradable plastics that spread into soil and water.

Collaborative research between UC San Diego and a company called Algenesis Materialshave created an algae based material that had actually biodegraded 97% within 200 days in soil or compost, recreating conditions you’d have at home. These are exciting developments but bags made from this material are not being handed out at your gym just yet.

Recyclable

Many plastic bags are technically recyclable, but only if they are clean and dry. A wet swimsuit or sweaty kit contaminates the bag, meaning it may not be accepted in standard recycling streams and many of these bags still end up in general waste.

So while degradable, biodegradable and recyclable labels create a reassuring impression, they do not necessarily prevent plastic from entering the environment or breaking down into smaller particles. The solution is not swapping one plastic bag for another with a greener sounding label.

What are the alternatives?

Waxed Cotton Bags

Some luxury hotels have switched to waxed cotton bags as a natural alternative to plastic but the issue, without delving into the sustainability of cotton production, is that these are not able to be machine washed. The wax coating is stripped off, leaving you with a regular cotton bag. For a bag used for holding sweaty gym kit, spot cleaning is just not a practical solution.

Reusable Bags, an imperfect answer

Any gym bag made from synthetic materials, including La Pochette’s bags, will release microplastics when you wash them. Studies show that recycled polyester (which is what we use) actually releases slightly more microplastic fibres per wash than virgin polyester.

So why choose a reusable bag at all? Because we think longer term.

If you're going to the gym three times a week and using a single use bag each time, that's 156 bags a year going in the bin, each one eventually breaking down into microplastics in landfill.

A reusable bag that you wash every couple of weeks? 26 washes a year, releasing a small amount of microplastic fibres each time.

We estimate that a reusable bag, washed every couple of weeks releases roughly 16.2mg of microplastic fibres per wash, or 421mg per year. If you look at this versus 156 single use bags, which breaking down completely would generate about 1.56kg.

That's over 2.5 thousand times less microplastic pollution from a reusable bag.

How you wash matters in reducing microplastic fibres. Wash at a cooler temperature, skip the pre-wash, wash full loads and use shorter cycles. A well made bag with tighter weave will also shed fewer fibres than a cheaply produced one. Our bags also have antimicrobial properties, which means they genuinely don't need washing as often as regular bags. It’s why we’ve estimated going a fortnight between washes rather than after every use.

Taking It One Step Further

Because we're honest about microplastics, including the fact that our bags do release some fibres when washed, we also want to help you reduce what does get released.

That's why we now sell Guppyfriend washing bags. Pop your La Pochette bag (or any synthetic clothing) inside before washing and the bag catches the microplastic fibres that shed during the cycle, stopping them from entering the water system. You can then dispose of the collected fibres in your general waste.

It's particularly useful for your gym kit, which is usually made from polyester, nylon or elastane, all of which shed microplastics with every wash. One Guppyfriend bag protects all your synthetic activewear, swimwear and gym essentials, cutting the microplastics entering our waterways by up to 86%.

It's not a perfect solution, everything has an environmental footprint, but we’re looking at how lightly we are able to tread.

Why it makes sense

La Pochette’s solutions are an alternative to single use plastic bags but they’re so much more than that, they are bags which have been designed to actually work for gym life. The Sweat Bag, for example, is lightweight and has antimicrobial properties so washing every fortnight is realistic and the separate front pocket holds your toiletries or grip socks, so your sweaty kit stays separate from everything else.

Our Wet Bag is made from the same signature fabric, but the lining is completely waterproof. So the rest of your stuff, whether in a tote, beach bag, backpack or suitcase, remains dry.

When the solution to a problem isn’t clear cut it can be tempting to wonder why to even bother but we think the choice isn't between perfection and pollution. It's between systemic single use waste that fragments into microplastics every time and a dramatically reduced impact through products that are built to last.

It's not perfect but it's a lot better than the alternative.