Cosmetic Pollutants & Environment: What Is Biodegradable?

Whatever you wash off in the shower, remove with your make-up or rinse out of your hair doesn't simply disappear. It flows down the drain, through the sewage treatment plant and finally into rivers, lakes and seas. Most ingredients are broken down along the way. But some are not: they stay in the water, settle in the sludge or accumulate in fish and mussels. Here you can read which substances in cosmetics pollute the environment, what “biodegradable” really means and how to recognise more environmentally friendly skincare. And why this goes together so well, especially for sensitive skin.

In short: what does biodegradable mean?
Biodegradable means that microorganisms break a substance down into water, carbon dioxide and mineral salts. A substance counts as readily biodegradable if it is largely broken down within 28 days in a standardised laboratory test (OECD 301). In cosmetics, the substances that are hard to break down are mainly certain silicones, synthetic polymers and musk fragrances.

The key points at a glance:

Rinse-off products such as shower gel and shampoo end up almost entirely in wastewater. This is where checking the ingredients pays off most.
Problematic for waterways are above all substances that are hard to break down: microplastics, liquid synthetic polymers, cyclic silicones, synthetic musk fragrances and some chemical UV filters.
The EU is tightening the rules: microplastics have been restricted step by step since October 2023, as have the silicones D4, D5 and D6.
“100 % biodegradable” is not a protected term. Always ask: for which ingredients and according to which test?
For sensitive skin: many substances that irritate also pollute wastewater. Using less, and less irritating, products helps both.

From the washbasin to the river: how cosmetics get into the environment

The journey is short: shower gel on the skin, rinse, drain, sewer, treatment plant, river. Whether an ingredient survives this journey or is broken down by microorganisms along the way depends on its chemical structure. That is exactly what the biodegradability of cosmetics is about.

Rinse-off and leave-on: what ends up in wastewater

Rinse-off means: product on, product off. Shampoo, shower gel, scrub, shaving foam. Practically the entire amount goes into the wastewater, and it does so immediately. With leave-on products it takes longer: cream and sunscreen first stay on the skin and then travel via towels, bed linen and clothing into the washing machine, or go straight into the water when you swim. Invisible, but not gone.

Rinse-off products are therefore the biggest lever. If you want to make your skincare more environmentally friendly, the best place to start is where the largest amount goes down the drain every day.

What treatment plants manage and what slips through

A sewage treatment plant is a biological system: microorganisms break down what they know. Heavily modified, synthetic molecules with no natural degradation pathway, on the other hand, often pass through the tanks largely unchanged. An additional, fourth treatment stage using ozone or activated carbon can help here, but it is far from standard everywhere.

Roughly speaking, there are three outcomes for an ingredient:

It is actually completely broken down.
It stays dissolved in the water and reaches rivers and lakes.
It binds to solids and settles in the sewage sludge, some of which is still spread on fields.

One example is volatile silicones: treatment plants do remove a good share of them from the water, but they collect in the sewage sludge instead of being broken down (Capela et al., 2017).

Clear forest stream with pebbles and ferns in the morning light

What “biodegradable” really means for cosmetics

Biodegradable sounds like “simply dissolves”. In fact, there is a measurement behind it: microorganisms break down a molecule, and in the end only carbon dioxide, water and mineral salts should remain. This is called mineralisation. If degradation stops halfway, intermediate products form, and these can be problematic in their own right. Biodegradability is therefore never a yes-or-no question, but a question of speed, completeness and conditions.

Readily vs. inherently biodegradable: the OECD 301 test in simple terms

OECD Test Guideline 301 is the classic. The substance is placed in water with microbes from sewage sludge, and then it is measured how much carbon dioxide is produced or how much organic carbon disappears. If a set proportion is broken down within 28 days (60 or 70 per cent, depending on the method), and quickly within a 10-day window, the substance counts as “readily biodegradable”.

There is also “inherently biodegradable”, tested according to OECD 302. In plain words: it works, but slowly and only if the conditions are right. In a cold river in February, they rarely are. And importantly: biodegradable does not automatically mean harmless. Whether a substance harms aquatic organisms (ecotoxicity) or accumulates in organisms (bioaccumulation) is assessed separately.

“100 % biodegradable”: what the claim refers to

The claim is not uniformly regulated. Ask yourself three things for every pack:

Does it apply to the whole formula or only to individual ingredients, such as the surfactants?
Which test is behind it: readily or inherently biodegradable?
Were preservatives, fragrances and film formers tested too, or left out?

Plant origin isn't a free pass either: if a natural substance is heavily modified chemically, it can turn into a molecule that is hard to break down. What matters is the structure, not the origin.

These pollutants in cosmetics harm the environment

Not every ingredient that sounds chemical is a problem. Everything is chemistry, even a plant oil. Conversely, some substances with harmless names stay in the water for a long time. What matters is how easily microorganisms can break a substance down and whether it accumulates in living organisms. This overview shows the most important groups of substances:

Substance group	Purpose in the product	Environmental problem	EU regulation
Solid microplastic particles	Exfoliation, glitter, filler	Remain as particles in water and soil	Banned step by step since 10/2023
Liquid synthetic polymers	Film formers, thickeners	Biodegradability often unclear	Not covered by the microplastics ban
Cyclic silicones (D4, D5, D6)	Silky skin feel, shine	Hard to break down, accumulate	Rinse-off limited since 2020, leave-on from 06/2027
Linear silicones (e.g. dimethicone)	Slip, conditioning film	Barely biodegradable, end up mainly in sewage sludge	Permitted
Parabens	Preservation	Readily biodegradable, but detectable in waterways everywhere due to constant input	Permitted, with maximum concentrations
Chemical UV filters (e.g. oxybenzone)	Sun protection	Damage corals in laboratory studies	Permitted, with maximum concentrations
Polycyclic musk fragrances	Scent, fixing fragrance	Not completely removed in treatment plants, detectable in seafood	Permitted
Artificial colourants	Appearance	Depends on the substance: some break down well, some barely	Positive list

Microplastics: solid particles and liquid polymers

Since 17 October 2023, EU Regulation 2023/2055 has restricted intentionally added microplastics, i.e. solid, insoluble plastic particles smaller than five millimetres. Microbeads for exfoliation were banned immediately. Transition periods apply to other products: until October 2027 for rinse-off cosmetics such as shampoo or shower gel, until October 2029 for leave-on products, and until October 2035 for make-up, lip and nail products (German Federal Environment Ministry).

The gap: liquid and dissolved synthetic polymers such as Acrylates Copolymer or Polyquaternium are not covered by the ban. Technically they are not microplastics, but their biodegradability is often unclear.

Silicones: why D4, D5 and D6 are a concern

With silicones, it pays to differentiate. The cyclic siloxanes D4 (Cyclotetrasiloxane), D5 (Cyclopentasiloxane) and D6 (Cyclohexasiloxane) are classed in the EU as very persistent and very bioaccumulative. In wash-off products, D4 and D5 have therefore been limited to below 0.1 per cent since 2020. Under Regulation (EU) 2024/1328, this limit will also apply to cosmetics that stay on the skin from 6 June 2027, and will include D6.

Linear silicones such as dimethicone are considered less problematic. However, they are also barely broken down in the treatment plant and end up mainly in the sewage sludge.

Parabens, UV filters, musk fragrances and colourants

Parabens are preservatives and can have a weak hormone-like effect. Treatment plants remove them relatively well, and they are biodegradable. But because new amounts arrive every day and in large quantities, they can be detected in low concentrations practically everywhere in surface waters and sediments (Haman et al., 2015).

Chemical UV filters such as oxybenzone (Benzophenone-3) damaged coral larvae in laboratory experiments, promoted coral bleaching and deformed the larvae (Downs et al., 2016). Hawaii has therefore banned sunscreen containing oxybenzone and octinoxate since 2021. How strong the effect is in the open sea is still being debated.

Polycyclic musk fragrances (for example galaxolide) are not completely removed in treatment plants and so reach waterways (Tumová et al., 2019). They have also been found in fish and seafood from European coastal regions (Cunha et al., 2015).

Artificial colourants cannot be assessed across the board: some break down well, others barely. In the EU, only colourants from a defined list may be used.

Via food chains, substances that are hard to break down can collect in ecosystems over the long term. That is exactly why the long-lived ones are the real problem, not necessarily the substances that sound the most toxic.

And what does this mean for your health?

Honest answer: the impact on the environment is much better documented than any direct harm to you. Under the Cosmetics Regulation (EC) No 1223/2009, cosmetics sold in the EU must undergo a safety assessment in advance, with maximum concentrations and bans for individual substances. Anyone searching for toxins in cosmetics and expecting a horror scenario will, in practice, find a strict set of rules instead. That doesn't mean every product suits your skin. It just means: the question of pollutants in cosmetics is a question of dose, approval and biodegradability, not of good versus evil.

There are still open questions, though. The EU's Scientific Committee on Consumer Safety (SCCS) regularly re-evaluates potentially hormone-active substances such as certain parabens or UV filters and lowers maximum concentrations when new data suggest it. And how substances that are hard to break down affect food chains in the long term is still being researched.

For you, this means: separate two questions. What irritates my skin? And what pollutes the wastewater? The answers often overlap, but they are not identical. Which ingredients can cause problems for your skin and how to find them on the packaging is explained in our guide How to recognise harmful ingredients in cosmetics.

Sensitive skin and the environment: where low-irritant and biodegradable go together

There is an overlap that hardly anyone talks about: some substances that irritate an impaired skin barrier are at the same time the ones that survive in wastewater for a long time. If you take a closer look at biodegradability, you will often filter out irritants along the way.

Fragrances and harsh surfactants: a double burden

Fragrances are among the most common triggers of contact allergies, and some of them, such as the synthetic musk compounds, are also hard to break down. It's a similar story with surfactants: harsh surfactants such as Sodium Lauryl Sulfate wash more fat out of the outer layer of the skin than already dry skin can cope with. Mild sugar-based surfactants such as Coco-Glucoside or Decyl Glucoside cleanse more gently and are considered readily biodegradable.

And then the honest part: mineral oil and petroleum jelly are not the problem for the skin. They form a protective film and slow down water loss, which is why they are found in many barrier creams. It's just that they are barely biodegradable. Plant oils and plant butters are readily biodegradable and provide valuable fatty acids. But plant substances can also cause allergies, essential oils in particular.

Why less is often more, including for atopic dermatitis and psoriasis

The shorter the ingredient list, the less there is to irritate and the less ends up in the wastewater. A short checklist for shopping:

fragrance-free rather than “delicately scented”, especially if your skin is prone to eczema
a few clearly named nourishing fats instead of ten secondary active ingredients
mild surfactants in everything you wash off

You can read more about what is true and what isn't when it comes to atopic dermatitis in Is atopic dermatitis contagious? 3 myths checked.

How to recognise more environmentally friendly cosmetics

The formula is printed on every pack, just in Latin, in small print and sorted by quantity. That works in your favour: whatever is listed first makes up the bulk. Ingredients below one per cent may appear at the end in any order.

Reading the INCI list: check these names and endings

You don't need to study chemistry. A few word components that keep cropping up are enough:

On the INCI list	What's behind it	Why check
-methicone, -siloxane	Silicones, e.g. Dimethicone, Cyclopentasiloxane	Hard to break down
Acrylates … Copolymer, Crosspolymer, Polyquaternium	Synthetic polymers	Biodegradability often unclear
Benzophenone-3, Ethylhexyl Methoxycinnamate	Chemical UV filters (oxybenzone, octinoxate)	Coral debate
Parfum, Fragrance	Fragrance blend	Common irritant, partly hard to break down
Paraffinum Liquidum, Petrolatum, Cera Microcristallina	Mineral oil components	Barely biodegradable

INCI apps scan the barcode and flag such names automatically. That's handy to get started, but the apps assess substances, not quantities. A silicone in last place weighs differently from one in third place.

Putting certification labels and advertising claims into perspective

Natural cosmetics labels such as NATRUE or COSMOS exclude silicones, mineral oil and synthetic polymers, among other things. That is a good direction. However, they don't guarantee that the whole formula is fully biodegradable, nor that it suits every skin. “Natural origin” figures according to ISO 16128 include water, so a high percentage says little. And “reef safe” or “reef-friendly”? Not legally defined, so mainly advertising language.

Packaging: glass, paper, recycled material and refills

Packaging counts too. Glass is heavy and costs energy in transport, but it is worthwhile if it is used for a long time or recycled. For single-use packaging, recycled plastic usually performs better than new plastic. Refill packs save material. The product that needs the least packaging is one without water, for example a bar of soap wrapped in paper.

Step by step: making your routine more environmentally friendly

Swap everything at once? No need. Whatever is already open in your bathroom gets used up, because throwing it away is the least ecological option of all. It makes more sense to go in order of impact:

Start with shower gel and shampoo. Rinse-off products go almost entirely into the wastewater. Check these for silicones and synthetic polymers first.
Use fewer products. Fewer layers means less potential for irritation for your skin and fewer residues in the wastewater. Two or three well-chosen products are often enough.
Choose fragrance-free if your skin is sensitive. Fragrances often irritate, and some are also hard to break down.
Try solid alternatives. Less water in the product means less packaging and less weight. But: classic soap is alkaline and doesn't suit every skin. Find out which is better for you in Bar soap or liquid soap?
Dose correctly. A hazelnut-sized amount instead of a handful. What you don't apply doesn't have to be broken down by a treatment plant.
Don't skimp on sun protection. Mineral filters are an option if you want to avoid chemical UV filters. More on this in the comparison of natural sun protection. But protecting your skin always comes first.

Small steps with a big impact

Environmentally friendly cosmetics are not a single advertising promise. They result from the ingredients, their biodegradability, the packaging and how much you use. You don't have to change everything at once: next time you shower, turn the bottle over, read the ingredients and look out for silicones, synthetic polymers and fragrances when you buy again. That's kinder to the water and often to your skin too.

Easier with ready-made skincare
If you don't want to check every INCI list yourself: natüür skincare contains no silicones, no mineral oil, no parabens, no acrylates and no polyquaternium. At its heart is NEEMAVERA®, an extract of neem leaves from our own plantation in Paraguay. All products are vegan and made in Germany. For sensitive skin, Cream, Cream forte and Skin Balm are fragrance-free. For the shower, there is the fragrance-free Solid Soap as a bar without a plastic bottle, or the skin-neutral pH Body Wash.

Frequently asked questions (FAQ)

What does biodegradability mean for cosmetics?

Microorganisms break a substance down into water, carbon dioxide and mineral salts. A substance counts as readily biodegradable if it is largely broken down within 28 days in a laboratory test according to OECD 301. But biodegradable doesn't automatically mean harmless: whether a substance harms aquatic organisms is tested separately.

Are silicones in cosmetics harmful to the environment?

The cyclic silicones D4, D5 and D6 are classed in the EU as very persistent and very bioaccumulative. In rinse-off products, D4 and D5 have been strictly limited since 2020; from June 2027 this will also apply to leave-on cosmetics and to D6. Linear silicones such as dimethicone are also barely broken down and end up mainly in sewage sludge. Their risk to waterways is considered lower.

Are microplastics in cosmetics banned?

Partly. Since 17 October 2023, the EU has restricted intentionally added microplastics. Microbeads in scrubs were banned immediately; transition periods apply to other products until 2027 (rinse-off), 2029 (leave-on) and 2035 (make-up). Liquid and dissolved synthetic polymers are not covered.

Which pollutants in cosmetics burden waterways the most?

Above all, the long-lived ones: synthetic polymers that are hard to break down, cyclic silicones, polycyclic musk fragrances and some chemical UV filters. They remain in water and sediment for a long time and can accumulate in living organisms.

Are natural cosmetics automatically biodegradable?

No. Certified natural cosmetics avoid many substances that are hard to break down, such as silicones or mineral oil, and are therefore a good direction. But this doesn't guarantee that the entire formula is fully biodegradable, and plant substances can irritate the skin too.

Is there environmentally friendly sun protection?

“Reef safe” is not a protected term. Mineral filters such as zinc oxide are considered an alternative to chemical UV filters such as oxybenzone, which damaged corals in laboratory studies. Important: adequate sun protection for your skin always comes first.

Cosmetics and the Environment: Which Pollutants Harm Waterways and What Is Biodegradable