Microplastics in cosmetics

Microplastics is generally defined as a collective term for different solid plastics made of different materials, whose particle size is <5mm. The following definition applies to plastic particles of all types:

Macroplastics (particle size >25mm), mesoplastics (particle size 5-25mm), microplastics (particle size <5mm) and nanoplastics (particle size <100nm) (Herrera A et al. 2017)

Due to its poor biodegradability, microplastics is one of the biggest environmental problems of modern times. Microplastics from various sources, mostly via waste water, often reach our environment in an uncontrolled and non-biodegradable way. Part of the microplastics contained in wastewater is bound in sewage sludge (but only in industrialized countries) if the wastewater can be treated in a "biological treatment plant". In most sewage treatment plants (cf. the often completely unmanageable conditions in developing countries), however, the microparticles are not retained and end up in rivers (Peng G et al. 2017) and oceans. There they accumulate in sediment and become environmentally relevant. Plastic particles bind e.g. at their surface pollutants that are already present in water (e.g. dioxin, DDT or other pesticides from industry and agriculture).

Up to now, the age-dependent degradation of macroplastics to micro- or nanoplastics (<1001nm) due to environmental influences has been little studied. These degraded microplastic particles of different size and origin do not only pollute seawater or freshwater but also the air we breathe due to their ability to float (Alimi O et al. 2017). Thus, another (so far hardly considered) environmental hazard becomes relevant for humans and animals.

Finally, microplastics accumulate in the food chain. Microplastics or nanoplastics can be detected in even the smallest zooplankton, in seafood such as mussels or shrimps (in molluscs, plastic materials made of polyethylene, polyethylene terephthalate = PET and nylon were detectable - Naji A et al. 2017) and upstream in the food chain in edible fish such as tuna, cod or mackerel. These products in turn enter the human food chain.

Macro-, meta- and microplasma lead to impairment of food intake and digestion of birds and fish. Especially non-digestible macroplasty leads to an accumulation in the gastrointestinal tract of birds and fish, to a constant feeling of satiety. This impairs growth, mobility and reproductive capacity.

Disturbances of the immune system in fish can be detected by microplasty (Espinosa C et al. 2017). Microplasty can have neurotoxic effects by inhibiting acetylcholinesterase (AChE), increasing lipid oxidation (LPO) in the brain and muscles. Furthermore, the particles are able to change the activities of the enzymes lactate dehydrogenase (LDH) and isocitrate dehydrogenase (IDH) (Barboza LGA et al. 2017).

Micro-, meta- and nanoplastics in cosmetics:

Micro (nano-)plastic is used in cosmetics or detergents (washing and cleaning agents) as an abrasive (e.g. in peeling agents and peeling shower gels) and in nanoparticle size as an opacifier in cosmetics. Face peelings, for example, can consist of up to 10% polyethylene particles. However, the environmental impact of peeling products is rather low in comparison to other sources, and the cosmetics industry has called for a voluntary recommendation to avoid the use of microplastics as abrasives in cosmetic products, which has successfully reduced the use of microplastics as abrasives in products such as peelings and toothpaste.

Liquid, gel and wax-like plastics in cosmetics

Little is known about the effects of liquid, gel and wax-like plastics such as Nylon-12, Acrylates Copolymer or Acrylates Crosspolymer. For the vast majority of these synthetic polymers (and their numerous blends) there is very little knowledge about their environmental impact.

The following synthetic materials are used in cosmetics:

• Polyethylene: supports the cleaning of skin or teeth or improves the shine. Depending on the particle size, polyethylene has an abrasive effect and forms a continuous film on skin, hair or nails when applied. (film forming), increase or decrease the viscosity of cosmetics.
• Polypropylene: Viscosity regulator (increases or decreases the viscosity of a cosmetic product).
• Polyethylene terephthalate: film former (forms a coherent film on skin, hair or nails when applied).
• Nylon-12: decreases the bulk density and/or transparency and light transmission of cosmetics, increases or decreases viscosity.
• Nylon-6: reduces the bulk density of cosmetic products, increases or reduces viscosity.
• Acrylate copolymer: acts as an antistatic agent (reduces static electricity by neutralizing the electrical charge on the surface), binding agent (provides binding in cosmetic products) and film former (forms a coherent film on skin, hair or nails when applied).
• Acrylates/C10-30 alkyl acrylates crosspolymer: acts as an emulsion former (aids emulsion formation and improves emulsion resistance and durability), film former (forms a continuous film on skin, hair or nails upon application) and as a viscosity regulator (increases or decreases the viscosity of a cosmetic).
• Polymethyl methacrylate: acts as a film former (forms a continuous film on skin, hair or nails when applied).
• Polyquaternium: acts as a film former (forms a coherent film on skin, hair or nails when applied), antistatic (reduces static electricity by neutralizing the electrical charge on the surface).

They are marketed under the following names: Acrylate Copolymer (AC), Acrylate Crosspolymer (ACS), Dimethiconol, Methicone, Polyamide (PA, Nylon), Polyacrylate (PA), Polymethyl methacrylate (PMMA), Polyquaternium (PQ), Polyethylene (PE), polyethylene glycol (PEG), polyethylene terephthalate (PET), polypropylene (PP), polypropylene glycol (PPG), polystyrene (PS), polyurethane (PUR), siloxanes, silsesquioxanes.

1. Alimi O et al (2017) Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport. Environ Sci Technol PubMed PMID: 29265806.
2. Barboza LGA et al (2017) Microplastics cause neurotoxicity, oxidative damage and energy-related c hanges and interact with the bioaccumulation of mercury in the European seabass, Dibecentrarchus labrax (Linnaeus, 1758). Aquat Toxicol 195:49-57.
3. Espinosa C et al (2017) In vitro effects of virgin microplastics on fish head-kidney leucocyte activities. Environ Pollut. 235:30-38.
4. Herrera A et al (2017) Microplastic and tar pollution on three Canary Islands beaches: An annual study. Mar Pollut Bull PubMed PMID: 29106939.
5. Lo HKA et al (2017) Negative effects of microplastic exposure on growth and development of Crepidula onyx. Environ Pollut 233:588-595.
6. Naji A et al (2017) Microplastics contamination in molluscs from the northern part of the Persian Gulf. Environ Pollut235:113-120.
7. Peng G et al (2017) Microplastics in freshwater river sediments in Shanghai, China: A case study of risk assessment in mega-cities. EnvironPollut234:448-456.