Microplastics are variously shaped plastic particles with a size of 0.1-5,000 µm (0.1 µm - 5 mm). 100 µm, i.e. 1000 times 0.1 µm, roughly corresponds to the thickness of a sheet of paper, while 5 mm corresponds to the average length of a red ant.

A basic distinction is made between primary and secondary plastic microparticles. Primary microparticles are produced specifically in the size intended for use, such as for shower gels, hand-washing soaps and toothpaste. They are used here for mechanical cleaning of the skin or teeth. Secondary microparticles are formed unintentionally from ordinary articles made of plastic as a result of aging and decomposition processes, such as abrasion from production equipment or environmental pollution. They occur much more frequently than primary plastic microparticles and are a problem in the oceans in particular. Microplastics can enter the food chain via fish and seafood.

Microplastics are found in soils, sediments, plants, animals, in the air and in the sea and can consequently enter the food chain. It is unintentionally introduced into the environment by humans, for example via textiles, tire wear, products such as cosmetics and detergents containing microplastics, waste, fisheries, agriculture and industry. For example, microplastics enter the sewage system via rinse water from the use of cosmetics, textile fibers from washing machine wastewater, or tire abrasion. Although wastewater treatment plants remove microplastics from wastewater, they enter the soil when sewage sludge is used as fertilizer.

According to the Austrian Federal Environment Agency, tire abrasion is the largest contributor to the release of microplastics into the environment, followed by waste disposal and textile washing.

In the course of some studies, it has already been proven that microplastics are mistaken for plankton by marine animals such as fish, mussels and shrimps, which are then ingested as food. In addition, it has already been shown that this microplastic can also be found in the gastrointestinal tracts of these animals. Nevertheless, an extremely low intake of microplastics from fish and seafood is to be expected here, since usually only gutted fish are consumed. In addition to the detection of microplastics in fish, there are also reports of the presence of microplastics in foods such as seafood, salt, sugar, honey, fruits, vegetables, rice, drinking water and beer.

Absorption of microplastics from cosmetics through healthy skin is not expected. Even through accidental swallowing of toothpaste, these particles can only be absorbed in extremely small quantities through the gastrointestinal tract due to their size, while the majority is excreted again through the stool.

The exact toxicological effects of microplastics on humans have not yet been comprehensively investigated. Both the BfR (German Federal Institute for Risk Assessment) and the EFSA (European Food Safety Authority) have already published recommendations to conduct further investigations with regard to microplastics. Due to the lack of relevant robust data, toxicological studies regarding the uptake and effect of microplastics in the human body as well as studies on the degradation of microplastics and the possible formation of nanoplastic particles in the human digestive tract, among others, are necessary for a better assessment of the health risk.

Since October 2023, so-called microbeads may no longer be contained in cosmetic products. Further bans on microplastics in cosmetics will follow across the EU in the coming years.

Since 2019, fertilisers may not contain more than 0.1 percent of plastics larger than 2 mm in dry matter. We focus on examining fermentation residues from biogas plants and compost-containing growing media (potting soils) as part of fertiliser monitoring. In the case of fermentation residues, limit values are occasionally exceeded.

Microplastics can be introduced via animal feed and thus also ingested by animals via packaging parts. Packaging and packaging parts of products from the agro-food industry are prohibited in animal feed (Annex III of Regulation (EC) 767/2009). Feed containing these substances is therefore not marketable. AGES checks this as part of the feed inspection.

With regard to secondary microplastics from environmental pollution, there are numerous projects and legislative initiatives within the EU that deal with marine pollution and aim to reduce it, which also reduces the formation of microplastics. Information on the EU Plastics Strategy or the Austrian Microplastics Action Plan can be found on the BMK Kunststoffe website (bmk.gv.at)

Investigation of microplastics in salt

As part of a focus campaign in 2021, we analysed twenty selected samples of salt for microplastics in cooperation with the Austrian Environment Agency. The aim was to obtain an overview of the composition and number of microplastic particles in table salt. Only one of the 20 samples was free of microplastics. Eight samples had a microplastic content of less than 500 particles per kg, seven samples had a microplastic content of between 500 and 5000 particles per kg and four samples had a content of over 5000 particles per kg. Ten different types of plastic were identified. The results showed that polypropylene(PP), polyethylene(PE) and polyethylene terephthalate(PET) were most frequently present in the ready-to-eat salt samples without a grinder. In samples from pre-filled salt mills, on the other hand, the plastic types polycarbonate(PC) and polystyrene(PS) were primarily identified, followed by polypropylene(PP). These originate predominantly from the abrasion of the grinders. The three salt samples from Austria showed little to no microplastics.

Avoiding the formation of further microplastics, for example by:

• Using reusable instead of disposable products (containers, bags, etc.), e.g. storage containers made of glass and cloth carrier bags made of natural fibers
• Correct disposal of plastic products that are no longer needed via recycling collection points or household waste
• Preference for textiles made of natural fibers
• Preference for cosmetics and detergents that do not contain microplastics

If microplastics are ingested orally, either by swallowing toothpaste or eating contaminated seafood, the actual uptake into the body's cells via the gastrointestinal tract is low. The particle size plays a major role here. According to the EFSA, only particles with a size of less than 150 µm can be absorbed, and of these only a maximum of 0.3 %. The toxicological relevance of such small quantities of microplastics being absorbed into the body's cells is still largely unclear.

Microplastics can also be a source of pollutants that are either added during plastic production (additives) and may contain plasticisers, for example, or that are adsorbed during the time they remain in the sea or in the environment. The organic and inorganic pollutants found in seawater that can adhere to microplastics and subsequently accumulate there include, in particular, compounds such as organic chlorine compounds (e.g. polychlorinated biphenyls (PCBs), pesticides) or polycyclic aromatic hydrocarbons (PAHs).

In a worst-case scenario calculation, the EFSA comes to the conclusion that around 7 µg of plastic would be ingested with 225 g of mussel meat (1 portion of mussels). This would correspond to less than 0.01% of the estimated daily intake of the pollutants PCBs and PHAs and less than 2% of the estimated daily intake of bisphenol A. Accordingly, the EFSA concludes that even excessive consumption of seafood does not have a significant impact on the intake of pollutants associated with plastics.

Cosmetics

In October 2023, an EU Commission regulation on the restriction of synthetic polymer microparticles came into force, which also affects cosmetic products. Restrictions on the use of microplastics apply to cosmetic products through the new entry no. 78 in Annex XVII of the REACH Regulation. These polymer particles ("microplastics") should gradually no longer be placed on the market. The broad definition of microplastics includes all synthetic polymer particles under 5 mm that are organic, insoluble and poorly degradable.

The first measures include a ban on loose glitter and abrasive synthetic polymer microparticles (so-called microbeads). These may no longer be placed on the market for use in cosmetic products and the corresponding cosmetic products from October 2023 (no transition period)

For other synthetic polymer microparticles used in cosmetics, different transition periods of between four and twelve years have been set in order to give the affected stakeholders time to develop and switch to alternatives:

• 4-year transition period (October 2027) applies to microplastics in rinse-off/rinse-off cosmetic products (excluding microbeads or microbeads).
• 6-year transition period (October 2029) applies to microplastics in products that remain on the skin/hair and for microplastics used to encapsulate fragrances (excluding microbeads or microbeads).
• 12-year transition period (October 2035) applies to microplastics in lip products, nail products and make-up products (excluding microbeads).

Microplastics and plastic residues in fertilisers

The European Fertiliser Regulation (EU) 2019/1009 will be amended by a delegated act in order to define new requirements for polymers with regard to biodegradability in EU fertiliser products. These degradation criteria relate in particular to polymers which, as coating substances, control the release of nutrients in fertilisers or increase the water retention capacity of the soil. In the soil, the polymer must achieve a degradation rate or mineralisation of at least 90% within 48 months plus the functional period stated on the label. The amendments to Regulation (EU) 2019/1009 will help to make the use of polymers in fertiliser products more environmentally friendly by imposing stricter biodegradability requirements and clear instructions for application and disposal. According to a current draft, these amendments are due to come into force in 2028.

Use of mulch films

Another delegated act, which is currently being prepared at European level, aims to include polymer mulch films as a permitted component in the EU Fertiliser Products Regulation.
The corresponding legal act amending EU Regulation 2019/1009 defines the relevant biodegradability criteria and test methods, which were determined with the support of an external study.
These films are intended to help improve or protect the physical or chemical properties, structure or biological activity of the soil. They retain water in the soil and increase the soil temperature, which promotes plant growth and makes the use of fertilisers more efficient.

The biodegradability criteria take into account both the function of the mulch films and the available test methods. Degradability in the soil should be guaranteed within 24 months. In addition, polymers in mulch films must pass a series of toxicity tests, including tests for acute toxicity to plants, earthworms and nitrification inhibition.
The amendments aim to make the use and disposal of mulch films environmentally friendly by ensuring that these films are biodegradable and have no long-term negative impact on the environment.

Soil Plastic App: Colorful Soil - How much plastic is hiding in our soils?

Minagris: Micro- and Nanoplastics in Agricultural Soils: Sources, Environmental Behavior, and Ecosystem Impacts.