Micro- and nanoplastics are being spoken about more and more in the media, by policymakers, and by consumers. But what are they? Is there a reason for concern? And what does AURORA’s research hope to achieve?
Take a look at some of the most frequently asked questions (and our answers) in the sections below grouped by theme.
Micro- and nanoplastics (MNP)
Micro- and nanoplastics (MNPs) are plastic (i.e., solid-polymer–containing) particles below 1 mm and 1 µm in diameter, respectively. They can have different shapes (e.g., fragments, fibers) and surface morphologies, be made of different polymers (e.g., polyethylene, polystyrene), and can contain different types and quantities of additives (e.g., plasticizer, UV stabilizer) and other chemicals (e.g., impurities, reaction-by-products).
According to ISO/TR21960:20201, microplastics are plastic particles of any shape with a size between 1 μm and <1000 μm, while nanoplastics have a size of <1 µm.
Biological, chemical, and physical conditions and processes, such as UV light, oxygen, temperature, and mechanical abrasion cause continuous degradation and fragmentation of plastic products. Upon reaching certain size limits, the particles are commonly referred to as microplastics or as nanoplastics. Apart from aging mechanisms in the environment, MNPs can also be generated from abrasion during use, as is the case for motor vehicle tire wear or MNPs generated by friction from opening plastic bottle screw caps. In contrast to these secondary microplastics that originate by abrasion from larger plastics, primary microplastics are intentionally produced in small sizes and added to products for a purpose, as is the case for microbeads in facial cleansers and many other types of products.
Not necessarily. Plastics degrade over time into smaller and smaller particles. When reaching sizes in the lower micrometer range, the small particles are not visible anymore to the naked eye but are still not completely mineralized.
Yes, you do. The majority of food packaging is made of plastics or includes components made of plastics (e.g., bottle lid, gasket, lining) and normal use of food packaging (e.g., bottle opening) can lead to the abrasion of small plastic particles and their transfer into food or beverages. Plastic food processing equipment that contacts foods during manufacturing steps can also be a source. Microplastics have been detected in several types of food, including table salts, honey, fruits and vegetables, and seafood, as well as beverages, including mineral water and milk. Humans ingest these plastic particles together with their foods and drinks. Given the variety of foods humans consume, the variety of ways they are processed and packaged, as well as the different dietary and behavioral habits, it is very difficult to estimate how many plastic particles an individual ingests over a lifetime. What makes it even more difficult is that there are still large knowledge gaps: Only a few plastic packaging types have been studied for their release of MNPs into foodstuff, and technical limitations restrict the assessment of all types of foods and plastic particles of a very small size.
The experimental evidence to date indicates that MNPs below 10 µm in diameter can cross various cell membranes in the human body. They might translocate from the gut cavity to the circulatory system and possibly accumulate in different organs and tissues. This has been shown in human cells in culture and experimental studies with rodents, however only for spheric polystyrene (PS) particles. But, MNPs come in various chemical compositions, shapes, sizes, and with different surface morphologies. The possible cellular uptake of other MNPs, with diverse shapes and sizes derived from other commonly used plastics such as polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET), is currently under investigation.
Exposure to MNPs through ingestion or inhalation is recognized as a potential human health hazard, but much uncertainty still exists in the current human health risk assessment. In a laboratory setting using cellular and animal models, MNPs at high exposure concentrations have been shown to trigger oxidative stress, inflammation, and cellular damage among others, but whether they pose a substantial risk to human health under environmentally relevant exposure scenarios is still not well understood. So far, the data on both health hazards and the extent of human exposure is too limited to provide a definite answer. Only very few epidemiological studies have looked at MNP effects and have focused on workers in the plastics and textiles industries (occupational exposure). One of the first diseases reported concerning the inhalation of synthetic fibers was in 1975 in which workers in the textile (nylon, polyester, polyolefin, acrylic) industry showed symptoms of allergic alveolitis. While it has been stated that MNPs are cleared from the lung over time, sometimes the condition evolved into fibrosis and respiratory failure. As another example, the inhalation of airborne polyvinyl chloride (PVC) dust has been associated with interstitial lung disease.
In general, pregnant women and their fetuses are more vulnerable to exposure to environmental contaminants than the general population. In the case of MNPs, developmental toxicity could arise from particles in maternal blood that cross the placental barrier and damage fetal tissues, or, from the damage to the placenta itself which may affect both fetal and maternal health during pregnancy. MNPs have recently been found in the human placenta from full-term deliveries, and experimental data suggest that they can be transported through the placenta and possibly reach the developing fetus. However, the extent to which the placenta and the fetus in the womb are exposed to MNPs, and the health consequences of such exposure, are still largely unknown.
There are many complementary ways to assess the human health impacts of MNPs. State-of-the-art analytical tools can be used to sample, isolate, detect, quantify, and characterize MNPs in environmental and human samples. Diverse in vitro (cellular) and in vivo (animal) experimental models can be used to look at the potential toxicity/hazards of MNPs at the cellular, organ, or individual level under laboratory conditions. Moreover, on a population level, epidemiological approaches can be used to determine different health outcomes associated with MNPs under real-life exposure scenarios.
MNPs are contained in indoor air and dust (e.g., textile fibers) and outdoor air (e.g., tire wear), in drinking water, food, and beverages. This means they are in the air we breathe and the foodstuff we consume. Studies have shown that human exposure occurs via both inhalation and ingestion. Exposure can be reduced, for instance by reducing plastic use in daily life (e.g., plastic packaging, synthetic textiles) but not avoided (e.g., plastic particles in the outdoor air).
The problem of MNPs in the environment cannot be solved by buying biodegradable plastics. First of all, biodegradable plastics are designed for microbial conversion into CO2, methane, biomass, and mineral salts. However, to what extent and how fast these materials are biodegraded depends on their composition as well as the environmental conditions, such as humidity, temperature, and the presence of certain microorganisms. The specific conditions necessary for full biodegradation are rarely provided, not even in industrial composting facilities. Thus, only for niche applications can the use of biodegradable plastics have advantages (e.g., tea bags) but are no solution to plastic litter. Instead, labeling a product as biodegradable can lead to consumer misunderstanding and even result in increased littering. Moreover, biodegradable products are made for single use and not for material circularity. Composting or environmental degradation are typical end-of-life options, leading to the loss of resources and the generation of CO2.
chemicals in plastics
There is no obligation for manufacturers to indicate the ingredients of a plastic product. Consequently, the consumer cannot find out the exact composition of a plastic product from its label. The polymer type (e.g., polyethylene, PE), which is often indicated, does not provide any conclusion on its chemical composition since the chemical composition of each product can be different. Therefore, to find out the number, types, and quantities of chemicals contained in a specific plastic product requires experimentally analyzing it. For downstream users such as the retailer or consumer, assessing each product is time–consuming, costly, and, therefore, just not feasible. Governments are now discussing how to increase the transparency of chemicals contained within plastic products.
The chemicals contained in plastics can transfer (i.e., migrate) from the plastic e.g., into food in the case of food packaging or processing equipment. In this way, humans take them up together with the foods and drinks they consume packaged in plastics. Chemicals present in MNPs in the environment can also migrate into the surroundings and expose wildlife.
Factors that determine the extent of chemical migration into foodstuffs include:
- Temperature: migration occurs faster and at higher levels when temperatures increase
- Storage time: longer storage times imply higher migration
- Packaging size: migration in smaller packaged portion sizes is proportionally higher than in larger portion sizes
- Food chemistry: migration of fat-soluble, lipophilic chemicals is faster into fatty foods, while migration of water-soluble, polar/hydrophilic chemicals occurs faster into aqueous foodstuffs
Some of the chemicals contained in plastics used to package goods are known to be harmful to human health. For instance, they have been found to interfere with the normal functioning of the hormone system (i.e., are endocrine disruptors), or are carcinogenic, mutagenic, or toxic to reproduction. Harmful chemicals only present a risk if humans are exposed to them at concentrations that have negative effects. The concentration that results in negative effects varies with the chemical and can in some cases be very low (e.g., for endocrine disruptors).
It is difficult to predict how much potentially harmful chemicals each individual takes up. However, several chemicals used in plastics have been detected in humans (e.g., metabolites of bisphenol A (BPA) and phthalate ester plasticizers).
What further complicates the risk assessment of chemicals in plastics is that a lot of them have not yet been analyzed for potential health implications whereas others are completely unknown. Moreover, humans are almost always exposed to mixtures of chemicals, and in combination chemicals may have a different (including stronger) effects than when exposed to a single chemical alone.
No. Just like conventional plastics, bio-based and biodegradable alternatives (i.e., bioplastics) are chemically complex materials. To offset limitations inherent to bioplastic materials, such as brittleness and low gas barrier properties, bioplastics often contain a large variety and quantity of synthetic, man-made polymers, fillers, and additives.
Also, from a toxicological perspective, bio-based/biodegradable materials are not better than conventional plastics. For instance, a direct comparison of their in vitro toxicity showed that the same percentage of tested products made of bioplastics and conventional plastics induced toxicity and to the same extent.
Yes. MNPs are just small versions of larger plastics. What is more is that they have a larger surface-to-volume ratio than larger (macro) plastics, which leads to a faster release (i.e., migration) of the chemicals contained in the material. This means the chemical composition, also depends on the time when a macro- or microplastic is analyzed. Furthermore, MNPs in the environment may absorb contaminants already present in the environment leading again to different chemical compositions.
The aurora project
It is the abbreviation for Actionable eUropean ROadmap for early-life health Risk Assessment of micro- and nanoplastics (AURORA). This name summarizes the key aim of the project: to create this roadmap.
It started in April 2021 and will run until March 2026, this means for 5 years in total.
AURORA is a consortium of researchers from 11 institutes across 9 countries. The project is funded by the European Commission and is coordinated by UMC Utrecht in the Netherlands.
AURORA is needed because we know little about how MNPs impact pregnancy and development in early life – vulnerable periods that are also critical for health later in life. It has been shown that MNPs are likely to cross the placental barrier in vitro and in vivo, underlying the urgent need for additional research to understand the impact of MNPs on reproductive and early-life health.
AURORA takes a unique approach by using in-depth characterization together with scalable technologies to advance methods for both detailed and large-scale toxicological, exposure assessment, and epidemiological studies. This will be combined with a novel tiered-testing approach and epidemiological investigations to provide the first extensive evaluation of maternal and fetal MNP exposures and health perturbations, including placental function, immune-inflammatory responses, oxidative stress, endocrine disruption, and child development.
AURORA will help to better understand MNP impacts on early life health. To this aim, the project will significantly enhance exposure assessment capabilities for measuring MNPs and MNP–associated chemicals (e.g. additives) in tissues relevant for biomonitoring and for assessing health effects in early life (e.g. placenta, blood). The developed techniques can then also be applied in other experimental studies.
AURORA is a member of CUSP – the European research cluster to understand the health impacts of MNPs. CUSP is a consortium of five research initiatives bringing together 75 organizations from 21 countries and comprising an interdisciplinary team of scientists, policymakers, and civil society. Funded by the European Union, the projects are working to understand MNPs in our environment and their exposures and impacts on health. The research aims to elucidate the complex relationship between MNPs and human health, from early life to adulthood, as well as to provide new evidence for better preventive policies. In this way, CUSP contributes to the health-relevant aims of the European Strategy for Plastics in a Circular Economy and the Bioeconomy Strategy, as well as the REACH restrictions on intentionally added MNPs.
Within CUSP, the role of the AURORA project is to assess human health impacts on the developing fetus that are linked to MNP exposures. Therefore, AURORA develops novel tools for measuring MNPs in human tissues and scales them up to allow for the detection of plastic particles in placentas and blood.