Nano- and Microplastics: Impact on Human Health
What we know and what we don’t know
Plastic is essential part of our life. Plastic is everywhere. Plastic provides us many great things, including a new level of hygiene. Plastic is overused. Plastic produces waste in amounts of millions of tons per year. Plastic environmental impact receives considerable attention by scientists, policy makers and public in general. However, many questions need to be answered to establish how dangerous for human and environment plastics really are.
Mainly, the term plastic is used to refer to various types of polymers — giant synthetic molecules comprised of long chains of shorter molecules (monomers). With no agreed upper size limit, microplastics are most often defined as small pieces of plastic particles less than 5 mm. They exist in different shapes and can be spheres, fragments, granules, pellets, flakes, beads, filaments, or fibers.
Microplastics occur in several forms: 1) primary microplastics, plastic particles specifically manufactured as original products in micro-sizes (microbeads, scrubbers, powders and pellets); 2) secondary microplastics originating from the fragmentation of parent materials such as discarded plastic items and synthetic textiles. They can be also result from environmental degradation of plastics through the action of sunlight, water, waves and living organisms.
In the past few years, scientists have started using the term nanoplastic for particles with the size between 1 and 100 nm. They can be produced by degradation of microplastics or might be released directly from domestic and industrial sources.
Beautiful untouched by tourists mountains, forests and lakes which is far from reality and reflects deep Planet’s breathing, hear…
“We appeared from plastic items under the light, waves, temperature and mechanic abrasion.”
“We are coming from synthetic clothes and reach the oceans through wastewater.”
“We are proud of our durability allowing us to persist in the environment for centuries.”
“We catch widespread attention.”
“We are easily ingested by marine life. We love to travel together.”
“We can be transported far away from our source, far away from urban streets and industrial workspaces, far away from civilization. You can find us among uninhabited islands, alpine lakes, snow mountains and arctic ice.”
“We come from industrial and agricultural waste, urban dust, tires, single-use plastics, fishing gear, paints, clothing and cosmetics.”
Each person released 610 g to soil and 15 g to freshwater of both macroplastics and microplastics in a single year.
Synthetic clothes is the main source of secondary microplastics in the world oceans.
Steeping one plastic tea bag in boiling water releases 14.7 billion micro- and nanoplastics into a single cup.
Up to 95% of river-borne plastic comes from just 10 rivers.
The main source of microplastics in the air is dust from vehicle tire wear.
The number of different marine species contaminated by microplastics is more than 690 (edible and non-edible).
Microplastics have already been found in beer, drinking water, honey, seafood, sugar and table salts.
Terrestrial plastic pollution may be four to 23 times greater than ocean pollution.
Recent reports suggest that micro- and nanoparticles of plastic can enter the human body by two main pathways: airborne through nasal passages into the lungs and ingestion through the mouth into the stomach therefore are entering the human body through the water, food, and air.
A person’s lungs could be exposed to 26–130 airborne microplastics per day.
Evidence suggests that human exposure to microplastics via seafood is plausible, however the contribution of microplastics from other food and beverage products is unknown.
Food can be contaminated by microplastics by direct exposure in the environment, during the processing and packaging phase or by trophic transfer of microplastics in the food web from prey to predators.
The food contamination by micro- and nanoplastic particles which are released spontaneously from the packaging material seems rather unlikely. Plastic food packaging could eventually break into plastic pieces and contaminate the food products if wrongly handled.
However, some plastic polymers used for food and beverages packaging degrade when they come into contact with acidic or alkaline foods, UV light, and heat. Therefore, chemical constituents, including residual monomers, additives and production aids might migrate from packaging into food product they come in contact with.
When considering the human health impacts of plastic, one must distinguish between the impacts of micro- and nanoplastic particles entering the human body and the impacts of the potentially toxic chemicals associated with plastic particles.
The potential mechanism of toxicity for synthetic particles is still not fully explained. These particles may accumulate in major organs for a long time as they are extremely durable in physiological fluids. Generally, the smaller the particle the further into the organism it can penetrate since they are able to pass through biological barriers, transport to deeper tissues and affect metabolism. Those effects are generally not due to the toxicity of the plastic per se, but rather a result of the physical features of the plastic particles and depend on they size, shape, charge and concentration.
Microplastics contain an average of 4–7% of chemicals and additives, including fillers, pigments, plasticizers, stabilizers, flame retardants and antimicrobial agents which are introduced during the manufacture process to achieve the desired performance and appearance criteria. Most of these additives are not bound to the polymer matrix, and due to their low molecular weight, they easily leach out of the polymer into the surrounding environment, including air, water, food, or body tissues.
Existing research shows that plastic additives such as phthalates, bisphenol A, some flame retardants and heavy metals are known endocrine disruptors, carcinogens and mutagens.
Therefore, hypothetically, microplastics entering the human body could lead to inflammation, genotoxicity, oxidative stress, apoptosis, necrosis, respiratory problems, cancer, etc.
At the current stage of research available data indicate that orally ingested and inhaled microplastic particles under the chosen experimental conditions do not pose major health risks to the consumer. However until we know more about the potential health effects, contamination of foods, water and air by micro- and nanoplastics remains worrying.
Challenges
1. To date, there is no standard methods and experimental designs for micro- and nanoplastic hazard testing, despite a rapidly rising number of reports on the effects observed under laboratory conditions. The heterogeneity of the applied analytical methods hampers to compare results and draw any scientific conclusions.
2. There is an urgent need to realize a comprehensive assessment of microplastic routes, including its distribution, transport, degradation and abundance in the various environments. Global research has focused predominantly on the movement of plastic and microplastics through marine ecosystems and food chains. However, microplastic pollution in air, soils, groundwater and inside land-based food chain remains poorly understood. It is clear that microplastics interact with every part of ecosystems and potentially could have long-term effects on food and climate security.
3. A typical food chain is composed of many different steps, each of them could potentially cause contamination by micro- and nanoplastics. It is difficult to estimate whether these particles were already in the food before processing or if their presence is the consequence of the processing step. The same question applies in the case of drinking water and beverages.
4. The absence of an international approved regulatory frameworks and global policy. Necessity to establish safe thresholds for human micro- and nanoplastic consumption considering nutritional habits and diet.
5. Much more research is required to establish the severity of the microplastic impact and to evaluate acute and long-term risks on human health. Necessity to conduct urgent studies to determine the fate and behavior of microplastics, their additives and chemicals in human organs.
6. The potential additives transfer from plastic to the land organisms and marine life demands urgent and sustained investigation. Ignoring the thousands of chemicals and their behaviour at every stage of the plastic lifecycle is dangerous.
7. New approaches to detect and quantify nanoplastics in the environment. Simple methods which is used for microplastics couldn’t be used for such small particles as nanoplastics. Today environmental exposure assessment for nanoplastics is largely speculative.
8. Actions should be undertaken at products design stage which could contribute to the reduction of micro- and nanoplastic release.
9. To fully assess the plastic impacts on environment and human health, one must consider each stage of plastic manufacturing process and lifecycle. To date, discussions are focused on the specific moments of plastic usage and disposal.
References
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