Microplastics

- Dr Julia Jaeger-Eurofins Environment Testing AU/NZ

In recent years the topic of microplastics has gained increasing public awareness. Is it the next emerging contaminant of concern? Why is there so much uncertainty regarding the extend of the problem as well as the toxicology?

What are Microplastics?

Plastic is such a versatile material that we can no longer imagine daily life without it. It has been estimated that 9 billion metric tons of plastic have been produced since 1950, and that annual production increases exponentially. However, the disposal and recycling pathways have not been keeping up with the demand and therefore a great proportion of plastic waste accumulates in the environment. Due to its extreme durability, plastic exhibits environmental persistence. Due to weathering and degradation it breaks down over time into small particles, fragments, and fibers – what we know as microplastics.

Additionally, use of personal care products (facewash, toothpaste, etc.) and industry activity (plastic pellets) have resulted in some of the microplastics being released directly into the environment. Although plastics have been in use for over 70 years, the notion that microplastics could be an emerging contaminant is new. Only in 2020, the California State Water Board adopted a definition of 'microplastics in drinking water', which is the first global legally binding definition.

Where can Microplastics be found?

After being discharged into the environment, microplastics undergo normal environmental processes, such as accumulation, degradation, and migration, so they can be now found everywhere. In 2019, the WHO reported that microplastics are widely found in different areas of the environment, including air, fresh water, wastewater, and seawater. Thus, humans are exposed to microplastics through the air we breathe, the water we drink, and the food we eat. The most abundant microplastics found in the environment are Polystyrene (PS), low/high density Polyethylene (LDPE/HDPE), Polyethylene terephthalate (PET), Polyvinyl chloride (PVC), and Polypropylene (PP) which is consistent with the production volumes.

What is the toxicity of Microplastics?

Throughout the past decade, numerous toxicological studies have postulated that microplastics pose significant environmental and health concerns due to their environmental persistence. Further studies have shown that they can be detected in human stools and embryos as well as have adverse effects on biota as cytotoxicity, inflammation, and oxidative damage. Yet, the field is still emerging as the current understanding of microplastic toxicity is limited. Particularly due to the fact that microplastics are a heterogeneously mixed contaminant suite, comprising a vast array of polymers, sizes, morphologies, and hydrophilicities. Additionally, the chemical (e.g., polymer composition, chemical additives, sorption of contaminates from the environment), and biological (pathogens, natural biofilms) characteristics of microplastics influence toxicological outcomes. Thus, more research, is necessary, in order to understand the complexity of the toxicological implication of microplastics and their long-term effects. Simultaneously, current legislative mandates (California and EU) have required regulators to develop strategies to mitigate microplastic pollution and develop health-based thresholds for the protection of human and ecosystem health, but no legal limits have been released yet.

How are Microplastics analysed?

Despite extensive research performed in recent years, the analysis of microplastics is a very new field of analysis. For an extensive analysis, the following information is required: particle enumeration/concentration, polymer type, size, morphology, and colour. Currently, three analysis techniques are being deployed: Microscopy, Spectroscopy (RAMAN/FTIR/LDIR), and Thermal Analysis (Pyrolysis or Thermal Desorption GC-MS). However, as shown in the Figure, not all the methods provide the same results, which makes comparing different methods difficult.
Additionally, there are further challenges due to the lack of certified reference materials and standardised sampling/clean-up procedures. This collectively leads to low reproducibility and accuracy compared to other established methods. Until today, only two standard methods have been published by the California State Water Board for Potable Water.

How can Microplastics be removed from the environment?

Removal methods include physical sorption and filtration, biological removal and ingestion, and chemical treatments. Currently, there is no large-scale solution to remove microplastics. Even our ordinary wastewater treatment plants are not equipped to remove the microplastics, they either tunnel through or end up in the biosolids fraction. And as biosolids are applied to the fields as fertiliser, the microplastics are returned to the environment and increase the load. However, recent studies and inventions showed promising approaches to removing microplastics from waters and optimisations of wastewater treatment plants which is a great way to start.

Article Published on 20/04/2023

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