Microplastics

All forms of plastics less than five millimeters in size are classed as microplastics. Particles below one micrometer are classed as nanoplastics. The presence of microplastics throughout our environment has been well documented in recent years, with studies reporting microplastic contamination in clouds, caves and rivers across the globe. Not enough information is available to fully understand the effects microplastic exposure may have on human health, but research suggests that ingestion of microplastics could damage cells, increase gut inflammation and damage the gut microbiome. Detecting and reducing the spread of these pollutants is vital. In this infographic, we look into the key sources of microplastic pollution, current and emerging detection techniques and regulatory action to combat this emerging pollutant. Wind dispersal Accumulation in soils Soil erosion and runoff Sediment retention Wastewater treatment Sewage sludge, application on land Accumulation and degradation in soils Tidal deposition Wastewater effluents River transport Direct input of maritime plastics, fishing gear, shipping waste, cargo, losses Marine environment Societal use of plastics domestic, industrial and agricultural Disposal and release to the enviroment Degradation into microplastics Microplastics everywhere Distrubution in the environment (wind, water, soil) Microplastics can be either primary (produced in “micro” form e.g., beads in personal care products like facial scrubs) or secondary (larger plastics that are broken down over time). The three main routes through which humans, animals and the environment might be exposed to microplastics are: Key sources of microplastic pollution Water While wastewater treatment plants can remove larger microplastics, smaller particles can evade removal. Microplastics are particularly problematic in our water systems as they are further eroded through physical abrasion, ultraviolet (UV) irradiation and biodegradation into smaller particles, making them more difficult to remove and more easily ingested. Microplastics can enter water systems through: Soil Once in the soil, microplastics can accumulate and affect the growth and biodiversity of organisms, which can impact soil quality and nutrient cycling. Coated fertilizer Mulch Sludge Sewage sludge containing microplastics from wastewater treatment plants is often used for agriculture irrigation Fertilizers are often coated with polymers to allow a slower release of nutrients Once in the environment, microplastics rise into the atmosphere via cycles of air, water and vapor movement. They are then transported across the globe by winds. Airborne microplastics typically occur as films and fibers, produced from plastic bag degradation and textile production, respectively. Research simulations suggest that humans may breathe in almost 300 microplastic particles during a day of light activity. Current detection techniques Chemical composition identification refers to the determination of the functional groups, molecular weight, structure and degree of polymerization of polymers in microplastics. Air Microplastic factors such as shape, color, size and abundance can be observed using a microscope or stereoscope. Microscopy is convenient and low cost, however, the quality of the data produced by visual identification depends strongly on the experience of the operator, the sample matrix and the microscope itself. Visual sorting is also limited by the size of the particles, as smaller microplastics cannot be distinguished from other materials. This method of identification is also extremely time-consuming. Techniques such as scanning electron microscopy can be combined with chemical composition analysis techniques to obtain more data. Microscopy Chemical composition analysis Fourier transform infrared (FTIR) spectroscopy Can be used to determine the chemical bonds and functional groups of samples in microplastics and can map the surface of large samples. Attenuated total reflectance FTIR (ATR-FTIR) can be used on irregular microplastics and those that are extremely small. With FTIR, samples must be dried thoroughly before analysis as moisture can interfere with identification. FTIR can analyze particles down to 20 μm. Spectroscopy Spectroscopic methods can be used to determine the shape and size of particles and provide their chemical fingerprint. Thermal analysis Thermal degradation paired with gas chromatography and mass spectrometry (GC-MS) can be used to determine the abundance of plastic in a sample and identify the plastic type. Thermal analysis also provides information on plastic-associated additives; however, this method does not determine particle sizes or shapes and is destructive. Raman spectroscopy Shows better spatial resolution than FTIR spectroscopy; the technique can analyze particles down to 1 μm. Raman also demonstrates wider spectral coverage, higher sensitivity to nonpolar functional groups, lower water interference and narrower spectral bands. Conversely, Raman spectroscopy is prone to fluorescence interference, has an inherently low signal-to-noise ratio and might cause sample heating due to the use of a laser as light source. Looking towards the future, researchers around the world are working on the development of new methods for microplastic detection: Scanning electron microscope-energydispersive X-ray Can analyze the surface morphology and elemental composition of microplastics simultaneously, but the samples must be conductive, meaning that this method comes with complex pretreatment procedures. Sources include: Compost Emerging detection techniques Plastic is produced and used by humans on an enormous scale, and there is no single method that can identify these pollutants quickly and without doubt. The development of novel practical methods for microplastic detection and the introduction of further restrictions will be essential in the crack down on these pollutants. A team from the Korea Institute of Materials Science developed a detection kit that can be used in the field to identify the type, number and distribution of microplastics within 20 minutes, without any pretreatment. Researchers from Bigelow Laboratory for Ocean Sciences and the University of Minnesota- Duluth developed a technique that combines Nile red staining, flow cytometry and pyrolysis GC-MS to characterize and count small varieties of microplastics. Over the last decade, regulatory bodies across the world have been working towards reducing the rate of microplastic release into the environment. In 2015, the United States Congress passed the Microbead- Free Waters Act of 2015, which prohibits the manufacturing, packaging and distribution of rinse-off cosmetics containing plastic microbeads. Then, in 2019, the United States Congress introduced a bill to establish a pilot program to test the efficacy and cost effectiveness of tools, technologies and techniques to remove and prevent the release of microplastics into the environment. In 2021, the European Commission established a target to reduce microplastics pollution by 30% by 2030. In 2023 it also adopted measures to restrict the intentional addition of microplastics to products by prohibiting the sale of microplastics and products to which microplastics have been added on purpose. Regulatory Action Degraded plastic waste Surface run-off Atmospheric deposition Wastewater and industrial effluent Combined sewer overflows While wastewater treatment plants can remove larger microplastics, smaller particles can evade removalremove larger microplastics, smaller particles can evade removal Untreated raw sewage can enter into superficial water bodies before treatment due to heavy rain.