Microplastics Pollution

Article 1: Every Breath You Take: High Concentration of Breathable Microplastics in Indoor Environments

L. Maurizi, L. Simon-Sanchez, A. Vianello, A.H. Nielsen, J. Vollertsen ^[1]

Inhalation is the most evident source of exposure to microplastics. The smallest, low-weight particles that tend to float in the air have a higher probability of being inhaled. In this very recent publication (June 2024), Raman micro-spectroscopy was employed to assess the concentration of indoor airborne microplastics >1 μm in indoor environments under different levels of human activity.

Sampling was conducted by actively pumping air through a Si membrane, which was then analyzed using Raman spectroscopy. A XploRA Nano confocal Raman microscope and ParticleFinder™ software were used for automated particle analysis. This publication provides detailed infomation about the instrumental settings and explains the functionality of ParticleFinder™, which allowed for the automatic characterization of thousands of particles on the filter.

The results revealed a concentration of microplastics between 58 and 684 MPs per cubic meter, depending not only on the type and level of human activity but also on the surface area and air circulation of the investigated locations. The authors estimated a human microplastics (MPs) intake from indoor air of 3,415 ± 2,881 MPs per day. A total of 15 polymers were identified, with polyamide (PA) clearly dominating the polymer composition.

It should be noted that this work presents a good example of quality control that must be applied while performing microplastics analysis. The authors presented the limit of quantification (LOQ) for each type of polymer based on multiple procedural blanks analyses. This approach is crucial to distinguish between microplastics contamination due to sample preparation (consumables, clothing, etc.) and microplastics collected from the sample itself.

Article 2: The Majority of Potable Water Microplastics Are Smaller Than the 20 μm EU Methodology Limit for Consumable Water Quality

O. Hagelskjær, F. Hagelskjær, H. Margenat, N. Yakovenko, J.E. Sonke, G. Le Roux ^[2]

In this publication, the authors studied the presence of microplastic particles down to 1 micron in bottled and tap water. First, 4.5 L of the tested sample was subjected to chemical digestion with H₂O₂ and HCl to reduce the quantity of organic matter and mineral deposits and then filtered on a filter suitable for Raman analysis.

LabRAM Soleil Raman microscope and ParticleFinder™ software were used for automatic particle detection and analysis. The ViewSharp™ option, which permits precise optical focus for each particle, was applied, guaranteeing high precision in Raman analysis.

Even though the authors mention some perspectives for improving sample preparation and quality control procedures, they demonstrated that Raman µspectroscopy is a reliable tool for detecting the smallest particles.

According to the findings, the majority of particles identified as microplastics were in the range of 1-20 μm. Thus, authors suggest an amendment to the guidance published in the EU directive 2020/2184 regarding water intended for human consumption. More precisely, the authors recommend including the fraction of particles below 20 microns in systematic monitoring and explain that the minimum sampling volume should be reduced from 1 m³ to several litres. This suggestion is in accordance with both realistic human daily/weekly consumption and the sensitivity of the methodology for particle detection and analysis.

Article 3: Detection and Characterization of Small-Sized Microplastics (≥ 5 µm) in Milk Products

P. A. Da Costa Filho, D. Andrey, B. Eriksen, R. P. Peixoto, B. M. Carreres, M. E. Ambühl, J. B. Descarrega, S. Dubascoux, P. Zbinden, A.Panchaud, E. Poitevin ^[3]

To understand potential exposure to microplastic pollution via ingestion, monitoring drinking water alone is not enough. Measuring the concentration of microplastics in different food products, especially those subjected to industrial production, is essential.

In this article published in 2021, the authors used Raman microscopy to study the presence of microplastic particles in milk-based products. Enzymatic and chemical digestion were used to dissolve the organic matrix and have been validated for 5 types of polymers. The liquid phase was then filtered through a Si filter and analyzed with a confocal micro-Raman LabRAM HR Evolution (now proposed as LabRAM Odyssey.) Instead of a particle-by-particle approach, Raman imaging was used to scan the surface of the filter and identify polymeric particles. This approach overcomes the difficulties related to the agglomeration of particles of different natures and thus offers high precision in terms of particle counting in complex matrices.