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PlasticsFatE's Progress at the End of Year Two

In this news item, we provide an update of recent research and results as we embark on the third year of our project.

PlasticsFatE has developed a test material portfolio that consists of various types of primary and secondary (cryo-milled, solubilized and reprecipitated) polymers (PE, PS, PET, PP and PLA) with different size (micro, sub-micro, and nano) and shape (round, spherical, irregular, fiber), as powder or dispersed, including aged (60 um HDPE cryo-milled) and labelled (Eu-PS) particles.

Also, protocols have been established to prepare stable stock and working suspensions for physicochemical and hazard characterization of MNP in various biologically relevant test and cell culture media (such as BSA, DMEM etc.).

To validate the performance of methods for detecting and characterizing MNP, but also to support current standardization efforts (e.g., ISO/TR 21960:2020, Plastics — Environmental aspects — State of knowledge and methodologies), 2 interlaboratory comparison (ILC) studies are prepared, also within CUSP and in close cooperation with VAMAS. These exercises include also sample preparation and templates for data reporting. The first ILC has already started and will test spectroscopic and thermo-analytic methods to detect and characterize 2 different MPs (< 100 µm), while the second ILC will include 2 different NPs (<1 µm) and spectroscopic, microscopic, and other size, shape, and mass related methods. The first results of ILC1 are expected in the second half of 2023.

PlasticsFatE will increasingly focus on test materials from our first measurement and testing campaign that have indicated potential effects, but also on more “real” test materials obtained from weathering, aging, and leaching of these materials, on particles with an eco-corona, and on new industrial materials that are with and without additives or chemical/biological contaminants. Here we will have a special focus on micro-fibers from in-house production (such as PLA and PP from polymer pellets without additives), from textiles (e.g., from polyester (PET), nylon (PA), or non-colored PE), or fibres from synthetic carpets that are derived from recycled and highly contaminated plastics, to assess exposure levels to both consumers (in private households), and workers (in offices).

To get a better understanding of MNP exposure levels in food and drinking water, new SOPs have been developed for MNP analysis (microscopy/µFTIR/µRaman/solid phase cytometry (MuScan) and first results have been achieved for bottled water, as well as indoor and outdoor air collected at two different locations (remote and suburban) (see Figure 1).

As part of these monitoring studies, we are currently testing the applicability of the MuScan, a fast-screening method for MNP in food (see Figure 2).

These studies will be complemented by assessing the occurrence of MNP in Personal Care Products (PCP), which includes the selection of suitable methods and products, to get some further indication, to what extent the ECHA restriction proposal on intentionally added microplastics in PCP has helped to limit the use of deliberately manufactured and added plastic particles.

As ingestion is one of the main exposure routes for MNP, we are adapting and using various Simulated Digestion Human Systems, such as the INFOGEST method and the dynamic gastrointestinal simulator “simgi®model”, to monitor possible physicochemical changes and the translocation and fate of selected MNP particles in the oral-gastro-intestinal (OGI) tract. 

When it comes to the occurrence of MNP in various secondary organs, we have collected various human tissues (kidney, lung, spleen, brain) and feces from 2 hospitals for a first screening attempt and developed protocols for digestion and analysis by using µ-FTIR/Raman (MP) and TED-GCMS (NP).

First studies on hazard assessment have been carried out in the first half of the project including particles of different size, shape and composition (Eu-doped PS, PE and PET and PP and various in vitro cell lines as well as biomarkers that represent main exposure routes and target organs, and possible short-term effects, on cell viability, barrier integrity, cellular uptake, bioaccumulation and immunological response (see Figure 3).

So far, no significant effects have been observed after acute exposure to selected MNP on cell viability and cell membrane integrity, while small induction of inflammatory response (by IL6 and IL8 production) was observed by HDPE (4-5 um) and PET (50-2000 nm) at doses ≤ 200µg/mL, which may indicate potential risks that may trigger a cascade of events that can lead to severe cell and tissue damage. Next steps will include ling-term studies and polymers that showed acute effects, the study of the role of additives (such as plasticizers or flame retardants) and contaminants (such as BaP, LPS, LTA, or Vibrio parahaemolyticus) on particle toxicity, as well as weathered particles and particles with an eco-corona. Also the effect of size and shape (spherical vs fiber)​ on toxicity will be further investigated as well as the use of homologous non-synthetic polymers (e.g., CB and TiO2), as particle control. In the coming months, several animal (mice) test are planned starting with high doses to study acute and subacute effects.

To see how well the methodology, we are developing in PlasticsFatE is performing under more real conditions, a series of case studies have been launched. This includes occupational exposure monitoring and air collection at 5 different locations, including a recycling plant (Norway)​, 2 plastic packaging producer plants (Norway), a plastic and bioplastic bag plant (Italy)​ and a thermoplastic plant (Italy)​. These studies will be supported by human biomonitoring and clinical studies that include the collection of biological samples, such as urine, blood, stool and breath exhalate, and the identification and evaluation of specific pro-and anti-inflammatory, DNA and oxidative stress biomarkers, also taken from a subgroup of a population that undergoes annual health surveillance, to monitor long-term effects.

Another focus of PlasticsFatE is to assess the role of MNP to act as vectors for biofilm formation and pathogens. Preliminary results include an SOP for the characterization of biofilm generation and indicate that MPs released from tyre wear can promote horizontal gene transfer.

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