Tracking the bioaccumulation, the metabolization and synergy between Nanoplastics and Per- and polyfluoroalkyl substances (PFAS) in the food web

Investigations on the effects of nanoplastics (NP) on aquatic organisms used concentrations between 2 to 7 order-of-magnitudes higher than those predicted in the open ocean. This divided the community between those sounding the alarm due to the observed toxicological effects, and those predicting that NP concentrations in the environment are far below any threshold-effect. Fit-to-purpose experimental designs have been hindered by a lack of appropriate NP models, tracking methods, and monitoring strategies for environmentally realistic concentrations.
Using 14C-labelled-NP and conventional nuclear techniques, we recently modelled potential accumulation of NPs in scallops, chronically exposed (Fig 1) to 15 ug/L NP. Astonishingly, this suggests that NP might already be beyond threshold-effects in organisms and harming the marine biota.
Perfluoroalkyl and polyfluoroalkyl substances (PFASs), a large class of persistent chemicals and known to be an additive of plastics products, are widespread through consumer products and present in various environmental bodies. A small number of PFASs have been shown to bioaccumulate and/or toxic to different taxa, with PFOS and PFOA listed under the Stockholm Convention on persistent organic pollutants. However, the transport and and toxicological mechanism still unclear and the potential vectorisation by NPs misunderstood.
The combination of NPs and PFASs could potentially lead to higher health risks in humans and animals. Therefore, the three relevant questions i-iii are relevant for the mixture of NPs/PFASs.
Despite the significance of the topic, relevant questions remain unanswered; specifically:
i) Are NPs accumulating through a chronic exposure at sub-ppb levels and reach high tissue concentrations?
ii) Can we track and quantify sub-ppb concentration of NP in tissues?
iii) Do NP accumulate in the food web over time at sub-ppb levels?
iv) Does NP and PFASs have a synergy effect on the biota?
We propose an innovative approach that will overcome the analytical limitations of tracking and quantifying the transformation of NPs and their co-contaminants (PFASs) at sub-ppb concentrations. By combining 14C-labelling with the ultimate sensitivity and analytical power of the Accelerator Mass Spectrometry (AMS), this new approach will answer whether NP and PFASs are accumulating and transforming in the food chain?
The labelling of 14C-nanoploystyrene was pioneered by the PI. This approach is however currently only available for polystyrene polymers and concentration 10 ug/L. Further innovations are necessary to label NPs composed of the most produced plastic worldwide, i.e., polyethylene (32%) and polypropylene (23%), which may have different toxicokinetic and tissue distribution due to their different physico-chemical properties.
Only the higher sensitivity of AMS measurements will enable work at sub-ppb levels by using 14C-labelled NPs. The AMS technique generally used for detection and datation of 14C in geological samples. Here, it will be applied for the first time to ecotoxicological issues by measuring 14C-labelled contaminants (i.e., NPs). 14C micro-dose AMS measurements performed in pharmaceuticals studies, using elemental analyser (EA) combustion and double-trap interface, look promising for measuring 14C-labelled NPs at sub-ppb levels.
However, sample preparation for AMS is indeed a central challenge, even for geological samples. Each application must develop their own preparation method, which should: 1) uses carbon-free chemicals; 2) avoid degradation of material into CO2 prior AMS analysis; 3) avoid carbon isotope fractionation; 4) avoid cross-contamination, and 5) enable a high throughput analysis for ecotoxicological application.