At present, the distribution of plastic debris in the ocean water column remains largely unknown. Such information, however, is required to assess the exposure of marine organisms to plastic pollution as well as to calculate the ocean plastic mass balance. Here, we provide water column profiles (0–300 m water depth) of plastic (0.05–5 cm in size) concentration and key planktonic species from the eastern North Atlantic Ocean. The amount of plastic decreases rapidly in the upper few meters, from ~ 1 item/m3 (~ 1000 µg/m3) at the sea surface to values of ~ 0.001–0.01 items/m3 (~ 0.1–10 µg/m3) at 300 m depth. Ratios of plastic to plankton varied between ~ 10–5 and 1 plastic particles per individual with highest ratios typically found in the surface waters. We further observed that pelagic ratios were generally higher in the water column below the subtropical gyre compared to those in more coastal ecosystems. Lastly, we show plastic to (non-gelatinous) plankton ratios could be as high as ~ 102–107 plastic particles per individual when considering reported concentrations of small microplastics < 100 μm. Plastic pollution in our oceans may therefore soon exceed estimated safe concentrations for many pelagic species.
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BackgroundConcerns on microplastics (MPs) in food are increasing because of our increased awareness of daily exposure and our knowledge gap on their potential adverse health effects. When particles are ingested, macrophages play an important role in scavenging them, potentially leading to an unwanted immune response. To elucidate the adverse effects of MPs on human health, insights in the immunotoxicity of MPs are essential.ObjectivesTo assess the effect of environmentally collected ocean and land weathered MP particles on the immunological response of macrophages using a state-of-the art in vitro immunotoxicity assay specifically designed for measuring particle toxicity.MethodsEnvironmentally-weathered macroplastic samples were collected from the North Pacific Subtropical Gyre and from the French coastal environment. Macroplastics were identified using (micro)Raman-spectrometry, FT-IR and Py-GC-MS and cryo-milled to obtain size-fractionated samples up to 300 μm. Physiochemical MP properties were characterized using phase contrast microscopy, gel-permeation chromatography, nuclear magnetic resonance, and differential scanning colorimetry. Macrophages (differentiated THP-1 cells) were exposed to particles (<300 μm) for 48 h before assessment of cell viability and cytokine release. Using both the physiochemical particle properties and biological data, we performed multi-dimensional data analysis to explore relationships between particle properties and immunotoxicological effects.ResultsWe investigated land-derived polyethylene, polypropylene, polystyrene, and polyethylene terephthalate, water-derived polypropylene macroplastics, and virgin polyethylene fibers and nylon MPs. The different plastic polymeric compositions and MP size classes induced distinct cytokine responses. Macrophages had the largest response to polyethylene terephthalate-particle exposure, including a dose-related increase in IL-1β, IL-8, and TNF-α secretion. Smaller MPs induced cytokine production at lower concentrations. Additionally, a relationship between both physical and chemical particle properties and the inflammatory response of macrophages was found.DiscussionThis research shows that MP exposure could lead to an inflammatory response in vitro, depending on MP material and size. Whether this implies a risk to human health needs to be further explored.
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