Absence of microplastic bioaccumulation in cod fillets from plastic-polluted western Norwegian waters

Abstract

Plastics are synthetic, persistent materials that are distributed worldwide. An important concern is whether microplastics (MP) can bioaccumulate in the food chain and pose a threat to human consumers. We studied MP in the fillet of resident coastal cod from a plastic-polluted area in Western Norway, where long-range transported marine litter accumulates and MP are generated on shore. We dissected the fish and processed the samples in an MP-free lab using gentle enzymatic treatment. Micro Fourier transform infrared spectroscopy (µFTIR) was used for identification of particles down to 10 µm. The fish were 40 to 74 cm, corresponding to 2-6 years old. 29 particles were observed in fillets from eight of the 23 individuals. The mean particle count was 1.55 ± 2.75 nMP/100 g, and the mean concentration was 2.81 ± 8.33 µg/kg wet weight. Six polymer groups were identified, where polypropylene (33%) and polyethylene (30%) were the most frequent. The majority (86%) of the particles were fragments ranging from 32-100 µm. Fibers and fragments over 200 µm were observed. The largest particle was a PP particle of 258.2 µm. Controls showed minimal contamination and the procedural blanks were negative. There was no significant correlation between age, body condition, time of capture, and MP concentrations, and no evidence of bioaccumulation of MP in the fillet of older fish after in situ exposure. MP in food is of concern for human consumption and emphasizes the importance of understanding MP distribution and fate as well as reducing and controlling plastic release into the environment.