A recent study has estimated the annual microplastics intake by adult humans based on the presence of microplastics found in the gastrointestinal tracts of 160 fish species.

Fish samples were obtained from Nigerian coastal waters immediately after landing at a community seafood market. The study looked at the occurrence of microplastics and their composition in the guts of the cassava croaker (Pseudotolithus senegalensis), sompat grunt (Pomadasys jubelini), lesser African threadfin (Galeoides decadactylus), Maderian sardinella (Sardinella maderensis), flathead gray mullet (Mugil cephalus), West African ilisha (Ilisha Africana), and blackchin tilapia (Sarotherodon melanotheron).

Microplastics were detected in each of the 160 fish specimens assessed. A total of 5,744 microplastics were counted, with a mean of approximately 40 items found per fish. Six types of microplastics were identified based on shapes: microbeads, fragments, burnt film, fibers, pellets, and thread. Microbeads occurred in all of the assessed fish guts, accounting for 43 percent of all microplastics found, followed by fragments (27 percent), burnt film (14 percent), thread (9 percent), fibers (4 percent), and pellets (3 percent).

Based on the size classes estimated for the study, the researchers believe that close to 15 percent of the microplastics found in the guts of the assessed fish have the potential to translocate through the fishes’ gut barriers into their muscles. The contaminated muscles are then ingested by humans, and may subsequently translocate to other human organ tissues.

The annual intake of microplastics from the consumption of whole fish by the adult population for each species was estimated as follows: M. cephalus (178,220), I. Africana (131,670), P. senegalensis (115,710), P. jubelini (109,060), S. maderensis (101,080), G. decadactylus (101,346), and S. melanotheron (65,170). Estimated annual intakes were generally higher for fish species with broad habitat and feeding preferences.