The accumulation of microplastics in fish freshwater in the Mun river, Thailand

Abstract

Background: Microplastic pollution mainly occurs from terrestrial sources, but research on plastic contamination in aquatic environments is limited. Freshwater fish are widely consumed throughout Southeast Asia. Microplastic contamination is becoming an important issue that leads to human health risks from consumption. Objectives: The study aimed to determine the accumulation of microplastics ingested by fish in freshwater in the Mun River. Methods: Freshwater fishes in the Mun River caught by local fishermen and the most dominant species consumed in the Mun River include Paralaubuca typus, Phalacronotus bleekeri, and Morulius chrysophekaion. Twenty-four samples from each species were collected. Microplastics in these species were analysed for abundance, size, shape, color, and type of polymer. Results: The results showed that the average amounts of microplastic contamination in the gastrointestinal tracts (GIT) and gills of Morulius chrysophekadion were 17.70±8.20 pieces/fish, Phalacronotus bleekeri were 11.83±8.74 pieces/fish, and Paralaubuca typus were 10.25±7.56 pieces/fish, respectively. The average number of microplastics found in the urban area was 26.50±4.21 pieces/fish; in the agricultural area, it was 9.77±4.10 pieces/fish; in the confluence of the Mun and Chi River areas, it was 9.50±3.51 pieces/fish; and the natural area had 7.27±4.15 pieces/fish, respectively. The average size of microplastics found in fish was 878.29±904.41μm. The most common polymer type microplastic was polyethylene (PE) where the most common shape was Fiber-shaped, and the most common colour was blue. Conclusion: The study findings indicate a prevalent form of microplastic accumulation in three fish species especially among Morulius chrysophekaion. And findings show that every fish species in the urban area have the most contamination. As a result, fish GIT and gills should be removed before consumption to reduce exposure to microplastics instead of consuming them.