Surveillance and histopathological study of microplastics in marine fish from the gulf of Thailand

Microplastic (MP) problems have been threatened aquatic environment worldwide for decades. This study demonstrated current MP contamination characteristics in marine food fishes from the upper Gulf of Thailand. MPs were found in gastrointestinal tracts of 46.86% of fish samples, which were 1.556±0.47 pieces per fish or 0.035±0.014 pieces per gram of fish bodyweight. No plastics were detected from muscle, liver, kidney or gonad of the fishes. There was a significant relationship between MP contamination and fish species or the fish grouping. Benthic fish had a higher contamination rate than pelagic fish. Fiber-type and blue color were the most abundant MPs characteristic observed. The most common polymer was polyester, followed by polyethylene. Polyester was a dominant polymer among benthic fishes while polyethylene dominant in pelagic fishes. The contamination of MPs was not related to histopathological lesions in natural marine fishes. The expected MPs exposure of Thai marine fish consumers were 0.06 pieces per person per day for general marine fish and 0.095 pieces per person per day for Short Mackerel. The expected exposure risk from consuming fish muscle and risk from fishmeal consuming animal were still relatively low. Continuing surveillance and exposure assessment are crucial in determining MP risks to human health in near future.