First discoveries of microplastics in terrestrial snails

Abstract

Microplastics (MPs) are widely recognized as pollutants of the marine environment, while their presence, diffusion and distribution in the terrestrial ecosystem have been investigated so far. The aim of this study is to evaluate, for the first time, the presence of microplastics in three different species of edible snails belonging to the genus Helix (H. aperta, H. aspersa and H. pomatia) in order to improve the knowledge about the distribution of MPs in the terrestrial ecosystem, and the consequent MPs human exposure deriving from their consumption. Their breeding techniques, the frequent response in rural areas close to agricultural activities and their food behavior, suggest us that they can be exposed to the main contamination sources of MPs in terrestrial ecosystem. A total of 425 specimens were collected in nature or in breeding and divided in 85 samples (5 snails for each sample). All the specimens belonging to the H. aspersa (44 samples) and H. pomatia (4 samples) were in active life phase, while those belonging to the H. aperta (37 samples) species were in resting phase. The digestion of the samples was carried out through the nitric acid and a stereomicroscope was used for the physical identification of MPs. Out of 85 samples of snails examined, 44 (51.75%) presented MPs. A total of 78 MPs were isolated, ranging from 1 to 3 in each sample, with a mean value of 0.92 ± 1.21 particles/sample and an amount of 0.07 ± 0.01 MPs/g. Among these 78 MPs, 43 were plastic line with variable length between 200 μm and 2500 μm and the remaining 35 plastic fragments, whose longest lengths varied between 200 μm and 1000 μm. Although the quantity of MPs/g found is relatively low, in any case their presence in terrestrial snails contributes to the risk assessment of human exposure deriving from their consumption.