環境：大西洋全域で高濃度のナノプラスチック粒子が検出される

High concentrations of nanoplastic particles were found in locations across the North Atlantic Ocean, particularly in the top 10 metres of water and near coastlines, according to an analysis in Nature. The findings also reveal that the scope of this pollution may have been underestimated, and nanoplastic could pose a major threat to marine wildlife, owing to its ability to accumulate in biological organisms such as fish.

A substantial amount of plastic pollution will eventually make its way into the ocean. There, stress from waves and ultraviolet radiation from the sun can break plastic down into nanoplastic particles, which are less than 1 micrometre (one millionth of a metre) in diameter. However, the extent to which nanoplastics have spread across the globe has been understudied.

Dušan Materić and colleagues analysed the concentration of nanoplastic particles in the Atlantic through water samples taken at various water depths at 12 stations across the ocean. They found that, on average, the nanoplastic concentration at a depth of 10 metres was approximately 18.1 milligrams per cubic metre of water, while samples taken near the sea floor saw a nanoplastic concentration of 5.5 milligrams per cubic metre. Samples taken near coastlines in Europe saw a nanoplastic concentration of 25 milligrams per cubic metre of water. Materić and colleagues estimate that the total amount of nanoplastic pollution in the top 10 metres of water in the North Atlantic is 27 million tonnes, which is what previous estimates have gauged for the entire ocean.

The authors note that based on these figures, nanoplastics are likely to represent the largest fraction of plastic mass in the ocean. The size of nanoplastics enable this pollution to move across biological barriers and accumulate in living organisms; thus, nanoplastics may represent the most problematic plastic size fraction for ocean life, the authors conclude.