One after another, scientific publications document the accumulation of microplastics in the oceans and, through it, the threat posed by this out-of-control pollution to marine ecosystems. Much less attention has been paid to the presence of microplastics in soils. A ground-breaking study published on Thursday, December 26 by the French Agency for Ecological Transition (ADEME) fills in this gap for France. The results reveal an "almost systematic presence": Three-quarters of French soils are contaminated by microplastics, in other words, plastic fragments less than 5 millimeters (mm) in diameter.

To establish the "first national references" on microplastic contamination of French soils, ADEME has mobilized the soil quality measurement network of the French National Research Institute for Agriculture, Food and the Environment (INRAE). A total of 33 soil samples from all over mainland France, representing a variety of uses, were analyzed by the Dupuy de Lôme research institute in Lorient, western France. Microplastics were found in 25 samples, i.e. 76% of the total.

No soil type is spared. The vast majority of grassland soils (4 out of 4 samples), vineyards and orchards (3 out of 4) and field crops (17 out of 21) are contaminated, unlike forest soils (1 out of 4). This leads the authors to conclude that "there is an increased risk of pollution in soils subjected to human intervention compared with natural areas." On average, the soils analyzed contained 15 plastic microparticles per kilogram of dry soil. Another finding is that 70% of these microplastics measure less than 2 mm.

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