The claim that wind turbines spread tons of microplastics stems from Norway and has been investigated and found false by NORWEA. The investigation showed that the weight loss of the blades consists primarily of color wear and is up to 2.25 kg per turbine during a period of 15 years, which translates into 0.15 kg per turbine per year. As materials are continuously developed and improved, this amount will continue to diminish. The whole report can be read here (in Norwegian):
Faktaark: Vindkraft, plast og bisfenol A
These numbers need to be viewed in context. The main sources of microplastics in nature are tire abrasion, artificial grass, washing synthetic clothing, and hygiene products. The Swedish Environmental Protection Agency estimates that around 13 million tons of microplastics are released into the environment each year. Vehicle tire abrasion, road coating and color account for 8,190 tons per year. This is approximately four times as much as the amount released by the next greatest source, artificial grass.