Global production of fibrous material is significantly growing reaching an expected 145 million metric tons in 2030. Fiber production includes mostly synthetic polymers, cotton and man-made cellulose (viscose). The main uses are in clothing, household and furnishing, industrial construction, automotive and other. Increasing consumption of fabric material causes the accumulation of single fibers into the natural environment. Significant numbers are discharged via wastewater from washing clothes, deposition from atmosphere or by other ways of transport. Fibers are now the most prevalent type of anthropogenic particles found by microplastic pollution surveys around the world. Substantial fiber concentrations are found in surface water, deep-sea and fresh water ecosystems. Consequently, fibers are present in food, drinking water, human lungs and digestive tracts of aquatic animals. Currently, there is great concern for the release of plastic nano- and micro fibers and microparticles (microplastics) to the natural environment for which nobody knows, so far, the ultimate consequences for health and ecological homeostasis. The potential risk introduced by the presence of fibers in the environment induces significant interest.These challenges were the source of inspiration for organizing our workshop . A group of scientists from different parts of the world met on Nov 4/5 2019 at Wetsus, European Centre of Excellence for Sustainable Water Technology in Leeuwarden, The Netherlands, to discuss all known aspects of synthetic nano- and microfibers. This included morphology, physicochemical properties, production and origin of nano/micro fibers entering the atmosphere, water and food chain; the potential consequences of inhalation and ingestion for human health; exposure and ingress via life cycle for aquatic biota; analytical and measurement methods; techniques to clean air and water, and protection means against inhalation or other ways to enter the human body.