The fiber microparticle pipeline in the marine water column – from source to mitigation strategies

Global fiber production, including both synthetic and natural fibers, has increased dramatically in recent decades. In 2018, global fiber production reached 107 million metric tons (MMT), more than double the fiber production twenty years earlier. Synthetic fibers have begun replacing natural fibers (e.g. cotton, wool, and silk) due to their low price, mass production, and customization. Microfibers (fibers < 5 μm) have typically been discussed in terms of microplastics as they are frequently the most abundant category in microplastic sampling globally. However, recent research has indicated that the ‘microfibers’ found in the environment are not just of plastic descent; rather they can be categorized as natural, semi-synthetic, or synthetic. As a result, ‘microfibers’ cannot solely be categorized as ‘microplastics’, but rather, ‘fiber microparticle (FMP)’ (fibers < 5 μm) to be inclusive of synthetic, semi-synthetic, and natural FMP. FMP are a complex social problem that warrants a transdisciplinary viewpoint. With this perspective in mind, this review paper showcases the state of the science for FMP while also discussing mitigation strategies and data gaps. This review paper focuses solely on fibers found within the marine water column. It does not address FMP in freshwater environments or soil compartments.