Still, removing existing microplastics directly from waters is very difficult and would require unrealistically large amounts of time and effort, and related research is very sparse. Furthermore, the research and development efforts bring in little financial return and must rely on sponsorship or donations. In comparison, capturing microplastics before they enter water ecosystems is far more feasible. The most widely used methods are wastewater treatment plants (WWTP), which have been studied in large numbers of publications. WWTPs were not originally designed to capture microplastics; the facilities purify sewage water via a variety of physical, chemical and biological processes before discharging it to water ecosystems. WWTPs treat wastewater in a series of stages, referred to preliminary/primary (skimming, sedimentation, etc.) secondary (coagulation, flocculation, etc.) and sometimes tertiary (dissolved air flotation, rapid sand filtration, membrane bioreactors, etc.) treatments. WWTPs, especially those carrying out tertiary treatments, are typically found to be quite effective at removing microplastics (90% and above). Still, research efforts in further improving removal efficiency are ongoing. 107 Also, the removed microplastics in WWTPs end up in sewage sludge and will eventually go into the environment again. Separation of microplastics from sludge is difficult, yet their utilization through pyrolysis into hydrocarbon fuels has been studied. To get insights on the research interest in microplastics removal, the same pool of publications obtained as described in the Methods section were analyzed. Figure shows the numbers of publications involving various keywords related to microplastics removal: coagulation, filtration, floatation, flocculation, membrane bioreactor (MBR), and wastewater treatment plants (WWTP). It can be seen that the publication volumes featuring most of the keywords grew significantly since the mid-2010s, a trend very similar to that observed in the overall publication volume (Figure ). This suggests that researchers in the corresponding fields reacted quickly to growing concerns in microplastics, with removal-related research efforts increasing at a pace similar to that of microplastics research in general. Of all the keywords in Figure , "filtration" produced the largest number of documents. However, it is worth noting that filtration may have been used in many microplastics studies unrelated to removal, so the publication volume shown here is likely higher than that for actual removal studies; the same may be true for "WWTP". The document counts for "coagulation", "floatation", and "flocculation" are low, reflecting less interest in these basic removal techniques (often used in primary and secondary treatments in WWTPs). "MBR", on the other hand, produced many more documents, almost equaling those for "WWTP", suggesting the popularity of this newer, highly efficient removal method, which has been frequently used for tertiary treatments in WWTPs. Since microfibers lost from synthetic textiles during laundry make up the majority of microplastics in sewage water, and comprise an estimated 35% of primary microplastics, efforts to reduce their release will go a long way toward microplastics mitigation. Microfibers shed from textiles made from natural fibers such as cotton are less of a concern as they are generally biodegradable. In-drum accessories capable of capturing microfibers during laundry, such as laundry bags and laundry balls, as well as filters to catch microfibers from the effluent, are commercially available to consumers. Also, studies on reducing microfiber loss by reducing friction or improving the mechanical integrity of garments have been reported. Microplastics-related regulatory activities have taken place in the past few years in countries including the US, China, Canada, and some EU countries. Most laws and regulations involve the banning or restriction of cosmetics and drugs containing plastic microbeads, which are intentionally added into the products to facilitate scrubbing or exfoliating. These primary plastic particles are designed to be eventually rinsed down the drain into domestic sewage, thereby entering water ecosystems. Banning of cosmetic microbeads is a critical and straightforward step toward microplastics mitigation, but far from sufficient, since they constitute a mere 2% of primary microplastics. 109 Regulations concerning synthetic microfibers, which make up 35% of primary microplastics, has been nonexistent except a law in France requiring microfiber filters to be installed in new washing machines by 2025. Regulations targeting particles generated from tire wear, another major contribution to primary microplastics, are also rare, although EU lawmakers are considering setting standards on tire abrasion and durability. A regulation recently proposed by the California Department of Toxic Substances Control will require tire makers to seek alternatives to 6PPD, a commonly used antioxidant found to be directly related to the death of spawning coho salmon. This, as well as another regulation targeting zinc compounds in tires that will likely be proposed in 2023, will undoubtedly be critical pioneering efforts to control tire particles, although they are triggered by concerns over additives rather than the polymer matrices.