Think Global, Act Local: Local Knowledge Is Critical to Inform Positive Change When It Comes to Microplastics

M contamination in the marine environment is a global issue. Across the world, policies at the national and international level are needed to facilitate the scale of change needed to tackle this significant problem. However, sources and patterns of plastic contamination vary around the world, and the most pressing actions differ from one location to another. Therefore, local policies are a critical part of the solution; recognizing local sources will enable mitigations with measurable impacts. Here, we highlight how investigating the contamination comprehensively in one location can inform relevant mitigation strategies that can be transferred globally. We examine the San Francisco Bay in California, USAthe largest estuary on the West Coast of the Americas, and home to over 7 million people. The local contamination of microplastics in surface water, sediments, and fish from this urban bay is reportedly higher than many places studied to date. This example demonstrates the value of local monitoring in identifying sources, informing local mitigation strategies and developing an array of solutions to stem the multifaceted tide of plastic pollution entering our global oceans. In the recent study of plastics in the San Francisco Bay area by Zhu et al., a sampling campaign of more than 400 samples found that urban wastewater effluent and stormwater runoff were important pathways for microplastics to reach the urban bay. Combined, they release an estimated annual loading of seven trillion microplastics. In wastewater samples, fibers were the most frequently identified morphology, followed by fragments. This is consistent with studies documenting the discharge of fibers shed from textiles during washing. However, urban stormwater runoff was a significantly greater pathway of microplastics than wastewater. Fragments were the most frequently identified morphology in stormwater, followed by fibers. Nearly half of the fragments were black fragments with a distinctive rubbery texture. Analysis of several of these fragments by pyrolysis−gas chromatography−mass spectrometry demonstrated tire wear as a source. Overall, the local results from this case study inform mitigation options specific to the region (Figure 1). For wastewater, mitigation strategies can be aimed at reducing fibers, perhaps through the use of filters on washing machines to keep fibers from entering wastewater, promotion of different washing practices, development of standardized methods to measure fiber shedding, and the creation of textiles with lower shed rates. For urban runoff, technologies to capture plastic trash and microplastics in storm drains or tributaries before they reach the Bay would be effective solutions. This may include green stormwater infrastructure, such as bioretention cells or raingardens on storm drains, and trash trapping technology, such as Seabins or a Trash Wheel in tributaries. In addition to mitigation strategies to trap particles in stormwater and wastewater, actions can be implemented to prevent contamination further upstream. This may include reducing plastic use, particularly the low-value single-use items that are commonly littered and observed on coastlines around the world. Local and statewide policies that reduce single-use plastics were identified as effective legislative actions that communities can take to address plastic pollution. The San Francisco Bay study also highlighted the need for further study to fully identify and evaluate other potential microplastic sources and transport pathways, for example from