The Cowichan River delta on Vancouver Island, B.C. Researchers found fibreglass particles in more than 96 per cent of sediment samples collected across the Cowichan-Koksilah Estuary. (Gerry Thomasen/Flickr), CC BYWalk along British Columbia’s shorelines and you quickly notice the signs of human-made activities and marine industry: boats anchored and hauled out for repair in marinas, abandoned vessels, the smell of fresh paint, workers sanding hulls and stacks of fibreglass materials waiting to be used.Most people would not see these activities as a source of pollution. Yet our research suggests they are releasing tiny fibreglass particles into coastal environments.We found that fibreglass particles are accumulating in coastal sediments in British Columbia, particularly near marinas and boat maintenance sites. These particles are largely overlooked in monitoring programs, but they may represent an emerging form of pollution with implications for coastal ecosystems and food webs.We first became interested in this issue while studying microplastics in the Cowichan-Koksilah Estuary on Vancouver Island’s east coast. These synthetic particles are prevalent in the estuary, raising concerns for marine fauna and traditional seafoods. Our conversations with Bernhard Juurlink, Bill Heath and Goetz Schuerholz of the Cowichan Estuary Restoration and Conservation Association (CERCA) led to a new question: what about fibreglass? In our new study, we found fibreglass particles in more than 96 per cent of sediment samples collected across the Cowichan-Koksilah Estuary. The results suggest fibreglass contamination is widespread in coastal waters. How fibreglass affects the estuaryFibreglass behaves differently from many small plastics particles. Because it is denser than seawater, it sinks quickly and accumulates in sediments where many coastal organisms live and feed.Fibreglass, or glass fibre-reinforced plastic, is widely used in boats, docks and marine infrastructure because it is strong, lightweight and resistant to corrosion. But those same properties make it persistent once it enters the environment. As boats age and marine infrastructure weathers, tiny fragments can be released. These particles are often invisible to the naked eye but can build up in sediments over time.Working with CERCA, we sampled 26 sites across the roughly 400-hectare estuary. The highest concentrations were found near marinas, boatyards and industrial waterfront areas, exactly where fibreglass use and repair activity is most intense.The Cowichan-Koksilah Estuary is more than a coastal landscape. It supports shellfish, salmon and migratory shorebirds, and holds cultural significance for the Cowichan Tribes, who have stewarded these waters for generations. Read more: Abandoned fibreglass boats are releasing toxins and microplastics across the world Our findings are particularly concerning because of what lives in the sediment. In a companion study, we examined the estuary’s surface biofilm; a thin layer of algae and bacteria covering mudflats. Although easy to overlook, this biofilm is a key food source in the ecosystem. It contains essential fatty acids that fuel migratory shorebirds in stopovers along the Pacific Flyway. These same sediments and biofilm also act as sinks for human-made particles. Previous research from our team has also found microplastics in sediments and in varnish clams collected from Vancouver Island estuaries. Fibreglass adds another concern because many fragments are sharp, irregular and persistent. They settle where clams filter-feed and where many small organisms form the base of the food web.Practical solutions to fibreglass pollution The Cowichan River rushes through Marie Canyon in Cowichan River Provincial Park on Vancouver Island, B.C. (David Stanley/Flickr), CC BY One reason fibreglass pollution has remained largely invisible is that it is difficult to identify. Under a conventional microscope, fragments can resemble natural mineral grains or broken shell material. Confirming them requires advanced analytical techniques. As a result, fibreglass has largely fallen outside routine environmental monitoring. Canada currently has no dedicated monitoring programs for fibreglass particles in marine environments, and existing plastic pollution policies do not explicitly include them. The ecological consequences are still being studied. It remains unclear whether fibreglass particles damage tissues, transport contaminants or move through food webs. Fibreglass research in the southern England coast has found evidence of fibreglass ingestion in oysters and mussels and potential health risk effects causing inflammation in shellfish. And experience with microplastics suggests that waiting for full certainty may delay action to tackle pollution.The good news is that practical solutions already exist. Boat yards can reduce emissions through vacuum sanders, dust containment systems and enclosed work areas. Better end-of-life vessel management could prevent abandoned or deteriorating boats from becoming long-term sources of pollution. Expanded monitoring would also help track where these particles are accumulating and whether levels are increasing.Canada has made real progress in addressing plastic pollution by prohibiting single-use-plastics and categorizing harmful plastics as toxic substances. Fibreglass deserves similar attention. It’s a material that supports coastal economies, but its environmental footprint does not end when a boat leaves the yard.Emerging pollutants are often recognized only after they become widespread and contaminate the environment. Our findings suggest fibreglass may already be on that path. Paying attention to it now gives us a chance to understand, manage and limit its impact on coastal ecosystems.Zeinab Zoveidadianpour was previously a postdoctoral researcher at Simon Fraser University and received funding from Mitacs. She is a Registered Professional Biologist (RPBio), registered with the College of Applied Biology (British Columbia).Juan José Alava received partial funding from the Cowichan Estuary Restoration & Conservation Association (CERCA) to conduct fibreglass ecotoxicological research at the Cowichan Estuary. He is an active member and part of the Steering Committee of the Scientists' Coalition for an Effective Plastics Treaty. He is also the Science Director of the Fundación Ecuatoriana para el Estudio de Mamíferos Marinos (FEMM) (Ecuadorian Foundation for the Study of Marine Mammals) in Ecuador, a volunteer position he has held for over two decades.