Most people have heard of microplastics in the ocean. Far fewer people have heard of microfiber glass. Researchers have now discovered it buried in the sediments and surface layers of the Cowichan Estuary on Canada’s Vancouver Island. The estuary supports unique wildlife, shellfish harvesting, and food security for indigenous peoples.
This new study, led by scientists at Simon Fraser University, is one of the first baseline assessments of coastal fiberglass pollution in Canada.
In collaboration with the Cowichan Estuary Restoration and Conservation Association (CERCA), the team sampled 26 sites across the estuary from 2020 to 2024 to determine how widespread the material was.
Estuary filled with fiberglass
By 2023, 96 percent of estuary sediment sampling stations will detect glass fiber particles, up from 64 percent in 2020.
Concentrations in the sediment ranged from 6 to 286 particles per kilogram of dry sediment, with the highest levels concentrated near industrial activities and along log transportation routes.
Glass fibers were also present in surface biofilms throughout the estuary. This is a thin, nutrient-rich layer of algae and microorganisms that covers the top few millimeters of sediment and provides food for migratory birds.
Biofilm concentrations ranged from 30 to 62 particles per kilogram dry weight, particularly near the Western Forest Products plant pond, Westcan Terminal, and the busy marina in Cowichan Bay Village.
Higher levels were consistently occurring around marinas, slipways, boat maintenance areas, and areas where sanding, repairs, and hull cleaning are frequently performed. The increased concentration near the West Can Terminal suggests that industrial runoff may also be contributing.
Estuary sediment debris
Fiberglass is more than just a piece of plastic. Made of silica-based fiberglass, often reinforced with plastic resin. When a boat is repaired, polished, abandoned, or left to deteriorate, these fibers can break down into small needle-like pieces.
“We are just beginning to understand the potential toxicity of[glass fibers]to animals and humans,” said lead author Juan José Alaba, a marine ecotoxicologist at Simon Fraser.
Unlike lightweight plastics, fiberglass is denser than seawater, so it tends to sink and accumulate in sediments. That’s exactly where clams, mussels, and other invertebrates live and feed.
“Knowing that these particles are present in estuaries, which are home to shorebirds and shellfish and central to food security for Indigenous peoples, is enough to justify precautionary, precautionary action. We don’t have to wait until we know all the toxic thresholds to take action.”
More than just plastic
Researchers are clear on what they still don’t know. They do not reveal how much exposure causes harm, how easily animals can eliminate these particles, or whether glass fibers accumulate in the food chain.
“Now that we know this substance is present in active estuary sediments and biofilms, we need to understand the extent to which it is impacting wildlife, marine life, and people, including local indigenous peoples, who depend on shellfish and seafood,” Alaba said.
The last point has weight. The Cowichan Estuary is used for harvesting clams, geoducks, crabs, waterfowl, codfish, sea urchins, and salmon.
If glass fiber fragments get into small organisms at the base of the food chain, they can eventually reach species eaten by humans.
Glass fiber contamination is slowly broken down
One concern is that this is not a one-time event. Glass fiber reinforced plastics are widely used in boat hulls and marine infrastructure. As boats age, are repaired, or abandoned, they can steadily release fibers over time.
This study suggests that in the same way that derelict ships contribute to microplastic pollution, deteriorating vessels may be a source of continuously unmanaged microfiberglass.
Fiberglass is durable and degrades slowly, especially when embedded in resin. Once settled in the sediment, it can remain there.
“Our data serves as evidence for management’s immediate actions and policies,” Alaba said. “Prevention is better than cure.”
Preventing further pollution of the estuary
Researchers claim the evidence already supports practical steps. They recommend increased controls on sanding and debris cutting at boatyards and docks, and stronger regulations for end-of-life boats, including requirements for safe dismantling and recycling.
We also need to improve the management of stormwater and industrial wastewater, and invest in more environmentally friendly materials.
Fiberglass pollution exists in active estuaries that support wildlife and food systems. Science is still figuring out exactly how harmful it is.
But the material is already there, lying in the mud. As Alaba says, waiting for complete knowledge before acting may not be the wisest approach.
The research will be published in a journal Marine pollution bulletin.
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