Study reveals widespread microplastic contamination in U.S. West Coast fish and shellfish

By Dr. Liji Thomas, MDReviewed by Benedette Cuffari, M.Sc.Jan 9 2025

Anthropogenic particles found in edible tissues of Pacific seafood highlight evidence of microplastic contamination across trophic levels and market chains

Study: From the ocean to our kitchen table: anthropogenic particles in the edible tissue of U.S. West Coast seafood species. Image Credit: RussieseO / Shutterstock.com

In a recent study published in Frontiers in Toxicology, researchers measured the levels of anthropogenic particles (APs) present in various seafood caught along the West Coast of the United States. 

What are APs?

APs, which are materials produced or modified by humans, can include microplastics (MPs), which are plastics less than five millimeters (mm) in size. MPs permeate both the terrestrial and aquatic environments in the form of foams, films, pellets, fibers, fragments, and tire particles.

Polyester, polyethylene terephthalate (PET), high-density polyethylene (HDPE), and polyvinyl chloride (PVC) MPs can originate from various sources, including clothing, worn tires, and personal care products. These MPs are carried into freshwater sources like lakes, rivers, and streams by wind, as well as wastewater treatment plants (WWTPs) and urban runoff. Rivers, along with WWTP effluent, carry MPs into the ocean.

As a result, APs can be present in aquatic organisms at all trophic levels. Exposure to APs can cause physical damage to both animal and human tissues by inducing immune dysregulation, oxidative stress, dysfunctional proteins and enzymes, stress, and altered responses to food.

Previous studies have measured AP concentrations in bivalves, as well as the guts of fish and shellfish. However, it remains unclear how AP contamination affects commercial finned fish intended for human consumption.

About the study

The researchers of the current study quantified AP levels present in edible tissue from several seafood species that are economically, historically, and culturally important in Oregon. These species included black rockfish, lingcod, Chinook salmon, Pacific herring, Pacific lamprey, and pink shrimp, with varying trophic levels and feeding modes.

The goal of the study was to evaluate AP concentrations across trophic levels and identify potential sources of contamination. AP levels in fish from national and state government fishing vessels were compared to those present in fish caught by commercial vessels.

Types of APs

Of the 182 collected samples, 122 were finfish and 60 shellfish. Edible tissue samples were isolated and microscopically analyzed, which led to the identification of 1,806 suspected APs. A total of 230 APs were subsequently subjected to micro-Fourier transform infrared (μFTIR) spectroscopy.

Fibers comprised 82% of APs, followed by 17% for fragments and 0.66% films. About 70% of fibers were white or clear, whereas 13% each were blue or black. The average length of the AP fibers was between two and 3.62 μm.

Approximately 17% and 9.5% of AP fibers were synthetic and semisynthetic, respectively, and consisted of various materials including PET, fiberglass, semisynthetic cardboard, and HDPE, with only 8% of these fibers considered natural.  

Universal contamination

About 99% of the collected samples contained APs, with the highest number of APs for each organism present in pink shrimp. In fact, the highest number of particles in all species and across both sources was in five grams of pink shrimp purchased at a retail outlet, which contained 36 APs.

Chinook vessel-retrieved samples exhibited the lowest number of APs ranging from one to 11 APs for each fish, which reflected a mean concentration of 0.028 AP/g. Finned fish species had varying AP concentrations at 0.02-1.08 AP/g of muscle tissue.

Vessel-retrieved and retail samples of pink shrimp had 25 and 36 APs for each organism, with mean AP concentrations of 10.68 AP/g and 7.63 AP/g, respectively. Lingcod retail samples exhibited higher AP numbers and concentrations at 7.33 APs/individual and 0.09 AP/g, respectively, than 3.91 AP observed for each vessel-retrieved sample at a concentration of 0.022 AP/g.

AP contamination may occur during post-catch processing; however, ambiguous results were obtained across all seafood categories, thus indicating the need for further investigation.

Pacific lamprey

AP concentrations in Pacific lamprey were dependent on the catch site. For example, riverine lamprey exhibited approximately one AP/g as compared to 0.60 AP/g in ocean-phase adult lamprey.

Riverine lamprey are an endangered species; therefore, it is crucial to clarify how AP exposure affects this risk. Riverine lamprey are also considered a culturally valuable food source for indigenous people in this area, thus emphasizing the social significance of regulating AP exposure and reducing the potential risks of consuming contaminated fish in these these communities.

Risk factors for AP contamination

Color, shape, and size also affect AP ingestion by aquatic organisms and their translocation into muscle tissue. For example, the smaller the organism, the greater AP burden present in muscle tissue, thus revealing the inverse relationship between trophic level and AP concentration reported in other studies.

Current AP pollution loads in the environment have reached a level irreversible by current technologies.”

New measures are being studied to prevent the entry of APs into the environment, such as prohibiting virgin plastic production, microfiber capture from laundry machines, monitoring AP concentrations in water and air, as well as regional or national policies. Single and multi-generation studies of exposed individuals are essential to understand the impact of these particles on current and future health.

Conclusions

The study findings demonstrate the significant presence of APs in commercially important finfish and crustaceans along the coast of Oregon. Importantly, the sample size was small, which may limit the generalizability of these findings. Thus, additional research is needed using samples obtained along a greater proportion of the West Coast to explore the spatial distribution of APs in aquatic species.

These findings suggest a need for further research into technologies and strategies to reduce microfiber pollution entering the environment.”

Based on these observations, researchers recommend replacing current food containers with those made from natural packaging materials and purchasing whole local fish to minimize the risk of contamination from processing.