Above photo: Crowds gather on a bridge at the Issaquah Salmon hatchery to watch as salmon return to spawn.
A new study led by the Washington Department of Fish and Wildlife’s Toxics Biological Observation System unit explores an unseen threat to the Pacific Northwest’s Chinook salmon — chemical contamination.
Among the findings of this research — published online earlier this summer and in the October issue of the journal Environmental Pollution — is the discovery that a half-dozen “contaminants of emerging concern” are found in juvenile Chinook salmon throughout Puget Sound, indicating sound-wide exposure to these contaminants. In the Duwamish, the most developed watershed included in the study, 11 contaminants also exceeded thresholds indicating the potential to affect fish physiology, behavior, and fitness.
Chinook salmon are vulnerable to contaminants in part because of the time they spend in nearshore marine habitats and estuaries, areas that can be subject to high pollutant runoff. As these fish transition from freshwater to saltwater on their way to the open ocean, they undergo a stressful physiological change called smoltification, which heightens their susceptibility to other stressors.
Ultimately, WDFW researchers, in partnership with researcher James Meador of the University of Washington, found a cocktail of contaminants of emerging concern (CECs) in the sampled salmon. The CECs tested for include a mix of chemicals found in everyday products, stormwater, and wastewater, such as pharmaceuticals, personal care products, PFAS (‘forever chemicals’), and pesticides currently in use.
“The results of this study suggest that juvenile salmon are exposed to a variety of emerging contaminants as they migrate through urbanized river systems within Puget Sound,” said Molly Shuman-Goodier, WDFW research scientist and lead author on the study. “Many of these CECs have little to no previous data to describe their potential impacts on salmon or other marine life.”
The study detected dozens of these chemicals, including:
• Pharmaceuticals: Antibiotics like oxytetracycline and other substances like ibuprofen and caffeine.
• Personal Care Products: The insect repellent DEET and compounds found in soaps and cleaners.
• PFAS: So-called “forever chemicals” — used to waterproof clothing and as coating for non-stick cookware — that do not break down in the environment.
The study analyzed Chinook salmon from five Puget Sound watersheds — the Skagit, Snohomish, Green/Duwamish, Puyallup/White, and Nisqually. The data included samples collected over the course of a decade (2013–2023) representing Chinook less than a year old. WDFW tested these fish for up to 219 contaminants of emerging concern, including pharmaceuticals and personal care products, PFAS, pesticides currently in use today, and alkylphenols, which are found in everyday products like detergents and other household cleaners.
In all, six chemicals were observed to be ubiquitous in juvenile Chinook salmon collected across all five watersheds, including the alkylphenols 4-NP and NP2EO, X-ray contrast agent iopamidol, PFOS, oxolinic acid, and DEET.
In the region’s most urbanized watershed, the Green/Duwamish, 11 contaminants also exceeded biological effects thresholds, including the antibiotics oxytetracycline, tetracycline, and erythromycin-H20, the insect repellent DEET, and the pharmaceuticals metformin, ibuprofen, valsartan, norfluoxetine, citalopram, caffeine, and hydrocortisone.
Testing, monitoring, and regulation for most CECs in surface water is not required, making it difficult to assess their full impact on the ecosystem. However, by comparing the detected concentrations to existing data and models, researchers could infer some of the potential biological effects. Several of the detected chemicals, particularly pharmaceuticals, were at levels that could negatively impact the salmon’s physiology, behavior, or survival. For example, the study found antidepressants like citalopram and norfluoxetine, as well as caffeine, at levels that could alter fish behavior.
While the study revealed general regions where PFAS may be entering the studied waterways, identifying where these pharmaceuticals and personal care products are entering the watersheds proved much more difficult, suggesting they may be largely entering the water through multiple generalized inputs, like stormwater runoff or wastewater.
To protect threatened salmon species and promote population recovery efforts, the study authors recommend continuing efforts to identify the sources of these varied contaminants, alongside strategies to remove or reduce CECs in stormwater and wastewater. WDFW is among the organizations working to better understand the varied ways contaminants enter and concentrate in the waters of Puget Sound, as well as identifying methods to address contamination.
“There’s a large gap in understanding how and where these contaminants are entering our waterways, which makes the problem difficult to address,” said Shuman-Goodier. “By identifying which contaminants are present and at potentially concerning levels, we can help prioritize where to focus future research and management actions.”
Additionally, the 11 CECs identified as a potential concern could be prioritized for future research to clarify the impacts on salmonid growth or survival.