Contaminants in fish from U.S. rivers: Probability-based national assessments

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Public Health

Background:

• Fish consumption advisories in the U.S. primarily address mercury and PCBs.
• Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants of concern for fish consumption.
• Assessing national-scale contamination in river fish is crucial for public health protection.

Purpose of the Study:

• To characterize mercury, PCB, and PFAS contamination in U.S. river fish on a national scale.
• To estimate the extent of river systems with fish tissue concentrations exceeding human health screening levels.
• To inform fish consumption advisories by providing national distribution estimates for key contaminants.

Main Methods:

• Utilized an unequal probability survey design for national fish sampling in rivers (≥5th order) during 2013-14 and 2018-19.
• Collected and analyzed fish fillet samples for total mercury, all 209 PCB congeners, and up to 33 PFAS, including PFOS.
• Applied fish tissue screening levels to national contaminant probability distributions to estimate exceedance percentages.

Main Results:

• All analyzed fish fillet samples contained detectable mercury and PCBs.
• PFAS were detected in 99.7% (2013-14) and 95.2% (2018-19) of samples.
• Exceedances of screening levels for average fish consumption were estimated at 23.5-26.0% for mercury, 17.3-51.6% for PCBs, and 0.7-9.1% for PFOS.

Conclusions:

• Mercury, PCBs, and PFAS are widespread contaminants in U.S. river fish.
• A substantial proportion of river systems have fish with contaminant levels that may pose risks to human health.
• Findings support the need for updated and comprehensive fish consumption advisories considering multiple contaminants.