Information on the occurrence of contaminants of emerging concern (CEC) in the aquatic ecosystems that North American indigenous communities depend on is scarce. Given the particular importance of these ecosystems for food and economic security of indigenous communities, assessing the presence of contaminants becomes very important. Therefore, we wanted to highlight an excellent study  by a group of researchers from the University of Minnesota, the Grand Portage Band of Lake Superior Chippewa, Minnesota Pollution Control Agency (MPCA), US EPA, Hokkaido University and SGS AXYS (Dr Coreen Hamilton) that provides key initial CEC occurrence data in the water, sediments and fish across the watershed. The researchers characterized their objectives as follows:
“To address the gap in knowledge regarding the distribution of CECs in rural and tribal areas, we surveyed water, sediment, and subsistence fish species within tribal lands and adjacent territory, much of which is within the watershed of the largest freshwater lake in North America, and assessed the presence of contaminants across varying anthropogenic pressures: waterbodies with no human development along their shorelines, those with development, and those directly impacted by wastewater effluent. This initial study characterizes the distribution of CECs across key waterbodies for subsistence fishing on tribal lands in and near the Lake Superior watershed.”
The researchers selected 28 sites across the period between 2016 to 2018 within the Grand Portage Indian Reservation and 1854 Ceded Territory in northeastern Minnesota. Sites varied by level of human impact based on wastewater effluent impact and human development impact. The researchers decided to understand levels of the CEC in water, sediment and fish to get a more complete picture of overall exposure.
SGS AXYS methods for pharmaceuticals and personal care products (PPCPs by MLA-075) were used in this study to generate the occurrence data. As the originators of EPA Method 1694, SGS AXYS has pioneered in the measurement of a large list of PPCPs and has, since the validation of 1694 in 2007, extended the method’s capabilities significantly to cover more targets and more matrices including passive samplers and tissue. In this study, 158 PPCPs and hormones were analyzed by SGS AXYS. The list covers a variety of analgesics, antibiotics, anti-asthma drugs, chemotherapy agents, X-Ray contrasting agents and more to generate comprehensive and low-reporting limit occurrence data in the ambient environment and in wastewater treatment plants. The method uses multiple LC-MS/MS runs with isotope-dilution and surrogate standard quantification as well as customized extractions for each matrix type to maximize breadth and quality of data.
For the water analysis, polar organic chemical integrative samplers (POCIS) were used in order to get an integrated estimate of occurrence in the water. As the researchers mentioned in the study:
“(POCIS) passive samplers used to collect a time integrated sample for potentially bioavailable hydrophilic organic chemicals that is more representative (than grab sampling) of what aquatic organisms are exposed to over a given time period and covering several precipitation events. POCIS sampling represents respiratory exposure of aquatic organisms to dissolved chemicals and can be used to determine a time-weighted average concentration of water-soluble organic contaminants.”
For the fish monitoring, the researchers selected both food subsistence and recreational fish from multiple trophic levels including walleye, yellow perch and lake trout.
Of the 158 PPCPs targeted, 117 were detected in at least one of the three matrices, and summarized in the image from the journal article below. The advantage of time-averaged POCIS data for the aqueous data is evident from the water detects data. Wastewater treatment plant impacted sites had the highest concentrations of the PPCPs monitored. The researchers grouped all CEC into 23 primary use categories from pharmaceuticals to insect repellent (DEET). Across all media, DEET was the most ubiquitous find, but prominent pharmaceuticals such as anti-depressants amitryptyline, sertraline, venlafaxine and fluoxetine, antimicrobials like enrofloxacin and miconazole, anti-diabetics such as metformin were detected across all compartments. Many hormones including those used as oral contraceptives were detected in most sites. Therapeutic classes of particular concern, such as antimicrobials, antineoplastics (chemotherapy agents) and cardiovascular modulating agents, were found at occurrence frequencies of more than 35%.In fish, DEET, hormones, antimicrobials, antidepressants and antineoplastics were all detected. X-Ray/CT contrasting agents iopamidol and diatrozoic acid were both commonly detected (15%). While levels are low, the researchers note that even some of these low levels have been shown in several studies to disrupt fish metabolism and behavior.
The advantage of monitoring across all these matrices is evident from the different patterns seen in POCIS and fish tissue samples. In the fish, it is expected that only lipophilic and pseudo-persistent compounds would be found, whereas the POCIS data picks up water soluble PPCPs. The researchers found that using simple properties such as the octanol-water partition coefficient (LogP) were insufficient to predict occurrence. This further underscores the importance of measuring across multiple matrix compartments for comprehensive assessments.
In conclusion, the researchers note that:
“The detection of CECs in remote, undeveloped locations, where subsistence fish are harvested, raises scientific questions about the safety and security of subsistence foods for indigenous communities. Further investigation is warranted so that science-based solutions to reduce chemical risks to aquatic life and people can be developed locally and be informative for indigenous communities elsewhere.”