Arsenic Speciation in Alberta Freshwater Fish
Creators: Lau, Chester J
Publisher: name: University of Alberta Library
Year: 2024

<p>Arsenic is a naturally occurring element widely distributed throughout the environment. Natural and anthropogenic processes can mobilize arsenic from the earth crust and introduce arsenic into waterbodies. More than 200 arsenic species exist in the environment and biological systems. Toxicological profiles of arsenic species depend on their chemical forms (structures) and oxidation states. While inorganic arsenite (iAsIII) and arsenate (iAsV) have been implicated in many neurological and cardiovascular complications, as well as cancers of the lung, bladder, and skin. On the other hand, exposure to arsenobetaine (AsB) is considered non-harmful. Therefore, arsenic speciation is crucial for assessing potential health risk arising from exposure to arsenic. <br>
Fish is an excellent source of essential nutrients for people worldwide. Fish uptakes inorganic arsenic species from water and metabolizes them into various organic forms of arsenic. Previous research on arsenic speciation in fish is largely limited to marine fish, partly due to the relatively higher concentrations of arsenic species present. The quantification of arsenic species in freshwater fish is more challenging due to low concentrations of arsenic species, requiring techniques with appropriate extraction procedures, efficient separation capability, and sensitive detection. The first objective of this thesis project was to develop an analytical method enabling the determination of arsenic species in freshwater fish. Fish samples underwent extraction using a 1:1 (vol/vol) methanol/water mixture as solvent, followed by sonication and centrifugation. Arsenic species in the extracts were separated using anion-exchange high-performance liquid chromatography (HPLC) and detected using inductively coupled plasma mass spectrometry (ICPMS). HPLC efficiently resolved AsB, iAsIII, dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), iAsV, and three new arsenic species in 19 min. A series of experiments were conducted to validate the analytical method and confirm the accuracy of the results. The limit of detection of the method was 0.00025 mg arsenic per kilogram fish tissue (mg/kg) for all five targeted species: AsB, iAsIII, DMA, MMA, and iAsV. <br>
The developed HPLC-ICPMS method was applied to the analyze arsenic species in more than 1400 freshwater fish samples representing 14 common fish species from 48 waterbodies in Alberta, Canada. Arsenobetaine, DMA, and iAsV had the highest detection rate among fish samples that were analyzed. Seven unknown arsenic species were detected, of which at least one unknown arsenic species was detected in more than 50% of fish samples. The concentration of unknown arsenic species could make up as much as 94% of the sum of arsenic species in some fish samples. This study revealed significant variations in the concentrations and arsenic speciation patterns among individual fish samples, indicating biological variability. There were differences in arsenic speciation patterns between lake whitefish, northern pike, and walleye fish samples. Lake whitefish samples collected from Cold Lake had elevated levels of AsB and sum of arsenic species relative to samples from other lakes. <br>
An assessment of arsenic species intake suggests that moderate consumption of freshwater fish from Alberta waterbodies does not cause significant exposure to toxic arsenic species. However, future research is necessary to elucidate unknown arsenic species and to determine additional factors that affect arsenic species patterns and concentrations. The results of this thesis work will contribute to the development of meaningful consumption guidelines that protect the public from excess exposure to toxic species of arsenic.</p>