As an ecotoxicologist with selenium risk management experience, and with a commitment to sound environmental protection, I appreciate Ross McKenzie’s efforts to raise awareness of selenium (More on selenium and its agricultural, environmental and human concerns, Grainews, April 8, pgs. 18-19). His article gives a perspective of potential selenium-related risks via the comparison of regulatory thresholds and guidelines. However, it requires greater balance when it comes to the broader context of his thesis pertaining to the likelihood of elevated selenium from coal mine effluent posing risks to irrigation or livestock water. When it comes to aqueous selenium guidelines, exceedance does not necessarily result in risk.
I agree with Dr. McKenzie that selenium is naturally-occurring, and that it is essential for animal and human health. It supports immune function, reproduction and antioxidant systems in livestock. In fact, selenium supplementation of feed is routine across the Prairies, especially in cattle operations where local forage may be selenium-deficient. For many producers, selenium is a nutrient to be managed, not feared. Selenium is also naturally present in soils across Western Canada. The natural variability of its occurrence reflects long-term geologic conditions, and not recent human activity. Plants don’t require selenium, but they absorb it passively, especially in areas with well-oxygenated, alkaline soils. When selenium uptake is properly monitored, forage and food crops remain safe and sustainable for both livestock and consumers.
Unfortunately, McKenzie makes a giant leap that is not based on data or evidence. Without any case studies or real data from an Alberta coal mine, McKenzie extrapolates from hypothetical selenium accumulation scenarios to suggest that effluent from a potential coal project on the Eastern Slopes could have deleterious impacts to irrigated farmland, and possibly even drinking water. The 2010 irrigation water study cited by McKenzie (Little et al., 2010) reported that all samples met Alberta’s irrigation guideline of 20 µg/L (micrograms per litre), and the average selenium concentrations (of 607 samples) was just above the British Columbia and Alberta aquatic life guidelines. Even the highest reading (i.e., 10 µg/L) remained well within provincial and federal irrigation standards.
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As is often the case with recent anti-coal mining narratives, McKenzie neglects to cite current allowable selenium discharge limits for coal mining projects in Canada that are already well below thresholds that would pose risk to agricultural waters. British Columbia, for instance, enforces site performance objectives of below 10 µg/L for effluents discharging to diverse aquatic environments; this value aligns with British Columbia’s irrigation and drinking water guidelines and is half of Alberta’s irrigation guideline. This latter observation clearly indicates that protection of aquatic life downstream of a coal mine will necessarily protect other downstream receptors and users (e.g., livestock, humans).
McKenzie also does not mention any of the methods or technologies which make up the “multiple-lines-of-defence” approach employed by industry to mitigate and treat selenium in effluent. This is a crucial element, which needs to be taken into consideration. He extrapolates from elevated selenium in surface coal mine discharge to risks posed to the safety of irrigation water. If effluent downstream of an operating coal mine must meet a < 10 µg/L limit, then how will irrigation and drinking water — safe at higher concentrations — be affected and result in risk?
I assume McKenzie is suggesting coal mines will not comply with provincial permits, guidelines and regulations (note: federal coal mining effluent regulations are about to be issued). This is not a reasonable suggestion. Water quality from coal mines will always require monitoring and evaluation to ensure environmental protection; it must be held to high environmental standards. However, invoking speculative selenium accumulation scenarios to argue against development of an entire resource sector of great economic importance risks conflating hazard potential with actual risk. Scientific and regulatory tools exist to evaluate and manage selenium effectively. Blanket statements suggesting “devastation” of irrigated farmland are unhelpful and alarmist, especially when there is growing evidence of successful mitigation, evaluation and management.
Let’s continue to protect aquatic life, soil, food safety and drinking water, but let’s also ensure that our debates are based on current science, realistic exposure pathways, and an ethic of responsible development. Prairie producers are capable stewards of their land, and they deserve reliable and science-based information (e.g., the North American Selenium Working Group and Coal Association of Canada websites) that helps inform both policy and public dialogue.
Guy Gilron
Borealis Environmental Consulting Inc.
North Vancouver, B.C.
Editor’s note: We do welcome feedback and perspectives from readers. If you’ve something to say about anything you’ve read in Grainews or about Prairie farming, please submit your letter to the editor via email.
