Selenium has become a prominent and contentious topic in discussions about mining and environmental protection. Public debate, regulatory scrutiny and media narratives have intensified, often without a shared understanding of the underlying science. In some cases, this single element exerts more influence on permitting, operations and profitability than the commodity being mined. 

I spend a lot of time thinking about selenium (after all, it is my favourite element). I have spent more than 15 years advancing scientific research and water treatment technologies to better understand selenium. Over that time, several aspects of its regulation have come to stand out to me as unresolved and increasingly difficult to justify. 

Selenium is a required dietary micronutrient for humans and animals alike. It is also one of the few elements where the line between “necessary” and “harmful” is narrow, context-dependent and still poorly defined. At elevated concentrations, selenium can be problematic for egg-laying aquatic vertebrates such as fish, salamanders and turtles. In some cases, it can bioaccumulate through the food web into higher-level egg-laying vertebrates such as birds that eat fish. The precise threshold where selenium shifts from acceptable to problematic is not only animal specific, but ecosystem dependent. 

In response, policy has largely defaulted to a precautionary posture: less is better. That position is understandable. What is more difficult for me to reconcile are the inconsistencies that have accumulated around it. 

First, there have been orders of magnitude more fish killed in laboratories and field studies to investigate the potential effects of selenium than have been demonstrably harmed  by environmental selenium exposure itself. At this point, it  could be argued that we are killing more animals than we  are helping. 

Could the means justify the end? Perhaps, but in the decades this has been ongoing, that has yet to be seen. 

Second, selenium guidelines are often described as being science-based. If that is true, then the way they are applied should be coherent. They are not. In Canada, mining is regulated more stringently than other industries that release selenium into the environment, and even then, coal mining is treated differently from metal and diamond mining. 

Interestingly, municipalities are generally exempt from comparable scrutiny of the sewage or stormwater they discharge into the environment, both of which are known to contain selenium. Moreover, the beef and dairy industries, which are known to have extremely high selenium discharges (driven in part by the intentional addition of selenium to cattle feed for animal health), are typically not required to monitor selenium at all, let alone manage or treat it. 

If the mechanism of concern is bioaccumulation through food webs, then regulation should follow exposure pathways, not industry labels. The current frameworks do not. 

If the science is settled, this variability makes little sense. If the science is unsettled, the confidence embedded in enforcement is difficult to explain. 

In practice, selenium regulation is often driven by lobbying and management of perceived reputational risk, rather than by science or demonstrated potential for environmental harm. 

Third, public narratives around selenium risk have increasingly drifted from evidence. 

For example, in Alberta, we have recently seen a rising spread of intentional misinformation that selenium from mining threatens cattle and agriculture. Yes, the very cows that are receiving selenium supplements with their feed. A cow would need to drink roughly 1,000 litres per day of fully regulatory-compliant mine water just to meet its basic nutritional selenium requirement. That is not physically possible. 

These narratives persist anyway, creating fear that shapes public perception and policy long after they have detached from plausibility. 

Finally, increasingly stringent selenium limits placed on the mining industry drive demand for complex water treatment systems. That demand is rarely framed as the trade-off that it is. 

Every water treatment process requires chemicals. Every process generates waste. Every system consumes energy. The risks and impacts from these processes are real, and they must be weighed against the actual environmental benefit achieved, not against hypothetical or exaggerated harm. 

This does not even account for the tens to hundreds of millions of dollars mines spend on the construction of selenium treatment facilities, or the millions spent on annual ongoing operations. 

After decades of research, regulation and investment, the gaps between evidence, application and outcome are too large to dismiss as noise. 

I wrestle with that reality, because systems that stop reconciling inputs and outputs rarely correct themselves. The real question is not whether or not selenium carries risk. It is whether environmental attention and capital are being directed towards scientifically defensible outcomes or towards lobbying and optics. 

Progress requires setting emotion aside and examining trade-offs honestly. Scientists are required to publish their methods, assumptions and limitations. Anyone shaping selenium policy should be held to the same standard. 

Monique Simair, PhD, is a biogeochemist specializing in mine water management and treatment. She continues to do advisory work in this space, while serving as the inaugural director of the Slogotski Hunt Centre for Entrepreneurship at the University of Saskatchewan.