Cows, coal, copper and cereals: what’s the deal with selenium?

Mine opponents will often leave the impression that “any selenium is toxic,” or say that “selenium cannot be managed,”. As a result, selenium is often presented as an inevitable, unmanageable environmental risk and a central reason to oppose new mines.

So the question is: are these claims true? What does the science tell us?

Selenium is a naturally occurring element found in some coal-bearing rocks and other mineral deposits, particularly where sulphide minerals are present. It is present in trace quantities in some sedimentary rocks, particularly those containing ancient organic materials, as plants can absorb selenium and have done so for hundreds of millions of years.

And it is this rock’s exposure to air (oxidation) and water — largely not the coal itself — that is the primary mechanism of soluble selenium that may make its way into the biosphere.  This exposure occurs naturally in the Rockies through erosion and precipitation, but mining can serve to accelerate this process which is why it is a management issue, and something miners take seriously.

In short, mobile, soluble selenium is produced via exposure to oxygen and so reducing the selenium-bearing rocks’ exposure to air and water can significantly limit its release to the environment (more on this later) and reduce concerns about it.  

Not surprisingly, but little known, Selenium isn’t limited to coal mining.  As it likes to hang around with sulphur (they behave in a very similar way chemically), it is also a trace element in zinc, copper, lead, gold and other sulfide-hosted minerals and is a by-product during smelting or refining.

Soluble selenium can also be liberated through other activities, such as agriculture, urbanization (eg. Wetland disturbance), wastewater treatment, and other industrial activities.

Interestingly, Canada is a top world producer of selenium for industrial and consumptive uses. For example, selenium is important for dandruff shampoo and health supplements like vitamins.

Selenium is an essential micronutrient that supports neurological, reproductive, immune, and other important bodily functions. When selenium intake is too low, human health can be impaired.

At levels where humans typically encounter selenium, such as through normal food and water consumption, it isn’t toxic. And in the case of humans or livestock it would take extraordinarily high levels to approach toxicity. Health Canada lists the upper limit for humans at ~400 µg/day. While the average daily intake for neurological, reproductive and immune functions is 45 µg/day. It is worth noting that modern mining operations are subject to regulatory oversight. Modern mines and proponents of new operations have wastewater management requirements, monitoring programs and water quality guidelines that they must meet, and these include protecting human health and the environment. In terms of livestock, a cow would need to drink approximately 1,000 litres per day of fully compliant mine release water just to meet its daily selenium needs.  In Alberta, coal mine wastewater management is managed through EPEA approvals and the Alberta coal mining wastewater guidelines, while in British Columbia, mine effluent discharges are managed under the Environmental Management Act as well as provincial water quality guidelines.

Anti-coal mine groups often operate in a selenium gray zone, making claims that people or livestock are at risk from selenium, but never communicating what they believe that selenium risk level to be if a mine is constructed. One could very credibly call this at best a scare tactic. The reality is that selenium is more prevalent in our lives than many realize.