By Tanya Shanoff and Justin Hains

We see that PFAS—or per- and poly-fluorinated alkyl substances—are showing up around the world. In Canada, regulators looking for the source of PFAS releases have focused mostly on manufacturing facilities, airports, and military bases. These are places where PFAS have been used for decades.

But recently, governments have started to look into PFAS releases from other types of industries, including mining.

We both live in Canada. And we’ve spent years helping clients investigate and remediate their sites, including mines and those containing contaminants like PFAS. Since there are many operating and abandoned mines in Canada, it’s worth examining what you should consider if you suspect PFAS at a mining site and what risks they pose, as well as how you can remediate related chemicals.

PFAS use in the mining industry has been long established. If there is suspected PFAS at a mining site, it’s wise to work with a consultant to investigate. Credit: Adobe/Stantec.

PFAS and environmental releases at mines

PFAS are a group of more than 4,700 man-made chemicals. They’re found in many products, from frying pans and water- and stain-resistant clothing to dental floss, food wrappers, and more. Evidence shows PFAS exposure can lead to adverse human and ecological health effects.

We are starting to see mines identified as potential sources of PFAS releases into the environment. For example, at the Sugar Camp mine in Illinois a firefighting material called aqueous film forming foam (AFFF) containing PFAS was used to fight an underground mine fire. It was unsuccessful. The fire burned for more than a month, contaminating nearby waterbodies and resulting in litigation.

In western Australia, BHP’s Mount Whaleback Iron Ore mine has been identified as the source of low-level PFAS in groundwater. The chemicals may threaten a nearby drinking water supply, prompting BHP to evaluate PFAS use across its site. Meanwhile, in Williamtown in eastern Australia, a sand mine has been exporting sand that has PFAS contamination that came from a nearby military base.

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The mining industry has used PFAS for years. It is used in industrial processes. These include ore floating, ore leaching in copper and gold mines, separation of uranium from ore and minerals, concentration of vanadium compounds, acid mist suppressing agents, and wetting.

PFAS can be found at mine sites due to the use of firefighting foam retardants that contain the harmful chemicals. Credit: Adobe/Stantec.

PFAS may also be present for secondary uses in mining operations. This includes AFFF for firefighting (including training), in concrete where PFAS was previously released, and in landfills and dump sites. Other sources can be cleaners for metal surfaces; foaming agents in drilling fluids, paints, and coatings; and the use of fluoropolymer in pipes, cables, hoses, and conveyor belts.

These potential sources of PFAS in the environment need management.

How PFAS exposure can happen at mining sites in Canada

Exposure to PFAS for humans, animals, and the environment can occur at Canadian mining sites and off site as well. A mining site’s location influences the contaminant routes of exposure. Off-site exposure could happen through PFAS in groundwater or through wind dispersion of PFAS molecules from sources like AFFF, a common source of PFAS. PFAS use in processing can cause the chemical to end up in effluent, tailings ponds, or landfills. PFAS treatment at these sites is unlikely.

PFAS exposure for mining site workers is easy. They may accidentally ingest soil, inhale dust or aerosols, drink potable water, or contact products containing PFAS. Similar exposure paths can occur to people living near the mining site, such as mining workers living in off-site camps. Others who face exposure include Indigenous communities, recreationalists, and hunters and anglers.

Plants and animals are vulnerable to PFAS in many ways. They can come in contact with PFAS through soil, on-site surface water, or sediment. Contaminated groundwater or off-site surface water are also sources, along with contaminated food sources.

Canada mining site sampling and characterization challenges

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Let’s briefly touch on three characterizations of PFAS at mining sites in Canada.

  1. PFAS behavior: How PFAS change and move within the mining environment can vary. PFAS include many compounds with different physical and chemical characteristics that control their behavior. They can persist for decades at mining sites, can bioaccumulate, and are regulated at extremely low concentrations (nanograms). Many industries have used them since the 1950s.
  2. Field sampling procedures and QA/QC: Although you should follow standard environmental sampling best practices, field sampling for PFAS have additional concerns. For example, PFAS can be found in some of the equipment and supplies typically used to collect environmental samples. This creates the potential for sample contamination. You should also store PFAS sampling materials separately from other potentially PFAS-containing sampling supplies.
  3. Laboratory QA/QC: Choosing a certified laboratory to complete PFAS analysis is key for accurate and reliable data. The lab should use appropriate containers to collect samples. Segregate samples with high concentrations of PFAS during sampling and shipment. Flag the samples so the lab can support the right preparation for analysis.

stantecs-hard-rock-miners-handbook.pdf

Mining workers can be exposed to PFAS through drinking water supplies and products used in the industry. Credit: San Xavier Laboratory/Stantec/Laszlo Bencze.

Remedial options for remote mines

Historical PFAS use may contaminate the drinking water that comes from groundwater at unsafe levels. Beyond the use of AFFF, treatment of process water at most mining sites doesn’t usually address PFAS. This means that PFAS can be discharged into the environment in treated process water and impact drinking water. It may also be present in soil at and around the mine site, or in the sediment of nearby water bodies.

As the main risk at mining sites, it’s wise to focus on soil and drinking water treatment technologies.

Consider the following treatment options for PFAS:

  • There are proven methods for treating water. They include options like sorption (using activated carbon), ion exchange, nanofiltration, reverse osmosis, and foam fractionation.
  • For soil and residual waste from water treatment, the best options are containing the chemicals in place or landfilling.
  • There are also emerging technologies that involve destruction of PFAS in water and soil. They are still in development.
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It’s important to note Canada mining sites are typically remote and can operate under harsh conditions. They face unique challenges. Power generation can be costly, and transporting PFAS-impacted treatment media for disposal off site is expensive. Also, sensitive specialized equipment can break down and on-site disposal of highly soluble contaminants like PFAS is not practical.

No PFAS regulation for mining sites yet

To date, there appears to be no official Canada PFAS guidelines for the mining industry. But many jurisdictions have produced regulated concentrations that could apply to soil and water at mining sites.

Regulators have developed standards and guidelines for surface water, drinking water, groundwater, and soil for up to 20 PFAS in Canada, the US, and globally. Drinking water is the primary route for human exposure at mining sites. For that reason, you should focus on water standards and guidelines that protect people.

Don’t ignore potential impacts and liabilities

If you suspect PFAS at your Canada mining site, it’s wise to work with a consultant to investigate for the chemicals and then develop a plan for remediation or risk management.

Many jurisdictions are advancing regulation around the use of PFAS and its presence in the environment. So, mining owners and operators need to think about the potential impacts and liabilities associated with PFAS use at their operations. If there are contaminants on your Canada mining site, the time to deal with the problem is now.

Tanya Shanoff is a senior hydrogeologist, federal sector leader of environmental services (Canada) and Justin Hains  is project manager and environmental scientist with Stantec.

Featured image credit at San Xavier Mining: Mining workers can be exposed to PFAS through drinking water supplies and products used in the industry. Credit: Stantec.

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