Cover photo: A Mad Tea-Party by Lewis Carroll with the Hatter, March Hare and Alice.

It turns out that using a lot of mercury, as human beings have done for centuries — in everything from haberdashery to gold production to medicine — wasn’t such a great idea after all.

Although this realization came only in the last half of the 20th century, there were signs long before that that mercury was dangerous. The term “mad as a hatter” came from the crippling neurological syndrome that hat-makers suffered after breathing vapours from the mercury nitrate they used to cure felt in the 18th and 19th centuries.

The technical term for the syndrome is erithism mercurialis. But in the 1950s mercury poisoning became known as Minamata disease, named for the bay in Japan where mercury-contaminated wastewater poisoned thousands of people.

After that, the awful truth emerged that the heavy metal, once considered harmless and extremely useful, actually poses a global threat to human health and the environment.

Mercury is on the Canadian government’s list of toxic substances, regulated by the Chemicals Management Plan under the 1999 Canadian Environmental Protection Act.

The list of health effects of mercury poisoning is long and horrific, including degeneration of the nervous system, damage to the immune and digestive systems, lungs, kidneys, skins, and eyes. Even small amounts are a threat to the development of the child in early life and even in utero. Mercury’s health effects are “crippling, untreatable and stigmatizing.” It often causes death.

Nearly six decades after the Minamata tragedy, the global community finally decided it was time to try to “Make Mercury History” with the Minamata Convention on Mercury, a binding international treaty “to protect human health and the environment from the adverse effects of mercury” by limiting emissions and releases of mercury from human-made sources.

In 2017, Canada ratified the Minamata Convention, which now has 128 signatory countries.

The convention requires signatories to “develop appropriate strategies for identifying and assessing sites contaminated by mercury or mercury compounds,” and “adopt guidance on site identification and characterization, engaging the public, human health and environmental risk assessments, options for managing the risks posed by contaminated sites.”

Nova Scotia has a particular interest in trying to do these things. The province has some of the highest levels of mercury contamination in Canada, some naturally occurring, others not.

Nova Scotia has a mercury problem

In 2013, scientists from Saint Mary’s University – Professor Linda Campbell, David Depew, and Neil Burgess – analysed more than 230,000 records of fish from lakes and rivers across Canada, and developed the first-ever national map of mercury concentrations in the common loon and in fish species that eat other fish. [1]David Depew, Neil M Burgess & Linda M Campbell. Spatial patterns of methylmercury risks to common loons and piscivorous fish in Canada. Environmental Science & Technology. DOI: … Continue reading

They found that mercury concentrations increased from the west to the east, which Campbell said raised “an environmental red flag for the Atlantic provinces, our sport fish, and fish-eating birds like the common loon.”

The Depew Burgess Campbell mercury map.

Lakes in Nova Scotia tend to be acidic because of the geology, and elemental mercury is more likely to transform into the extremely toxic methyl mercury in acidic aquatic conditions.

Mercury is particularly dangerous. It doesn’t just bioaccumulate, or build up in living tissue, as do other heavy metals such as arsenic, cadmium, chromium, and lead. Rather, mercury biomagnifies, which means it increases in concentration as it is consumed by organisms and moves its way up the food chain.

Mercury is found extensively in historic gold mine tailings in the 64 gold mining districts in the province.

Nova Scotia underwent three gold rushes between 1861 and the 1940s, and scientists from the Geological Survey of Canada report that about one ounce of mercury was used to recover each ounce of gold in a process known as “amalgamation.” [2]Parsons, M.B., LeBlanc, K.W.G., Hall, G.E.M., Sangster, A.L., Vaive, J.E., and Pelchat, P., 2012. Environmental geochemistry of tailings, sediments and surface waters collected from 14 historical … Continue reading

Given the total reported past gold production of 1.2 million ounces, the federal scientists estimate that between 3.7 and 9.1 tonnes of mercury may have been lost to the tailings or the atmosphere as “a direct result of gold milling in Nova Scotia.” They say this is a minimum figure because “gold production at most mines was routinely under-reported to avoid paying royalties to the Province.”

Display at a mining museum in Moose River. Photo: Joan Baxter
A 1937 mine office near Upper Musquodoboit. Photo: Joan Baxter

The mine wastes — tailings laced with mercury, arsenic, and other toxic substances — were generally allowed to run off into rivers, swamps, lakes, and oceans. However, until scientists began looking at legacy mining sites between 2003 and 2006, almost nothing was known about toxic contaminants in aquatic environments in these mining districts, and the risks they posed to ecological and human health.

A map of historic gold mines in Nova Scotia. Click to enlarge.
Photos of mine tailings. Source: Nova Scotia Department of Environment

The Geological Survey of Canada has looked at 14 former gold mines. Linda Campbell’s research team from Saint Mary’s University has been looking at a few others.

The Saint Mary’s researchers have been studying bioaccumulation of mercury in invertebrate species in wetlands around tailings from legacy mines sites. They have found that these key species have the highest concentrations reported for invertebrates in the province, compared with those in wetlands not affected by legacy mining, and with results from other published studies done in Nova Scotia and in New Brunswick.

“This concerns us because aquatic invertebrates are fundamental to ecosystem health,” says Campbell. “[The invertebrates] form the base of a larger food web which leads to sport fish, migratory song birds, bald eagles and even little brown bats.”

“We don’t quite fully understand the ecological and environmental health implications in Nova Scotia,” she adds. “[We] need more resources to better assess the risks and threats from such elevated mercury entering our environments.”

Campbell notes that these elevated mercury concentrations in living aquatic invertebrates around historic gold mine tailings are some of the highest she’s ever seen, including in far-flung places she’s worked such as East Africa, China, and South America.

But human-made sources of mercury in Nova Scotia are not limited to old mining sites or atmospheric pollution. There is also plenty of mercury on the Canso Chemicals property in Pictou County.

Contamination at Canso Chemicals

As the Halifax Examiner reported on March 7, in “The Canso Chemicals mystery – With the chemical plant long gone, why is the company still alive? And what about all that mercury?,” there is mercury contamination on site of a former chlor-alkali plant on the Canso Chemicals property, right beside the Northern Pulp mill and the site where the mill is proposing to construct a new “activated sludge treatment” plant for its effluent.

The Canso Chemicals plant opened in 1970, and for the next 22 years used large amounts of mercury to produce chlorine and caustic soda for the pulping process. According to a Canadian Press report of June 20, 1977, provincial and federal government officials had been unhappy with high levels of “unaccountable mercury losses” from the Canso Chemicals plant, causing the provincial environment department to order the company to sharply reduce the losses.

“The plant’s annual unaccounted mercury losses have averaged several tons [a year] since reporting to the federal environment department began in 1972. It reached a high of five tons in 1975,” says the CP report.

When the pulping process was changed because of new pulp and paper effluent regulations in Canada, the Pictou County pulp mill switched from chlorine to chloride dioxide for its bleaching process, and the chemical plant was no longer needed. It closed in 1992.

The subsequent decommissioning program lasted eight years. During that time, mercury-contaminated soil and bedrock were excavated to a depth of eight metres, and placed in a “secure landfill” on the property, along with contaminated materials from the cell room, brine basement structure, and the process building after they were demolished. The landfill was designed “to federal hazardous waste disposal guidelines with a double liner system, leak detection and leachate [liquid that may pass through the liner] collection and removal sumps.”

Contaminated “brine sludge” was placed in another landfill nearby.

Then the remediation team discovered there was more mercury deep underground. According to the 2000 “Canso Chemicals Site Decommissioning Final Report” prepared by Dillon Consulting, in 1999 the consultants found that “elemental mercury had migrated into the bedrock below the former cell room,” and formed a mass measuring “18 m wide and 10 m deep [no length was given],” and how much deeper it went was “uncertain.”

According to the report, the underground mercury mass was about five metres below the water table, so it had the potential to dissolve into the groundwater and “migrate towards Pictou Harbour.” Modelling done at the time suggested the migration could take up to two centuries, but there is no mention of testing of that modelling for the site.

The report also states that monitoring wells nearby found mercury levels exceeding Fresh Water Aquatic Life guidelines.

It notes that the mercury in the bedrock could not be excavated, as it was deeper than eight metres. To attempt to do so could have affected remaining buildings (the Canso Chemicals administrative maintenance building remains to this day), and risked “increasing the areal extent and depth of mercury impact due to mercury’s physical properties.”

In other words, they didn’t want to touch the mercury mass lest they cause it to spread outwards and downwards.

So it’s still there.

Is Nova Scotia managing the risks?

Even from deep underground, mercury poses a threat to those on the surface. The decommissioning report for Canso Chemicals states that mercury monitoring of the site should ensure that mercury vapours from the underground deposits do not migrate “into the air of the current building or any future building placed on-site.”

It stipulated that there should be regular mercury monitoring of the site.

Nova Scotia Environment (NSE) confirmed to me that the monitoring has been going on for 20 years, but before the March 7 Halifax Examiner article on Canso Chemicals was published, had not replied to other questions about the site.

NSE spokesperson, Adèle Poirier, has now provided some answers.

The annual mercury monitoring, she specifies, is done at the secure landfill site where the mercury-contaminated soil, bedrock, and materials from demolished buildings are stored, and at the site of the former buildings.

Upper photo is an aerial shot of the Northern Pulp Mill from the environmental assessment for the proposed effluent pipe, showing the proposed facilities related to the effluent pipe. The lower photo is a Google Earth view of the same location, but with annotations showing the proximity of the mercury contamination (as related in the Dillon Report) on the Canso Chemicals property and the proposed effluent treatment facility; annotations provided by Michael Jensen.

Nova Scotia Environment doesn’t do the monitoring itself. Rather, Poirier says:

The property owners, Canso Chemicals (whose parent company is Olin Corporation) is required to pay for a third party consultant to complete the monitoring and submit it to us.

Poirier adds that NSE requires Canso Chemicals to advise the department if their “monitoring shows that mercury levels exceed the levels established for the site,” which are contained in the decommissioning report.

Poirier also provided a copy of the “Certificate of Compliance” issued by Nova Scotia Environment in 2005, as part of the management of contaminated sites in the province. It states that Canso Chemicals agreed to document the site conditions on its property deeds, and that the adjacent landowner (at that time Kimberly-Clark and now Northern Pulp) had been notified of the “site conditions.”

The certificate also requires that the future “development and use of the entire Canso Chemicals Limited site is limited to commercial and/or industrial uses (i.e., no residential use or development of the property will be permitted.”

Public left in the dark

Results of the monitoring done for provincial compliance are not available without a freedom of information request, so the public is not entitled to know whether the mercury contamination on the site has changed over the past 20 years.

The modelling used by Dillon back in 1999 predicted that the mercury “plume” from the underground mercury mass could take two centuries to reach Pictou Harbour, but there is no evidence that this model has been tested for the site.

Given the extreme risk of mercury in aquatic systems, one might expect the province to be already monitoring Pictou Harbour for mercury. Not so.

According to NSE spokesperson Adele Poirier:

Monitoring is conducted in the projected path of the plume, however, there is no monitoring in Pictou Harbour because there is no evidence to warrant such monitoring.

Asked whether there is any monitoring for mercury being done on the Northern Pulp property that is adjacent to the contamination at the Canso Chemicals site and on the projected path of the mercury plume, the same spokesperson replied, “No.”

Nor was she able to shed any light on whether the province was concerned about the proximity of the mercury contamination to the site of Northern Pulp’s proposed effluent treatment facility, saying that it is “not appropriate” to comment while the environmental assessment process is underway for the project.

As the Halifax Examiner reported here, the mercury contamination was not even mentioned in the documents that Northern Pulp submitted to Nova Scotia Environment for the environmental assessment of its new treatment facility adjacent to the Canso Chemicals property.

According to Olin Corporation filings to the US Securities and Exchange Commission, as of December 31, 2018, Olin owns only 50% of Canso Chemicals, and Northern Pulp owns the other 50%. Paper Excellence / Northern Pulp has two people on the Canso Chemicals Board. This means that Northern Pulp should have full knowledge about the mercury monitoring that goes on next door to the mill on Abercrombie Point.

Graphics and maps in Northern Pulp’s environmental assessment (registration document 1-7-1) indicate that the primary clarifier basin will have a water depth of 5.5 metres, and by my estimate, be located between 100 and 150 metres from the underground mercury deposit, and between 50 and 100 metres from the remaining Canso Chemicals building.

This raises some important questions: Has Northern Pulp examined the potential risks of constructing the basin in this area? Is any testing planned, should approval be granted to the project, to ensure there is no mercury contamination in the groundwater in the area where the new treatment facility is proposed?

I asked the Northern Pulp / Paper Excellence Communications Director and Northern Pulp’s media contact about this but have not received a reply.

“Thank you for your donation”

Canada has its own egregious history of Minamata disease and environmental racism among the people of the Grassy Narrows and Wabaseemoong First Nations, who live downstream from a paper mill site on the Wabigoon River, near Dryden, Ontario. A 2015 study shows more than 90% of those First Nations populations have symptoms of mercury poisoning.

That issue is far from being resolved; Grassy Narrows First Nation recently protested at a Liberal Party fundraiser in Toronto, demanding that the Trudeau government fulfill promises to fund a specialized mercury treatment facility for their community. Prime Minister Justin Trudeau later had to apologize for a snide “thank you” he offered the First Nation protestor for her “donation” to the fundraiser.

Like the contamination on the Canso Chemicals property beside the Northern Pulp mill in Nova Scotia, the mercury at the site of the former Reed Paper mill, currently owned by Domtar, was buried on the property decades ago. The mill also dumped its effluent into the Wabigoon River, which in turn contaminated fish with mercury, and led to mercury poisoning among First Nations residents who ate the fish. Because the government of Ontario indemnified the mill in 1979, industry cannot be held responsible for monitoring the mercury contamination.

In 2013, Canada participated in negotiations that led to the Minamata Convention on Mercury, according to Environment and Climate Change Canada (ECCC), and ratified the legally binding treaty in 2017.

Some of the things the convention addresses are “interim storage of mercury and its disposal once it becomes waste, sites contaminated by mercury as well as health issues.”

In its mandatory reporting to United Nations Environment (UNEP) on its compliance with the Minamata Convention, the Government of Canada states:

Canada has information on individual stocks and sources of mercury or mercury compounds and will continue to have the ability to seek this information in future. Canada’s last mercury-cell chlor-alkali facilities closed between 1990 and 2008, and have all been safely decommissioned. All mercury resulting from the decommissioning of these facilities was sent for appropriate treatment as waste.


Canada has well-established federal, provincial and territorial programs to identify, assess, remediate and risk manage contaminated sites, including those contaminated by mercury or mercury compounds.

Nevertheless, the federal government’s Federal Contaminated Sites Inventory appears to include only federal lands, and the Canso Chemicals property does not appear on the inventory for contaminated sites in Nova Scotia.

As for the convention’s Article 17 on “information and exchange,” the Canadian government reports to UNEP that:

Canada provides its citizens with public information awareness and education related to mercury and mercury compounds in numerous ways, most of which are accessible on-line. This information has been and will continue to be disseminated through media interviews, assessments, reports, posters, fish consumption guidelines and / or advisories, public consultations, and journal publications.

Sounds good, doesn’t it?

Too good to be true, in fact. I’ve not had any luck getting any information out of Environment and Climate Change Canada on the mercury contamination at the Canso Chemicals site.

On March 22, 2019, I asked ECCC whether the federal ministry was in any communication with or receiving results from the province about the mercury monitoring, if the contaminated site had been included in the Canadian Mercury Science Assessment, and if monitoring was being done in Pictou Harbour.

I also requested that ECCC link me with someone in the department who could speak to me about mercury and to Canada’s “Focal Point for Canada to the Minamata Convention on Mercury.” These requests were ignored.

It took ECCC two weeks to send me the following response to the questions about Canso Chemicals and mercury:

Environment and Climate Change Canada is aware of possible mercury contamination at the site of the former Canso Chemicals plant in Nova Scotia. However, as the plant is not a federal facility or a federal contaminated site, the monitoring and assessment of the site falls under the jurisdiction of the province of Nova Scotia.

Every province and territory has legislation, regulations, guidelines and/or a program in place to govern contaminated sites management. Through these measures, provinces and territories identify, assess, and remediate contaminated sites, including those contaminated with heavy metals such as mercury.

In 2005, the Government of Canada established the Federal Contaminated Sites Action Plan (FCSAP) to address contaminated sites under the responsibility of the federal government. Under the FCSAP program, contaminated sites are identified and assessed, and remediation or risk management strategies are developed and implemented, where warranted.

Whether that Action Plan includes the Canso Chemicals property and if so, what that means, the ECCC spokesperson and the “multiple teams” that spent two weeks coming up this “complete and fulsome response” to my questions, neglected to answer.

So much for the Canadian government’s pledge to UNEP that it “provides its citizens with public information awareness and education related to mercury.”

Crucial and unanswered questions

With the limited information I had from government and the Dillon report, I approached Queen’s University Professor Peter Hodson, a fish toxicologist who has assessed the extent of mercury contamination of fish in the St. Lawrence River at Cornwall.

Hodson replied that there are indeed important questions that still require answers, particularly at the planning stage of any developments, such as the proposed Northern Pulp effluent treatment facility next to the mercury contamination.

There is the need to understand how construction of any new facilities in the area would affect surface penetration of water and groundwater flow rates and directions. To prevent any changes in groundwater flow that might affect the movement of the underground mercury, new facilities [such as the proposed effluent treatment facility] should be located well away from upstream or downstream of groundwater flow.

The following are some of the questions that Hodson raises:

  1. There was no estimate made of how much residual Hg [mercury] was in soil or bed rock underneath the chlor-alkali cell. Without such an estimate, it is difficult to have any confidence in models predicting future movement of Hg from the site. If the Hg has penetrated deep into fissures in bedrock, and there are deep pathways for groundwater flow, what is the total movement of Hg off-site at all depths, and is any Hg migrating vertically (up or down)?
  2. The groundwater surveys (flow, Hg concentration) were made within a few years of dismantling and excavating the site. How much has groundwater flow changed in response to these surface disturbances and to subsequent re-vegetation? Is the model still valid?
  3. The monitoring of Hg in groundwater demonstrated that one sample well (W-4) was particularly contaminated. However, the [Dillon] report included a recommendation that this sampling well be closed (p 49)!  This seems counter-intuitive if the intent of long-term monitoring is to track Hg concentrations over time.
  4. Was a long-term monitoring program implemented and are the results available? Has the database of groundwater flow and Hg concentrations and overall assessment of risks been updated to reflect the two decades of Hg movement since the last studies? Is monitoring well W-4 still sampled?
  5. Have surveys been done of soil and groundwater Hg concentrations around the sludge-disposal sites, and are there groundwater wells that are sampled regularly? Even though these sites are described as ‘secure,’ they can age and start to leak due to frost damage, disturbance by animals, and construction or maintenance activities.

I sent Hobson’s questions to Nova Scotia Environment, and was told I would need to go through freedom of information for the information.

On its website, Environment and Climate Change Canada reports that as part of its obligations to the Minamata treaty, it would collate and disseminate “valuable information on the presence, fate, transport and effects of mercury in the environment.”

After weeks of research, and many questions to federal and provincial environment departments, it looks to me as if neither level of government is keen to live up to its Minamata obligations and disseminate “valuable information on the presence” of mercury on the Canso Chemicals property beside the Northern Pulp mill.

Joan Baxter is author of The Mill: Fifty Years of Pulp and Protest.

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1 David Depew, Neil M Burgess & Linda M Campbell. Spatial patterns of methylmercury risks to common loons and piscivorous fish in Canada. Environmental Science & Technology. DOI: 10.1021/es403534q
2 Parsons, M.B., LeBlanc, K.W.G., Hall, G.E.M., Sangster, A.L., Vaive, J.E., and Pelchat, P., 2012. Environmental geochemistry of tailings, sediments and surface waters collected from 14 historical gold mining districts in Nova Scotia; Geological Survey of Canada, Open File 7150. doi:10.4095/291923 

Joan Baxter is an award-winning Nova Scotian journalist and author of seven books, including "The Mill: Fifty Years of Pulp and Protest." Website:; Twitter @joan_baxter

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