Canadian Mining Journal

Feature

Cleaning Up a Community

From the time humans first smelled a roasting lump of iron sulphide, we have known that taking metals from rock gives off unpleasant waste. To protect the environment and our health, regulators have set ever-shrinking limits on how much toxic mate...


From the time humans first smelled a roasting lump of iron sulphide, we have known that taking metals from rock gives off unpleasant waste. To protect the environment and our health, regulators have set ever-shrinking limits on how much toxic material can be released.

Inco Ltd.’s Port Colborne facility in Ontario’s Niagara district refined nickel from 1918 to 1984, and is currently processing precious metals and refining cobalt. “Early last century the Port Colborne refinery was practically state-of-the-art, but its emissions of smoke and dust were significantly higher than they are now,” says Dr. Bruce R. Conard, vice-president, environment & health sciences for Inco. “Ninety-seven per cent of our nickel particulate was emitted pre-1960, the lion’s share before 1940.”

Port Colborne is currently the site of the world’s first comprehensive environmental and human health risk assessment of a fairly large community (about 18,000 people). Inco has handled the situation in an inno-vative way, drawing other stakeholders into the decision-making process while maintaining rigourous scientific methods. This, however, has not been enough to shield the company and the town from controversy, pitting some people’s emotional aversion to pollution against the faith of others in the scientific evidence of “safe” levels of metals in soil.

In 1998, the company publicly accepted responsibility for the nickel, copper and cobalt (and arsenic in 2001) in the surface soils of Port Colborne. Since then, Inco’s objective has been to identify if the contaminants are causing harm to anything or anyone, and to remediate soil that presents an unacceptable risk. “We want Port Colborne to get a clean bill of health,” says Conard.

Risk assessment

Based on soil studies that began in 1972, the Ontario Ministry of the Environment (MoE) released a series of reports between 1997 and 2000 concluding that operation of the nickel refinery had caused surface soil in a large area around Port Colborne to have nickel levels higher than the “generic clean-up level based on toxicity to plants.” The ministry called for further study to find out if the soils were actually harming vegetation. The MoE found no elevation of the rate of birth defects or reproductive failure, or the rate of cancer incidence in the Port Colborne population, compared with the Ontario population. (There was a higher-than-expected rate of lung cancer among local males in 1979-83, possibly related to earlier occupational exposures.)

Inco began discussions with the City of Port Colborne and the MoE in 1998, about how to assess the situation. “This process doesn’t come with a manual about ‘How To Do a Large Community Risk Assessment’,” says Conard. “There are site-specific ones for a defined piece of land with a deed. But what do you do when you have nearly 30 km2 with many land uses–residential, schools, farms, woodlots–and five soil types?” It took two years for Inco to convince the MoE and the city that it would be better and faster to do one community-based assessment than a multitude of individual property assessments.

In 2000, Inco, the city and the MoE launched the Inco-funded Community-based Risk Assessment (CBRA) process, and retained Jacques Whitford Environment Ltd. to carry it out. “Essentially we treated the area as five big properties (one for each soil type), making sure that all the receptors (the people and animals) are taken into account,” says Conard. “We’re trying to develop a community-wide toxicity model.”

The CBRA is looking into four aspects: assessing the risk to the environment, agricultural crops, and human health, and a health survey of the population. Technical aspects are guided by Inco, the city, the MoE and the Niagara Public Health Department. Also involved is a citizens’ Public Liaison Committee (PLC) chosen by the city council. Stantec Consulting (paid for by Inco) has been retained to help the city and PLC understand the technical details of the work.

Conard explains some findings of the risk assessment so far.

Metals can be harmful only if they are bio-available to an organism, which depends on how strongly bound they are in the soil. The study has found NiO in the top two inches of the soil, unchanged from when it was deposited up to 80 years ago, because it is very stable. On the other hand NiSO4.6H2O is highly soluble, but its resulting nickel ions do not move far because they are quickly captured by naturally-occurring chelating compounds, especially clays and organic matter. “We find all the nickel, copper, cobalt and arsenic in the top eight inches of soil–the ‘plow layer’–or in the top few inches in unaltered soils, so the metals haven’t moved into the ground water and aquifers and traveled significant distances,” says Conard.

The “safe” human dosage of an ingested metal is usually set by government agencies as a small fraction (up to one-thousandth) of the dose that begins to cause adverse effects in laboratory animals. For example, the safe dosage of bio-available nickel is 20 ug per kilogram of body mass every day for a lifetime. A child eating a teaspoon (100 mg) every day of the most contaminated Port Colborne soil would get about 25% of this dosage. If you take into account all forms of ingestion–soil, store-bought food, garden vegetables, inhaled dust and skin contact–all humans, even the smallest child, would get <20 ug/kg/day.

So far the risk assessment part of the CBRA has cost Cdn$8 million; final results are expected the end of this year.

Health survey

Another part of the CBRA process is an independent current health status survey of Port Colborne residents known as the Community Health Assessment project (CHAP), conducted by Ventana Clinical Research Corp. Conard described the health effects that might be caused by nickel exposure.

A gigantic accidental dose of bio-available nickel causes acute gastrointestinal problems, an unlikely scenario outside a plant.

Prolonged, intimate contact of elemental nickel and soluble nickel salts with the skin can cause an allergic sensitivity, “contact dermatitis”, which started to occur when pure nickel studs and costume jewelry containing nickel were worn in pierced ears in the 1950s and 1960s.

Respiratory cancer can be caused by high concentrations of fine particulates of Ni3S2 and, less potently, NiO, both of which were given off by certain operations in the Port Colborne refinery. Workers exposed to these high concentrations in the 1920s, 1930s and 1940s suffered a high rate of respiratory cancer 20 to 40 years later. (The dust levels in the ambient air in Port Colborne today are on the order of a million times lower than the exposure that the affected workers had.)

The CHAP survey, which began in December 2002, will determine if these or any other health conditions occur at above-normal levels in Port Colborne, and if they do, whether the disease is linked to exposures to soils. The study will be completed in 2005, at a cost similar to the risk assessment part of the CBRA.

Rodney Street community cleanup

The locus of controversy in Port Colborne has been approximately 200 properties in the Rodney Street area right next to the refinery. Soil and health investigations reported by the MoE in 2001-2 identified that 25 of the properties required soil remediation because the soil measured >8,000 ppm Ni. The MoE ordered Inco to clean up the 25 properties. (High lead levels on 11 properties were deemed by the MoE to be not the fault of industrial activity; other metal levels in soil were not considered dangerous to health.)

Inco remediated five of the properties in late 2001 at an undisclosed cost. This involved removing and replacing the soil to a 30-cm depth. The properties were then restored as much as possible to their original state.

The owners of the remaining 19 residential properties did not accept Inco’s offer of remediation. They are represented by the Toronto law firm Markel, May, Phipps that also represents the plaintiff in a class action filed against Inc
o. Whether the action will be allowed as a class action is currently in the appeal process.

How to remediate soil

Soil that has been contaminated with metals can be remedied in different ways, depending on its use.

As with the Rodney Street properties, the contaminated soil can be removed and taken to a landfill site, as it is not considered hazardous waste. Then clean soil is laid down and resodded. The site will present no further problems.

This should not be done for the full 30-km2 affected area for two reasons, according to Conard. No landfill site in Ontario is big enough to accept that much soil. Also, some of the soil is very organic-rich, nutritious agricultural soil that could not be replaced, but which now lies fallow because of its metal content. Before returning it to productive use, this soil could be treated by adding limestone to increase the pH, fixing nickel in a more stable form not bio-available for plants.

Another method is phytoremediation, using plants such as Alyssum that can bio-accumulate up to 2.5-wt% nickel into their biomass.

Viridian Resources of Houston, Tex., is selectively breeding Alyssum genotypes for rapid uptake of nickel. The bush can be harvested and incinerated. The resulting ash contains up to 30% Ni and low iron, and would make excellent feed for late-stage furnaces in nickel smelting.

“We’ve tested Alyssum on a third of an acre,” says Conard. “Once the CBRA is over, I want to select the best genotype and plant it on 10 acres to show people the technique and communicate that it’s a viable process.”

Other communities take note

The Port Colborne team is creating a comprehensive way to assess risks and remediate soil that is being keenly watched by researchers around the world. Owners of any smokestack industry that was active in the first half of the 20th century should be interested. Inco has already begun working with Falconbridge Ltd. in Sudbury on a similar process.

“I give full marks to the City of Port Colborne for confronting this situation,” says Conard. “The attention means that Port Colborne is pointed to as a place with a soil problem, but they haven’t flinched. Ultimately they will be able to get on with life and leave behind a process that will be used around the world.” He adds, “I am also proud of Inco for taking the risk to spend the time and money necessary to develop this method.”


Print this page

Related Posts



Have your say:

Your email address will not be published. Required fields are marked *

*