Dalhousie University researcher Emma Hoffman has come forward to defend her 2017 ambient air quality study about cancer-causing air emissions detected near the Northern Pulp mill after finding that her study was “misrepresented” in the mill’s recently registered Environmental Assessment [EA] for its proposed effluent treatment facility. 1
In Part 3 of the “Dirty Dealing” series, I reported that a study by Hoffman and five other Dalhousie University researchers revealed that air levels of three of the seven volatile organic compounds (VOCs) assessed near the Northern Pulp mill exceeded cancer risk thresholds.
Over an eight-year period (2006-2013), 1,3-butadiene, benzene, and carbon tetrachloride were found to routinely exceed US Environmental Protection Agency (EPA) cancer-risk levels, which refer to the probability of contracting cancer if exposed to a concentration of a substance every day over the course of a 70-year lifetime.
According to the public and peer-reviewed study published in Environmental Science and Pollution Research — one of the few on record about airborne VOCs in rural Canada — many VOCs are either known or suspected of having direct toxic effects on humans, ranging from carcinogenic to neurotoxic and that “combinations of air toxics may have additive or synergistic adverse health effects.” By analyzing the available data, the study authors were able to show that the Abercrombie pulp mill (currently Northern Pulp) was a likely source of the contaminants.
At the time, I contacted both Emma Hoffman and Tony Walker, two of the lead researchers, to ask about their work but neither were able to speak to me. They both cited “ongoing consultations” with the Boat Harbour Remediation Project. Hoffman said she was unable to speak “due to the sensitivity of the subject matter.” Both are members of the Boat Harbour Environmental Advisory Management Committee (BHEAC), which was formed in 2016 after the governing Liberals set in law the January 2020 closure of Boat Harbour as Northern Pulp’s waste lagoon. At the time, the provincial department of Transportation and Infrastructure Renewal handed over the responsibility for the remediation of Boat Harbour to Nova Scotia Lands Inc., a crown corporation, which is now the proponent of the project.
Minutes obtained from the BHEAC meetings dating back to 2016 indicated at the time that the consultants, including Hoffman, were instructed to avoid speaking publicly since the subject matter was “sensitive… until [the] strategy is finalized.”
But Hoffman, who is still involved with separate Nova Scotia Lands-funded studies, has decided to speak publicly now, given that the ambient air study was not funded by the province. She also said she wanted to “defend” the study “due to the misrepresentation put forth by [Northern Pulp’s] Environmental Assessment of the scientific contributions it provides.”
Hoffman’s full statement provided to me in response to Northern Pulp’s EA can be found here. Her supervisors and study co-authors, Dr. Judith Guernsey and Dr. Tony Walker also contributed to her statement. 2
Northern Pulp says Hoffman’s study is flawed
The Northern Pulp EA says that the limitations of the study make it impossible to point definitively at the pulp mill as being the source of the VOC emissions. It says that while the seven VOCs referenced in Hoffman’s 2017 study “may be emitted in small amounts in stack and fugitive emissions at the NPNS mill…a number of other point and mobile local sources also emit these substances within the local airshed.”
In response Hoffman, Guernsey, and Walker say that the study was a “pilot” and “was not intended to provide causal evidence to implicate the mill as the sole source of the VOCs. Nevertheless, the study was able to show a very plausible association.
By analyzing publicly accessible emissions data from a provincially operated National Air Pollution Surveillance (NAPS) monitoring site located in Granton, southwest of the mill and combining this with local meteorological conditions at Caribou Point, Hoffman and her colleagues were able to show a positive correlation with wind direction and the Granton NAPS site’s ambient VOC concentrations in relation to the location of the pulp mill. In other words, when the prevailing winds were blowing from the mill toward the Granton air monitor, the VOC concentrations typically went up for all of the compounds assessed, except carbon tetrachloride, suggesting that the mill is likely a contributor to the increased concentrations. “The largest point source emitter northeast of the Granton NAPS site is likely the mill,” she says, but “the origin(s) of the VOCs are inconclusive.”
Northern Pulp’s EA also stated that the study did not attempt to rule out the contributions of other potential sources. But Hoffman, Guernsey, and Walker say this “is clearly not a true statement,” and that the study did not disregard other potential sources of VOC emissions. The study openly acknowledged and discussed in detail the other potential local emission sources in the area, including a coal-fired generating station in Trenton and a tire manufacturing facility. The study even provided a map indicating these other potential sources relative to the Granton NAPS site.
Study Findings Warrant Further Investigation, says Hoffman and co-authors
Northern Pulp’s EA states that “When other study uncertainties are considered… there is no current air quality issue with the seven targeted VOCs in the Pictou area.” Hoffman and her colleagues say this statement is “misleading.”
They say that despite some of the study limitations — including a limited number of air sampling sites in relation to the mill and the short duration of the study — the fact that VOCs routinely exceeded EPA air toxics-associated cancer risk thresholds, regardless of whether the mill contributed to these VOC levels, should not be ignored. “Absence of evidence is not necessarily evidence of absence,” they say. “The limitations caused by sparse data does not necessarily mean there is no problem with air emissions in this community and there is no justification for [Northern Pulp’s] erroneous conclusion.”
Instead of more ambient air data, particularly in areas where there is higher residential exposure to the mill’s toxic emissions, there appears now to be less. In 2015 Environment and Climate Change Canada (ECCC) decided to decommission the Granton NAPS site, the only one in Pictou County that measured VOCs.
According to the Nova Scotia Department of Environment, the Granton site was decommissioned after the feds analyzed 10 years of data and determined that the average annual levels of VOCs picked up by the monitor were “below or comparable to average levels” over time, elsewhere in Canada.
But air monitors are stationary devices meant to measure contaminants in outdoor (ambient) air. When they are located properly, like in Halifax where there is a relatively steady pollution source (cars), they can indicate levels of pollutants, like smog, quite accurately. But not so when it comes to “point sources,” like the mill. One of the limitations with accurately measuring ambient point source contaminants is there is often a lot of variability.
When there were northeast prevailing winds blowing from the mill toward the Granton NAPS site, higher concentrations of VOCs were typically captured. But when the wind was blowing in another direction, it wasn’t. So the high levels — the ones that routinely exceeded the cancer-risk thresholds, with the exception of carbon tetrachloride, reported by the Dalhousie researchers — were averaged down by the lower concentrations when the wind was blowing in other directions. That doesn’t necessarily mean there were lower VOC concentrations in the surrounding community; it means that VOCs were likely blowing where they could not be captured by the Granton NAPS site.
The study also found that the prevailing winds (southwest) that blow toward the town of Pictou dominate during the summer months, when “people are more vulnerable to ambient air pollution exposure.” In fact, because of Pictou’s geography, air toxics from across the Eastern Seaboard of the United States converge with the local emission sources, including the mill, and as a result higher VOC concentrations are expected in Pictou in the summer.
The study authors point out that given Pictou’s considerably larger population base, compared to the rural area of Granton, there is a need for “installing and maintaining additional strategically placed NAPS sites,” to more accurately represent levels of air toxics where there is higher residential exposure.
Hoffman and her colleagues say that decommissioning the air monitor left an “information vacuum” and “only emphasizes the need for more research on these questions.”
What is the cancer risk?
Northern Pulp’s EA points to the study’s use of USEPA cancer risk levels, which are expressed as 1-in-1 million, saying that the study authors should have adjusted the values to 1 in 100,000, in keeping with “current public health policy in Nova Scotia and most other provinces.” Northern Pulp argues that this “correction would alter the conclusions of the study substantially,” and that the exceedances would have been “negligible.”
This will take a few steps to unpack.
First, Hoffman and her colleagues say this criticism is not relevant “given that Health Canada has no formal standards for air toxic emissions.” Many agencies and provinces use an increased chance of 1-in-1 million for expressing cancer risk.
Since there are no air toxics standards in Canada, the study authors turned to the US and the Environmental Protection Agency’s National Air Toxics Assessment (NATA), which calculates concentration and risk estimates from a single year’s emissions data. 3
The NATA risk estimates assume a person breathes these emissions each year over a lifetime (or approximately 70 years), and establishes an air concentration value when excess cancer is observed. Hoffman, Guernsey, and Walker say the US NATA process is based on a 2005 scientific risk assessment process that established the cancer risk levels to which they compared the ECCC data. 4
To illustrate, let’s take benzene as an example. The International Agency for Research on Cancer (IARC) has classified benzene as a Group 1 agent, which means it is “known” as being carcinogenic to humans. According to Carex Canada, a national carcinogen surveillance program that was established in 2007, there is no safe exposure level for benzene.
Hoffman’s study used the US EPA estimate that if an individual were to continuously breathe the air containing benzene at an average of 0.13 μg/m3 over his or her lifetime (roughly 70 years), that person would have no more than one-in-a-million increased chance of developing cancer as a direct result of breathing benzene. If the exposure level goes up, so does the risk.
So, if the numbers for benzene, say, were adjusted to one-in-100,000, as Northern Pulp suggested, this would effectively increase the value ten-fold from 0.13 μg/m3 to 1.3 μg/m3 — meaning that if an individual were to continuously breathe air containing 1.3 μg/m3 for a lifetime that person would have no more than one-in-100,000 increased chance of developing cancer.
But increasing benzene’s threshold concentration, as Northern Pulp suggests, does two things.
First, it does exactly what Northern Pulp said it would do: expressing cancer-risk levels as one-in-100,000 means that benzene concentrations detected at the Granton NAPS site would have been close to negligible.
But Hoffman and her colleagues point out it also does something else: It effectively increases the allowed ambient air concentration for benzene, a chemical for which there is no safe exposure. Therefore, the threshold is “less protective” of human health, they say.
In defence of the study, Hoffman, Guersey, and Walker also noted that it met all the quality control standards of Environmental Science and Pollution Research, the internationally-recognized, environmental science peer-reviewed journal in which it was published.
Boat Harbour could be adding to the problem
Northern Pulp’s EA also states that the seven VOCs cited in the ambient air study “are not known (based on literature review) to be associated with pulp and paper mill activities and air emissions to any significant extent.”
However, the study notes that the mill’s own self-reported data show otherwise. National Pollutant Release Inventory (NPRI) data showed that in 2012 the company emitted 143 tonnes of VOCs from its stacks. In addition, an estimated 3.2 tonnes of benzene were released to the air from a stack higher than 50 metres, and 0.02 tonnes were released within 50 metres of the ground.
Hoffman, Guernsey, and Walker tell me that what’s also worrying is that benzene can combine with chlorinated hydrocarbons associated with the Kraft bleaching process to form a range of toxic compounds which can become airborne. The study points out that although trichloroethylene, tetrachloroethylene, and carbon tetrachloride were not officially reported to have been released by Northern Pulp, these toxic VOCs “may become airborne through evaporation from pulp and paper wastewater.” 5
In other words, Boat Harbour — the mill’s current effluent lagoon — could also be contributing to ambient concentrations of VOCs.
Despite a long history of non-compliance with regards to air emissions at the mill, and without providing any evidence of its own, Northern Pulp’s EA simply concludes that when it comes to the seven targeted VOCs in the Pictou County area, “there is no current air quality issue.”
It’s a statement that rings hollow given that the company has failed repeatedly and spectacularly when it comes to pollution emission tests.
For instance, in 2014 the mill reported the release of 1,290 tonnes of fine particulate matter — the equivalent of 13 Irving pulp mills in one location. A lot of the excess particulate pollution at the time was blamed on a faulty electrostatic precipitator (ESP) in the recovery boiler — which was replaced in 2015 — but this still didn’t address the issue of combustion gases, including VOCs. While all of the stacks at the mill would emit the cancer-causing substances, most would be coming from the recovery boiler, where the “black liquor” — the waste from the Kraft process — is burned to recover the sodium and sulphides, dispose of the unwanted dissolved wood components, and generate steam. ESP units are not designed to remove combustion gases. To do that you need properly functioning scrubbers, but the 50-year old scrubber in the recovery boiler is well past its best-before date and can’t handle the high levels of pulp production now common at the mill.
Add to all this the fact that issues with the power boiler, first noted to be problematic in 2006, have never been addressed. Particulate matter emissions have been exceeded from that aging stack on numerous occasions, which is particularly disconcerting when we consider that the mill is planning on using it for a key part of its proposed effluent treatment plan: the “dewatered sludge” that would be a product of the activated sludge treatment process it proposes will be “burned along with bark in the mill’s power boiler, which reduces or eliminates the problem of landfilling,” according to the mill.
Not knowing what chemicals will be in the sludge, coupled with a glaring lack of properly functioning pollution-abatement equipment in the stack that will be burning it, could spell much worse air quality for local residents.
I ask Hoffman what she thinks about burning the sludge in the power boiler. While she concedes that she doesn’t have “experience” with this matter, or “the knowledge of how these emissions produced by incineration would be mitigated or controlled for,” she doesn’t think it’s a good idea.
Incineration of the sludge could result in emissions of “compounds of concern,” such as heavy metals and other VOCs, she says, and “there are no standards in Nova Scotia to apply against these emissions.” She notes that there are studies that investigate the re-cycling of pulp and paper mill sludge, but doesn’t know if such practices would be “feasible” at Northern Pulp.
According to Hoffman, the intent of the ambient air study was to increase awareness and encourage government to “adopt more stringent air quality regulations and monitoring programs to ensure health of all citizens is safeguarded and prioritized.”
In addition to the ambient air study, Hoffman was lead author on another 2015 study that highlighted the environmental impacts and lack of compliance at the mill. While Hoffman’s work as a researcher with Dalhousie’s School for Resource and Environmental Studies has specialized in investigating industrial pollution impacts on human and environmental health, it has been particularly focused on the reality of living near a pulp and paper mill and that’s because for Hoffman, the mill is personal. She is from Pictou and says she has “a vested interest in issues surrounding local industry.”
The abstract to the 2015 study concluded that, “After decades of local pollution impacts and lack of environmental compliance, corporate social responsibility initiatives need implementing for the mill to maintain a social license to operate.”
That expiration date appears to be fast approaching.
Linda Pannozzo is an award-winning freelance journalist and author of two books: The Devil and the Deep Blue Sea (2013) and About Canada: The Environment (2016).
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- A critique of the Hoffman et al. (2017) ambient air quality study can be found on pp. 504-505 of Northern Pulp’s Environmental Assessment Registration Document. ↩
- Hoffman’s supervisors from the School for Resource and Environmental Studies — Dr. Judith Guernsey in the Department of Health and Epidemiology and Dr. Tony Walker — contributed to her statement and responses to my questions. ↩
- Furthermore, at the federal level there are no legally binding guidelines for air pollution, only voluntary guidelines. The Canadian Environmental Protection Act (CEPA) outlines national air objectives and emissions standards for certain industries, but nothing is legally enforced, unlike the US, UK, and the EU, where national air quality standards do have legal teeth. ↩
- According to the US EPA Health Effects Fact Sheets, cancer risk when it comes to hazardous air pollutants is “the inhalation unit risk for a chemical, which is the increased probability of a person developing cancer from breathing air containing a specified concentration of the chemical for a lifetime. The inhalation unit risk is derived using mathematical models that assume a non-threshold approach; i.e., there is some risk of cancer occurring at any level of exposure…The risk-based concentrations corresponding to a one-in-a-million, one-in-a-hundred thousand, and one-in-ten thousand excess risk attributed to exposure to the chemical are presented. This means that EPA has estimated that, if an individual were to breathe air containing these concentrations of the chemical over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million, one-in-a-hundred thousand, or one-in-ten thousand increased chance of developing cancer as a direct result of breathing air containing the chemical.” ↩
- In Hoffman et al. (2017) the reference provided is: Soskolne CL, Sieswerda LE (2010) Cancer risk associated with pulp and paper mills: a review of occupational and community epidemiology. Chronic Dis Can 29:86–100. ↩