Salt has been used in de-icing since the 1940s, providing safety and mobility for motorists, as well as for commercial and emergency vehicles. Without it, winter would be hazardous and chaotic. In Canada, the primary type used is rock salt, which is mined directly from the earth and requires no additional processing. In excess of 4.5 million tons of salt is used yearly to keep roads safe in Canada alone.


Highway Sales Manager
Patrick Gagnier

Telephone: (514) 428-7792
Toll-Free: 1-800-361-5765
Fax: (514) 694-2451


Highway Sales Manager
John DeMeo

Account Executive
Perry Kerasiotis

Telephone: (905) 795-1771
Toll-Free: 1-800-387-7258
Fax: (905) 565-1551

Is Road Salt “Toxic” to the Environment?

As a result of the steady progress between Environment Canada and the stakeholders towards a voluntary approach to proper environmental management of “road salts”, Cabinet has seen fit to defer a decision on labeling road salts CEPA “toxic”.

The Canadian Governments decision has given an opportunity to improve salt management voluntarily rather than being coerced through federal regulations.

Environment Canada has published a proposed Code of Practice for Salt Management designed to minimize environmental impacts from the storage and application of “road salts” in Canada.

The new Code builds on the 1999 Road Salt Management Guide produced by the Transportation Association of Canada; our company and the Salt Institute were actively involved as TAC members in producing that Guide and, more recently, TAC’s nine new Syntheses of Best Practices – Road Salt Management that are endorsed explicitly in the proposed Code.

The Code also broadens the Salt Institute’s “Sensible Salting” program and will require municipal agencies to develop their own Salt Management Plan. To assist you in the implementation of your Salt management Plan, we have available for your use, today, a series of training programs, videos and printed materials for use in training your crews.

At Windsor Salt, we support the Salt Institutes “Sensible Salting” program and Environment Canada’s “Code of Practice for Salt Management”. This approach emphasizes maximum effectiveness and economy in the use of salt for road safety, while working to safeguard the environment.

For more information we encourage you to refer to our Assessment Report response and Global Tox attachments, and to the Canadian Salt Institute Web Site and TAC Road Salt Web Info Site links for additional information.

CSL Response to Environment Canada Draft Assessment Report on Road Salt

October 11, 2000
Windsor Salt Ltd.gratefully acknowledges Environment Canada for the opportunity to comment on the draft Assessment Report on Road Salts.
The Canadian Salt Company extracts, processes and markets salt under the well-known brand name of Windsor.

The company’s head office is located in Pointe-Claire (Quebec) and employs 1,000 people in its four evaporated salt plants and three mines in Canada.

Guy L. Leblanc, ing.
Production and Administration
755, boul. St-Jean, bureau 700
Pointe-Claire (Québec)
H9R 5M9

1.0 The context

Road salts are among the substances currently being assessed. Environment Canada and Health Canada have produced a report on the toxicity of road salts (Environment Canada and Health Canada, 2000). The process is now at the public comments stage. The Canadian Salt Company wishes to comment on this report.

The Canadian Salt Company’s approach is essentially an analysis of the assessment method used to conclude that road salts constitute a toxic substance. Our comments discuss the scientific rigour of the assessment report and, in particular, the first two stages of the document “Environmental Assessments of Priority Substances under the Canadian Environmental Protection Act” (data collection and production, and problem formulation) that were used to document and assess the issue. These stages should allow to demonstrate the existence of a problem in order to subsequently verify the toxicity of a substance.

The Act provides for two criteria to guide the work of the ministers and the governor in council: the definition of a “toxic substance” (Article 64) and the type of information that the ministers could collect to determine if a substance is effectively or potentially toxic (Article 68).

On toxicity, “a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that:

a) have or may have an immediate or long-term harmful effect on the environment or its biological diversity;

b) constitute or may constitute a danger to the environment on which life depends on; or

c) constitute or may constitute a danger in Canada to human life or health.”

The document “Environmental Assessments of Priority Substances under the Canadian Environmental Protection Act. Guidance Manual Version 1.0” (Environment Canada, 1997) presents the methodology used by Environment Canada and Health Canada in the environmental assessment of priority substances. This manual proposes six stages for the assessment of substances:

data collection and production;
problem formulation;
entry characterization;
exposure characterization;
effects characterization;
risk characterization.
The Canadian Salt Company has limited its views and comments to certain key aspects of the decision-making process as to the existence of an factual environmental issue, as found through the analysis process proposed by the assessment guide.

2.0 Comments on the Assessment Report on the toxicity of road salts

2.1 First stage of the analysis process: data collection and production

The document “Environmental Assessments of Priority Substances under the Canadian Environmental Protection Act. Guidance Manual Version 1.0” defines the procedure to efficiently and rigorously collect and produce data to be used in the analysis.

The document stipulates that the quality of data used to assess priority substances must be acceptable. All important data must be verified with their main source. Assessors should obtain original references in order to assess data in a critical and scientific manner. When information sources are incomplete (e.g. if detection limits, sample size, measured concentrations, etc., are not mentioned), assessors should communicate with each author to obtain the information required to assess the study. (p. 2-1).

Having analyzed the Assessment Report, we have found three significant flaws in the methodology used to collect and produce data, i.e.:

the use of data out of context, without specifying limitations and without providing the conclusions of the studies from which the data were extracted;
the lack of impartiality by omitting to quote literature demonstrating the relative harmlessness of road salts;
the age of the literature and case studies used.

2.1.1 Use of data out of context

We have observed that certain data referred to in the Assessment Report were removed from their context which, in the absence of defined boundaries and with the omission of their reports’ conclusions, introduces a significant bias in the interpretation of the data. For example, to demonstrate a heavy chloride load in well and surface water, the author presents data from a case study carried out in Trois-Rivières-Ouest (Gélinas and Locat, 1987). However, the main conclusions and recommendations of the Gélinas and Locat report present a very different perspective:

Chloride concentration in the Trois-Rivières-Ouest has municipal wells that are below the recommended guideline for drinking water and is not expected to increase unless road salt application rates are suddenly increased to unrealistic levels of 4 to 5 times their historical maximums.
There is no serious risk of well contamination by road salts. The average chloride content will stay below the recommended guideline.
Road salt application can continue as per the usual procedure.
The present highway artificial drainage system is adequate. No modification is required.

2.1.2 The lack of impartiality in the choice of literature

Although the “Environmental Assessments of Priority Substances” guide recommends the exhaustive and impartial collection of scientific data on the concerned substance, Sections 3.1 to 3.6, for instance, do not mention studies that tend to document the relative harmlessness of road salts.

It is our opinion that the conclusions of a scientific evaluation should be based on the weight of evidence approach, as stipulated in Article 76.1 of CEPA 1999, and not on extreme negative or positive cases.

We are also perplexed by the fact that over 16% of the references quoted in the Assessment Report are not available for consultation.

2.1.3 The age of the literature and case studies used

Given the age of the data used (over 50% of the quoted case studies and literature are prior to 1990), we may ask whether local problems cited in the Assessment Report still exist or have been remedied through the implementation of recent practices better adapted to environmental protection. CEPA requires the assessment of current and future impacts, as opposed to the simple listing of extreme historical cases.

The fact remains that road salt utilization and road construction techniques have been greatly improved since the publication of the cases cited in the Assessment Report.

2.2 Second stage of the analysis process: Problem formulation – analysis of critical pathways subsection

The “Environmental Assessments of Priority Substances” guide produced by EC (1997) mentions that this stage consists in planning the assessment of ecological risks. Environment Canada (1997) identifies the following sub-stages:

determination of the scope of the assessment;
analysis of critical pathways;
study of the sensitivity of receptor;
ecological relevance of potential receptors;
selection of criteria and indirect effect variables;
creation of a conceptual model.
We have found significant flaws and biases in the “analysis of critical pathways” and “ecological relevance of potential receptors” subsections. Due to these flaws and biases, the interpretation of data leads to conclusions that are not representative of the Canadian reality.

According to the guide, the subsection “analysis of critical pathways” consists in assessing the entry path and the probable endpoint of a substance in the environment, and serves to predict its geographic distribution and its endpoint in the Canadian environment (p. 3-2). The assessment guide mentions the importance of documenting released quantities, the frequency of substance releases, the substance’s distribution between air, soil, surface water, groundwater, etc., the geographic distribution and the concentration intervals in the environment, as well as the ecosystems that may be exposed.

In this sub-stage, we have identified the following methodological flaws:

the excessive simplification of dispersion models used for surface water and groundwater;
the failure to consider distribution between air, soil, water, etc., and the seasonal and temporary character of road salts.

2.2.1 Use of simplified dispersion models for surface water, groundwater and soil

The endpoint of road salts in the environment was assessed using simplified models that do not allow to define the evolution, in space and time, of road salt concentrations in the environment. The following simplifications were noted:

aquifers are considered as homogeneous and well mixed environments while in reality, the situation is very different;
estimated salt loads were uniformly distributed in each watershed to obtain average loads per unit of area. This approach does not take into account the topographic and geological heterogeneity within a same watershed;
in the case of surface water, the data reported were interpreted without taking into account the hydraulic parameters of the receiving environment. It is however essential to consider these parameters which govern dilution capacity, particularly in the case of chlorides which are highly water-soluble.
Although we consider it normal to simplify a dispersion model to better understand a complex phenomenon, we find it unacceptable not to integrate into the model a minimum of key components that are at the basis of the analyzed substance’s behaviour in surface water, groundwater and soil. We also find it unacceptable to use and to draw conclusions from a model that produces results that do not correspond to the reality, as in the case of surface water model (as discussed later in this report), or to fail to validate the groundwater and soil model by comparing the model’s theoretical results with factual data.

Also, the results obtained with a simplified model must be interpreted while taking into account the limitations imposed on the model. In the present case, there is no scientific demonstration of a geographic distribution of significant road salt concentrations beyond roadway limits. Thus, the Assessment Report does not demonstrate that the road salts are entering or may enter the environment in a quantity or concentration or under conditions that endanger essential environments or biological diversity.

In summary, the effects are limited in both space and time.

2.2.2 Failure to consider the probable distribution and the seasonal and temporary nature of road salts

In order to characterize the endpoint of a substance, EC (1997) proposes determining its distribution between air, soil, surface water, groundwater, etc. However, in the section of the Assessment Report discussing surface water, the entire estimated load, i.e. 4.7 million tons, was applied to run-off water without taking soil infiltration into account. On the other hand, when discussing chlorides in groundwater, the report estimates that 55% of the estimated load ends up in groundwater, while 45% is found in run-off water. The report does not consider that this infiltrated load is diluted before reaching surface water after a period of time that depends on underground hydraulic and geological conditions. Also, the concentrations in run-off water, which were obtained theoretically, overestimate the proportion of chlorides from road salts in the observed concentrations. Due to this fact, the Assessment Report sometimes presents proportions exceeding 100%. For instance, on the island of Montreal, where the model predicts concentrations of 499.77 mg/L of chlorides, the average measured concentrations are of 21.42 mg/L (see appended Table 1).

In the determination of the endpoint of a substance, EC (1997) also proposes defining concentration intervals in the Canadian environment. These intervals are not mentioned in the Assessment Report which also fails to take into account the seasonal and temporary nature of road salts.

We consider that it is essential to take these factors into account to rigorously assess road salt concentration intervals and variations in the environment.

2.3 Second stage of the analysis process: problem formulation – ecological relevance of potential receptors

According to the methodological guide prepared by Environment Canada (1997), the “ecological relevance of potential receptors” subsection should study the ecological role of highly exposed or sensitive receptors in order to determine their ecological relevance and predict the possible indirect effects on other components of the ecosystem (p. 3-4). To carry out this study, the life cycle of the receptors must be studied and the specific functions that these receptors fulfil in the environment must be identified.

For road salts, the Assessment Report identifies the landscapes modified by rights of way and man-made lakes located along roads as the main extremely exposed and sensitive receptors. The report also ascribes a significant ecological role to these modified and man-made habitats, but without defining this role. Section 3.1.1 of the report, page 41, first paragraph, asserts: “modified landscapes such as rights of way or impoundments can in fact offer the only habitats available for many species locally or regionally. The assessment of priority substances therefore does not distinguish between effects on natural and modified environments.”

2.3.1 Unjustified generalization

We find very questionable the justification given in the Assessment Report to ascribe a significant ecological role to modified habitats, to the point of failing to distinguish between modified and natural habitats: “…modified environments are critical to the survival of many individuals and populations.” This statement is questionable for several reasons:

both federal and provincial environmental processes seek to protect essential habitats and species, and not man-made habitats, individuals or populations;
an essential habitat is by definition a location where species perform activities that are essential to their survival, i.e. reproduction, rearing offspring and migration;
since the implementation of federal and provincial environmental legislation in the early 1970’s, major road projects are subject to environmental assessments aimed at selecting road corridors and limits with the least environmental impacts to avoid disrupting essential habitats. By this very fact, numerous man-made environments and areas located along these roads do not correspond to habitats that are essential to the survival of species.

2.4 Sixth stage of the analysis process: risk characterization

The Assessment Report and supporting documents put considerable emphasis on the theoretical quantities of chlorides originating from road salts and on concentrations that are measured and attributed, rightly or wrongly, to road salts. This information is then used to argue that certain environments are subject or may be subject to “effects”. Also, in the report’s context, the reader is led to believe that these effects have a harmful impact on the environment.

We also note that the report does not specify the threshold beyond which an effect should be considered as harmful and the substance, e.g. road salts, could be deemed “toxic”. Science can serve social ends only if society establishes measurement criteria and standards. Without such criteria, the measurement of roadside chloride concentrations does not constitute evidence of a harmful impact on an organism that Canadians ask Environment Canada to protect.

We therefore consider that in the absence of a clear definition of a harmful impact or the determination of a critical threshold, the Assessment Report does not conclude to the toxicity of road salts, as evidenced by the generalised use of expressions such as “probable”, “may”, and “it appears” in the report.

3.0 Discussion of the scientific scope of the Assessment Report

3.1 Surface water

In the conclusion of the section pertaining to surface water, the author mentions that “in most of Canada, the portion of chloride from road salt application is 40% or less” of the chloride quantity measured in bodies of water.

We consider this affirmation to be misleading since the 40% proportion mentioned is obtained with an extremely simplified method and model with a high level of inaccuracy, as demonstrated by percentages exceeding 100% in several locations.

We also believe that the additional arguments to support this affirmation, i.e. “spatial and temporal sampling may under-represent pulsed, localized entry of salts…”, are biased and attempt to convince the reader that these proportions are averages that do not represent extreme occurrences. However, the reality is that the high sporadic concentrations mainly occur during the snow thaw period when the flow of the receiving bodies of water is high, which compensates for these peaks by diluting chloride concentrations.

To determine the actual impact of road salts, one must consider the diluting capability of the final receptor. Spot measurements near a point of release or in run-off water reflect only transitory conditions that subside under the diluting effect. The intensity of this hydraulic effect depends on the type and size of a water body.

It is difficult to establish a strong correlation between increased chloride concentrations and road salt spreading, particularly in rivers and large streams that have a substantial diluting capacity. In small streams near roads, the intensity of the impact of road salts depends on several factors including the flow rate, precipitations, topography, drainage, and the salt spreading rate. The results of studies carried out on this type of water body remain specific to the studied site. The extrapolation of results and the generalization of impacts are therefore not valid.


The Assessment Report establishes a correlation between the spreading of road salts and increased chloride concentrations in lakes. However, lakes are often refilled by a watershed’s various run-offs, including underground water, which increases dilution.

Also, the contribution of the various run-off sources makes it difficult to identify chloride sources, particularly in urban lakes where various chloride sources (municipal and industrial) are present.

The Assessment Report’s conclusions overestimate the actual and perceived effects of road salts on surface water. The conclusions of other studies, which are not considered in the Assessment Report, tend to demonstrate that the effects of road salts on surface waters are generally local and minor. As mentioned earlier, there is no scientific demonstration, in the present case, of massive road salt contaminations beyond road limits and patrol yards.

3.2 Groundwater

The section on groundwater presents, through the biased use of case studies and an overly simplistic model of which certain aspects are mentioned in Section 2.2.1, an apparently problematic situation. However, Environment Canada and Health Canada do not provide any explanation to the fact that road salts have been used in large quantities for many years without the emergence of a generalized environmental problem as suggested in the report. For example, according to the mass balance spreadsheet model from Johnston et al. (2000), chloride concentrations between 900 and 3,600 mg/L are to be expected in groundwater where road density and spreading rates are high. There is however no actual case where chloride concentrations have reached these peaks. Municipal wells cited as examples in Figure 19 of the Assessment Report are well below these concentrations. In fact, the only cases where measured concentrations were in the order of those suggested by Johnston et al. are in control wells near unprotected storage sites, and are therefore non-representative of the effects of seasonal road salt spreading.

We therefore believe that the impacts on groundwater are real but rather limited in extent and duration. In several cases, the small size of affected hydrogeological systems causes resurgences to be very near spreading areas, and observed concentrations to fluctuate yearly according to a well-defined seasonal cycle.

In short, we believe that the Assessment Report’s conclusions significantly overestimate the actual observed impacts. These impacts are in fact limited in both extent and duration.

3.3 Soils

3.3.1 Physical and chemical aspects

The Assessment Report concludes, in Section, that “Application of road salts can result in deleterious effects on physical and chemical parameters of soils.”

However, the report provides only a few quantitative numbers on the effects of an increase of the soil’s salinity on the yield of certain species of fruit-bearing plants along roads. The report says nothing about the actual effects of salinity on the chemistry and physical behaviour of soil, i.e. about the effects of hydraulic conductivity, the dispersion potential of silt and clay, or about shear strength.

3.3.2 Biological aspects

Most of the literature cited in the Assessment Report on the biological effects of road salts on soils is based on studies in laboratories and man-made environments.

In reality, indigenous microbial populations change in reaction to numerous factors, including temperature and the availability of nutrients. Also, the effects of road salts are partly diminished by the natural calcium present in soil, as mentioned in the supporting document by Butler and Addison. However, this fact is ignored in the Assessment Report which also fails to mention the exposure duration times used for soil organisms to be “moderately or strongly inhibited”.

We therefore consider that the Assessment Report does not present sufficient data to conclude to a generalized effect of road salts on soils. Potentially affected soils are generally within road limits which have already been affected by road construction. Effects on the biota, agriculture and forest are, in our opinion, isolated cases and limited to restricted areas along roads.

3.4 Ecotoxicology

Regarding ecotoxicological effects, the guide (Environment Canada, 1997) states (p. 1-2) that the observed effects in a population, community or ecosystem are generally deemed more harmful to the environment and a greater cause for concern than those observed at lower levels. The effects on an individual can be significant for endangered species whose populations are small.

The Assessment Report contains no clear demonstration that road salt concentrations affect the upper levels of the biological organization. However, the report asserts that very high concentrations can affect certain individuals. Also, changes in some communities were mentioned but are not extensive, nor of a nature to have an immediate or long-term harmful effect on the environment or biological diversity. This condition is essential to classify road salts as toxic substances as defined by CEPA 1999, since the two other conditions mentioned in Section 1.0 do not apply to the present case.

3.5 Essential habitats

It is our opinion that the Assessment Report lacks perspective and rigour when it tends to impart to roadsides an important role as habitats, especially since the report does not specify which special functions these so-called habitats fulfil in the environment and that no comparison is made with essential habitats that are not subjected to the effects of road salts.

3.6 Scientific scope of the Assessment Report

Persuant to our analysis of the Assessment Report on the toxicity of road salts, it is our opinion that the only conclusions of this report that are supported by an objective scientific retionale, are as follows:

There are some sites that appear problematic because of road salts;
these problems remain isolated, limited in scope and range, and result from specific circumstances;
these sites are generally located near roads or patrol yards, or rarely extend more than a few tens of metres beyond;
these are mainly relatively unproductive or secondary man-made environments whose essential function to the subsistence of species is not demonstrated (breeding, feeding, migration, etc.);
the problems associated with road salts are localized and do not reflect the general situation in Canada;
measured chloride concentrations are quite variable due to the seasonal and temporary character of road salt application, local spreading rates and to the specific characteristics of each site;
the documented effects concern mainly individuals and populations at the lower level of the biological organization, or isolated individuals at higher trophic levels.
The Canadian Salt Company shares the opinion that a few problematic situations may still exist locally and supports the promotion of adequate handling and storage practices of road salts. However, the Assessment Report has a number of flaws. Certain biases were introduced and led to exaggerated conclusions that are not representative of Canadian reality.

5.0 Conclusion

According to Article 64 of CEPA 1999, a substance is toxic if:

1. it is entering or may enter the environment (in the sense CEPA gives to the word “environment”) in a quantity or concentration or under conditions that:

a) have or may have an immediate or long-term harmful effect on the environment or its biological diversity;

b) constitute or may constitute a danger to the environment on which life depends on; or

c) constitute or may constitute a danger in Canada to human life or health.

The Assessment Report produced by Environment Canada and Health Canada (2000) has demonstrated that road salts are entering or may enter the environment, by way of surface and groundwater. However, except in isolated cases, there are no significant accumulations given the diluting capacity of surface water and groundwater, and the highly soluble nature of chlorides.

With respect to harmful effects on the environment or its biological diversity, the Assessment Report only mentions a few specific cases of immediate effects on individuals and populations at the lower level of the biological organization or on isolated individuals at the higher trophic levels. However, the report fails to demonstrate the presence of harmful effects on the environment or the biological diversity of populations at the upper level of the trophic chain. Road salts are soluble and transient in the environment. The report also fails to demonstrate any bioaccumulation in the food chain. This makes it impossible to compare road salt with dioxins, PCB’s, PAH’s and heavy metals as far as an accumulation in the upper trophic levels is concerned. In this respect, literature suggests that harmful effects must compare with those that are caused by the entry, into the environment, of substances such as PCB’s, Mirex, asbestos, etc.

The Assessment Report does not rigorously and scientifically demonstrate that road salts are entering or may enter the environment in quantities or concentrations, or under conditions that endanger essential environments or biological diversity.

The Assessment Report mentions that “the basis for inclusion by the Ministers’ Expert Advisory Panel on the Second Priority List of “road salt” was limited to environmental effects, and did not identify concerns with respect to human health” (Assessment Report, p. 5). Thus, road salts are not present in the environment in sufficient concentrations or under conditions that may induce risks to human health.

It is our opinion that the Assessment Report has failed to rigorously and scientifically demonstrated that any one of the essential conditions required to consider a substance as toxic can be attributed to road salts.

In light of the considerations mentioned in Section 3 and the report’s other serious deficiencies, it appears that the road salt issue is based on isolated cases. The implementation of appropriate salt storage and handling procedures would control and prevent such occurrences.

Finally, it is our opinion that it would be entirely inappropriate to consider road salts as toxic under CEPA together with the PAH’s, PCB’s and other products already on the list of toxic substances.


Table I.
Watersheds with theoretical road salt chloride concentrations higher than observed concentrations.

(Reproduced from: Mayer et al. 1999)

Watershed / City | Observed chloride concentrations (mg/L) | Theoretical chlorides from Road salts (mg/L) | Ratio between observed and theoretical concentrations (%)
2O – Island of Montreal 21.42, 499.77, 499.77
2O – Ile Jésus (Laval) 21.42, 191.13, 892
2H – Toronto 19.90, 33.36, 168
2L – West Island (Montreal) 26.40, 44.24, 168
2M – Cornwall 14.20, 23.63, 166
5E – Edmonton 7.24, 11.53, 159
7B – West Edmonton 1.23, 1.75, 142
1A – Fredericton 2.73, 3.21, 118
2O – North Shore of Montreal 10.90, 12.71, 117
2K – Bancroft to Kanata area 3.50, 3.97, 113
2O – South Shore of Montreal 12.27, 13.10, 107

Is Salt “Toxic” to the Environment?

Ronald W. Brecher, PhD, C.Chem., DABT
presented to The Salt Institute of Canada November 1, 2000

Presentation Overview

Overview of the Canadian PSL Assessment Process
Status of Road Salts Assessment
Rationale for Inclusion of Road Salts on PSL2
GlobalTox’s Assignments
Key Findings Review of Documents
Key Findings Review of Reference List
Key Findings Peer Review of Draft Report
Is Salt “Toxic” to the Environment?

Scientific excellence, professionally managed, effectively communicated

GlobalTox Logo

Overview of the Canadian PSL Assessment Process
Identify: Expert Advisory Panel recommends substances to Ministers of Health and Environment. PSL1: 44 substances. PSL2: 25 substances (including road salts)
Assess: PSL Assessment Report prepared to determine whether substance is “toxic” as defined in the Canadian Environmental Protection Act
Manage: Strategic Options Process to identify possible controls for “toxic” substances

Status of Road Salts Assessment
Identified on PSL2
Assessment under way
Draft report undergoing public comment
Draft concludes that road salts are “toxic”

Rationale for Inclusion of Road Salts on PSL2
The Panel recognizes the benefits associated with the use of road salts. However, these substances have negative effects on the environment. Large volumes are released through road salting, particularly in Ontario, Quebec and the Atlantic provinces. There is evidence of adverse local environmental effects to groundwater and to plant and animal life following exposure. Algae and benthic fauna have been shown to be particularly sensitive to changes in chloride ion concentrations, resulting in a reduction of fish populations. The Panel recognizes that there has been considerable progress in upgrading storage facilities. However, given the widespread exposure to these substances, and their release in large volumes in the Canadian environment, the Panel believes that an assessment is needed to determine their ecological effects.

GlobalTox’s Assignments
Review supporting documents to assess support for determination of “toxic” under Sec. 64(a) of CEPA (1999) (for Salt Institute and Environment Canada)
Evaluate PSL Assessment report reference list
Provide strategic advice to Salt Institute and its consultants
Today’s presentation

Phillipus Aureolus Theophrastus Bobastus von Hohenheim-Paracelsus (1493-1541):
all substances are poisons; there is none which is not a poison.
The right dose differentiates a poison from a remedy.
doses est solo venium.

Implication: The relationship between exposure and effect must be understood to evaluate toxicity. Toxicity depends on both intrinsic and extrinsic factors.
Canadian Environmental Protection Act (1999), Section 64:
… a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions that

(a) have or may have an immediate or long-term harmful effect on the environment or its biological diversity;
(b) constitute or may constitute a danger to the environment on which life depends; or
(c) constitute or may constitute a danger in Canada to human life or health.

Key Findings Review of Documents

Weight of Evidence
not clear if literature search was exhaustive
focus on most extreme findings

Focus on Loadings
limited information on effects
focus on concentration changes
vegetation effects: mostly visual changes
animal effects: focus on individuals
primarily laboratory, not field, studies
Limited Dose-Response Data
lack of dose-response data
end-point / species to be used for determining toxicity not well defined

Definition of “Adverse Effect”
no guidance on when an effect is considered “adverse”
“effect” is any change; “adverse effect” must be subjectively defined
Tiered Assessment Methodology
tiers 1 – 3 assessments performed inconsistently

Temporal / Spatial Issues
very large temporal /spatial variations in loadings not considered in detail
differences in toxicity between short- vs. long-term exposures not considered in detail

Level of Organization
focus is generally on individuals
higher levels of organization not extensively considered
Road Salt Management Practices
Little discussion of changing management practices
Assessment focused on historical management practices (storage and application)

“The Environment”
report’s definition includes the engineered environment
had not been defined prior to GlobalTox comments to Environment Canada
no guidance to authors of supporting documents

Confounding Variables
road salts identified as causal factor with little consideration of possible confounders
possible confounders include
– noise
– traffic
– fuel combustion by-products (for example, lead and particulate emissions)
– other substances
– altered drainage patterns affecting soil chemistry/stability
– other sources of chloride, etc. (e.g. brine)

Impact of Winter Road Salting on the Hydrogeologic Environment (Stantec, 2000):
some generalizations not supported, e.g. “regional scale groundwater chloride concentrations greater than the [ODWO] will likely result under high density road networks … for … application rates above 20 tonnes NaCl per 2-lane-km; impacts expected to be site-specific
Toronto / Southern Ontario case studies do not consider background processes which may increase salinity, for example, upwelling of deeper saline waters
local information concerning chloride levels and trends not used, for example Ontario DWSP, Regional Muncipality of Waterloo

Other hydrogeology and related issues
reviews for Salt Institute are in progress
worst case models allow total loadings to go to both surface water and groundwater(?)
lack of concordance between model predictions and field observations, but there is a suggestion that model predictions could form the basis of controls(?)
lack of peer review of these aspects of the report, although they are the foundation for the effects analysis(?)
Key Findings Review of Reference List

Availability for Examination
nearly 25% of references “not available” from Environment Canada; others were confidential and couldn’t be obtained or reviewed
Environment Canada suggested contacting authors (or their organizations), but they were not always willing to share.
could not evaluate either accuracy of referencing or quality of source information

Dated Information
more than 50% of citations were published before 1991

Peer Review Status
peer review could be confirmed for only 25% of references dated 1995 or later
only about 20% of peer reviewed studies dated after 1990 contained field study components
little or no recent information on locations / situations identified as being of concern on the basis of older studies
suggests a need to update inventory of information with up-to-date, high quality field studies focused on historical areas of concern

Inconsistencies in Referencing
several references never cited in text
several cited publications are not in the reference list
duplicate references (e.g. English /French)
typos, inaccurate dates, inconsistent identification of multiple publications by single authors
“cited in” issues these issues make it difficult to independently verify appropriate citing of literature

Key Findings Peer Review of Draft Report
Not clear that draft PSL2 report is being scientifically peer reviewed.
Three toxicology reviews were prepared before the final document was prepared.
Multidisciplinary review required, and individual components must be integrated.
Peer reviews of supporting documents are not included in the draft report (they may be obtained through FOI).

Support for “toxic” under CEPA (1999) is tenuous (but this does not mean “non-toxic”)
Insufficient policy guidance given to authors of supporting documents:
“the environment”
“adverse effect”
Definition of “the environment” open to challenge
Public comment process compromised by inability to access all source material:
a house is only as strong as its foundation
“onion skin” effect
As presented, the draft report is an assessment of historical problems associated with road salts storage and use
Language of CEPA: “…if it is entering or may enter…”, not “if it has entered in the past”
Further work is required to determine whether road salts are “toxic” as defined under CEPA

Is Salt “Toxic” to the Environment?

Further work is required to determine whether road salts are “toxic” under CEPA (1999) paragraph 64(a) definition
science to evaluate this question must be performed within a defined policy framework: “environment”, “adverse effect”, “present and future” vs. “the past”
absence of evidence is not evidence of absence – need to design studies to provide evidence, one way or the other
future work should provide field updates in historically “impacted” areas