| Physical-Chemical Properties |
The structural representation and physical/chemical properties of the assessed compounds should be presented differently. |
Information on structural representations and physical/chemical properties were updated in the screening assessment. |
Uses and Releases |
There has been a significant shift in the use of cobalt, and changes in use are expected to continue. These changes need to be considered, in particular, how they affect manufacturing and use levels, and releases and disposal amounts. |
The screening assessment considers information submitted in response to the notice published under section 71 of CEPA 1999. This information includes quantities of manufacture, import, use, release and disposal in 2006 in Canada. The Government of Canada has stated that the absence of new information will not preclude the Ministers from issuing a decision that safeguards human health and the environment. Thus the process being used for Challenge substances is to act on what we know now. All substances that have undergone assessment remain subject to future evaluation if new, substantive information is identified that indicates that further consideration is warranted. |
| Increases or decreases of releases and disposal amounts should not only be presented in percentages alone but also in absolute values. The names of specific facilities should be included when mentioning quantities from major sources of releases. |
The information has been added in the screening assessment. The names of specific facilities were not mentioned to prevent the potential disclosure of confidential information. |
| The emission factor calculated for smelters is significantly less than the generic smelter emission factor determined by the European Commission. A higher emission factor may yield a significant underestimation of the total releases and disposal quantities for the “zero release” facilities. |
The calculated emission factor that appears in the draft Screening Assessment Report is believed to be more specific to the sites assessed than the generic European Commission emission factor and is thus assumed to be more relevant to the releases of the Canadian facilities. A clarification sentence has been added in the Screening Assessment Report (SAR). |
| Releases to air represent a large part of the releases reported to National Pollutant Release Inventory (NPRI). The assessment indicates that these releases “were not examined further as cobalt releases are expected to be essentially oxides, which are not part of this assessment”. No evidence has been presented to validate this statement. |
Clarification has been added in the SAR: in addition to oxides, it was found that cobalt hydroxides and cobalt sulfates are possibly also included in the air releases. The reference to oxides being the most important fraction was removed in the document as no clear evidence was found. |
| Persistence |
Elemental cobalt, cobalt chloride and cobalt sulfate meet the persistence criteria for all media (i.e., air, water, soil and sediment) as set out in the Persistence and Bioaccumulation Regulations. The Long-Range Transport Potential (LRTP) of these substances was not addressed in the assessment, although it was considered to be low according to the original substance profile. |
The long range transport potential has been added to the SAR: “Long-Range Transport Potential (LRTP) was not quantified in this screening assessment as the sources from the assessed substances are not expected to contribute significantly to the Predicted Environmental Concentrations (PECs) presented.” |
Bioaccumulation |
Cobalt is an essential micronutrient and is available for uptake by many organisms. Indeed, the assessment states that “experimental evidence suggests that cobalt can cause harm to aquatic organisms after acute or chronic exposures at low concentrations.” However, the substances assessed do not meet the bioaccumulation criteria under the Persistence and Bioaccumulation Regulations. |
The bioaccumulation criteria under the Persistence and Bioaccumulation Regulations has been defined to target very bioaccumulative substances. Cobalt may accumulate in organisms to a certain extent as it is a required essential micronutrient. It is also possible that cobalt accumulates to higher levels than those required for essential purposes and causes acute or chronic harm to organisms. However, the experimental lines of evidence suggest that cobalt does not meet the bioaccumulation criterion under the Persistence and Bioaccumulation Regulations. |
| The range of BCF values (7.4-3110 L/kg) is large: information about the distribution of the values should be provided. |
The arithmetic average and the median values are respectively of 878 and 720 L/kg. This information has been added to the SAR. |
Fate |
Please explain why a fate analysis based on log Kow, Koc and typical mass-balance fugacity modeling is not applicable to elemental cobalt, cobalt chloride and cobalt sulfate. |
These are not applicable to the three substances assessed nor to the metal ions they release upon dissolution, because, as for other non-volatile chemicals, these substances exert zero or negligible partial pressure and fugacity in air. This modified explanation is included in the SAR. |
| Hydrolysis is a function of pH and should be described by indicating it is not applicable to ionic species as they readily dissociate in water. Please consider adding such a statement. |
A sentence to this effect was added to the SAR. |
| Inherent Toxicity |
Increased incidences of bronchial and adrenal tumours were observed in mice and rats exposed by inhalation to the highest concentration of cobalt sulfate. However, the assessment indicated that the relevance of data from these routes of administration to carcinogenicity in humans is unclear. |
The statement in the dSAR regarding the questionable relevance of the exposure route to humans refers to studies done in rodents by injection or implantation, and does not refer to the inhalation study in rats and mice. The inhalation study was considered relevant to humans and was discussed in detail (p.63). |
Data Gaps and Deficiencies |
It is necessary to fill noted gaps and provide more accurate release data. Neither the data from Section 71 surveys nor the National Pollutant Release Inventory (NPRI) data used in this assessment are adequate. Also, research on the mechanisms of cobalt-induced genotoxicity is needed. |
The Government of Canada has stated that the absence of information will not preclude the Ministers from issuing a decision that safeguards human health and the environment. Thus the process being used for the Challenge substances is not to wait until data gaps are filled, but to act on what we know now. There is evidence that cobalt likely induces DNA damage through the generation of reactive oxygen species (ROS) and increased cellular oxidative stress. Although the mechanism of genotoxicity is not fully explained, supporting evidence for an indirect mode of action is presented in the screening assessment and forms the basis for the conclusion. |
| Lower effect level values for reproductive and developmental toxicity in margins of exposure (MOE) calculations are not considered. |
The margins of exposure (MOE) presented in the screening assessment was based on the overall lowest observed effect level, which was based on cardiomyopathy in humans. Evidence of reproductive and developmental toxicity was only observed in rodents at doses more than 100 times greater than the critical effect level in humans. The MOE is considered to be adequately protective including potential reproductive and developmental effects. |
While dermal exposure was mentioned, no useful information was given on this route.
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Cobalt is not well absorbed by the dermal route and does not pose a risk by this route of exposure. Dermal exposure through the use of personal care products was characterized in the screening assessment (Appendix VI). A margin of exposure was calculated based on a comparison of the critical effect level for repeated-dose oral toxicity with a conservative estimate of dermal exposure to cobalt chloride in personal care products. |
| The ecological assessment ignores inadequate Risk Quotients (RQs) by stating that the amount of anthropogenic substances produced is small in comparison to that naturally occurring. Quantified amounts of the naturally-occurring substance are needed to provide validation/invalidation of this statement. |
The information presented about anthropogenic versus natural inputs is contradictory and presented in the SAR. The calculated RQs support the likelihood that anthropogenic release of these substances result in concentrations of the metal at levels higher than local background concentrations in the Canadian environment.” The information about anthropogenic versus natural inputs was not used to discuss (or discount) the RQs in the risk characterization section of the SAR. |
| The synergistic and cumulative effects from exposure to multiple metals need to be acknowledged and addressed given that exposures to several chemicals occur simultaneously. |
Consideration of cumulative, synergistic and antagonistic effects is not precluded from a screening assessment. However, in order to be considered, sufficient information to undertake such analyses would be needed. Under the Challenge, the information typically available for assessing effects is representative only of an individual substance’s inherent ability to elicit adverse effects.
A margin of exposure was calculated based on a comparison of the critical effect level for repeated-dose oral toxicity with a conservative estimate of dermal exposure to cobalt chloride in personal care products (see p.67 of SAR). |
Risk Characterization |
While there are significant gaps in information as noted in this submission, there is sufficient information and concern to find that these substances are causing ecological harm. Without information on what a moiety-based assessment entails, it is difficult to justify the need for this. |
Elemental cobalt, cobalt chloride and cobalt sulfate, identified during the categorization of the Domestic Substances List, were assessed together as they generate Co2+ (the moiety of concern) under physiological and environmental conditions, and are thus considered to be toxicologically equivalent. However, this exposure assessment does not consider other substances contributing to this moiety loading. Additionally, measurements of cobalt in environmental media and foods were not able to distinguish between forms of cobalt. A moiety-based assessment would significantly reduce the level of uncertainty through the use of monitoring data and the possible use of release data for all additional substances potentially contributing to the total loadings of the cobalt moiety in the environment.
The potential for efficiency gains in applying possible risk management measures was also considered in decision making. Further assessment of the cobalt moiety is being considered. |
| The assessment indicates that “releases of cobalt to soil occur mainly as oxides which were not assessed in this document. Overall, releases of the assessed substances to soils are not likely to be important.” There is no basis to support this assertion. |
There is uncertainty about the exposure resulting from the cobalt released to soils from the substances assessed. Releases of cobalt to soil occur as a mixture of different cobalt forms possibly including oxides and hydroxides. These forms were not assessed in this document but could be considered in a future moiety-based assessment. |
Risk Assessment Conclusion |
There is a high concern about the proposed conclusion regarding CEPA-toxicity of these substances, particularly in light of the diversity of their uses which could lead to the exposure of many vulnerable populations and their potential carcinogenicity, mutagenicity, developmental and reproductive toxicity, and potential to lead to lethal cardiomyopathy. The findings of the draft assessment are not supported and re-consideration of its conclusions is strongly recommended. |
Exposure of the general population to chemicals through environmental media (e.g., food, ambient air, soil, consumer products) is taken into account in the SAR. Hazard information obtained from occupational settings, in particular epidemiological information, is considered in the risk assessment.
The various conservative exposure scenarios used are considered to be protective of both the general and vulnerable populations in Canada. However, if the commenter provides information which suggests that a specific sub-population would be particularly vulnerable, this information would be considered in the assessment. |
| In light of the information that is provided, the persistence of metals, the potential to accumulate over years in the environment, and the results showing elevated Risk Quotients (RQs) in the aquatic compartment, the proposed conclusion that the three cobalt substances are not individually causing ecological harm in Canada cannot be supported. |
The assessment has identified a potential risk for aquatic organisms from total dissolved cobalt. However, the extent to which any of the three substances would individually be accountable for causing a risk is still unclear. A moiety-based assessment would significantly reduce the level of uncertainties through the use of monitoring data and the use of release data for many additional cobalt-containing substances that contribute to the overall loading of cobalt in the environment. A moiety-based assessment would therefore allow further consideration of all possible sources for all substances potentially contributing to the total loadings of the cobalt moiety in the environment, and potential for effects in all environmental compartments and reduce uncertainties in source apportionment and multiple additive releases. |
| Concerns exist relating to the harm caused by cobalt to aquatic organisms following short-term (acute) and longer-term (chronic) exposure at very low concentrations, and the lack of information and degree of uncertainty mentioned throughout the report. |
Concern was identified in this assessment for total dissolved cobalt ions in the aquatic compartment, and recognizing that many other cobalt-containing substances may contribute to the loadings of total dissolved cobalt in the aquatic compartment in Canada, a moiety-based assessment of cobalt is desirable and being considered. |
