Summary of Public Comments Received for Batch 1 substances on the Domestic Substances List

Draft assessments reported Bioconcentration Factors using the highest BCFs reported in the summary documents from the Japanese NITE database. Industry obtained further details from the NITE database showing that steady-state BCFs were < 5000.

The reported BCFs in the NITE database may be overstated if correction for analytical recovery efficiency failed to account for metabolic losses.

This more detailed information from the NITE database was not available at the time the draft screening assessment report was issued.

Information about the metabolism of the three substances has been taken into consideration in the revised assessment.

Industry submitted a study showing that 21% of substance 1068-27-5 hydrolysed by 2 hours at 25°C and pH 2.6 (to simulate a fish stomach).

The same study showed that the substance was hydrolytically stable after 5 days at 50°C at pH 7 and 9, but 38.2% decomposed at pH 4.

The temperature cited is higher than water temperature in Canada over much of the year and favours hydrolysis. Fish are poikilotherms (ectotherms) and can be expected to have a gut temperature close to the ambient water.

The temperature cited is much higher than water temperature in Canada, but the substance is still hydrolytically stable at relevant pH levels. 

The draft assessment report stated that there could be sorption to particulate matter and also to vessel walls under the test conditions. Industry subsequently submitted further information stating that likely metabolites were detected in at least one of the studies. This information was considered in revising the assessments.

Also, the report has been revised to specify that since the vessels were made of glass, sorption of the substance to vessel walls was probably insignificant.   

Environmental exposure values were recalculated, taking into consideration the accepted information submitted by industry to replace some of the default values. Revised exposure values were used to re-calculate risk quotients.

The flow rates used in the calculation are based on a database of river flows, and the flow rates reflect a generic situation that may reasonably exist under low-flow conditions.

Stakeholders have the opportunity during public comment periods to submit information that could make exposure estimates more “realistic”. In the absence of specific data, conservative estimates are used.

Companies submitting data sometimes claim the data are confidential. In order to protect this confidentiality, we mask data by presenting them as order-of-magnitude ranges, for example. This can result in an overstatement of releases and therefore of exposure. Information submitted by industry has been considered and release rates have been revised.

The release scenarios from the Organisation for Economic Co-operation and Development (OECD) are generic and intended for multi-agency use. When available, information specific to industry handling practices in Canada is used to refine model inputs for assessments of specific substances. If stakeholders believe that estimated release values are incorrect, they have an opportunity during public comment periods to submit information that would be more valid for Canada. Stakeholders are also encouraged to engage during the development of exposure scenario documents relevant to their industrial sector or uses.

While releases at some stages have been estimated to 0.1% based on available information, as often summarized in exposure scenario documents, it is clearly stated in the draft screening assessment report that there can be significant uncertainty in the overall fraction of a substance released to the environment, particularly at later stages of the life cycle.

In estimating the PEC [predicted environmental concentration], the number of days of operation should be 365, not 150.

Flow rates of receiving water and treatment plant effluent appear to be low.

Treatment plant removal rate of 81% appears to be low.

A proposal was made for a revised PEC.

In the revised assessment, the number of days of operation is 250, as suggested by another stakeholder.

The flow rates used in the calculation are based on a database of river flows, and the flow rates reflect a situation that may reasonably exist under low-flow conditions.

A higher removal rate is used in the revised assessment.

The PEC has been revised, considering information submitted by industry.

One of the expected transformation products would be tertiary-butanol, CAS No. 75-65-0.

The organoperoxide molecules are composed of carbon, hydrogen, and oxygen, so the major incineration products would be carbon dioxide and water.

There is very little environmental release of these substances. The assessment pointed out that the risk quotient for sediments would be similar to that for water.

There is no information available about toxicity of the substance to soil organisms. However, the substance is no longer believed to meet the criteria for persistence.

It is believed that only small amounts of the substance would be released to air. These small amounts would be very quickly dispersed, so exposure to the substance would be negligible for air-breathing organisms.

Stakeholders have the opportunity during public comment periods to submit information that can be used to revise exposure estimates.

The final assessments conclude that the 3 organoperoxides not be considered to meet the definition of “toxic” underCEPA 1999. Risk management options are no longer being considered.

Laboratory and field data are extremely sparse for many substances on the Domestic Substances List; therefore, the best available estimation methods (models, quantitative structure-activity relationships (QSARs), etc.) have been used to fill data gaps. Public comment periods provide stakeholders with the opportunity to submit unpublished information, etc., to reduce uncertainties. Many stakeholders have taken advantage of these opportunities.

More complete citations have been given in the assessment report for some statements or to explain assumptions used in models. Uncertainties about overall conclusions are discussed in the assessment report, but not necessarily for each individual study or model result.

The document [RM Scope] does not suggest a specific potential action or instrument. If the government can suggest a single or a list of potential instruments, stakeholder feedback can be solicited earlier. […] if the objective of the CMP [Chemicals Management Plan] is to expedite the risk management process, as much as possible, advanced discussion of options should be encouraged. With the explicit understanding that discussion and consultation will occur pertaining to the option(s).

Dow Chemicals

While we agree and support the use of CEPA 1999 processes for virtual elimination; the act is very specific. The objective of eliminating the release of the substance requires establishing a level of quantification and then a “release rate”. […] The approach required by the Act will be problematic for the peroxides in products, but it should be noted that this has been overcome with the first substance subject to virtual elimination – hexachlorobutadiene. To address peroxides in products, a process similar to that which was conducted for hexachlorobutadiene should be considered.

In a parallel analysis there should be a determination if it is necessary to regulate products. If products encapsulate or consume to a residual point or the peroxides are present at low enough concentrations; there will not be a need to act under the virtual elimination provisions as there is no risk.

Dow Chemicals

There is no evidence that the three substances [DMHBP (1,1,4,4-tetramethyl-1,4-butanediyl) bis[(1,1-dimethylethyl)peroxide], DBTMC (3,3,5-trimethylcyclohexylidene) bis[(1,1-dimethylethyl)peroxide], and DMBP (1,1,4,4-tetramethyl-2-butyne-1,4-diyl) bis[(1,1-dimethylethyl)peroxide]] are at detectable levels in the Canadian environment at this time as presented in the Draft Screening Assessments. The Draft Screening Assessments only establish that it is possible that the substances have been released to the environment.  Given that it is likely that no significant environmental releases of the substances are taking place when current industry standard risk management practices are being followed, focus should be on monitoring the existing use of the substances to ensure that users have developed and are using appropriate risk management practices.

SILON Compounds

A mass flow tool, in which various assumptions were made, was used to estimate the quantities of DMHBP, DBTMC, and DMBP released and the proportions of those releases to the various environmental media. The tool is based on a life-cycle analysis and on emission scenario documents published by the Organisation for Economic Co-operation and Development (OECD2004, 2006). The goal of this tool is to quantify the mass of a substance released to the environment during its life cycle.

The tool results indicate that more than 90% of DMHBP, DBTMC, and DMBP is lost by transformation, mostly during the processing phase at polymer manufacturing facilities. Between 2 and 7% of these peroxides may end up in waste disposal sites as a result of handling and cleaning processes, manufacture, and disposal of off-spec product. The calculations assume that there is no release of any of the substance from these sites, although long-term releases may be possible. It is estimated that between 1 and 2% may be released to water.

OECD] Organisation for Economic Co-operation and Development. 2004a. Emission Scenario Document on Plastics Additives [Internet]. Paris (FR): OECDEnvironmental Directorate, Environmental Health and Safety Division. Available from: OECD.org/ehs/">http://OECD.org/ehs/

[OECD] Organisation for Economic Co-operation and Development. 2004b. Emission Scenario Document, “Additives in Rubber Industry”, JT00166668, ENV/JM/MONO(2004)11, June 24, 2004, Paris, France.

[OECD] Organisation for Economic Co-operation and Development. 2006. Draft Emission Scenario Document on Transport and Storage of Chemicals. Prepared by the Environment Agency (UK). Available on request from: Environment Canada, Existing Substances Division, Ottawa, K1A 0H3.

The three final screening assessment reports will provide conclusions as to whether or not DMHBP, DBTMC, or DMBP meets the virtual elimination criteria set out in subsection 77(4) ofCEPA 1999. If the following criteria are met, virtual elimination will be implemented:

• the substance meets the criteria under section 64 ofCEPA 1999;
• the substance meets the criteria for “persistence” and “bioaccumulation” as defined by the Persistence and Bioaccumulation Regulations made under CEPA 1999;
• the presence of the substance in the environment results primarily from human activity; and
• the substance is not a naturally occurring radionuclide or a naturally occurring inorganic substance.

In this case, the risk management will be based on the objective of eliminating the releases of the peroxide to the environment.