Summary of public comments received on the Draft screening assessment and Risk management scope for Thiocarbamates

Comments on the Draft Screening Assessment (dSAR) for Thiocarbamates (TMTD, DPTT) and Risk Management Scope for TMTD under the Chemicals Management Plan were submitted by 3M Canada Company, Canadian Vehicle Manufacturers’ Association (CVMA), Global Automakers of Canada, Subaru Canada Inc., Tire and Rubber Association of Canada (TRAC), and United States Tire Manufacturers Association (USTMA).

Summarized public comments and responses are provided below, organized by topic:

Overarching comments

Summarized commentSummarized response
Stakeholders provided additional information on quantities, uses, function and concentrations of TMTD in some products in Canada. Data submitted was considered when developing the final screening assessment. 

Transformation in products

Summarized commentSummarized response
Stakeholders commented that TMTD is consumed, off-gassed or reacted in the curing or application processes when used as an accelerator/vulcanizing agent in manufacturing of rubber products or in sealants and adhesives in automotive manufacturing. Therefore, environmental releases during curing and from products are expected to be negligible.It is noted in the screening assessment that when TMTD is used as an accelerator/vulcanizing agent or additive in automotive sealants and adhesives, the substance is considered to be transformed during curing/application processes, so that only residual amounts of TMTD are expected to remain as the parent compound in these products. As such, TMTD releases to the environment from the use of final vulcanized/cured products and from its application in sealants and adhesives in automotive manufacturing are not quantified in the assessment; rather, the quantitative exposure assessment focuses on TMTD releases during rubber compounding.

Releases in exposure assessment

Summarized commentSummarized response
Stakeholders commented on assumptions used in the exposure scenario, in particular that the use of production capacity results in overestimation of the daily quantity of TMTD used, resulting in inconsistency between imported tonnage and the “average” daily use. It is recognized that there is a range of sizes/capacities of facilities compounding rubber. The exposure assessment for TMTD does not assess any particular facility in the sector manufacturing tires or other rubber products. The representative quantitative scenario is focused on the compounding process in solid rubber manufacturing and is representative of shorter-term (non-continuous) processes relevant to compounding, recognizing that process accelerators other than TMTD are also used to manufacture rubber products. Therefore, the variability of the number of TMTD use days per year was noted. Import volumes for various known users were considered in the development of the quantitative exposure scenario and were used to verify the estimated daily production capacities for the representative exposure scenario. The assumed daily production capacities have good correlations with the reported import volumes. The representative exposure scenario was developed based on the average of the daily maximum rubber compound production capacities for the identified industrial compounders. Therefore, it does not represent the largest capacity possible.

Risk characterization

Summarized commentSummarized response
Stakeholders provided calculations for exposure resulting in risk quotients which are lower than 1, suggesting low risk to the aquatic organisms.Stakeholders calculated the daily use volume on the basis of annual imported tonnage divided by the total number of industrial facilities and 250 operational days per year. These calculations do not reflect the non-continuous use of this substance in Canada and, therefore, underestimate use quantity on days when TMTD is being used.


Summarized commentSummarized response
Stakeholders commented that the approaches outlined in the OECD Emission Scenario Document (ESD) on additives in rubber should be applied rather than those in the OECD ESD on plastic additives. In addition, they stated that emission factors proposed in the ChemRisk guidance document (developed for the European Tyre & Rubber Manufacturers’ Association (ETRMA)) should have been used.

The exposure scenario in the screening assessment used approaches considered most suitable based on scope and information outlined in the OECD ESD on additives in rubber compounds and the OECD ESD on plastic additives. The emission factors recommended in the ChemRisk guidance document (developed for ETRMA) were used for comparative purposes.

The OECD ESD on additives in rubber industry is intended to provide information on the sources, use patterns and release pathways of chemicals used as additives in rubber industry to assist the estimation of releases of chemicals to the environment. However, this guidance document does not specify the emission rates associated with raw material handling or equipment. Therefore, to support the quantitation of releases from these two sources, the OECD ESD on plastic additives was used to estimate releases associated with raw material handling losses as these practices are considered to be similar for rubber and plastic additives. 

The ChemRisk document was used to gain insight on the measured accelerator releases, since such data are not provided in the OECD ESD on additives in the rubber industry. However, as outlined in the screening assessment, the emission factors recommended by ETRMA do not have sufficient associated information to allow extrapolation to the Canadian context. Therefore, they were considered to be supporting information. ETRMA emission factors associated with small/medium facilities with no pretreatment were used in the generic exposure scenario for comparative purposes.

Environmental fate and behaviour

Summarized commentSummarized response
TMTD undergoes rapid photodegradation and hydrolysis in water prior to and during wastewater treatment. As such, and considering the low quantity of TMTD expected to be released, it may be undetectable in wastewater.It is recognized in the screening assessment that TMTD undergoes rapid abiotic degradation in the aquatic environment. The empirical hydrolysis half-life was used in modelling of removal rate during wastewater treatment.

Risk management – general, alternatives and socio-economic impacts

Summarized commentSummarized response
One stakeholder supports risk management measures focusing on the primary sources of potential releases of TMTD into the environment via regulatory and non-regulatory controls.The information presented in the draft screening assessment indicates that releases from current uses of TMTD in compounding of solid rubber products may pose a risk to aquatic organisms. Risk management actions would focus on addressing identified exposure sources of concern. 
One stakeholder stated that alternatives for TMTD are available but might not be suitable or economically viable for the manufacturing of auto parts (both new and replacement). Substitution would require a high level of effort and could only be considered in the long-term and take into account cost-benefit balance.Risk management instruments are being considered in the context of preventing or minimizing the release of TMTD to levels that are protective to the environment and that are technically and economically feasible, taking into consideration socio-economic factors. Risk management would focus on identified sectors with exposure sources of concern (i.e. the rubber products manufacturing sector). 
One stakeholder indicated that the use of alternatives to TMTD is considered confidential business information.Companies reporting information can request that it be handled as confidential pursuant to section 313 of CEPA.
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