Summary of Public Comments received on the Challenge Substance 1,4-Benzenediamine, N,N'-mixed Phenyl and tolyl derivatives (BENPAT) (CAS No. 68953-84-4) and 1,4-Benzenediamine, N,N'-mixed tolyl and xylyl derivatives (BENTAX) (CAS No. 68478-45-5) Draft Screening Assessment Report and Risk Management Scope for Batch 11

Use of additional physical-chemical properties data that was submitted during the public comment period was recommended.

The fugacity modelling estimates are not realistic given the physical/chemical properties of the structures. It is believed that if released to the environment, BENPAT will partition primarily to soil and sediment, not water.

Experimental physical chemical properties should be used as model inputs.

Data from two newly submitted studies on physical chemical properties were incorporated into the final screening assessment.

Use patterns of the substance including releases from manufacturing processes and from products indicate that water is one of the receiving environmental compartments. Therefore, fugacity scenarios presented in the final screening assessment are realistic and results are consistent between those obtained for the whole substance and the components. Fugacity modelling results were presented as a range for each environmental compartment, based on physical chemical properties available for the substance as a whole and for individual components. The model was run several times to accommodate the combination of model inputs.

Modeled values were used as inputs when experimental values were not available.

BENPAT is mainly composed of components 1, 2 and 3 identified in the screening assessment at a distribution of approximately 25%, 50% and 25%, respectively. The empirical aquatic data indicates the bioaccumulation potential of an individual component.

However, the conclusion for the bioaccumulation potential of BENPAT was revised in the final screening assessment. It was determined that the results from the available aquatic bioaccumulation study were uncertain. Additional information including experimental depuration rates, experimental log K_ow values, and mammalian studies that were submitted during the public comment period, were considered in the final screening assessment of BENPAT. While it is acknowledged that the substance has a significant potential to bioaccumulate in aquatic organisms, it is concluded based on the available weight of evidence, that it does not meet the bioaccumulation criteria as set out in the Persistence and Bioaccumulation Regulations of the Canadian Environmental Protection Act, 1999 (CEPA, 1999).

Releases to the environment from the Mass Flow Tool estimation are provided in percentages. These can be applied to the quantity range of BENPAT imported in 2006, resulting in lower and upper estimates of the potential quantities released into the environment.

The estimates of potential releases into the environment provided in the screening assessment for BENPAT and BENTAX are based on section 71 of CEPA 1999 survey results. Response to this survey was mandatory for industries involved in the manufacture, import and use of these substances above the reporting thresholds. The exact import quantities provided to the government are considered confidential business information and cannot be disclosed.

Estimations of environmental concentrations of antidegradants based on a tire marker study were provided in the draft screening assessment since information on the environmental levels of antidegradants including BENPAT stemming from tire wear was not available. These semi-quantitative estimations were were removed from the final screening assessment. Revisions considered in the final screening assessment included site specific industrial release scenarios, consumer release scenarios, risk quotient analysis and additional information (e.g., reliability of tire markers and detection of BENPAT in tire particles).

Information provided in the public comments submissions was reviewed and incorporated in the final assessment when deemed appropriate. Assumptions presented without supporting documentation or referencing were not incorporated as it was not possible to review their basis. All available information, including that submitted during the public comment period, was considered in determining the most appropriate approach to estimate environmental exposure resulting from tire wear.

1. Data gaps and deficiencies along with claims of confidentiality weaken the argument that general population exposure to consumer products is unlikely.
2. Reproductive and developmental effects should be researched further.
3. Exposures in vulnerable populations should be considered.
4. Synergistic effects of chemical mixtures needs to be examined.
5. Water solubility should be experimentally evaluated to determine modeled toxicity accurately.
6. Lack of information on environmental releases and concentrations in Canada needs to be addressed and quantified.
7. There is an absence of toxicity data for soil or sediment organisms for both substances.
8. Exposure estimates need to be more thorough using information derived through environmental monitoring.
9. Disposal and legacy issues from the use of these substances need to be addressed.

1. Data gaps and deficiencies were associated with modeled estimates of environmental exposure in the SAR. However, these estimates were based on conservative assumptions, and margins between upper-bounding estimates of exposure were considered adequate to address uncertainties in the health effects and exposure databases. With regards to consumer products exposure, information was available but not reported in the SAR for confidentiality reasons. Based on this information, general population exposure to consumer products is considered unlikely.
2. Reproductive and developmental effects were taken into consideration in the risk characterization and margins of exposure were considered to be adequate to address uncertainties in the health effects and exposure databases.
3. Exposure scenarios assessed in the screening assessment are considered conservative enough to be protective of vulnerable populations in Canada.
4. The synergistic effects of chemical mixtures are not precluded from screening assessments as long as sufficient information is available. This information was not available for BENPAT and BENTAX, so the assessment focused on the substances’ inherent ability to elicit adverse effects.
5. Solubility of BENPAT that was determined experimentally was described in the screening assessment. Since several reliable aquatic toxicity studies are available for BENPAT, modelling of aquatic toxicity is not required and, therefore is not considered in the final screening assessment.
6. Information regarding measured environmental releases and concentrations for BENPAT and BENTAX is not available. It is recognized that data gaps exist in the environmental monitoring of these substances. It is additionally noted that reliable environmental monitoring is scientifically and technically difficult as these substances are multi-component, complex reaction products. Estimates of environmental releases from manufacturing sites in Canada determined for BENPAT were submitted during the public comment period and substantiated information has been considered as appropriate in the final screening assessment.
7. Soil and sediment toxicity studies for BENPAT were submitted to Environment Canada and are considered in the final screening assessment. Soil and sediment toxicity data were not available for BENTAX, and models to address toxicity in soil and sediment are not currently available.
8. As reliable environmental monitoring data is not available for BENPAT and BENTAX, exposure assessment is based on appropriate assumptions for release and exposure.
9. Disposal sites and contaminated sites are under provincial jurisdiction. The risk management process consults all relevant stakeholders at every stage