Polymer Rapid Screening Initiative Public Comment and Answer Table
Comments on the Draft Rapid Screening Assessment of Polymers Identified from Phase Two of the Domestic Substances List Inventory Update to be addressed as part of the Chemicals Management Plan were submitted by Dow Chemical Canada and the Industry Coordinating Group for the Canadian Environmental Protection Act, 1999.
A summary of comments and responses is included below organized by topic:
| Topic | Comment | Response |
|---|---|---|
| Methodology | Consider using a statistical approach in Step 4 with the 95th percentile of a Species Sensitivity Determination (SSD) rather than using the worst case acute effect value, to more appropriately accommodate the 1000 or more ecotoxicity data endpoints. | Applying a SSD approach would have made use of the full range of available polymer data endpoints. However, it was decided for the purpose of simplicity to use the most sensitive effects endpoint instead. While use of the most sensitive value is recognizably a more conservative approach, this did not result in a different outcome for any of the polymers due to the values used in the generic exposure scenarios for all of the polymers. |
| Methodology | An examination of the mathematics of both Scenario A and Scenario B raises the questions: Are results pre-determined to remove the substances from further assessment? Should some unique parameter per substance be examined to confirm the finding? | In step 4 of the ecological assessment, exposure scenarios that reflect reasonable worst case scenarios for each substance were selected. These parameters identify substances that are unlikely to pose any environmental concerns, and are generally the same as those applied in Rapid Screening Evaluation of non-polymers. These scenarios returned uniform results because the same quantity and Critical Toxicity Value (CTV) was applied to all polymers in this assessment. |
| Information and data gaps | In the synopsis, the ecological assessment approach is very conservative and is a positive aspect of the process. Inclusion of a hazard screen for human health is also positive. However, it was not apparent that a hazard screen was considered for human health. The hazard screen should be given greater emphasis in the synopsis. | The synopsis has been revised to include a description of the hazard screen for human health. |
| Information and data gaps | In the draft assessment, the context of what constitutes “professional judgment” is presented only for some steps. The criteria or considerations on which professional judgment is based should be presented and discussed in each section of the assessment where it is utilized. | The document has been revised to clarify how professional judgement was used during the rapid screening process. |
| Information and data gaps | Figure 2 is confusing and should provide a clearer presentation of how exposure scenarios on page 6 are tied to the assessment. | Figure 2 has been simplified to better indicate the possible outcomes of the assessment. |
| Information and data gaps | Provide a description of the term “other available information” (page 14 of the assessment) for determining potential for direct exposure. | For each substance, general literature searches, including a web-based search, were conducted on publically available information. |
| Risk characterization | The potential for compounding or excessive conservative assumptions is appropriately recognized in the report, and should be routinely considered in other assessments conducted by the Government of Canada. However, characterizing the conservatism of the individual parameters as "moderate" in Step 4 (aquatic exposure scenarios) is questionable. A review of the parameters illustrates that the values utilized tend to be the maximum (i.e. quantity) which makes it unclear if the individual parameters are moderate or if these values should be recognized as "high." |
Polymers included in this evaluation were those that were not reported in the second phase of the Domestic Substances List Inventory Update by any individual reporter, above the required reporting threshold of 1000 kg/yr. For the purpose of rapid screening, it was conservatively assumed that the polymers are in commerce at exactly 1000 kg/yr. Wording of the document has been revised to recognize this assumption. Other parameters used in the scenarios in step 4 generally represent only a moderate level of conservatism. |
| Risk characterization | Consider using more accurate representative values for quantities of the substance being used and duration of its use. In particular, use a more accurate yet protective input value of 750 kg or 500 kg because the polymers in the assessment were reported as “not in commerce” or less than 1000 kg in use. The standard practice of taking 1/2 of the limiting value (i.e., 1000 kg) when estimating potential presence should also be considered. Also, a more accurate duration of use per year for most polymers is 250 days (reflects a five day work week), rather than 150 days, because polymers are used regularly and not seasonally. |
Conservative modelling was conducted using 1000 kg to provide a worst case scenario for potential exposure based on the available information. Based on the low quantity of these substances used annually (i.e. 1000 kg or less), it is considered reasonable that the substance of interest will not be used throughout the year on a daily basis. For this reason, 150 days of activity is considered appropriate. |
| Risk assessment | If a polymer was found to meet Reduced Regulatory Requirements (RRR), no further action on the polymer should be required. | No polymers in the draft rapid screening assessment were found to meet the RRR definition which is described in the New Substances Notification Regulations (Chemicals and Polymers). |
| Risk assessment | The hazard screening criteria used in this assessment should be considered for future polymer assessments under the Chemicals Management Plan. A hazard screen may be used to “off ramp” polymers that have no unacceptable hazard or reduced hazard characteristics. | This comment will be taken into account for future screening assessments on polymers. |
| Other | There is a statement in the synopsis, “The second and third steps of the process involved identifying polymers that will likely have water extractability less than 2 %...”. This should be revised to say: "greater than 2%". |
The assessment was updated with the correct wording (“greater than 2 %”). |