Summary of Public Comments Received on the Draft Screening Assessment for Ethene [Chemical Abstracts Service Registry Number (CAS RN) 74-85-1]
Comments on the draft screening assessment for ethene to be addressed as part of the Chemicals Management Plan were provided by Dow Chemical Canada and Imperial Oil.
A summary of comments and responses is included below organized by topic:
| Topic | Comment | Response |
|---|---|---|
| General | The scientifically justified conclusions and positive aspects identified in the assessment are supported. | Comment noted, and was considered in the final Screening Assessment. Comment did not result in changes. |
Methodology |
Use the conservative no observed adverse effects concentration (NOAEC) of 11.5 µg/m3 rather than the critical toxicity value (CTV) of 5.6 µg/m3. | Plant sensitivity to ethene varies and the CTV of 5.6 µg/m3 is considered to be a NOAEC derived from a large experimental data set for a sensitive species and was used to predict concentrations that decrease seed yield by 10%. Assessments are based on the best available information and conservative measures are used when assessing risks. |
| Methodology | The use of an application factor of one for the short and long-term CTVs is well supported as the CTVs are likely very conservative in relation to real world exposure scenarios. | Comment noted, and was considered in the final Screening Assessment. Comment did not result in changes. |
| Methodology | A methodology should be developed to determine and account for background concentrations of substances considered in the Chemicals Management Plan. Considering the large amount of data on background concentrations of ethene, this substance could be used for developing this methodology. | Comment noted, and was considered in the final Screening Assessment. Comment did not result in changes. |
| Environmental Fate | The assessment should not consider degradation products. Consider deleting references to formaldehyde as a degradation product of ethene. | Degradation products are considered in assessments as appropriate. Formaldehyde was previously assessed and it is appropriate to acknowledge it as a degradation product of ethene. |
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