Summary of public comments received on the draft federal environmental quality guidelines for benzene, toluene, ethylbenzene, xylene (BTEX)

Comments on the draft Federal Environmental Quality Guideline for BTEX were submitted by the Alberta Ministry of Environment and Protected Areas and Stantec Consulting Ltd.

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

Editorial/background information

Comment summary 1: Editorial comments related to formatting and edits for clarifications.

Response 1: Editorial suggestions were addressed and edits made.

Methodology

Comment summary 2: Consider providing the rationale for using the selected log K_ow values, clarifying that the reported log K_ow values from McGrath et al. (2018) are estimates and not directly measured experimental values, and clarifying why other values available in the literature were excluded.

Response 2: Log K_ow values from other sources, summarized in Mackay (2006), have now been added and the inputs for the TLM changed to a geometric mean of reported Log Kow values (see TLM tab in the Appendix). This change in approach does change the final TLM HC₅ estimates and therefore those changes have been made throughout the document. Log K_ow values reported in McGrath are stated in the factsheet as computer (EPI Suite Ver 4.11) estimates.

Comment summary 3: We agree that not invoking the protection clause is appropriate.

Response 3: Thank you for your comment.

Comment summary 4: Clarify if the ACR (acute to chronic ratio) approach has been used to develop other FEQGs, or by other jurisdictions as no approach was referenced.

Response 4: Additional text and references have been added to the factsheet.

Comment summary 5: Was this risk of additive toxicity considered in the derivation of the FEQGs?

Response 5: A Hazard Index approach has now been added to the factsheet to address this.

Data

Comment summary 6: Did ECCC calculate SSDs (Species Sensitivity Distributions) with and without marine species?

Response 6: Yes, SSDs were calculated without marine species and the resultant HC5 were either the same or very minimally different than when included. BTEX are not expected to vary in toxicity in the two environments. Additional text was added for justification.

Comment summary 7: Why was the L. pipiens LC20 value of 0.4 mg/L (Kennedy 2006) not included in the SSD dataset?

Response 7: The endpoint was considered but not included in the SSD because there was a more preferrable endpoint. Justification has been added to column T in the Appendix.

Comment summary 8: Clarify why Kennedy (2006) chronic toxicity data for toluene do not appear to have been considered for inclusion in the SSD.

Response 8: Kennedy (2006) was considered for inclusion in the SSD (see appendix). The O. mykiss LC20 of 0.005 mg/L from Kennedy (2006) is now included in the SSD since even though the Black et al. (1982) is a more preferred LC10, the LC20 values is lower. This change had no change to the HC₅ value.