Comments in response to the Draft Screening Assessment re Hydrogen Sulfide (H2S), Sodium Sulfide (Na(SH)) and Sodium Sulfide (Na2S)

A joint statement from five environmental and health organizations opposing a Draft Screening Assessment by Environment and Climate Change Canada that proposed hydrogen sulfide (H2S), sodium bisulfide (Na(SH)), and sodium sulfide (Na2S) do not meet toxicity criteria under the Canadian Environmental Protection Act, 1999 (CEPA). The organizations argue that H2S should be classified as toxic due to risks to communities near oil and gas operations, the adverse health effects of olfactory nuisance, and flaws in the government's neurological and respiratory risk analyses.

• The organizations oppose the government's conclusion that hydrogen sulfide (H2S) does not meet the toxicity requirements of subsection 64(c) of the Canadian Environmental Protection Act, 1999 (CEPA), arguing that the government failed to use a "science-based, precautionary approach".
• Evidence is provided of severe H2S releases from oil and gas operations in Saskatchewan, including reports of concentrations reaching 150,000 ppm—which is 150 times the level that causes instant death—and 11 facility audits that all failed with "serious infractions".
• The organizations argue that olfactory nuisance should be considered an adverse health effect, citing legal precedents in Ontario, British Columbia, and Alberta where odours caused symptoms such as nausea, headaches, anxiety, and irritation.
• The statement claims the Draft Screening Assessment's neurological risk analysis is flawed for using a no observable adverse effect concentration (NOAEC) of 30 ppm from rat studies, whereas the California Office of Environmental Health Hazard Assessment (OEHHA) uses a much lower acute reference exposure level of 0.03 ppm.
• The organizations assert that the Draft Screening Assessment failed to apply uncertainty factors to the chronic inhalation NOAEC of 10 ppm, which they argue is contrary to standard risk assessment practices.
• The document states that the Margins of Exposure (MOEs) for acute respiratory effects (60 to 200) and chronic inhalation (320 to 10,000) fall below the 1,000 threshold established by Health Canada policy, which requires further analysis.

APA

Canadian Association of Physicians for the Environment (2017). Comments in response to the Draft Screening Assessment re Hydrogen Sulfide (H2S), Sodium Sulfide (Na(SH)) and Sodium Sulfide (Na2S). https://cape.ca/wp-content/uploads/2018/04/1.Re-Hydrogen-sulphide-Nov.-8-2017.pdf

Chicago

Canadian Association of Physicians for the Environment. Comments in response to the Draft Screening Assessment re Hydrogen Sulfide (H2S), Sodium Sulfide (Na(SH)) and Sodium Sulfide (Na2S). 2017. https://cape.ca/wp-content/uploads/2018/04/1.Re-Hydrogen-sulphide-Nov.-8-2017.pdf.

Wikipedia

{{cite press release |author=Canadian Association of Physicians for the Environment |title=Comments in response to the Draft Screening Assessment re Hydrogen Sulfide (H2S), Sodium Sulfide (Na(SH)) and Sodium Sulfide (Na2S) |date=8 November 2017 |url=https://cape.ca/wp-content/uploads/2018/04/1.Re-Hydrogen-sulphide-Nov.-8-2017.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@misc{canadianassociationofphysiciansfortheenvironment2017comments, author = {{Canadian Association of Physicians for the Environment}}, title = {{Comments in response to the Draft Screening Assessment re Hydrogen Sulfide (H2S), Sodium Sulfide (Na(SH)) and Sodium Sulfide (Na2S)}}, publisher = {Canadian Association of Physicians for the Environment}, year = {2017}, month = nov, url = {https://cape.ca/wp-content/uploads/2018/04/1.Re-Hydrogen-sulphide-Nov.-8-2017.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }