Toxic substances list: methane

Methane is a colorless, odorless, flammable gas that is the simplest hydrocarbon and is the major constituent of natural gas. Like carbon dioxide, methane is exchanged naturally between the Earth’s surface and the atmosphere, however, methane is lighter than air and is removed from the atmosphere primarily through chemical processes involving the chemical hydroxyl radical, OH[1]. These chemical interactions finally produce water and carbon dioxide. A small amount of methane is also absorbed directly by soils. Methane is present in the Earth’s atmosphere at low concentrations and acts as a greenhouse gas. Methane, usually in the form of natural gas, is used as feedstock in the chemical industry (e.g., hydrogen and methanol production), and as fuel for various purposes (e.g., heating homes and operating vehicles). Methane is produced naturally during the decomposition of plant or organic matter in the absence of oxygen, as well as released from wetlands (including rice paddies), through the digestive processes of certain insects and ruminant animals such as termites, sheep and cattle. Methane is also released from industrial processes, fossil fuel extraction, coal mines, incomplete fossil fuel combustion, and garbage decomposition in landfills.  

Methane was added to Schedule 1 of CEPA in November 2005. Under subsection 90(1) of CEPA , a substance tcan be added to Schedule 1 of CEPA by the Governor in Council on the recommendation of the ministers of the environment and health if it is determined that a substance is entering or may enter the environment in a quantity or concentration or under conditions that:

(a) have or may have an immediate or long-term harmful effect on the environment or its biological diversity;

(b) constitute or may constitute a danger to the environment on which life depends; or

(c) constitute or may constitute a danger in Canada to human life or health.

Based on an analysis of the existing science, most notably documented in the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC) and in subsequent reports including the Fifth Assessment Report (2014), there is sufficient evidence to conclude that the principal greenhouse gases, namely carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6) constitute or may constitute a danger to the environment on which life depends. The addition of methane to schedule 1 of CEPA gives the Government the power to put in place a variety of preventative or control actions to control CH4 under that same Act. The reporting on releases of CH4 to the atmosphere is regulated under section 46 of CEPA and is required from large industrial and commercial facilities that meet a certain threshold for their combined emissions in CO2 equivalent of the six principal greenhouse gases.

CAS (Chemical Abstract Service) registry number: 74-82-8

[1]An Introduction to Climate Change - A Canadian Perspective; Environment Canada 2005

Risk Assessment


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