Toxic substances list: nitrous oxide

Nitrous oxide is a colourless, nonflammable, sweet-smelling gas, which is heavier than air. Used as an anesthetic in dentistry and surgery and as a propellant in aerosol cans, nitrous oxide is most commonly produced via the heating of ammonium nitrate (NH4NO3). It is also released naturally from oceans, by bacteria in soils, and from animal wastes. Other sources of nitrous oxide emissions include the industrial production of nylon and nitric acid, combustion of fossil fuels and biomass, soil cultivation practices, and the use of commercial and organic fertilizers.

Nitrous oxide is present in the Earth’s atmosphere at low concentrations and acts as a greenhouse gas. Nitrous oxide was added to Schedule 1 of CEPA in November 2005. Under subsection 90(1) of CEPA, a substance can 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 nitrous oxide to schedule 1 of CEPA gives the Government the power to put in place a variety of preventative or control actions to control N2O under that same Act. The reporting on releases of N2O 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: 10024-97-2

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Chemicals Management Plan
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