Toxic substances list: carbon dioxide

Carbon dioxide, also called carbonic acid gas, is a naturally occurring colourless, odorless, incombustible gas formed during respiration, combustion, decomposition of organic substances, and the reaction of acids with carbonates. Carbon dioxide is used in carbonated drinks, fire extinguishers, and as dry ice for refrigeration. Carbon dioxide is heavier than air. It is present in the Earth’s atmosphere at low concentrations and acts as a greenhouse gas. Carbon dioxide is constantly being removed from the air by its direct absorption into water and by plants through photosynthesis.  In turn, it is naturally released into the air by plant and animal respiration, decay of plant and soil organic matter, and outgassing from water surfaces. Small amounts of carbon dioxide are also injected directly into the atmosphere by volcanic emissions and through slow geological processes such as the weathering of rock[1]. Anthropogenic sources of carbon dioxide emissions include combustion of fossil fuels and biomass to produce energy, building heating and cooling, land-use changes including deforestation, manufacture of cement and other industrial processes. 

Carbon dioxide 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:

  1. have or may have an immediate or long-term harmful effect on the environment or its biological diversity;
  2. constitute or may constitute a danger to the environment on which life depends; or
  3. 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 carbon dioxide to schedule 1 of CEPA gives the Government the power to put in place a variety of preventative or control actions to control CO2 under that same Act. The reporting on releases of CO2 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: 124-38-9

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

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