Kyoto Protocol European Union-15, made up of 15 states at the time of the Kyoto negotiations) commit themselves to binding targets for GHG emissions. The targets apply to the four greenhouse gases carbon dioxide (), methane (), nitrous oxide (), sulphur hexafluoride (), and two groups of gases, hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs). The six GHG are translated into CO equivalents in determining reductions in emissions. These reduction targets are in addition to the industrial gases, chlorofluorocarbons, or CFCs, which are dealt with under the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer. Under the Protocol, only the Annex I
Nitrous oxide that cuts off their supply of fresh air. Long-term exposure to nitrous oxide may cause vitamin B deficiency. It inactivates the cobalamin form of vitamin B by oxidation. Symptoms of vitamin B deficiency, including sensory neuropathy, myelopathy, and encephalopathy, may occur within days or weeks of exposure to nitrous oxide anaesthesia in people with subclinical vitamin B deficiency. Symptoms are treated with high doses of vitamin B, but recovery can be slow and incomplete. People with normal vitamin B levels have stores to make the effects of nitrous oxide insignificant, unless exposure is repeated and prolonged (nitrous oxide abuse). Vitamin