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In a worst-case scenario, inhalation of nitrous oxide can lead to hypoxia, where the brain does not get enough oxygen.

Some researchers say xenon increases production of a protein called erythropoietin that fights hypoxia, a condition that occurs when the body can't get enough oxygen.

Drinking them — even in tiny amounts — causes a type of blood poisoning that turns victims blue from sudden hypoxia.

The jet returned to Manchester, with no injuries reported, but investigators said it was likely those on board "were exposed to a progressive hypoxia risk".

The scientists note that climate change and pollution are combining to force marine ecosystems to experience unprecedented stressors including harmful algal blooms, ocean acidification and hypoxia.