Over a year since controversy around carbon monoxide inhalation in cycling began, the World Anti Doping Authority (WADA), has announced it will ban the use of the gas for performance enhancing methods from 2026.
Carbon monoxide (CO) inhalation involves breathing in a dose of the gas through a measurement tool called a CO rebreather. The exposure to the gas can trigger hypoxia (a lack of oxygen), which can lead to the release of red blood cells in the body, improving aerobic capacity like VO2max and maximal oxygen uptake. This form of blood manipulation as a tool to enhance athletic performance is to be banned.
“The non-diagnostic use of carbon monoxide (CO) was added to the Prohibited Methods as a new section, M 1.4,” WADA wrote in an update to its Prohibited List. “It can increase erythropoiesis [the overproduction of red blood cells] under certain conditions.”
Despite teams including UAE insisting that “carbon monoxide […] is a well established, safe, professional method that is backed by a very large amount of research,” the UCI maintained its position.
The practice of CO doping was first exposed by Escape Collective in July of last year, who warned that its use could infringe WADA’s rules around the artificial manipulation of blood.
The article concluded with a clear warning: “There is no hard evidence that WorldTeams are using CO inhalation for performance enhancement. But their exploration of the technique alone makes it more likely that someone else will cross that line.”
Teams were quick to respond. Uno-X Mobility told the outlet that the use of CO rebreathers for diagnostic purposes “is not something we are even considering”, and UAE Team Emirates dropped its use of the tool post-publication.
