Humans have an invisible aura around our bodies which could be cleaning the air we breathe, scientists have found.
A study has shown, for the first time, that an invisible haze of air-cleansing molecules is produced on human bodies when ozone in the air reacts with oil made by our skin.
Short-lived molecules called OH radicals make up the aura, and they are known to neutralise toxic molecules when they are made by sunlight outside, earning the nickname "detergents of the atmosphere".
But the discovery of the aura, technically known as an oxidation field, around people shows for the first time that OH radicals are also made by human bodies.
However, experts do not know if the field is a force for good or bad because the impact of the aura remains unknown.
Compound could 'become toxic'
"[The field] may be cleaning the air before I breathe in, but we don't know," Prof Jonathan Williams, of the Max Planck Institute for Chemistry in Mainz, Germany and the lead author of the study, told The Telegraph.
He said: "The other possibility, which is more concerning, is perhaps a compound which is considered to be harmless could become more toxic than its precursor when it's oxidised in the OH field. Now we've discovered this, more research has to be done."
Williams and his team put four people in a sterile room with oxygen masks on and measured the level of OH radicals in the air. They then added ozone to the room and saw a dramatic spike in the level of the chemicals and made images from the data showing the oxidation fields.
The chemical silhouette, Williams said, somewhat resembles the glow of green radiation around a barrel of nuclear waste in a cartoon.
Closer analysis revealed that squalene, a chemical which keeps skin supple, reacts with ozone and produces the OH oxidation field via a sequence of complicated chemical reactions.
"When I'm breathing in there is chemistry going on, which is changing emissions from the sofa I am sitting on into other compounds," Williams said.
"We simply do not know whether those compounds are more or less harmful than the sofa's emissions themselves.
"There's an immediate health implication [to this research]. We need to study them rather than just measuring what a sofa emits. We need to measure what a sofa and a person make together as the interaction of the emissions with our field is more important."
Another mechanism for formation
Previously it was thought the air-cleaning OH chemicals only formed outside in sunlight, but the new finding shows another mechanism for their formation.
"Radicals are extremely ephemeral and created in the air in sunbeams," Williams said.
"Then they react like kamikaze pilots and immediately attack any compound around them. They're like snarling lions, horrible beasts that only want to snatch a hydrogen atom off anything else to make itself into water and become stable.
"We should be mounting statues to this radical," he said. "In every city there should be a monument to the OH radical because it's preventing us from poisoning ourselves every day."
The findings are detailed in the journal Science, and the team are now looking to see if similar auras exist around other animals, specifically dogs.