The Human Volatilome: A Complete Catalogue of the Gases We Emit

The human body is constantly releasing gas — not just from breath, but from skin, urine, and more. For decades these emissions were studied piecemeal. This landmark 2014 review pulled the entire literature together into a single reference: the “human volatilome.”

What the researchers did

The team — the same leading group behind much of the field’s foundational work — synthesised every published study on volatile organic compounds (VOCs) emitted by apparently healthy people. They assigned each compound a standard chemical identifier and grouped them by chemical class and by where in the body they appear: breath, skin, urine, feces, saliva, blood and breast milk.

What they found

• 1,765 distinct VOCs were documented across all body compartments.
• 279 of those were catalogued from urine specifically. Urinary compounds span ketones (such as acetone, a marker of metabolic state), sulfur compounds and aromatics like p-cresol and indole (products of gut-microbial protein fermentation), plus amines such as ammonia and trimethylamine.
• Several gut-derived compounds — p-cresol, dimethyl sulfide, indole, acetone — appear in both urine and stool. These molecules travel from the colon, through the bloodstream and liver, and out via the kidneys: the gut-kidney axis made visible in chemistry.

Why it matters

This catalogue established that urine is not a chemically empty fluid but a window onto the whole body’s metabolism. As the authors note, urinary VOCs “reflect dietary intake, gut microbial activity, host metabolic status, and renal function — providing a window into systemic physiology through a non-invasive matrix.” It remains the canonical map of what a healthy body emits, and the baseline against which disease-related changes are measured.

“A total of 1765 VOCs are listed… of which 279 have been assigned from urine in apparently healthy individuals.”