Scientists Make a Smell of a Difference For Residents Downwind of Farms

Researchers George Preti and Charles Wysocki, from Philadelphia's Monell chemical senses centre, have hit upon a way to make the lives of people who live near farms more bearable at times of the year when farmers fertilise their land the natural way - they've come up with a chemical that makes you think that manure smells nice! It's been known for some time that when an odour is present for a long period of time the nose learns to ignore it, a process called adaptation. But certain chemicals can also fool the nose into ignoring other smells too, termed cross-adaptation, and this is the approach taken by the Monell scientists. They first tracked down the identity of the molecules that make manure hard to live with, and then set about testing pleasant-smelling chemicals to find examples capable of "blinding" the nose to the "bouquet de manure". They eventually tracked down the perfect example - the ethyl-ester of 3-methyl-2-octanoic acid which, when added to manure, can counteract its odour. Naturally, the smell still reaches your nose, but you just don't notice it. If combined with other odour-combating chemicals, say the scientists, it could make a smell of a difference to life downwind of the farm at fertilising time.