Air Pollution and the Smell of Cut Grass

Recently we have demonstrated that grass and cut grass are important sources of volatile organic compound (VOC) emissions into the atmosphere. The production of these VOCs can be traced back to plant growth, maintenance and wound defence mechanisms. The gases emitted as part of these wound defence mechanisms are responsible for the smell of freshly cut grass, and are also highly photochemically reactive. These emissions from grass and cut grass are not currently included in urban and global emissions inventories. Our preliminary estimate is that, within an urban airshed, during the growing season, about one third of the emissions of photochemically reactive VOCs come from grass and cut grass. These grass emissions should be included in models of urban photochemical pollution so that accurate smog predictions can be obtained.