What you're seeing here is an unlikely source of pollution.

No, not the mower, the grass. It's been known for a long time that as they grow, trees release volatile organic compounds but no one had studied grass. So Ian Galbally of Australia's science agency CSIRO and Wayne Kirstine from Monash University decided to find out.

"It was totally lets see if they do. And as it turned out we did find emissions from grass but the most exiting aspect of it was we looked at cut grass. And it turns out that the emissions from cut grass are hundreds of times higher than the emissions from normal grass."

What they found was, when grass is cut, it releases a gas, which is an antibiotic, to both seal the wound and protect it against infection.

"But it has very interesting consequences because these gases are quite highly reactive and so within an urban region, the regular mowing of grass can in fact contribute to the hydrocarbons within the air that contribute to urban smog."

Scientists are comparing grass gas emissions, with those from cars and industry, to determine their overall impact on photochemical smog.

There may need to be an encouragement to grow less traditional grasses, which don't require regular mowing. Already scientific bodies in other countries, including the United States, are following and extending the Australian research into this sweet smelling cause of pollution.

CSIRO Enquiries
Email: Enquiries@csiro.au
Phone: 1300 363 400
Locked Bag 10
Clayton South
VIC 3169