How Grass Gets Revenge After You Mow I T
Sun Herald
Sunday April 25, 1999
MOWING the lawn is bad for the planet.
US scientists have given us the perfect excuse to stop that weekend chore: the sweet scent of cut grass is a nasty cocktail of chemicals adding to smog.
A Colorado University team discovered cut grass gives off an instant blast of volatile organic compound followed by an intense emission lasting for several hours as the cuttings dry.
The scientists believe that when the grass is "wounded" by the mower blades it resorts to chemical warfare - releasing large amounts of pollutants, including acetaldehyde, methanol, acetone and butanone.
These volatile organic compounds are an important ingredient of the summer smog which increasingly covers cities, according to Professor of Biochemistry Ray Fall.
Grazing animals also add to the problem. "Every time even a cow chews the grass you get these little surges of emissions," he said.
His research found 1.6 million tons of acetone was added annually to the atmosphere by harvesting crops, against eight million released naturally.
Some of the organic compounds can cause cancer but Professor Fall's team is keen to avoid a health scare over suburban lawn-mowing.
"It just doesn't seem likely that the smell of fresh grass can be toxic," he said. "I don't think people will be chemically challenged by it."
And science commentator Dr Karl Kruszelnicki said he wasn't scared of defensive vegetation.
"Grass can't run so its defence system is chemical warfare," he said. "If we run at it with a lawn mower it's not going to just sit there and take it.
"It does all depend on the magnitude of cut-grass pollutants; I don't think this is going to be a problem in those leafy northern-suburb gardens but more of a concern for allergic people in the country."
© 1999 Sun Herald
