A new study has found that some plants can increase the rate of ozone production by up to 50 times.
Rosemary, juniper, and pine trees are among certain plants that emit chemical compounds known as terpenes, thought to help deter insect predators, or protect the plant from other stresses like high temperatures.
However, upon mixing with pollutants like nitrogen oxides, produced by industry and traffic, terpenes react to produce ozone-a key ingredient of photochemical smogs, and a health hazard that can trigger breathing difficulties and may cause cancer.
Mark Potosnak, from DePaul University in Chicago, Illinois, measured terpene emissions from plants lining the sidewalks of Las Vegas.
He and his colleagues also studied air quality, including levels of nitrogen oxides and ozone, in a number of central and suburban regions.
The researchers said that, in all cases, ozone levels exceeded the US Environmental Protection Agency safe standard-an average of 75 parts per billion (ppb) over an eight-hour period-and that in the worst case reached 107ppb.
Upon modelling the data, the researchers came to the conclusion that the mixing of terpenes and pollutants was responsible for a significant rise in ozone levels - boosting production rates by up to 50 times - particularly downwind of the plants, in suburban neighbourhoods.
"It's surprising because Las Vegas has relatively little urban vegetation," New Scientist magazine quoted Potosnak as saying.
He believes that the problem of temperature can be solved across the world by choosing plants carefully.
"Some plant species are very low emitters. Shoestring acacia is a great plant: low water use and low terpene emissions," he said.
A research article on the study has been published in the journal Atmospheric Environment.