According to the EPA approximately 5% of the Nations Air Pollution is created from mowing our lawns. Millions of Americans tend to there lawns and gardens each weekend with all types of gas powered gadgets. A rough estimate is that over 800 million gallons of gas per year is used to maintain our yards. Until recently the emissions from the machines where unregulated and emit high levels of nitrogen oxides, volatile organic compounds and carbon monoxide. In addition, large amount of gas and oil are spilled during refills. It is estimated that in a one hour time period a conventional lawn mower can produce the same amount of pollutants as a 100 mile trip in your late model vehicle.
Electric mowers and trimmers are one alternative. There are also many types of adapter kits that you can use to reduce your emissions on older equipment. Proper planning during initial and redesigned landscapes can also be a big bonus for both the environment and your wallet. By planting less grass and more native plants that are adapted to your local Ecosystem, you can reduce emission, time spent on maintenance and a great reduction in water use.
I have attached a website that can help you calculate the amount of air pollution your mower produces. There are many sites available and I randomly stubble across this one.