An hour’s cutting the grass with a petrol-engined mower generates the same air pollution as a 100 mile car journey. If the mower is old, the pollution could be equivalent to a 650 mile journey, says Dr Roger Westerholm.* He recommends that all petrol mowers are fitted with catalytic converters, which can cut emissions of carcinogenic polycyclic aromatic hydrocarbons (PAHs) by up to 80% and make significant reductions in the other emissions.

In the US, every weekend during the mowing season 54 million Americans with petrol mowers spend an hour on average cutting their lawns. This uses 800 million gallons of unleaded fuel every year and produces 1.2 million tons of air pollution at the very time of year - the hottest months - when ground level ozone is highest, aggravating the problem for people with breathing disorders or heart conditions. The US Environment Protection Agency has calculated that this represents 9% of some types of air pollution. In March 2000 it announced new standards to cut these emissions 70% by 2007.
The European Union has taken note. In December 2000 it proposed a Directive governing air pollution from non-road mobile equipment such as lawnmowers, chain saws and strimmers.

* of Stockholm University’s Department of Analytical Chemistry