The Information Office, University of Sussex, Falmer, Brighton, BN1 9RH.
TREE TRAPS: AN EFFECTIVE FILTER FOR AIR POLLUTANTS
Roadside trees help to improve air quality in urban areas and near traffic blackspots, say researchers from the Plant Stress Unit at the University of Sussex. The study shows that trees act as 'biological filters' to remove airborne particles which settle on their leaves. These pollutants have been correlated with increased incidence and severity of respiratory illness; this study hopes to identify which trees are the most effective filters.
Research by Paul Beckett and Dr Gail Taylor from the School of Biological Sciences shows that particulate pollution is a real and serious problem. High concentrations of particles with a diameter of less than 10 microns (PM10s) are linked with the exacerbation of health problems such as asthma and bronchitis. The most dangerous substances are those smaller than 2.5 microns and 80% of these are produced by traffic, especially from diesel-powered vehicles.
Trees filter these materials on a mechanical basis as the particles stick to the surface of their leaves. The best trees for efficient filtering are those with large leaf areas, or those with sticky or hairy leaves. Studies indicate that lime trees, which have hairy leaves, can collect four times as many PM10s than plane trees. However, the ideal tree must be both an efficient filter and have the ability to cope with polluted environments. Conifers such as the Leyland cypress have large leaf areas and retain their foliage during the winter, but suffer more than deciduous trees because pollution levels tend to be higher at this time.
Research in progress using the Leyland cypress suggests that trees may be effective on a wider scale than in urban areas alone. "The finer particles, or PM10s, can spread far from their source, and our recent research suggests that trees in suburban and rural areas also have an important role in reducing pollution," said Paul Beckett. "Trees are not a cure-all; they may improve air quality, but this should not be an excuse for avoiding reduction measures."
Note to editors:
A government-commissioned report published last month said that air pollution is responsible for up to 24,000 premature deaths annually in the UK. The Committee on the Medical Effects of Air Pollutants said that the fine particles, or PM10s, cause an estimated 8,100 deaths each year.
For further information please contact Paul Beckett on (01273) 606755 ext 2748, Dr Gail Taylor on (01273) 678872 / (01962) 735025, or Laura Miles, Information Office on (01273) 606755 ext 4353
This file produced by USIS - 20th February 1998