SMALL BUT DEADLY

This article explains why levels of particulate emissions from vehicles must be monitored, and why more attention should be paid to measuring the emissions of smaller particles. In the UK, new evidence is emerging that millions of tiny particles, with aerodynamic diameter below 0.1m, entering the interiors of vehicles on busy roads, could risk the health and comfort of drivers, despite considerable uncertainty about their effects. AEA Technology has developed several techniques for measuring the number of such particles. Its initial research results suggest that drivers in a city, or stuck in a traffic jam, or travelling along a busy motorway, could be in danger of asthma or some other illness caused by the pollution. Scientists drove a car fitted with monitoring equipment from rural Oxfordshire to London and back; they found that the number of particles per sq cm inside the car rose from about 2000 at the start of the journey to about 10M as they left London on the M4 motorway. Numbers rose uphill as engines needed to work harder, but fell as vehicles began to go downhill. Following vehicles around corners showed changes of particle concentrations due to deceleration, acceleration, and changing gear. The number of particles inside the car rose considerably when other vehicles on the motorway overtook it.