Trevor Lawson
Just when you thought it was safe to go back on the motorway in your lead-free petrol, fuel-efficient, catalytic-converted car, along comes a report which suggests that your exhaust pipe is just the tip of a very noxious pollution iceberg.
According to a report by a British environmental group, vehicles, like people, decay as they age. Just as we drop hair, eyelashes and skin cells whenever we move, vehicles dump a dozen unpleasant pollutants.
Friction is a major cause of the problem: cars and trucks literally rub themselves up the wrong way, releasing particles of heavy metals as they go. Samples of heavy metals collected from the motorway surfaces, dust and storm-water run-off by students at the University of Surrey have been linked to a variety of moving vehicle components.
Chrome plating releases chromium, nickel and copper, and brakes release zinc and copper. Vulcanised tyres are one of the main sources of cadmium. In addition, there is vanadium, iron and nickel from the welding of the car, and the bodywork releases iron, aluminium, nickel and copper. Apart from the metals, we have fuel, brake fluids, anti-freeze compounds, transmission box oils, engine oils and grease falling on to the road, too.
The impact on human health is not yet known, but high doses of iron, zinc and copper are toxic. Cadmium, which can cause kidney and liver damage, is particularly worrying, as it is readily taken up by plants at levels that closely match those in the soil.
The study has also found that lead has not disappeared with the advent of lead-free petrol and is still being deposited alongside roads.
What really worries environmental scientists is where this pollution goes. Motorway cuttings can prevent pollutants being blown on to surrounding crops, but they are still washed away into the ground and water supply.