Dust on some London roads contains high levels of platinium. Research commissioned by the Department of the Environment showed that busy commuter carrying roads have up to 33 parts per billion of platinum in their dust (platinum is mined from ore containing as little as 200 parts per billion).

The researchers think that catalytic converters are responsible as they discharge platinum in the form of a fine metallic dust. In 1993 2.6 million cars had catalytic converters. By the year 2000 it is estimated that 13 million cars will have them.

In a letter to New Scientist (2.8.95 p49), Gerald Hurst pointed out that:

• particles of platinum reaching the lungs would probably stay there with disastrous effect, and that the fact that they will accumulate must be taken into account, regardless of the initial concentration in the dust

• platinum's catalytic properties make it more damaging than other pollutants because it will activate these as well

Analyses of dust next to the M6 and in Birmingham City Centre found concentrations of platinum up to 1000 times higher than naturally occurring background levels. They also found high levels of rhodium and palladium, suggesting that the source was catalytic converters. The health risk is not known, but platinum can react with salt in cold conditions, which could, in turn, lead to its absorption by plants, and there is a disease amongst workers in the platinum industry called platinosis, which suggests that it may have a medical effect.

The study also demonstrated that exhaust fumes are not the only way cars pollute the environment. At both sites, safety limits for nickel (from diesel fuel). zinc and cadmium (from tyres), copper (from brake linings and wiring ), chromium (from chromium plating) and lead (from leaded petrol) were exceeded. In parti cular, zinc exceeded the safety limits by a factor of eight, and copper by a factor of four.

If similar levels of pollution were found on buuilding land, regulatprs would insist that was decontaminated before work could begin.

Platinum concentrations in road dusts and in soil increase with traffic density but there is no evidence yet that platinum emitted from catalytic converters adversely affects health, said a report from the Department of t he Environment.
The report on platinum in the environment also:

• admitted that platinum is in the food chain

• accepted that we are exposed to platinum in our drinking water

• admitted that certain varieties of platinum can cause cancer

• suggested that most of the platinum released into the environment in the UK comes as a result of cancer chemotherapy hospital waste