Heavy Metal (Including platinum): 

DEVICES FOR CLEANING CAR EXHAUSTS ARE BACKFIRING ON THE ENVIRONMENT an exclusive from New Scientist magazine. 

Catalytic converters, intended to clean up car exhausts, are polluting the environment. Italian and French researchers have found heavy metals from the devices in remote regions of Greenland. 

"The fact that we found the metals in Greenland means that it's a global problem. It's not just close to the cities or the highways." say chemist Carlo Barbante of the University of Venice. 

Seth Dunn of the World Watch Institute, an environmental watch dog based in Washington DC, agrees. "They have broken new ground," he says. "The implications could be very significant in terms of human health." For instance, workers involved in refining platinum, one of the metals used in catalytic converters, are known to suffer from higher than normal levels of severe asthma. 

The US, Canada and Japan introduced cars with catalytic converters in the mid-1970's. Europe followed in the early 1990s. In these devices platinum, palladium and rhodium catalyse reactions that convert hydrocarbons, carbon monoxide, and nitrogen oxides into less noxious emissions. 

But a recent European Commission study found that exhausts from fast-moving cars erode catalytic converters, ejecting microscopic particles containing the metals. 

To assess the global impact of these particles, Barbante and his colleagues went to central Greenland and extracted ice and snow cores dating from 1969 to 1988 and from 1991 to 1995. They also took samples from the Greenland Ice Core Project, dating back nearly 7500 years. 

They found that metal concentrations in the snow have been rising steadily since 1976. Palladium and platinum levels have increased 80 and 40-fold respectively. 

The ratio of platinum to rhodium in the snow from the mid-1990s resembled the ratio in car exhausts from another study. This suggests that most of the increased platinum and rhodium comes from catalytic converters, Barbante says. 

According to the European Commission study, concentrations of these metals in urban air are still too low to create a significant health risk. But the metals, especially palladium, can accumulate in plants and animals, and enter the food chain. 

Kym Jarvis, an environmental geochemist at Kingston University in Kingston upon Thames, and her colleagues have discovered the palladium is soluble in a dilute acid solution. "The high solubility of palladium suggest that, once it reaches the road surface, it would be in a form that can be more readily absorbed by vegetation, or which can go into the watercourse," she says. 

Both Jarvis's and Barbante's finding will appear in future issues of the journal Environmental Science and Technology. 

7 February 2001