Catalytic converters are backfiring on the environment

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

According to environmentalists, 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 U.S., Canada and Japan introduced cars with catalytic converters in the mid-1970s. 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, researchers 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. Rhodium levels are already 120 times higher than in the 7,500-year-old ice.

  • 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.

    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.

    Source: Kym Jarvis and Carlo Barbante, Environmental Science and Technology (forthcoming), New Scientist Online, February 7, 2001.

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