Platinum Pollution -- Law of Unintended Consequences

The planet has been covered with a fine layer of osmium thanks largely to efforts to clean up car exhausts, according to a global survey of rainwater.

Since the 1970s, many cars have been fitted with catalytic converters to keep nitrogen oxides and carbon monoxide out of the air. This cuts down on smog and has huge health benefits. But catalytic converters created a demand for platinum, which has its own environmental impact. The smelting of platinum can release metals into the air, for example — particularly osmium tetroxide.

Now a report in the Proceedings of the National Academy of Sciences2 points to a global spread of osmium.

The team publishing today's survey, led by Mukul Sharma of Dartmouth College in Hanover, New Hampshire, found a tiny amount of osmium in rainwater or snow in all their samples, from the United States to India, the Netherlands and the Antarctic.