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.
Although there's no reason to think that this tiny amount of osmium is doing harm, some scientists are growing concerned about rising levels of platinum-group metals such as osmium, and think we should be keeping a closer eye on them. Even if they don't turn out to be a problem, measuring the levels of these metals means scientists could use these pollutants as tracers to study environmental processes such as ocean circulation.
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.
