Lest you think environmental news is all gloom, all the time, here’s a little pick-me-up: Thanks to the Clean Air Act, the U.S. has all but eradicated carbon monoxide pollution, one of the most hazardous air emissions, the U.S. National Academy of Sciences reported yesterday. In 1971, when the act set federal standards for carbon monoxide, 90 percent of monitored areas violated them. Now, just a handful of places still have CO troubles (including Anchorage, Alaska, and some Southern California cities), and usually only for one or two days per year. As a result, the health impacts, which include accidental poisoning and premature death from heart disease, have also radically declined. The NAS attributed the success to stringent emissions standards for automobiles and refineries.