Today, April 22, is Earth Day, which has been marked each year since 1970 as a day of reflection on the state of the environment. At least that's the idea, so let's begin with some figures.All this and more can be found in the PRI's 2006 Index of Leading Environmental Indicators [PDF].
Since 1970, carbon monoxide emissions in the U.S. are down 55%, according to the Environmental Protection Agency. Particulate emissions are down nearly 80%, and sulfur dioxide emissions have been reduced by half. Lead emissions have declined more than 98%. All of this has been accomplished despite a doubling of the number of cars on the road and a near-tripling of the number of miles driven, according to Steven Hayward of the Pacific Research Institute.
One of my favorite charts in the report:
Automobile Carbon Monoxide Emissions Rate per Mile [Source: CARB]