Washington state's top polluter isn't a pulp mill, a power plant or refinery. It's the newly awakened Mount St. Helens.
Since the volcano began erupting in early October, it has been pumping out 50 to 250 tons a day of sulfur dioxide, the lung-stinging gas that causes acid rain and contributes to haze. At peak, that's more than double the amount from all the state's industries combined.
Alas, humans have still got her beat.
Worldwide, sulfur dioxide emissions from volcanoes add up to about 15 million tons a year, compared to the 200 million tons produced by power plants and other human activities.