You wouldn't think of smog being an issue in Hawaii, but some parts of the islands have to regularly deal with a "natural" smog called "vog."
Vog is the term they use for the haze caused by sulfur dioxide emissions from their active volcanoes. When the trade winds weaken and the air gets stagnant, a murky haze can hang around, and just like in LA or Houston, this stuff isn't exactly what you want to inhale either.
Terry Pennington sent me this photo (above) as he took some visitors out on a whale watch boat out of Lahaina.
The photo was pretty for the pod of whales in the foreground (what he called a "competition pod" of 20 male humpback whales.)
But he says normally, the West Maui Mountains in the background would be vivid on a day like this with some scattered high altitude streaks and a few low clouds.
"Not so here," he said. "In the far distance you can just about make out the south end of the island which features our 10,000-foot volcano Haleakala. There was nothing obstructing its view today other than the SO2 from Hale MauMau crater on the Kilauea volcano over on the big island of Hawaii."