Did you know that the worst sulfur dioxide air pollution site in the US is a volcano? Kilauea volcano on the Big Island of Hawai'i to be exact. In fact, when the lava flows into the sea, a cloud of, among other things, hydrochloric acid is produced (you can read more about this from Yahoo! News here).
Now, before we go too far, you potential visitors out there don't need to go running and screaming like the Japanese in fear of Godzilla. It's mostly something residents of the Big Island need to be aware of. Ongoing studies are being done to determine just how bad this toxic mix is to residents (visitors don't need to worry too much because they aren't exposed long enough to have long-term, ill-effects. YMMV. Insert disclaimer here). But it is well known that the state of Hawai'i has the highest asthma death rate in the country.
Although, here on O'ahu, we are usually too far from the Big Island to have any problems, it does reach us when the winds are from that direction. When it is, we have what we call "vog", short for volcanic smog. But when the trade-winds return, all is blown out to sea.
