In 1968, the state considered the possibility, though remote, of evacuating Hilo because of high sulfur dioxide levels in volcanic emissions spewing from Kilauea.

At the time, air monitors in Hilo were recording short-term periods of sulfur dioxide levels from .8 to 1.0 parts per million — well above current federal standards for air quality and comparable to some levels communities downwind of Kilauea have seen since March 2008, when emissions started spewing from Halema'uma'u Crater.

Back in 1968, government officials thought they could evacuate Hilo residents elsewhere on the Big Island. But they also considered putting them on a Navy ship.

The emissions abated before any evacuations were called. But the episode illustrates what most people already know: Big Island residents aren't strangers to heavy vog, though many also point out the Halema'uma'u emissions are affecting communities more than they have in the past — and for a much longer period.

Interestingly, there wasn't much discussion about volcanic haze in Hawai'i newspapers until about 1950, though several volcanic events before that time would have undoubtedly made for some very voggy days, volcanologists say.

Around the the mid-part of the last century is also when the term "vog" — a mash-up of "volcanic" and "smog" — became part of the vernacular in the Islands.

Scientists have different theories about why volcanic emissions weren't much talked about in Hawai'i newspapers until fairly recently. Jim Kauahikaua, scientist-in-charge at the U.S. Geological Survey's Hawaiian Volcano Observatory, said it could be because the population was so small, so fewer were affected.

It could also be "people were concerned about other things," he said.

Or, perhaps they saw the vog as the least of their worries.

Whatever the reason, by the mid-1960s, there were regularly stories in both Honolulu dailies about volcanic haze settling over Big Island communities and photos of rare vog days obscuring the view of the Downtown skyline or Diamond Head.

What makes the ongoing vog events somewhat different than those in the recent past is their duration: The Pu'u 'O'o vent has been active for 27 years, and now emits about 1,000 metric tons of sulfur dioxide every day. Since it went off, Kona has seen voggy skies more often than blue ones. The start-up of the Halema'uma'u Crater emissions changed life again for Big Island residents downwind of the vent.

Donald Thomas, director of the Center for the Study of Active Volcanoes at UH-Hilo, said certainly vog is a nuisance — and, in some cases, a threat — on the Big Island. But it's not likely to go away anytime soon. "There isn't a heck of a lot we can do" to stop the vog, Thomas said. "It is just there and it was always there."