"Vog" warning as volcanic haze lingers over Hawaii

As a haze generated by a new vent in Kilauea volcano settled over most of the Hawaiian islands, the Hawaii County Civil Defense issued a health advisory for areas closest to the steaming crater on the Big Island.

Officials advised residents and visitors in part of the Big Island near the volcano — in South Hilo and Upper Puna — to limit exposure today (and Thursday) today to the haze known locally as vog, a volcanic smog caused by Kilauea's emission of sulfur dioxide.

The Code Yellow condition issued by the agency warns residents and visitors who are especially sensitive to air pollution to avoid outdoor activity. A Code Green warning was in effect for other Big Island districts for low levels of vog which do not pose health risks.

No risk is reported for any other island, and the air is expected to start clearing Saturday when tradewinds return. Hawaii Volcanoes National Park, which includes Kilauea, remained open today. However, part of its scenic Crater Rim Drive near the vent and some hiking trails are closed. And park authorities urged those with respiratory sensitivites to remain indoors or in their cars with air conditioning on.

After the normal tradewinds died down earlier this week, the National Weather Service reported hazy conditions for every island zone except the breezy summits of Haleakala on Maui and Mauna Kea on the Big Island. In Honolulu, the vog obscured views of Diamond Head and the Koolau Mountains.

The National Weather Service predicted the tradewinds would return by Saturday; the winds sweep the volcanic emissions out to sea.

Kilauea has been erupting continuously since 1983, mostly oozing out slow-moving lava. But in mid-March, a new vent formed at the summit and has been spewing volcanic gases, giving the volcano two large sulfur dioxide outlets instead of one.

Sulfur dioxide in the air can lead to asthma and other respiratory illnesses and aggravate lung and heart disease. When combined with dust and sunlight, it makes vog. Mixed with atmospheric moisture, it produces acid rain.

Kristin Jackson of Seattle Times Travel contributed to this report.