In addition to dangers from the bubbling, scalding-hot lava from the Kilauea volcano, residents on the Big Island of Hawaii are enduring threats from both vog and volcanic ashfall.
In fact, the U.S. Geological Survey issued a "code red" for ashfall late Tuesday, due to the hazard it poses for airplanes and jets.
One of the many hazards of the ongoing eruption of Kilauea volcano on Hawaii's Big Island is vog. But what is it?
Vog, short for volcanic smog, is the haze formed by gas and fine particle emissions from volcanoes, according to the American Meteorological Society.
Specifically, vog is produced when the noxious sulfur dioxide gas and other air pollutants from volcanoes react with oxygen, atmospheric moisture and sunlight, the U.S. Geological Survey reported.
It's a fairly common weather phenomena in Hawaii. A weather service forecast from Wednesday said that recent eruptions near the volcano will likely produce thick vog across the Puna, Kau and Hilo districts of the Big Island, at least through Wednesday evening and possibly beyond.
A typical trade-wind pattern, which features a breeze from the northeast, will persist across the Hawaiian Islands through much of the week, according to AccuWeather.
This will direct hazardous vog to southern and western areas of the Big Island. The smaller islands of Maui, Lanai, Molokai and Oahu will be largely spared from the pollutants in this wind flow.
Evacuees leave dangerous Hawaiian volcano area
Vog can be hazardous to human health.
It contains smoke, dust and gases from the volcano and can cause respiratory problems, including allergies and asthma, the National Weather Service said.
At higher concentrations, vog can cause headaches and irritation to the lungs and eyes, according to the University of Hawaii at Hilo.
If exposed to vog, “short-term symptoms include itchy eyes, a sore throat, coughing, nausea and trouble breathing," AccuWeather meteorologist Faith Eherts said. "These are especially pronounced for the elderly, the very young and anyone with pre-existing respiratory and cardiovascular health issues such as asthma.”
"Smoke and other particles in the air such as sulfur dioxide enter the bloodstream through the lungs, leading to longer term health problems down the road," she added.
Ashfall a hazard to aircraft
In most eruptions, volcanic ash causes relatively few health problems for people, according to the International Volcanic Health Hazard Network
However, ash, small particles of glass and tiny rocks, is extremely dangerous to aircraft. Aviators need to be wary of airborne ash, as the particles are large enough to impact the aircraft's engines and cause total engine failure.
The ash can be sucked into jet engines, jamming the mechanical systems. And jet engines could melt the ash particles, coating compressor blades and turbines. That could block air flow, stopping the engine.
"Ash has been rising nearly continuously from the vent and drifting downwind to the southwest," the U.S. Geological Survey said. "Radar and pilot reports indicate the top of the ash cloud is as high as 10,000 to 12,000 feet above sea level, but this may be expected to vary depending on the vigor of activity and wind conditions."
At this time, its a hazard only to low-flying aircraft, as the ash hasn't reached typical cruising altitudes of 30,000 to 37,000 feet.
A bigger explosion remains a concern: "At any time, activity may become more explosive, increasing the intensity of ash production and producing ballistic projectiles near the vent," the Hawaii Volcano Observatory said in a statement on the change in aviation alert level from orange to red .
There are now 20 active fissures that have cracked open since this episode of the volcano's eruption began on May 3, and 37 structures have been destroyed.