The volcano's daily output of air pollution is roughly equal to that many power plants, calculates Bruce Anderson, state Health Department deputy director for environmental health.
"I wouldn't want to live downwind of 3,650 power plants, but people on the Big Island are living downwind of that," he said.
The volcano spews out more than 1,000 tons of sulfur dioxide (1,200 tons, according to a recent study) and other pollutants every day, compared with about 100 tons a year from major air pollution sources elsewhere, Anderson said.
Nothing can be done to cork the 13-year-old eruption, he pointed out, so officials are doing the next best thing - trying to inform people about concentrations in the air and their health effects, he said.
Proposals are being developed to collect air quality data and add the Big Island to a national study comparing the respiratory health of fourth- and fifth-graders, Anderson said. Haze concentrations also will be reported daily.
The information can help people plan less strenuous activities and minimize health problems, he said. It will also help tourists "see the Big Island without worrying too much about some unknown health problem," he said.
People with chronic respiratory and cardiovascular diseases, including asthma, chronic bronchitis or emphysema, are most at risk from volcanic pollution, Anderson said. But the risks haven't been well-defined, he said.
Aside from anecdotes by physicians, patients and others, no data are available to say how dangerous vog is to health, said Hilo Hospital emergency physician Fred C. Holschuh.
However, the problems are serious enough, that the Hawaii Medical Journal published a special issue on vog last month.
Anderson said studies indicate that the byproducts of vog probably are more harmful than emissions directly from Kilauea's Puu Oo vent.
Looking at standard pollutants, he said, "Air quality on the Big Island on the worst days is probably better than the best day in Los Angeles."
But looking at byproducts, he said, the island's pollutant level is comparable to many of the most polluted cities.
He said sulfur dioxide and other sulfur compounds may be combining with oxygen and water to form sulfuric acid mists, which can irritate respiratory tracts.
Most of Kilauea's vog gets blown to Kona, but sometimes the winds shift and carry it to Hilo.
On those days, as he drives to Hilo from his rural Honokaa home, Holschuh said, "I can see this mist - it looks like Los Angeles smog over Hilo."
On a clear day, he can see a huge volcano plume miles away "going up, doglegging and going straight to Kona." For people there, he said, "it's quite terrible" with "a kind of acid material burning your eyes."
On bad vog days in Hilo, Holschuh said he began noticing more people showing up at the hospital complaining about vog triggering asthma or aggravating chronic lung disease.
He found a lot of times "the asthma went away just sitting in an air-conditioned waiting room. ... Also, mothers were telling me they didn't think their kid was bad enough to come to the ER, so they would go to the mall or a movie and the kid stopped wheezing."
Holschuh participated in a study that looked at emergency room visits and hospitalizations for respiratory disease on the island from 1981 to 1991.
Figures were significantly higher for chronic lung disease in the Kona area than in Hilo in 1983, the year eruptions started, and from 1988 to 1990. Emergency visits for asthma increased 15 percent in Hilo when winds blew volcanic pollution that way.
But the study was incomplete and inconclusive, Holschuh said.
Anderson said old-timers on the Big Island told him pollen and fungus spores might be just as responsible for respiratory problems as volcanic pollution is.
Pointing out that Hawaii has the highest rates of asthma in the country and the Big Island has the state's highest rate, he said:
"It's important to tease out the real environmental factors responsible."
The Health Department has no environmental epidemiologist - other than him - to do the studies, he said.
But the National Institute of Environmental Health Sciences has set aside $100,000 for vog studies, and the University of Hawaii is cooperating, he said.
"We have a unique opportunity to study effects of those pollutants, which are serious problems nationally, and have some results not confused by the presence of other industrial pollutants," Anderson said.
Besides studying respiratory health, air quality data will be collected at a monitoring station recently established near Kona Hospital, he said.
It will measure sulfur dioxide and particles, and equipment is being installed to measure sulfates and acid aerosols, he said.
A haze meter may be installed to measure sulfates in the air rather than relying on visual observations, he said.
A proposal also has been made to set up the same equipment in Hilo.