CORVALLIS, Ore. – Hawaiian residents who live downwind from the long-active Kilauea volcano may have elevated risks of adverse health conditions because of high levels of sulfur dioxide and aerosol particulates that drift downwind, according to a new study by researchers at Oregon State University and Hawaii.
During a three-week period of average volcanic activity, the researchers measured the sulfur dioxide level in the Kau district south of Kilauea at 17.8 parts per billion – above the minimal risk level of 10 parts per billion, a guideline set by the U.S. Agency for Toxic Substances and Disease Registry. In comparison, Honolulu – located on another island and not in the path of the Kilauea plume – measured just 1.0 ppb during the same time interval. Measurements taken in Los Angeles during that same period averaged a level of 7.0 ppb.
Results of the study have been published in the March issue of the journal Geology.
"When Kilauea began erupting in 1983, there were a number of studies that looked at emissions directly from the volcano, but they haven't looked at the dispersal pattern, or the long-term associated health risk," said Bernadette M. Longo, a recent doctoral graduate in public health at OSU and lead author on the study. "What we found is some cause for concern."
Sulfur dioxide is emitted from Kilauea as a gas and then it begins to change, forming tiny particles and becoming an aerosol. The particle size gradually grows larger and a visible haze develops.
About 70 percent of the time, the Pacific tradewinds blow the emissions southward, toward the small communities of Pahala, Na'alehu and Ocean View. Yet what monitoring has been done has taken place in Hilo, north of the volcano, and on the Kona Coast, which is on the other side of the island well down the plume's path, Longo said.
Longo said sulfur dioxide gas at elevated levels can cause bronchial irritation and trigger asthma attacks in susceptible individuals. Potential health risks expand to a broader section of the public when the gas turns to particulate matter, she pointed out.
"The particles can affect lung defenses and the ability to clear material out of the lungs," she said. "They can cause bronchitis. And some of the newest research suggests that prolonged exposure to these particles may be associated with cardiac problems."
Longo, who worked for more than 20 years as a nurse before pursuing her doctorate at Oregon State, has surveyed long-time local residents in communities south of Kilauea to see if they have experienced health problems at a higher rate than other Hawaiians. She has compiled that data and hopes to publish a second paper later this year.
Assisting Longo with the study were Anita Grunder, a professor in the OSU Department of Geosciences and an expert in volcanism; Raymond Chuan, a retired physicist in Hawaii who conducted some of the first air assessments of Kilauea in the late 1990s; and Annette Rossignol, a professor in OSU's Department of Public Health and an epidemiologist.
Grunder said effusive basalt volcanoes – like Kilauea or Masaya in Nicaragua – can emit a great deal of sulfur dioxide into the lower atmosphere even when not erupting. By contrast, Washington's Mount St. Helens is a dacite volcano that emits sulfur dioxide primarily during eruptions, and even then injects it high into the atmosphere, where the immediate impact on humans is less.
Kilauea is the top "point source" for sulfur dioxide in the United States, the researchers say.
"They found that sulfur dioxide from Kilauea in the Kau district is concentrated near the coast and is less at higher elevations," Grunder said. "Aerosol concentrations were the opposite; low at the coast and higher at higher elevation. The SO2 can react with moisture in the lungs to create sulfuric acid. If you flush rain through an SO2 atmosphere, you get acid rain.
"Plants don't like it; cars and signs get rusty," she added. "At Masaya (in Nicaragua), when they hang clothes on the line, they can get holes in their clothes."
Grunder said the study has application for millions of people around the world potentially at-risk for exposure to volcanic gas, as well as industrial air pollution.
Longo said the study was conducted during a three-week period in 2003 during which the tradewinds blew in a normal pattern every day, the volcano had average emissions, and it typically rained in the afternoon. In short, she said, the conditions were typical, not extreme.
She found the volcano's plume moves offshore over the ocean at night, and then comes inland by mid-morning. "If that pattern holds – and we need more data to confirm it – we could identify times when it is best to exercise or work in the garden," Longo said, "as well as times when it might be best to refrain from physical activities."
The island of Hawaii does have a monitoring system and a Vog index, the researchers point out, but it is measured only along the Kona Coast, not in Kau. This "volcano-smog" index – Vog is a locally coined term - also is based on aerosol visibility, not SO2.
"Unfortunately, sulfur dioxide is invisible, so people can't see that they are being exposed," Longo said. "One of our recommendations is to establish monitoring in the region directly south of the volcano, not just in the more heavily populated areas."
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