What is Vog?
The term “vog” is familiar to most Hawaiians on the Big Island who live downwind from the Kilauea volcano. But in November 2021, New Zealanders made their acquaintance with what those who have experienced it call “volcano breath” when gases from Whakaari, the country’s most active volcano, made their way to shore.
The term “vog” is a combination of two words, “volcano” and “smog.” Vog is created when sulfur-based volcanic gases mix with moisture in the atmosphere to form an aerosol that can travel deep into the lungs, causing harm in humans and animals. People can experience irritation of the nose, eyes, throat, and sometimes skin; wheezing, chest tightness, shortness of breath; and headache, nausea, and fatigue, stated Carol Stewart, in speaking to The Earth & I. She is a co-director of the International Volcanic Health Hazard Network, an international group of scientists who research the health impacts of volcanic activity and create helpful resources.
“Our experience with vog in New Zealand is far less than the United States experience,” Stewart says. New Zealanders do not know how to prepare for vog or what to do to protect themselves when “volcano breath” happens in their own environment, she says.
While even the words “volcano breath” might be unfamiliar to most U.S. residents, the U.S. is home to about 169 active volcanoes.
Most of these are located in Alaska, where some eruptions occur almost every year. But the Kilauea volcano in Hawaii is one of the most active on Earth. It has been erupting (and spewing its breath) almost continuously since 1983, according to the U.S. Geological Survey’s Volcano Hazards Program.
Sudden Rare Occurrences from White Island
Vog is rare in New Zealand, as the active volcano Whakaari (also called White Island) is located thirty-one miles offshore. The prevailing western winds do not bring the gases to land, Stewart says.
But on November 9, 2021, conditions suddenly aligned so that vog did come to the mainland. On that date, the volcano’s gases combined with weather conditions that were “just right”—along with sea fog in the Bay of Plenty—to create the “very rare” vog event, according to Scott Yeoman, writing in Stuff, a New Zealand media outlet.
In the days before the vog event, GeoNet—which monitors geological hazards in New Zealand, including volcanic eruptions—put out a warning about some approaching vog in the Bay of Plenty. Light northerly winds were driving vog onshore, although “there has not been an eruption to produce this” situation, the service said.
The volcano was simply experiencing a bit of unrest, GeoNet added. Essentially, on a low level, Whakaari was quietly churning and emitting gases.
Before putting out the warning, GeoNet scientists had flown near the volcano and saw a noted increase in gas emissions, compared with earlier flyovers and measurements they had taken two weeks earlier.
As the fog rolled in, some folks in the Whakatāne area described a strong smell of sulfur and an “ominous” grey, hazy sky.
As the fog rolled in, some folks in the Whakatāne area described a strong smell of sulfur and an “ominous” grey, hazy sky.
The local newspaper, the Whakatāne Beacon, described an “eerie haze and smell of sulfur” that enveloped the town and the nearby region in the afternoon. The town of Whakatāne, with a population of just over 37,000 people, is located on the eastern Bay of Plenty on New Zealand’s North Island. As the vog moved beyond the town, it could have affected, to a lesser extent, the entire eastern region.
For the past 100 years, Whakaari has seen a few small but hazardous eruptions. Often, the volcano emits a steady plume of water vapor and gases that are visible from the mainland, Stewart says.
During the November 2021 New Zealand vog, Stewart and her fellow volcano watchers noted the widespread comments posted in local social media feeds of people noticing the haze and a distinctive sulfuric smell; however, no mention of any adverse health effects was found.
Typical vog complaints include “headaches, stinging eyes, and shortness of breath,” Stewart and her fellow researchers wrote in an April 2022 paper published by the Australian Institute for Disaster Resilience.
“It is probable that the gas that was smelled was hydrogen sulfide (H2S), as this gas has an extremely low odor threshold and is more stable and unreactive in the atmosphere, compared to sulfur dioxide (SO2),” they wrote.
Both chemical compounds are gaseous compounds at room temperature and contain sulfur atoms. H2S is a hydride of sulfur while SO2 is an oxide of sulfur, according to the American Institute of Chemical Engineers (AIChE). An oxide is a compound in which one or more oxygen atoms is combined with a chemical element, in this case, sulfur. A hydride combines hydrogen with another element.
While both gases have a strong odor, H2S smells of rotten eggs while SO2 smells of burnt matches, according to AIChE. In nature, SO2 is the product of volcanic eruptions while H2S is the familiar “sewer” smell.
Hawaii Points the Way
Why has vog recently become an issue in New Zealand? The two ingredients needed to produce vog have emerged: a combination of elevated volcanic gases combined with certain weather conditions. “The weather conditions are much less common but can occur maybe yearly, or every few years,” Brad Scott, GeoNet volcanologist, told Stuff.
In New Zealand, the occasion wherein volcanic gases and weather conditions may combine to produce vog may occur every decade or so, although the truth of the matter is difficult to tell because the country has not kept official records on vog events, he said. Vog was not noticed after the 1995 eruption of Mount Rauehu nor after the 2012 Te Maari eruption in New Zealand.
In a country that has not knowingly experienced vog in many people’s lifetimes, information on how to deal with this potentially deadly weather event can be hard to find, Stewart says.
“Most of what we know about how vog impacts health comes from Hawaii, where there is long-term degassing of sulphur dioxide from Kīlauea volcano,” she says.
Indeed, the texts Stewart and her fellow researchers noted on social media during the 2021 vog event mirrored what Hawaiian residents commonly post about their own experiences with volcanic gases.
“Often, it’s like what you’d think of as smog but much smellier,” Big Island resident Diane Swanson—who has lived in a vog-prone area for the past decade—told The Earth & I. “It can burn your eyes and your throat. You cough a lot. It’s unpleasant. People usually stay inside while it’s going on.”
Prior to her move to the Big Island from Missouri, about a decade ago, Swanson had never heard about vog.
“Fog, yes; smog, yes. So, I was totally unprepared for this,” she says. “What’s weirdest is that other people weren’t thrown off by it. I guess it’s like living in California and experiencing a small earthquake or in Missouri, where we have tornadoes. You don’t think anything of it after awhile. It becomes a part of life.”
But just as earthquakes, tornadoes, and hurricanes can veer from the routine to become deadly, so can volcano breath.
For instance, in February 1979, at least 149 died after inhaling poisonous gas when the Dieng Plateau, a volcano in Java, Indonesia, erupted. In December 1997, two men died when sulfur dioxide concentrations reached dangerous heights around Mount Aso, Japan’s most active volcano. Since 1980, seventy-one people have been hospitalized due to inhaling volcanic gases from that volcano, according to the Oregon State University, which keeps a record of deadly gas outbreaks worldwide.
One of the most famous volcanic eruptions, a 1794 eruption at Mount Vesuvius in Italy, killed about 400 people. Some of them died from poisonous gases, according to Oregon State University.
Meanwhile, Hawaiians got a welcome break from vog in 2018, but in September 2019, the gases were back, reintroduced with the most recent Kilauea eruption, according to Hawaii News Now.
Tips and Guides for Living Through Vog
Little can be done to stop vog from happening because, by the time the volcanic eruptions and combined weather events carry gases to shore, the air cannot be cleansed. Smog can be reduced by maintaining better environmental air quality. But, in a way, vog is as inevitable as fog.
The best remedy is to stay inside with closed windows and doors. Run an air conditioner or use a “high efficiency particulate air” (HEPA) filter to clean the air. Avoid or limit physical exertion, and maintain adequate hydration, Stewart says.
Brochures and guides from the International Volcanic Health Hazard Network she co-directs include answers to questions like, “Are water catchment systems affected by vog?” The answer is yes, because rainwater that’s collected for drinking can become dangerously acidic with the effects of vog.
Other tips from the network include avoid smoking during vog events, immediately treat eye irritation by flushing the eyes, immediately treat congestion with over-the-counter drugs, and remain hydrated.
Hawaiians know the routine only too well, Swanson says. New Zealanders, where vog is much less common, will likely have to familiarize themselves with these tips the next time volcano breath rolls ashore.
Stewart, of course, does not know when the next vog event will envelope the Bay of Plenty. Like others, including Scott of GeoNet, she does not expect to see the thick, fog-like, pea-soup weather for the next several years.
“But we just don’t know when conditions will be right,” she says. “Really, New Zealanders must stay abreast of the weather and always be prepared.”
*Jean Thilmany is a freelance writer living in St. Paul, MN, who writes frequently about science and engineering topics.