What health hazards are posed by vog (volcanic smog)?

Vog poses a health hazard by aggravating preexisting respiratory ailments. Sulfur dioxide (SO2) gas can irritate skin and the tissues and mucous membranes of the eyes, nose, and throat, and can penetrate airways, producing respiratory distress in some individuals. Aerosol particles in vog can also penetrate deep into human lungs and, at elevated levels, can induce symptoms of asthma.

Physical complaints associated with vog exposure include headaches, breathing difficulties, increased susceptibility to respiratory ailments, watery eyes, sore throat, flu-like symptoms, and a general lack of energy.

Tiny droplets of sulfuric acid in vog creates acid rain, which can leach lead from roofing and plumbing materials, such as nails, paint, solder, and metal flashings. Leached lead poses a health hazard when it contaminates drinking water in rooftop rainwater-catchment systems.

The presence of vog reduces visibility, creating a potential hazard for drivers. Vog can also limit visibility for air and ocean traffic. 

Vog is a hazard that's associated with Hawaiian volcanoes in particular. See the Hawaii Interagency Vog Information Dashboard for more information, as well as the EPA's AirNow website.

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Image: Vog from Kilauea
January 31, 2008

Vog from Kilauea

The rim of Kīlauea Volcano’s summit caldera, normally clear on trade-wind days (left), became nearly obscured by vog (right) on some non-trade wind days beginning in 2008, when sulfur dioxide emissions from the volcano’s summit increased to unusually high levels. (This photo has been edited.)

Image shows two scientists on the slopes of Mount St. Helens with steam rising around them
September 24, 1981

Gas Sampling around the Mount St. Helens Dome

USGS geologists gathered samples by hand from vents on the dome and crater floor. Additionally, sulfur dioxide gas was measured from a specially equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano.

Image: Halema'uma'u Vent Gas Plume

Halema'uma'u Vent Gas Plume

The largely crusted surface of the lava lake in the Halema'uma'u vent slowly moves from north (top of the photo) to south. During high lava stands, like that shown here, this circulation is so slow as to be nearly imperceptible to the naked eye.

scientist with camera and spectrometer at the edge of smoking volcanic crater.
August 16, 2016

USGS HVO geochemist measuring gases released from Kīlauea Volcano

USGS Hawaiian Volcano Observatory geochemist measuring gases released from Kïlauea with a Fourier transform infrared (FTIR) spectrometer, an instrument that detects gas compositions on the basis of absorbed infrared light. The data obtained from FTIR measurements have been useful in identifying the many components of volcanic-gas emissions, which provide information on the

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