Vog is a form of air pollution

Air pollution

Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

 that results when sulfur dioxide

Sulfur dioxide

Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

 and other gases and particles emitted by an erupting volcano

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 react with oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 and moisture in the presence of sunlight

Sunlight

Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...

. The word is a portmanteau of the words "volcanic" and "smog

Smog

Smog is a type of air pollution; the word "smog" is a portmanteau of smoke and fog. Modern smog is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine...

". The term is in common use in the Hawaiian islands, where the Kīlauea

Kilauea

Kīlauea is a volcano in the Hawaiian Islands, and one of five shield volcanoes that together form the island of Hawaii. Kīlauea means "spewing" or "much spreading" in the Hawaiian language, referring to its frequent outpouring of lava. The Puu Ōō cone has been continuously erupting in the eastern...

 volcano

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

, on the island of Hawaii

Hawaii (island)

The Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the North Pacific Ocean...

, has been erupting continuously since 1983. Based on June 2008 measurements, Kīlauea emits 2,000 - 4,000 tons of sulfur dioxide every day.

Description

Vog is created when volcanic gases (primarily oxides of sulfur

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

) react with sunlight, oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 and moisture

Moisture

Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...

. The result includes sulphuric acid and other sulfates. Vog is made up of a mixture of gases and aerosols which makes it hard to study and potentially more dangerous than either on their own.

Vog in Hawaii

In Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, the gas plumes of Kīlauea

Kilauea

Kīlauea is a volcano in the Hawaiian Islands, and one of five shield volcanoes that together form the island of Hawaii. Kīlauea means "spewing" or "much spreading" in the Hawaiian language, referring to its frequent outpouring of lava. The Puu Ōō cone has been continuously erupting in the eastern...

 rise up from three locations: Halemaumau Crater

Halemaumau Crater

Halemaumau crater is a pit crater located within the much larger summit caldera of Kīlauea in Hawaii Volcanoes National Park. The roughly circular crater floor is x and is below the floor of Kīlauea caldera, located at coordinates . Halemaumau is home to Pele, Goddess of Hawaiian Volcanoes,...

, Puʻu ʻŌʻō vent, and from along the coastline where lava flows from the East Rift zone

Rift zone

A rift zone is a feature of some volcanoes, especially the shield volcanoes of Hawaii, in which a linear series of fissures in the volcanic edifice allows lava to be erupted from the volcano's flank instead of from its summit...

 enter the ocean. The plumes create a blanket of vog that can envelop the island. Vog mostly affects the Kona

Kona District, Hawaii

Kona is the name of a moku or district on the Big Island of Hawaii in the State of Hawaii. In the current system of administration of Hawaii County, the moku of Kona is divided into North Kona District and South Kona District . The term "Kona" is sometimes used to refer to its largest town,...

 coast on the west side of the Island of Hawaii

Hawaii (island)

The Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the North Pacific Ocean...

, where the prevailing trade wind

Trade wind

The trade winds are the prevailing pattern of easterly surface winds found in the tropics, within the lower portion of the Earth's atmosphere, in the lower section of the troposphere near the Earth's equator...

s blow the vog to the southwest and southern winds then blow it north up the Kohala

Kohala

Kohala may refer to:*Kohala, Hawaii, two districts on the island of Hawaii*Kohala , an extinct volcano in Hawaii*Kohala, Pakistan, a city*Kohala Bridge, a bridge*Kohala, Jalandhar a village in Punjab, India...

 coast.

Prolonged periods of southerly Kona winds

Kona storm

Kona storms are a type of seasonal cyclone in the Hawaiian Islands, usually formed in the winter from winds coming from the westerly "kona" direction. They are mainly cold core cyclones, which places them in the extratropical cyclone rather than the subtropical cyclone category...

, however, can cause vog to affect the eastern side of the Island on rare occasions, and affect islands across the entire state as well. By the time the vog reaches other islands, the sulfur dioxide has largely dissipated, leaving behind ash, smoke, sulfates, and ammonia.

Comparing Vog and Smog and Fog

Vog and smog

Smog

Smog is a type of air pollution; the word "smog" is a portmanteau of smoke and fog. Modern smog is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine...

 are different. Vog is formed when sulfur oxides emitted by a volcano react with moisture to form an aerosol

Aerosol

Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...

. The aerosol

Aerosol

Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...

 scatters light and so makes the vog visible. Smog is formed largely from the incomplete combustion

Combustion

Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 of fuel, reacting with nitrogen oxides and ozone

Ozone

Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...

 produced from carbon monoxide

Carbon monoxide

Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 by reactions with sunlight. The result is also a visible aerosol

Aerosol

Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...

.

When smog levels are high the sky looks yellowish grey because nitrogen oxides are yellow. In contrast, sulfur oxides are colorless and vog looks grey. Once vog dissipates, grey spots in the sky may for a time remain trapped in the inversion layer.

Health hazards

Most studies of vog have been in areas where vog is naturally present, and not in controlled conditions. Vog contains chemicals that can damage the environment, and the health of plants, humans and other animals. Most of the aerosols are acidic and of a size where they can remain in the lungs to damage the lungs and impair function. Headaches, watery eyes, sore throat, breathing difficulties (including inducing asthma

Asthma

Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...

 attacks), flu-like symptoms, and general lethargy are commonly-reported. These effects are especially pronounced in people with respiratory conditions and children. Vog generally reduces visibility, creating a hazard for drivers, and for air and ocean traffic.

The long-term health effects of vog are unknown.

Recent events

Several studies are underway to measure the air quality near volcanoes more carefully.
Sulfur dioxide emissions increased on March 12, 2008 when a new vent opened. The increased vog level has caused evacuations and damaged crops. In the summer of 2008, the County of Hawaii received a disaster designation due to the agricultural damage.

External links

• Current SO₂ conditions from Volcanoes National Park: http://www.nature.nps.gov/air/webcams/parks/havoso2alert/havoalert.cfm
• Hawaiian Vog Photographed from Space Shuttle
• Video of Vog in Hawaii: http://www.youtube.com/watch?v=x6zukeZ7aEg
• National Institute for Occupational Safety and Health Respirator Selection Logic: http://www.cdc.gov/niosh/docs/2005-100/