Vog is a portmanteau of the words "volcanic" and "smog," and a volcanic smog is formed when sulfur dioxide and other gases emitted by an erupting volcano mix with oxygen and moisture in the presence of sunlight. The term is most often applied to the island of Hawaii, where the Kīlauea volcano has been erupting continuously since 1983. Kilauea emits an estimated 2,000 tons of vog every day.
Vog is created when volcanic gases (specifically oxides of nitrogen) react with sunlight, oxygen and moisture. It 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. Although vog has not been as extensively studied as it could be, it has been found that most of the aerosols are acidic and of a size where they can remain in the lungs where they can damage the lungs and impair function. People who have been exposed to vog report headaches, breathing difficulties (including inducing asthma attacks), flu-like symptoms, and general lethargy. These effects are especially pronounced with children. Most studies of vog have been in areas where vog is present, and not of the effects of vog itself (in controlled conditions).
In Hawaii, vog mostly affects the Kona coast on the west side of the Island of Hawaii, where the prevailing trade winds blow the vog to the southwest and wind patterns then blow it north up the Kona-Kohala coast. Prolonged periods of southerly Kona winds, however, can cause vog to affect the eastern side of the Island on rare occasions, and affect the entire state as well.
Vog and smog both contain harmful chemicals that can damage the environment, human health, and the health of other animals. However, they are different. Vog is a volcanic mixture that includes gases and aerosols which react with oxygen, moisture, and sunlight. Smog is formed from certain chemicals resulting from the oxidation of fuels (sulfur dioxide), incomplete combustion of fuels (carbon monoxide), and the chemical union of O2 and N2 in internal combustion engines.
Vog and smog both share similarities as well, they both cause acid rain, and they are both hazardous for plants and animals (including humans) to breathe. Vog and smog both primarily contain the harmful chemical sulfur dioxide (SO2) which irritates the lungs. When vog and/or smog levels are high the sky will tend to look grey like the skies of Beijing, Kiev, Calcutta, Mexico City, and Los Angeles. Once the vog/smog has cleared up, the sky may have grey spots for a time due to vog/smog trapped in the inversion layer.
People with pre-existing respiratory conditions are more prone to adverse effects of vog which may include: headaches, breathing difficulties, increased susceptibility to respiratory ailments, watery eyes, and sore throat. The long-term health effects of vog are unknown.
State of Hawaii Office of the Governor Vog: Important Information and Facts [http://hawaii.gov/gov/vog ]
NIOSH Respirator Selection Logic: http://www.cdc.gov/niosh/docs/2005-100/