Lava is not the only thing flowing out of the fissures of Kilauea on Hawaii. Sulfur dioxide, a foul-smelling and toxic gas, has also driven people from their homes.

According to the USGS, sulfur dioxide levels near the volcano have been measured above 100 parts per million. That is a level considered dangerous to human health. Noxious on its own, sulfur dioxide is also the main ingredient in volcanic smog. Known as vog in Hawaii, it can have a variety of adverse health effects.

Vog occurs when the sulfur dioxide spewing from a volcano reacts with oxygen, moisture, and other particles in the air in the presence of sunlight. It is considered a form of air pollution, not unlike that given off by power plants burning sulfurous coal. Looking back to December 1948, a similar type of toxic smog caused by unregulated industrial pollution killed 26 people and sickened thousands of others in Donora, PA.

Volcanic smog can irritate the skin, eyes, nose, throat, and lungs. Shortness of breath and dizziness can also occur.  Its effects can be even worse for anyone with respiratory problems or lung disease.

This threat, on top of the flowing lava, has led public health officials to order an evacuation of areas around the fissures, such as the hard hit Leilani Estates.  Other parts of the Big Island, however, have reported moderate to good air quality. This is largely because the region’s prevailing northeast trade winds have been pushing the vog offshore. If those winds slacken and a southeasterly flow emerges, the vog could impact a wider area, including other islands in the Hawaiian chain.

Volcanic eruptions spew gas as well as lava. Credit: GoVisitHawaii