Vog is created when hot lava flows into the ocean. The heat causes sulfate ions from the lava and chloride ions from the salt in the water to dissolve in the steam that is generated and rises into the atmosphere. Wind currents blow the vog around south point where it is sucked into a vortex created by the trade winds blowing between the Big Island and Maui. This river of wind creates a vacuum on the leeward side of the island. Thus, anything coming around South Point will be sucked in. Vog contains nothing more than these ions and has a pH of 4.5, similar to pH balanced shampoo. It does not contain any heavy metals, organic hydrocarbons or carbon monoxide like industrial pollution does. It is not strong enough to smart the eyes.
A new source of vog is the Halemaumau crater smoke plume. What is coming directly out of the Halemaumau crater is not yet vog. This smoke plume contains a large amount of sulfur dioxide and is dangerous to breath. When the wind shifts and blows the smoke over Volcano Village, people have to evacuate. When it blows over to Hilo it makes breathing difficult and smells like sulfur. It has caused crop damage as far away as Ocean View. However, by the time it reaches the Kona side the SO2 has been converted to SO4 ions combined with water vapor and it has become vog. The problem is, because of this new source of vog, the vog is thicker on voggy days. But if you live here, the biggest problem is how it obscures the horizon; we love our ocean views here and the vog messes that up. However, it just makes us appreciate those crystal clear days all the more.
Most people are not allergic to vog. Allergies are usually caused by proteins, like those in pollen, mold spores, shellfish, dust mites and cockroach feces. However, some people are allergic to sulfur. You would know if you were, because sulfites (used on salads in restaurants to keep the lettuce from turning brown) will give an allergic person an anaphylactic reaction. This is a very specific and unusual allergy which would make it impossible for you to live in a city, because sulfites are emitted from autos with catalytic converters in their exhaust systems.
If vog and allergies concern you, Waikoloa Village might be a good place to settle. It’s dry there, so there is less pollen and mold spores, and it has way less vog than Kailua, because the wind blows in a different direction there, and keeps the vog offshore. Also, Waikoloa has an award winning grammar school and is closer to all the best beaches.
For more on vog, go to: http://volcanoes.usgs.gov/Hazards/What/VolGas/VolGasPollution.html