Vog is a term that refers to air pollution caused by volcanic emissions. It is a visible haze comprised of gas and an aerosol of tiny particles and acidic droplets created when sulfur dioxide (SO2) and other gases react with oxygen, atmospheric moisture, and sunlight. Vog can negatively affect human health and agriculture, and acid rain can contaminate household water supplies by leaching metals from building and plumbing materials in rooftop rainwater-catchment systems. Vog is a fairly common weather phenomenon in Hawaii, and it can be a respiratory hazard for children, the elderly, and those with respiratory conditions. The health department recommends reducing outdoor activities that cause heavy breathing and reducing exposure by staying indoors and closing windows and doors if vog conditions develop. It is important to note that vog is different from a "vog" in the context of event production, which refers to a voice of God, a term used to describe a disembodied voice that is heard by the audience but not seen.