Marsh vapor, also known as MIASMA, is a type of air pollution caused by the presence of pollutants in the atmosphere. It is often associated with foggy or misty conditions and can be hazardous to human health. Marsh vapor is created when pollutants such as sulfur dioxide, nitrogen oxides, and other gases are released into the air. These pollutants react with water vapor in the atmosphere to form a thick, smog-like haze. The effects of marsh vapor can range from mild irritation to serious respiratory problems.