Volcanic Eruptions

• Propylene oxide is found in smoke, as a by-product of the combustion process. When volcanoes erupt, propylene oxide is present in the smoke that the volcano belches into the air. However, the amount present is so small that the chemical is not among the chief concerns for the environment around the volcano.
  
  

Forest Fires

• As a forest fire spreads, burning hundreds and hundreds of trees, propylene oxide will enter the air. As with volcanoes, though, the concentration of propylene oxide present does not cause any lasting damage to the environment.
  
  

Manmade Source: Chemical Production

• Other than combustion processes in volcanoes and forest fires, there are no other sources of propylene oxide in nature. However, it is a by-product of several different chemical production processes, which release the chemical into the air. Producing soap and other cleaners, as well as plastics and synthetic resins, introduces more propylene oxide into the air than other industries.
  
  

Environmental and Medical Effects

• Unless an event like a tank spillage takes place, the environment can absorb propylene oxide without long-term damage. However, in people, propylene oxide can cause anything from lung irritation to pneumonia after inhalation, and can cause severe gastric distress if ingested. In animal studies, research has established propylene oxide as a direct cause of cancerous tumors; human studies are still inconclusive.