During World War II, acrylonitrile containing polymers was developed in the US and Germany due to its resistance to oils and the lack of access to natural rubber. The ammoxidation process for the manufacture of acrylonitrile from propylene, ammonia and air was developed in the 1960s. Hydrogen cyanide is removed by distillation in the lights column before acrylonitrile is purified by azeotropic and conventional distillation. Acrylonitrile is a highly reactive molecule and polymerizes readily. Acrylonitrile vapour is irritating to eyes, nose and lungs leading to laboured breathing, dizziness and nausea. Acrylonitrile will polymerize on exposure to light. Acrylonitrile must be kept away from waterways and drains. Acrylonitrile is a severe fire and explosion hazard, and the heavy vapour can lead to flashback. Growth in fibres and Acrylonitrile-Butadiene-Styrene resins have resulted in a strong market for acrylonitrile. Fibres will play the dominant role in determining increases in production since most fibre manufacturers are captive users.