sentences:  Orion will contain potentially hazardous material such as ammonia, hydrazine, freon, nitrogen tetroxide, and volatile organic compounds and it will be necessary to prevent or control exposure to these substances during flight.Astronautical hygienists in the United States together with colleagues in the European Union, individual United Kingdom astronautical hygienists and space medicine experts are developing measures that will mitigate exposure to these substances.Dr John R. Cain (a UK government health risk management expert) was the first scientist to define the new discipline of astronautical hygiene.