Some flight attendants were too ill to perform their safety duties, while others have been permanently disabled. Witkowski says that the complaints of flight attendants do not always prompt correct maintenance. They are not required to put filters in. The law does not even require that they put filters in. Some planes do not have filters at all.
Airlines are under great pressure to get their flights out on time.
The U.S. Department of Transportation tracks that. So they do not pay as much attention to systems that are not as critical to flight safety. According to Witkowski, recent research findings underline the concern that filters can introduce engine chemicals like lubricant derivatives into the cabin air. More than half of the 200 subjects reported health problems they attributed to cabin air. The health problems reported by the largest numbers of crew members were burning of the throat, headaches and burning of the eyes.