British Airways (BA) and KLM Royal Dutch Airlines (KLM) occasionally receive reports from flight deck and cabin crew of symptoms regarding the respiratory tract and eyes. Dry eyes, dry throat and respiratory discomfort may be a result of low relative humidity or may be due to raised ozone concentrations. It was decided to do a joint study on this subject. On 24 polar flights (12 KLM, 12 BA), ozone levels and relative humidity were measured and questionnaires were completed by crew members.
Ozone and relative humidity were measured on the flight deck. Flight deck and cabin crew members were asked to indicate if physical symptoms were present, before the flight and toward the end of the flight. The measured ozone concentration for both airlines was highly variable. On KLM flights (with catalytic converters) ozone levels were significantly lower than the ozone level on BA flights (no converters). Although BA aircraft used in this study have humidifiers installed for the flight deck, only on three BA flights was the mean relative humidity over 10%. This suggests that the humidifiers may not have been working properly, and no conclusions regarding their effectiveness can be drawn. Most of the crew members showed an increase in physical symptoms during the flight, as was expected. There was, however, no significant relationship between cabin air parameters and reported physical symptoms.