Charlotte Atkins: The Civil Aviation Authority compared the British Airline Pilots Association survey results with its mandatory occurrence reports. Much of the survey data related to low level events, often with inconclusive connections to contaminated air. Inclusion of the survey data in the Authority's database would not have advanced or improved the formal intervention action taken to mitigate the threat to safety posed by impairment of pilot performance through exposure to contaminated air. BALPA's data aligns with the CAA's assessment that there is a downward trend in the number of air contamination events now being reported.