Answer given by Mr Dimas on behalf of the Commission
The Commission is aware of claims that such trends and phenomena exist. However, the Commission is not aware of any evidence substantiating such claims. The extent to which aircraft condensation trails form and the speed at which they disappear are in the first instance determined by pressure, temperature, and the relative humidity of a given flight level. Fuel and combustion properties and the overall propulsive efficiency may also have an impact. Any changes or trends in the extent to which contrails are reported to remain visible and develop into more widespread clouds may thus be due to factors such as changes in:
2. The Commission is aware of such claims but is not aware of any evidence that particles of barium, aluminium or iron are being emitted, deliberately or not, by aircraft.
3. No. It cannot be precluded that the release of such particles might affect precipitation and climate change, but as indicated above the Commission is not aware of any evidence that such releases take place.
4. The Commission is not aware of any evidence that such methods are being employed in Europe.
5. None of the substances referred to are hazardous per se, but some effects on environment and public health can not be ruled out if large scale releases to the air occurred.
6. As indicated above the Commission is not aware of any evidence suggesting that there is any reason to act.