Birmingham International Airport has met targets for reducing most air pollutants, including carbon dioxide, it has revealed in a new study.

Its sixth annual Environment Report highlights the achievements of the Midlands' busiest airport in meeting targets on the environment, economic growth and community relationships.

However, environmentalists have described the report as a "sweetener" prior to the imminent publication of BIA's masterplan, including plans for a second runway involving a large-scale increase in operations.

BIA's managing director, Richard Heard, said: "The report shows some promising results and reflects the many ways in which sustainability is integral to how we manage and develop the airport.

"We are pleased with the results but will continue to work hard to manage the impact of the airport's operation on the local environment, ensuring that we make a positive contribution to local quality of life and the region's economy."

Key points in the report include:

* BIA became the first airport in Europe to install the ANOMS 8 package, a monitoring system which has upgraded its noise pollution tracking capabilities.

* the air quality target was achieved for all pollutants except ozone, which the airport put down to increased temperatures and lower wind speeds for much of the year.

* co2 emissions were reduced by 5.7 per cent since 1999, exceeding the target reduction of four per cent.

* 2004 saw the airport achieve the highest percentage share of people arriving by public transport since 1986, increasing from 14.2 per cent to 15.6 per cent.

James Botham, spokesman for anti-BIA expansion group BANG, said: "While this is all good work and, of course, we would rather the airport was doing this than not at all, it does all rather feel like a sweetener before the bitter pill of the masterplan. It is hard to see how all these targets can be reconciled in the face of plans for huge expansion."

The percentage increase in public transport was misleading, he said, because traffic overall to the airport had increased and, in real terms, there were far more car journeys than before.