BRUSSELS, Belgium (AP) - Airplane cabins could be contaminated by leaking toxic fumes that threaten the long-term health of passengers and crew, a pilot's group warned Friday.

The International Federation of Airline Pilots' Associations said regulators should immediately consider the issue of cabin air quality, after several incidents were reported of crew members falling sick from fumes in recent years.

``We'd like to see some proper independent scientific research into what is clearly ... a serious issue,'' group spokesman Gideon Ewers said.

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The London-based group - which represents more than 100,000 airline pilots worldwide - has instructed cockpit crews to immediately don oxygen masks whenever fumes are detected.

In December an eight-person American Airlines crew was treated after landing in Fort Lauderdale, Florida, for dizziness and nausea. In August, two Flybe cabin crew members became ill on a flight between Birmingham and Belfast from suspected toxic gas poisoning.

The group fears toxic vapors, leaking into passenger cabins through the planes' air conditioning systems, could put passengers and crew members at risk for developing chronic sickness.

``There has been some sample testing carried out which shows some very unpleasant chemicals reaching the air conditioning system,'' Ewers said in a telephone interview.

A study of cabin air samplings prepared for Britain's Department of Transportation in January found hazardous substances such as toluene, tributul and tricesil phosphates - found in hydraulic fluids and heated engine oils.

The effects of inhaling such substances are comparable to those experienced by breathing in volatile chemicals such as fresh paint, the pilots group said.

``It's a long-term health risk, rather than an immediate concern about somebody passing out,'' Ewers said.

When the world's first jet airliners were introduced in the late 1950s, they were generally fitted with separate intakes for cabin air. But with the advent of the high-bypass jet engines in the 1970s, designers began to focus on a much lighter and more efficient system that bleeds air into the cabin system from the engine itself.

Experts say this has allowed fumes from the engine's turbine bearings ahead of the cabin air intake to get into the air conditioning system.

Some aircraft types, such as the Boeing 757 and the BAe146 - both in wide use by commercial carriers - are considered particularly susceptible to such contamination, experts say.

In recent years, airframe designers have started reverting to the original separate intakes on new planes and shunning the engine bleed system.

05/30/08 11:31 © Copyright The Associated Press. All rights reserved. The information contained In this news report may not be published, broadcast or otherwise distributed without the prior written authority of The Associated Press.