A study this month at the Harvard Medical School in the US, external found that flight attendants and pilots had the highest level of radiation-related cancer deaths among more than 500 different professions.

In all, about 6.9% of deaths among flight attendants and 6.7% of deaths among pilots were from radiation-related cancers, according to the analysis.

These proportions were higher than for other professions including nuclear technologists, who are routinely exposed to radiation from non-cosmic sources yet placed 12th on the list, the authors said.

It has long been known that air travel at high altitudes exposes people to cosmic radiation, but the dose for most travellers is regarded as statistically insignificant, external. Exposure at the poles is more intense because elsewhere the earth’s magnetic field acts as a shield.

Jim Smith, professor of environmental science at the University of Portsmouth, said it was impossible to determine whether or not an individual case of cancer was caused by radiation.

“Current radiation protection guidance assumes that any small dose can potentially cause cancer, but the lower the dose the lower the risk. From the known cosmic ray dose to air crew, and based on this hypothesis, we might expect that air crew regularly flying at high altitudes would have a small additional risk of cancer,” said Prof Smith.

“In France the link between breast cancer and certain hazards has been established for a number of professions, such as nurses … but this is the first time for an air-hostess,” said Lainault’s lawyer Elisabeth Leroux.

Air France said it had played no part in Lainault’s legal case and had not seen the reasoning behind the court’s decision.

“The health and security of our staff is an absolute imperative,” it said. “Every employee has a medical accompaniment that goes well beyond the regulatory minimum.”