Flight attendants and pilots are at the highest risk of dying from radiation-related cancers – even more than people who work with radioactive materials, according to a new study.

Cosmic radiation comes from space. Only a small amount reaches the Earth’s surface, but exposure is greater for people flying at high altitudes.

There has been limited evidence from small studies suggesting that the exposure translates to higher cancer death rates among people who fly often – particularly pilots and flight attendants. The new study “brings important new evidence to bear on this question”, two Australian radiation experts who were not involved in the research wrote in an accompanying commentary.

The latest study, published on Monday by JAMA Internal Medicine, used national data from more than 12 million death certificates that included information about occupations. The authors looked at death rates from cancers that are tied to radiation exposures, including leukaemia, lymphoma, multiple myeloma, and cancers of the skin, breast, thyroid, prostate and central nervous system.

Among more than 500 occupations, flight attendants had the highest percentage of deaths from radiation-related cancers, and pilots were second, the researchers found. For those two occupations, the odds of dying were unusually high for each type of radiation-related cancer.

Neither group showed higher-than-normal death rates from cancers that are not tied to radiation exposure, said the commentary writers, Catherine Olsen and Ken Karipidis. That fact “supports the hypothesis that occupational radiation exposure, rather than lifestyle or socioeconomic factors, underlies the observed excess”, they said.

The researchers found that flight attendants had about 50 per cent higher odds of dying from a radiation-related cancer than the general working population, and pilots had about 36 per cent higher odds.