Nuclear industry workers exposed to chronic low doses of radiation have a slightly higher risk of developing cancer, scientists said on Wednesday.

“We have shown that even low doses of radiation cause cancer,” said Dr. Elisabeth Cardis, head of the radiation group at the International Agency for Research on Cancer (IARC) in Lyon, France.

But she added that the risk appears to be similar to what scientists had estimated based on data from survivors of the atomic bombings in Hiroshima and Nagasaki, Japan in 1945.

Radiation protection standards, which limit occupational exposure to ionising radiation to 100 millisieverts (mSv) over five years and 1 mSv per year for the public, are based mainly on data from survivors who had been exposed to high doses of radiation over a very short time period.

“There has been a controversy for decades about the use of data on A-bomb survivors for setting standards for the protection of the general public and radiation workers,” Cardis said.

But the findings, which are reported in the British Medical Journal, may settle the issue.

“Our study shows that the current basis for radiation protection appears to be reasonable,” Cardis added.

In the largest study of nuclear workers ever conducted, researchers from IARC estimate that cumulative exposure could lead to a 10 percent raised risk of death from all types of cancer and a 19 percent increase from leukemia, excluding lymphocytic leukemia.

The researchers studied 407,000 nuclear industry workers in 15 countries who had been exposed to low doses over an extended time span.

The results suggest only a small proportion of cancer deaths in the study group were due to chronic, low-dose exposure. The scientists estimated that 1-2 percent of deaths from cancers, except Leukemia, in the nuclear workers in the study may be due to radiation.

But they added that most were in older employees who had worked in the industry many years ago.

“Those who had the highest doses worked in the 1940s and 1950s when the radiation protection standards were much less than they are today,” Cardis said in an interview.