Cancer risk for radiation workers

The radiation comes from the black sands

People who are exposed to even low levels of radiation at work may be at risk of cancer, scientists have suggested.

They believe that current safety limits may be too high and that more research needs to be done to protect health workers, scientists and others who come into contact with radioactive materials.

Scientists from Britain and Germany have found that prolonged exposure to relatively low doses of radiation can cause mutations in human DNA.

Maybe it is happening to genes that have been linked to cancer

Dr Peter Forster, McDonald Institute

They have suggested that it may also affect genes that have been linked with leukaemia and other cancers.

The scientists analysed the effects of radiation exposure on nearly 1,000 people living in southern India.

Natural radiation

These people live in Kerala, which has one of the highest natural background radiation in the world.

The radiation is caused by monazite sands which contain the radioactive element, thorium.

These sands are washed down from nearby mountains and accumulate on the sea shore.

The study examined people from Kerala, India

The vast majority of people living in this area are fishermen and come into regular contact with the sands.

The scientists examined the effects of the radiation on mitochondrial DNA - the tiny energy factories which power cells.

They found that those exposed to radiation had higher levels of "point mutations" in their mitochondrial DNA.

A "point mutation'' takes place when a single "base'' - the genetic code is made up of four bases - along a DNA strand gets changed.

People who lived locally but were not exposed to the radioactive sands had significantly fewer mutations.

The mutations affect non-coding DNA and do not have an impact on health.

However, the scientists have suggested that encoding genes - those that can trigger disease - could also be affected.

They added that the findings raise serious questions about the levels of radiation people can be exposed to at work.

The people in the study were exposed to radiation which is 10 times greater than the worldwide average.

However, those who are exposed to radiation at work are allowed to receive up to 50 times the normal level.

Safety review

Dr Peter Forster of the Molecular Genetics Laboratory at the McDonald Institute at the University of Cambridge, said these safety limits should be reviewed.

"These findings may be cause for rethinking whether the maximum levels for radiation exposure at work should be brought down."

Speaking to BBC News Online, he added: "This section of DNA will always be non-coding but we only looked at this bit.

"Perhaps it is happening to other genes and maybe it is happening to genes that have been linked to cancer."

The study is published in the journal Proceedings of the National Academy of Sciences.