The cancer risk from plutonium exposure

Plutonium may be many times more dangerous than previously thought. The cancer risk from exposure inside the body could be 10 times higher than is allowed for in calculating international safety limits.

The danger is highlighted in a report written by radiation experts for the UK government, which has been leaked to New Scientist. The experts are unanimous in saying that low-level radiation emitted by plutonium may cause more damage to human cells than previously believed. Their opinion could provoke a rethink of the guidelines on exposure to radiation.

Several tonnes of plutonium have been released into the environment over the last 60 years by nuclear weapons tests and nuclear plants.

Concern over the harmfulness of plutonium is growing because of discoveries about the subtle effects of low-level radiation. Researchers in Europe and North America have shown that the descendants of cells that seem to survive radiation unharmed can suffer delayed damage, a phenomenon called "genomic instability" (New Scientist, 20 January 2001, p 4). Cells adjacent to those that are irradiated can also sustain damage, known as "the bystander effect". And an increase was found in the number of mutations in small pieces of DNA called mini-satellites that are passed from one generation to the next. The fear is that these effects could trigger cancers and other ill effects.

The report, which is due to be published in the next few months, has been drawn up by the Committee Examining Radiation Risks from Internal Emitters (CERRIE). The committee includes 12 specialists from the UK government's National Radiological Protection Board, the nuclear industry, universities and environmental groups.

All members of the committee agree that the margin of uncertainty over the risks of plutonium and similar radionuclides inside the body "could extend over at least an order of magnitude". This "should be borne in mind by those making judgements and policy decisions on low-level internal radiation", says CERRIE's chairman, Dudley Goodhead, the former director of the UK Medical Research Council's Radiation and Genome Stability Unit at Harwell in Oxfordshire.

By Rob Edwards of http://www.newscientist.com