Radioactivity in food: your questions answered

Yes. In the UK, strict legal controls govern how radioactive waste is disposed of and outline the acceptable levels of radiation found in people.

Yes. There are some common sources of natural radioactivity in food, one of which, for example, is a component of potassium called potassium 40. It forms 0.012% by weight of all natural potassium and occurs in the cells of all living things.

Natural radioactivity can also be transferred to crops from rocks and minerals present in the soil, while drinking water can pick up radioactivity from the earth, and fish and shellfish can take up radioactivity from the water or sea floor.

Artificial radioactivity can get into food after it has been discharged into the environment from civil or military nuclear operations. It then passes through the food chain in the same way as natural radioactivity.

A radiation dose is called a sievert, normally measured in thousandths (millisieverts) or even millionths (microsieverts) because most radiation in the environment is so small.

The major producers of radioactive wastes must monitor the environment around their site, while the government carries out secondary checks.

In addition, the levels of radioactivity in milk are closely watched, as this is a highly effective way to measure radioactivity around nuclear sites. Most sites have grazing cows nearby - radioactive elements they might ingest will usually pass into their milk.

The same goes for fish and shellfish, which are monitored after being caught..

Radioactivity can damage our body's DNA, a complex molecule found in all our cells that controls their function and growth. Low radiation doses can be repaired but higher doses can change our body's cells. In these cases cancer can develop.

Large radiation doses kill cells. Radiotherapy, for instance, uses radiation to target and destroy tumour cells while at the same time minimising damage to normal tissue.