MODEL RELEASED. Coastal radiation monitoring. Researcher gathering samples of mussels from a coastal environment at low tide. In the background, at right, is a detector being used to monitor levels of radioactivity. Mussels are sensitive to pollution and are an important indicator species, used to track the effects of pollution. The mussels will be tested to see if the levels of radioactivity in the area have harmed them. Most natural radiation is due to cosmic rays from space, and radon, a radioactive gas produced by the decay of radium from uranium ores. Human sources of radiation include nuclear power stations and pollution from coal-fired power stations. This work is being carried out by the UK's Health Protection Agency.