Electromagnetic radiation ranges from low frequency,relatively low energy, radiation such as radio and microwaves through to infra red, visible light, ultraviolet, X-rays and gamma rays. Radioactivity is associated with an exposure dependent risk of some cancers notably leukaemia. Contrary to popular belief however, most radiation to which the average person is exposed is natural in origin, and, of the man made sources, medical diagnosis and treatment is on average the largest source to the individual. A very important issue is the extent to which radon gas arising from certain rock types beneath dwellings can contribute to cancer risk. The explanation for leukaemia clusters around nuclear power plants is not yet resolved.
Similar clustering can occur in other parts of the country.
The effect of viral infections associated with population shifts may be important but requires further study. Non ionising electrical, magnetic or electromagnetic fields are an increasing focus of attention. If there are adverse effects yet to be proven, the risk is probably likely to be very small. To a much lesser degree of risk, these adverse effects apply to non-smokers exposed passively to sidestream tobacco smoke. General airborne pollution arises from a variety of causes but can usefully be subdivided into pollution from combustion or from other sources.