Jennifer, of Timaru, asks :-

Is natural radiation dangerous?

John Laban, a physicist at the Ministry of Health's National Radiation Laboratory, responded.

There are a wide range of sources of natural radiation to which we are being continuously exposed. Of these sources, the most familiar to us is the sun which produces infrared radiation that we feel as warmth, visible light, and ultraviolet light. The other sources are cosmic radiation which consists of high energy particles and rays that originate from outside our earth, terrestrial radiation which comes from naturally occurring radionuclides in the earth's crust, and internal radiation from radioactivity that is naturally present in our bodies.

Of these radiations, only one could be considered "dangerous", and that is the ultraviolet light from the sun. Over-exposure to the sun's ultraviolet light can prematurely age the skin, turning it hard and leathery, and can also cause sunburn which has in turn been linked to skin cancer. Unless we take precautions to cover up when outside it is easy to receive a fairly nasty sunburn. Although the nature of cosmic, terrestrial, and internal radiations is inherently hazardous and can cause cancer, these sources are not normally dangerous to us because the levels that are present naturally are sufficiently low that the risk of harm is negligible.

Cosmic radiation levels increases with altitude however, and some precautions may need to be taken for aircrew repeatedly flying on long distance flights to limit cosmic radiation doses.

Terrestrial radiation levels vary widely and while in some locations they are substantially higher than in other areas there is no clear evidence of increased incidence of cancer. New Zealand has a relatively low terrestrial radiation level. More information can be found at our web site: http://www.nrl.moh.govt.nz