Non-visible parts of the electromagnetic spectrumHazards of electromagnetic radiation

Over-exposure to certain types of electromagnetic radiation can be harmful. The higher the frequency of the radiation, the more damage it is likely to cause to the body:

• microwaves cause internal heating of body tissues
• infrared radiation is felt as heat and causes skin to burn
• X-rays damage cells causing mutations (which may lead to cancer) and cell death - this is why doctors and dentists stand behind protective screens when taking lots of X-rays
• gamma rays also damage cells causing mutations and cell death

We are exposed to gamma and other nuclear radiations all the time from sources including:

• radioactive rocks in the Earth's crust
• cosmic rays from space
• man-made sources such as nuclear weapons fallout and nuclear accidents

The level of background radiation and dose are affected by factors such as the jobs that people do and the places where people live. Normally the levels are so low that there is no danger to us.

Microwave radiation

Microwave radiation can be used to transmit signals, such as those for mobile phone calls. Microwave transmitters and receivers on buildings and masts communicate with the mobile phones in their range. There is concern that microwave radiation from mobile phones and masts may be harmful to our health.

Ultraviolet radiation

Ultraviolet radiation - UV - is found naturally in sunlight. We cannot see or feel ultraviolet radiation, but our skin responds to UV exposure by turning darker over time. This is called a sun tan. This happens as our bodies attempt to reduce the amount of ultraviolet radiation reaching deeper skin tissues.

Darker skins absorb more ultraviolet light, so less ultraviolet radiation reaches the deeper tissues. This is important, because ultraviolet radiation can cause cells to become cancerous.

We should wear UV blocking sunscreen on sunny days to avoid skin cancer. Overexposure of our eyes to ultraviolet radiation can cause blindness, so we should wear hats and sunglasses on sunny days.

The three main types of ultraviolet radiation and some of their effects