5.3 Radiation

Types of radiation and how they differ

The two main types are ionising and non-ionising radiation. The main difference is that ionising radiation carries more energy.

Ionising radiation includes:

• X-rays
• gamma rays
• particulate radiation (alpha, beta and neutron radiation)

It occurs as electromagnetic rays (X-rays and gamma rays) or as particles (alpha and beta particles). It happens naturally, for example in the radioactive decay of natural radioactive substances such as radon gas and its decay products, and it can also be produced artificially.

Radon is an odourless, invisible radioactive gas released naturally from rocks, soil and water. It can enter homes and buildings through small cracks or holes and build up in the air. Breathing high levels of radon over time can cause lung cancer.

Non-ionising radiation includes:

• radiofrequency and microwaves
• infra-red
• ultraviolet (UV) rays
• visible radiation from high-intensity light sources

Health effects of radiation

Radiation effects depend on source, dose, tissue and exposure pattern. Acute exposure occurs over a short period; chronic exposure is repeated or prolonged and is not necessarily low dose. The high-dose effects described below concern ionising radiation, not all sources of non-ionising radiation.

The amount of damage depends on several factors, including:

• the type of radiation
• the size of the dose
• how you were exposed: skin contact, swallowing, breathing it in, or rays passing through the body
• where the radiation concentrates in the body and how long it stays there
• the sensitivity of the exposed tissue and individual circumstances, including pregnancy. Obtain specialist advice about particular workers rather than assuming a simple ranking by age or health status.

A large dose over a short time, such as in a radiation emergency, can cause skin burns and may lead to acute radiation syndrome (ARS, or radiation sickness). Its symptoms include headache and diarrhoea, and they usually begin within hours. They then fade, and the person seems well for a while before becoming ill again. How soon the second illness comes, which symptoms appear and how severe they are depend on the dose received. In some cases ARS causes death within days or weeks. The effects of radiation exposure include:

• blistering and ulceration of the skin
• hair loss
• dermatitis
• cataracts
• anaemia
• a weakened immune system
• infertility
• cancer
• genetic mutation
• birth defects

Every cell in the body is affected by radiation, some more than others. With a high dose, death can follow within weeks, days or even sooner.

Typical occupational sources of radiation

Radiation is typically used in medical exposures, in industrial radiography equipment, and in gauges used for process control in industry. It can also come from naturally occurring radioactive substances, including radon gas.

Ionising sources

• X-rays: medical radiography and baggage security scanners
• gamma rays: industrial radiography
• particulate radiation: alpha particles in smoke detectors and science labs, beta particles in science labs and thickness gauges, and neutrons in nuclear power stations
• radioactive sources and naturally occurring sources such as radon gas

Non-ionising sources

• radiofrequency and microwaves, for example from plastic welding and some communications transmitters
• infra-red, for example from very hot, glowing sources in glass and metal production
• ultraviolet (UV) rays, for example from welding or the sun
• visible radiation from high-intensity light sources such as lasers

Summary notes for Element 5 · Cheat sheet · Glossary. A study aid, not published or endorsed by NEBOSH.