What type of radiation is most harmful to health?

In answering this question we will concentrate on ionising radiation (since that is what Ionactive mostly works with). Visit our glossary for a definition of ionising radiation and non-ionising radiation.

The main types of ionising radiation we can consider are:

  • Alpha Particles
  • Beta Particles
  • Gamma / X-rays
  • Neutrons (not directly ionising but will cause ionisation upon interaction).

In order to discuss harm we then need to consider if the potential harm is via external or internal radiation exposure. External exposure is where the body is exposed to ionising radiation from a source that is external to the body (e.g. via an x-ray machine or sealed radioactive beta or gamma ray source outside the body). Internal radiation exposure is where the body is exposed to a source of ionising radiation which is located inside the body (e.g. radioactive material). In some cases certain types of sources can present both an internal and external radiation exposure.

External Radiation Exposure

For external radiation exposure, gamma or x-rays will generally be capable of delivering the most harm. Actual harm will be related to the energy of the radiation, the dose rate (how fast the radiation is delivered) and the total dose. Beta particles of high energy are also capable of superficial harm to the skin and can cause radiation skin burns in extreme cases.

Internal Radiation Exposure

For internal radiation exposure alpha particles will generally be capable of delivering the most harm. A pure alpha emitter (e.g. Po-210, ignoring the very weak and occasional gammas) presents little harm externally. However, if a significant quantity (activity) of Po-210 was ingested or inhaled then a very large radiation dose could be delivered. The actual dose will depend on many factors including the physical and chemical form of the alpha emitter and how the body deals with the contaminant biologically.

In some circumstances a radiation source may present an external and internal radiation hazard. For example, Am-214 emits alpha, beta, gamma, and x-rays.

Hold on, can radiation do good as well?

Whenever considering harm from ionising radiation it is also useful to consider exposures in context. For example, low energy x-rays and certain radioactive substances are used in medical diagnostics. High energy x-rays / gamma rays (and others like protons and neutrons) are used in radiotherapy for the treatment of many cancers. These type of exposures, where carefully administered and controlled, can do more good then harm! It is all about weighing up benefit and risk.

Physics is, hopefully, simple. Physicists are not

– Edward Teller -