Total Indicative Dose in Drinking Water Information:

Properties:

The Total Indicative Dose measurement reflects the total, effective amount of both alpha and beta radiation a person has been exposed to in a year. Alpha particles are made of two protons and two neutrons and are emitted by compounds such as uranium-238 and radium-226.1 Beta particles are higher in energy and are either negatively-charged electrons or positively-charged positrons.2 Tritium is one example of a beta particle emitter.

Sources:

Naturally-occurring radionuclides relevant to drinking water include potassium-40, lead-210, uranium-238, radon-228, and tritium.3 Uranium-238, for example, can leach into groundwater supplies from bedrock and soil while tritium is formed in the upper atmosphere. Commercial and industrial operations can also contribute to elevated concentrations of both naturally-occurring and artificial nuclides: artificial nuclides include caesium-137 and strontium-90.3 Nuclear accidents and emergencies also influence the amount of radiation a population is exposed to, but these events are rare.

Regulations:

The limit for total indicative dose for an individual per year is 0.10 mSv/y (micro Sieverts per year). (1 Sv = 1 Joule/kg)

Health/Environmental Concerns:

Low to moderate radiation exposure can increase an individual’s likelihood of developing cancer.3 Additionally, ionising radiation is often considered mutagenic because of its correlation to gene mutation. Most water supplies comply with regulatory standards except during rare cases of nuclear emergencies, spills, or accidents.3

Action:

In general, total indicative dose is not regularly measured or monitored in drinking water due to the low occurrence of exceedances. However, exceedances require immediate action; mitigation requires quick identification of contamination sources and measurements of individual radioactive species.3 Due to the difficulty associated with removing radionuclides from water supplies, contamination should be treated at its source. Contact your Water Service Authority if you are concerned your water may be contaminated. If drinking water makes you ill, contact a doctor right away.

1 Understanding Radiation: Alpha Particles. Australian Radiation Protection and Nuclear Safety Agency (ARPANSA): Australia. Accessed Mar. 10, 2020.

2 Understanding Radiation: Beta Particles. Australian Radiation Protection and Nuclear Safety Agency (ARPANSA): Australia. Accessed Mar. 10, 2020.

3 Guide to the Parameters in the European Communities. What’s in your water?; S. I. No. 278 of 2007; National Federation of Group Water Schemes: Ireland.