FAQs

Gaseous tritium light sources are sealed glass vessels that give off light in various colours, though usually it is green light because the human eye is most sensitive to its wavelength. To fabricate a GTLS, the glass vessel is coated on the inner wall with luminous matter known as phosphor (different phosphors are used for different colours), and then it is filled with the radioactive tritium gas and sealed airtight. The beta particles emitted by the tritium during its decay will come into contact with the coating. The phosphor will absorb the energy of the beta particles and converts it into visible light.

Kit markers with gaseous tritium light sources (GTLS) are usually in the form of an outer polycarbonate casing enclosing one or more GTLS. They can be considered as one type of GTL devices.

GTLS kit markers are supposedly for marking vital equipment and devices used by military and emergency response personnel, professional mountaineers and divers, pilots, and other professionals such as disciplined or civilian forces who need to perform search and rescue operations and might need to quickly and readily locate safety-related or even safety-critical equipment in dark environments. And these kit markers are always marketed as such.

The activity of tritium in these markers usually ranges from about 1 GBq to a few GBq, but could be up to tens of GBq, depending on the luminosity required by the specific group of users for their specific working environments (e.g. military forces).

The Board maintains, as a fundamental principle for the use of radioactive substances, that the use of these GTLS kit markers, whether they each contain more or less than 1 GBq of tritium gas, has to be justified as a practice and source.

While use of GTLS kit markers by military and emergency response personnel and certain groups of specialists may be justified, the risk-benefit equation will change when it comes to unrestricted use of these kit markers by the general public. It is the view of the Board that kit markers for general use (home, casual outing, or the like) do not meet the criterion of justification.

In the USA, while the US Nuclear Regulatory Commission (NRC) licences the use of GTLS in timepieces and gun sights and compasses in the US, it does not seem that it would licence the use of GTLS in common kit markers, or in other frivolous applications.
[Reference: NUREG 1556, Vol. 8, Section 5; 10 CFR Part 32].

In Japan, the Japanese Government (Ministry of Education, Science and Technology) recalled about 5500 cell phone straps with GTLS indicated that such frivolous use of GTLS could happen, and that they are forbidden there.
[Reference: The Yomiuri Shimbun, December 8, 2008].

In the United Kingdom, while they may impose little restrictions on sale of these GTLS kit markers to members of the public, the UK supplier Tracer had posed such a note on its web site www.traser.co.uk, which stated that ‘glow rings (commercial name for GTLS kit markers) can only be delivered to the UK due to international regulatory differences regarding the use of GTLS’.
[Reference: EC Radiation Protection 146, Section 4.1.1, 2007].

This indicated that sale of GTLS kit marker as an ordinary consumer item has not been at all common among European countries.
(Remark: The website no longer exists, indicating that perhaps the company does not exist any more, or that it no longer maintains the website, or that it does not run the business of selling GTLS kit markers any more!)

That a very few member states in the European Union (notably the UK and the Netherlands) allow the sale of GTLS kit markers of limited tritium gas activity does not mean that this is the case for the majority of member states. This inconsistency merely reflects the differences of different member states in the judgement, the legislation, the effectiveness of control and hence the regulation of consumer products with small quantities of radioactive substances
[Ref. 2: EC Radiation Protection 146, Section 6.2, 2007]

It all boils down to the principle of justification. The benefit of introducing the GTLS kit markers to the public, which constitutes a new exposure situation, must be weighed against the risk associated with it.

In indoor or home environment, traditional lighting devices, including the common torches, are usually available. As to casual outdoor activities, there are also many non-radioactive alternative gears for illumination, including the increasingly common, and brighter, LED devices. In these circumstances, even though the risks of using the GTLS kit markers are small, the relative benefits offered by GTLS kit markers are so minimal that they are hardly adequate to outweigh the various risks involved, radiological or otherwise.

Radiological risks mainly come from the potential exposure due to breakage (accidental or due to vandalism), loss (unintentional or deliberate), and the subsequent uncontrolled disposal. They may be small for a limited number of GTLS used by professionals, but definitely will increase with their proliferation into the possession of the general public.

Non-radiological risks comprise possible non-acceptance or opposition, which is rather likely, of the use of these GTLS in seemingly mundane consumer items by the general public, and the amenability of regulatory control of these GTLS kit markers should the public or their representatives demand it.

There is a significant potential that these GTLS kit markers, if widely available, be proliferated into some frivolous uses, as we have seen these kit markers used in key chains, in mobile phone straps, etc. If these kit markers are to be marketed without restrictions, their likely inexpensive cost, coupled with the likely non-specialists and young people as the majority of users, the chances that these kit markers would be roughly handled, carelessly or maliciously, should not be underestimated. Their inadvertent and careless disposal would also be much more likely than that for the usually much more expensive timepieces.

It is anticipated that unrestricted distribution of these GTLS kit markers to the public would mean a low probability for the return of these kit markers to the supplier when they are disused. Any radioactive contamination due to their breakage (accidental or intentional) would more than likely be gone unnoticed by the user, let alone other members of the public and the regulatory authority. The rehabilitation of contaminated surfaces that would be needed to meet the clearance level for public use will also be an important issue from such considerations as public anxieties and cost of decontamination.