This ANDY-SEZ was to have thrown more light on the subject of lampenflora. However, I have decided to change my mind as another issue has become more topical. Cave people at Jenolan, Wombeyan, Yarrangobilly, Buchan, Yanchep, Yallingup, Augusta-Margaret River and probably elsewhere have had visits from strange scientists or the even stranger me muttering about radon.

There has also been some media interest in this matter following a small article and a letter in New Scientist (Vol. 135, No. 183, pp. 4 & 47,12 September 1992). The Hobart Mercury, perhaps predictably, lead the way with a fine front page beatup.

Radon is a radioactive gas produced by the decay of uranium to lead. It is found in buildings, the open atmosphere and in caves wherever there is uranium to decay. In some parts of the world it is a health hazard in homes and governments play active roles in managing the problem. The New Scientist pointed out that very high levels were found in some caves and suggested that those using caves regularly should be aware of this.

Radon gas, and its solid daughter products as microscopic particles in the air, are easily inhaled. If the particles lodge in your lungs - in close proximity to sensitive tissues - they will emit radiation energy. Such energy is implicated in the development of cancers. Radon does not produce acute radiation sickness but may initiate, or help initiate, lung cancer in the long term.

Those of you that smoke should be aware that this habit markedly increases the risk that may arise from radon alone.

There is little uranium in most limestones and thus radon is not a problem in most caves. However, elevated levels have been found at Jenolan, Wombeyan, Buchan and in Nullarbor caves. The levels in the Western Australian caves were generally low with the exception of Jewel Cave.

Measuring radiation, and radiation doses, is very complex and expensive and there are a number of factors which influence levels of radon in cave atmospheres. These include the concentrations of uranium in the rock, presence/absence of sediments and their type, the amount of ventilation and of moisture, cave geometry and so on. The problem is not helped by differing measurements, units and techniques and by the fact that radon levels change both daily and seasonally.

Earlier this year I convened a meeting in Canberra to discuss this issue with a view to see whether or not an occupational health and safety problem exists. Previous work at Buchan by Dr. Stephen Solomon and others at the Australian Radiation Laboratory in Melbourne had shown that some guides at Buchan were receiving a radiation dose about 20% of the maximum permitted for licensed radiation workers. Levels are higher still at Jenolan, Wombeyan, Yarrangobilly and King Solomons. The highest levels we have found are less than a tenth of the British high levels. But I must stress that we don't know enough about what is going on to be certain that a problem exists.

At the meeting we proposed a three tier program to investigate the issue more fully. This will require a very large sum of money, sophisticated equipment and much more work. It will also require knowing far more about the actual amounts of time that workers spend in caves on a yearly basis. I would appreciate it if each workplace tries to estimate, accurately, what are the actual amounts of time their workers spend underground and let me know the result. This program would be restricted to Australia but at least preliminary testing should take place in New Zealand.

It is important to say that there is no reason to panic, but neither should there be complacency. One should also emphasise that the cave tourist is not at risk - he or she spends very little time underground. Radon is but one source of naturally occurring environmental radiation. International jetsetters get far higher doses of natural environmental radiation in their aircraft than those found thus far in Australian caves. There is some evidence that small doses of naturally-occurring radiation such as those we have evolved with are actually good for you. Like one standard drink a day?

I will continue to let you know what is happening in this area as new information comes to hand. For those who are interested in learning more about this issue an upcoming edition of Helictite, The Journal of Australasian Cave Research, will have a paper by Ruth Lyons on the subject. [Since the above was written the Worksafe Australia report has been completed - all Australasian cave managers should have, and have considered, the Solomon et al. (1996) report. If help in interpreting this report is required do not hesitate to contact Ruth, Steve or myself].