Reply #3: Hmmm. I consider much of what you say misleading, at best.

[struggle4progress]

It is true that T can be a useful label in biochemical research. But its sometime use as a tracer in hydrogeological studies is completely unnecessary: stable isotopes provide a satisfactory alternative.

Nobody gets very excited about external beta exposure, but internal exposure is very different story. Because free T is naturally lost with the radiolytic decomposition of labelled compounds, and (being very small) passes easily through gloves and other normal laboratory protective gear, contact with labelled compounds or breathing air in contact with labelled compounds will likely provide an internal radiosource. Similarly, contact with or respiration of a tritiated water (say THO) will provide an internal source.

Mean residence time for absorbed T is believed to be of the order of a month, but this does not distinguish between pools, and any fraction of T incorporated chemically into tissue would not be expected to flush with the extra- or intracellular waters. Because of the low mean residence time, conventional wisdom holds that a small one-time T exposure is of relatively little concern: this reasoning, however, would not remain valid in the case of chronic exposure. Nor would the reasoning remain valid in situations involves substantial cell synthetic activity (such as embryogenesis), when the likelihood of producing T-labelled tissue is increased. Experiments, in fact, have demonstrated genetic damage in animal populations fed with constant low doses of THO and animal models indicate special vulnerability to higher doses earlier in life. Such effects are radiological in nature and occur at doses orders of magnitude below "the 50% saturation by body weight with THO" level needed to observe immediate fatality, which is sometimes attributed to isotope effects.

Much T produced by power plants is simply released into ambient air or
water, largely because nobody knows how to control it easily. It thus becomes a chronic source to specific populations downwind or downstream. Perhaps as an external source, T would be of minor concern; however, as it is prudent to assume contact with free T or THO essentially implies ingestion, some of this released T becomes a source of internal emission. It is not immediately comparable to isotopes dissolved in the deep sea, far from most humans.

And I find your cheery little paean to tritium to be a bizarre response to the news, that the USA is once again making the stuff to keep its apocalyptic fusion bombs functional ...