Ted is referring to the fact that Earth is less radioactive now than it was when life first evolved. Radioactive materials decay into non-radioactive materials over time. Its been a long time since life began on Earth. "Optimum", in my understanding, could refer to the fact that radiation can cause mutation, and evolution is driven by the few successful mutations, and without evolution, there would be no natural world as we know it. Optimum also could refer to the hormesis theory which greatly interests but remains controversial among the most legitimate and respected radiation experts. I.e. evidence that cells respond favorably to increased radiation in certain circumstances exists. He's saying if all life on Earth was exposed to a higher level of radiation, and I'm not sure here how high he feels it could be, obviously from somewhere between today's level up to a presumed limit, i.e. possibly the previous higher level prevailing when life first evolved, things would be better.
Perhaps he is flying the flag a bit, given the decades of ridiculous uberhyped selective concern about the radiation that can be pinned on the nuclear industry the public has shown.
Ted is emphatic that the National Academy is mistaken in their choice of words in their most definitive reports about radiation. I knew that. I had corresponded with him in the past over that. I disagree with him there. I say if the NAS says the LNT model is the "best fit" to all available data when you compile all available data for assessment, its not worth disputing, and it isn't necessary. The problem with LNT isn't that the NAS says that model is the best model that fits all available data, even as the French are reconsidering, even though LNT, i.e. Linear No Threshold says no matter how low the level of radiation, there is harm caused as a result. If "x" amount of radiation causes "y" amount of cancers, some infinitesimal amount times "x" radiation causes some infinitesimal amount of cancers.
The problem is that civilization has taken LNT out of context and applied a standard for radiation safety to the nuclear industry, and to the nuclear industry alone, that is ludicrously stringent given that all other industries and activities are given a free pass on radiation in comparison, and given the really wide variation in background radiation people are normally exposed to without detectable ill effects. If LNT was really the problem, civilization would not be possible as all activities of civilization would have to be directed into trying to reduce radiation exposure for all these other things to meet the standards presently required of the nuclear industry. Anti nukes have just exploited fear of the power in the nucleus, and used LNT in their campaign to raise the cost of nuclear power so much it won't be able to be used. Eg Yucca was required to limit exposure 10,000 years from now to 15 additional millirem at the surface to any human being living there. Never mind Yucca is in the middle of the desert where no one is going to live. Forget that almost 1000 nuclear bombs were blown up at the test range near by. You can move from where I live to Spokane some 400 miles away, and increase your exposure by more than 1000 millirem right now and it makes no discernable difference to anyone. No one is saying Spokane must be dismantled and trucked away to a nuclear waste dump. It is an insane situation and it is a major cost factor holding back nuclear power that is even more insane given that we need to replace fossil fuels before CO2 accumulates any further or we risk not only this age of life on the planet but the viability of the planetary life support system itself. The nuclear industry has been forced to pour billions of dollars down rat holes, or into rat's pockets as Ted likes to say, over nothing, anyway its a very long story.
My feeling was Ted was inviting criticism or rejection of the main thrust of his paper by using the word "optimium" at this time in this situation, and I almost suggested this to him. The context is what does he think about Fukushima after all. But LNT is a very old debate Ted has been involved with for decades and I am wet behind the ears when it comes to discussing radiation. His position has been to publicly oppose the President of the National Academy over LNT saying you are wrong.
My position is the National Academy of Sciences has its reasons. I believe we must preserve it as an institution where people can get authoritative assessments of science. This is vital, because as the NAS has repeatedly stated there are far greater issues at stake than nuclear power. The inhabitability of the planet is in question says Hansen. The current President of the NAS says Hansen, above all his peers, is the best living climatologist. And so, I point out, because no one ever asked the Academy for its opinion about should we continue to demand that the nuclear industry be forced to pour all these billions of dollars down rat holes in pursuit of a few millirem that make no difference, we should ask it, now that the Academy has become so concerned about climate, what will they say now. Let them speak clearly. The hour is getting late.
Rather than dispute LNT, because of the way the anti nukes have exploited it given irrational public fear, we should direct the Academy to tell us how best to deal with radiation in all aspects of our lives.