Document mpRkajvNNYO36K6r4LXBnVNN4

.223 have set for the future, a plan to carry out simultaneous dust and radiological surveys at twenty mines scattered throughout the whole of Great-Britain, which the coal board: ^ are organizing in collaboration with U3, and we hope to i i overcome the inaccuracies of the historical factor in this ! I way, and from follow-up surveys of this kind, to get really: good evidence, more precise than we've got at the moment 1 which, associated with and in addition to, animal experi ments, may help us to solve the why's and wherefore's in this difference we have found. I ! j I Now, what about 3afe limits? Next slide. Here i we have, for the Welch pits, where our working data is nuchi 1 more complete, these dose response curves for Category 1, aic for Category 2, and more and Cateogry 3/ and here we nave ' the dust dost. These are sigmoid curves, and are, o:' course, .i sound distribution curves. That is to say this curve :.er9 represents an ordinary - an ordinary normal distribution curve, and the fifty percent point is, of course, one most accurate point to take the relevant point on it from, ^nd *I I have mentioned in my paper that our ratio between our 1 categories is roughly speaking, but only roughly, linear, is about half as much dust again, at the fifty percent point here; two and three, 70U can see it isn't quite is accurate as it should be, but it's not bad, and tr.is s our: evidence that our categories are related to dust -x?00-re. ` ` ' -I -" ^ ***'5s '* v " SEVENTH SARANAC -0258