Document 2NJVQE3Y4ZZxaggm7jpbNrZQ7

Mar ch 26, 1932 Mr . A. R. Ri ddel l , Di vi s i on of I ndus t r i al Hygi ene * Depar t me nt of Heal t h, Tor ont o, Ont ar i o. 'I Dear Mr . Ri ddel l : I wi s h t o t hank you ver y much i ndeed f or your l et t er of Mar ch 17t h r epl yi ng t o my comment s of s ome t i me ago. I f i nd t hat i n the mai n we ar e not i n any s er i ous di s agr eement , t hough per haps t her e i s one poi nt at whi ch I di d not make mys el f ent i r e l y cl ear s I r ef er t o t he mat t er of t he f i ndi ng of l ead i n t he ur i ne. The f act s I n t hi s par t i cul ar mat t er ar e not as s i mpl e as we have pr evi ous l y t hought . I n t he f i r s t pl ace, al l per s ons i n or out of t he l ead t r ades ar e excr et i ng meas ur abl e quant i t i es of p. ead i n t hei r ur i ne. The onl y di f f i cul t y of f i ndi ng i t i s as s oci at ed wi t h a s ens i t i vi t y of chemi cal met hods , as wel l as t he empl oyment of a s uf f i ci ent l y l ar ge s ampl e of ur i ne. The var i at i ons i n nor mal i ndi vi dual s ar e f ai r l y cons i der abl e. Thus, t he mer e f i ndi ng of l ead i n t he ur i ne i s ent i r el y wi t hout any val ue what s oever , and t he onl y val ue of an anal ys i s ar i s es f r om a knowl edge of t he act ual quant i t y pr es ent . I t i s not f eas i bl e t o h. 've ei t her a qual i t at i ve or quant i t at i ve met hod of anal ys i s whi ch i s so compar at i vel y I ns ens i t i ve as t o s how t he pr es ence of l ead onl y when mor e t han nor mal amount s ar e pr es ent , f or t he r eas on t hat t her e ar e no met hods whi ch wi l l gi ve i nvar i abl e r e sul t s of s uch an or der of accur acy. Thus , met hods t hat ar e com par at i vel y uns at i s f act or y yi el d hi gh r es ul t s s omet i mes , and l ow r es ul t s at ot her t i mes. Thus , I t i s not s af e t o empl oy any ex cept a ver y r ef i ned met hod of anal ys i s . I f one goes t o t hi s ext ent t hen i t i s not pos s i bl e t o come t o any concl us i on unl es s t he amount f ound I s i n exces s of t hat whi ch may nor mal l y be pr es ent . I r ecogni ze t hat t hi s wi l l s ound l i ke a s omewhat ar bi t r ar i l y expr es s ed poi nt of vi ew, but t he evi dence back of I t i s over whel mi ng, and t he concl us i on i s hence ent i r el y unavoi d abl e. I t hi nk t hi s makes my pos i t i on on t hi s mat t er ent i r el y cl ear . I hope s hor t l y t o publ i s h t he dat a Whi ch f or m t he back gr ound ofi t hi s opi ni on. i Cor di al l y your s , RAK: EJ T N 6238