Document jg0zxLYdpdeOJ2y5J8QD8bdn2

FILE NAME Talc TALC DATE 1952 Apr 1 DOC TALC406 DOCUMENT DESCRIPTION Letter to CT Dept of Health from Dr. Vorwald Apri1l 1952 Mr. Alles L. Colema Chief Industrial Hygienist State of Gonnectient Hartford 1 Commecticut Dear Colemans Mr. | off zimtes ago I sent a telegram to let you know your letter Jasmary that wy reply to of Jasmary 21 vill bo in today's 2 decerely delivery mailsending you comments to but 16 has bean Esvoldable Unfortunately I cannotbe in Cincinnati on Saturday : April 19 and I en vendering whether number L. J. Eton an Associate Member of A.C.B.S.H. A.C.B.S.H. and number of us staff cannot act as 1 alterarte If She lo agreeable Mr. Urban rill planto some to Cincinnati in time to attand Arthur J. Vervald N.B. . Direster: 1671 000200 18. Allan L. Coleman - a April 1 1952 - comments These , we know serve only to emphasize the existence of obious obvious discrepancies and in no way aids in their remedy With regard to dusts the problem of setting a maximum allowable limit asbestos is one to which considerable thought has been given by various investigators From experiments condusted at The Saranac aboratory it has been shown that only asbestos fibers longer than about 20 microns are capable of causing peribronchio lar fibrosis typical of asbestosis in guinea pigs rats and rabbits The corresponding value for industrial workers is still a question but it is probably not less than 20 microns The upper limit is similarly indefinite From animal observations the actual concentration of these long asbestos fibers which must be considered hazardous is quite low possibly even less than one 1 million particles per cubic foot of | air However in an atmospheric suspension of asbestos dust even a suspension arising from fiber asbestos the number of fibers longer than 20 microns is generally only a small part of the total number It would be logical to fix a threshold limit for asbestos dust on a sliding scale which would be regulated by the proportion of long fibers in the dust We are probably not justified in adopting such an arrangement at present because the range in the length of Bibers hazardous to industrial workers is not known and because the determination of the size frequency | for each dust sample would be a burdensome task Some clarification of this problem however is essentials For this reason we suggest the following modification for consideration Tentative Standardfor Asbestos . __ Total count including fibers longer than 10 = 5 m.p. per bubic foot Exception The concentration of long fibers > 10...shall not exceed 1 mro per cubic foot i . In referance to silica dusts proper terminology should be considered at this time A distinction should be made between crystalline free silica and amorphous silica forms Diatomaceous earth and chemically prepared amorphous silica fumes are becoming ' industrially prominent These silicas may be hazardous and produce specific disease unlike classical silicosis We note that the same limit for tale and for soapstone 20 m.p. par cubic foot is used by most states Three however have a threshold of 50 million particles for soapstone Since soapstone is an impure form of tale and since commercial varieties of either tale r soapstone may contain an appreciable amount of quartz it would appear that the threshold limit for the two materials should not differ greatly greatly 1672 000201 B5 Allan L. Colezion = = Bow April , 1962 Further categories under Hineral Dusts three separate sapere, each of whicwhich heesentialyssentially mean the same thing silica 1. Dust Duisenes no Iree 2. Silics Len below % free 102 3. Total Dust below % free 9102 m.p. per cubic foot 2 8 8 a @ 8 8 .& 2. To wonder shother 1and carnot be combined er if all | categories could not be covered coveredcoveredcovered by one statqmebo beryllim hesitate our With respect to kecmledge to set linit forced to set a linit elons This view value woudilsdease sure to ve in view of present specific value for a threshold Unit If at this time the arises from experience experience obviously be called called In the interent of tale the valus experimental the threshold lizis studies have sat defined sammast Annotated properation project elsification elsification would Silica " Your on Asbestos for the of an Bibliograsiy Bibliograsiy BerylliumFree and Tale requires further To be gladto help in this my considerable that considerable can a but compilationcompilation of this part would moceszitate AJ . 1673 CRMC