Document wg8QJy563Mkb5R8g94Gy6byB6

ESSO LABORATORIES STANDARD OIL DEVELOPMENT COMPANY yytf /s-/r~S/ MEDICAL RESEARCH DIVISION ROBERT E. ECKARDT. PH. D.. M.D. DIRECTOR N. V. HENDRICKS, B. E.. CH. E. DIRECTOR, INDUSTRIAL HYGIENE SECTION P. O. BOX 51. LINDEN. N. J. December 14, 1951 Mr. 7. 8. Venable Medical Department Ssso Standard Oil Company Louisiana Division Baton Bouge, La. Dear Tre&t At the time of our informal meeting in Pittsburgh., you requested that ve supply you with information on tbe collection and counting of asbestos dust. Prank Church, has prepared some material on this subject and ve have obtained a copy of Public Health Service Bulletin Ho. 241, "A Study of Asbestosie in the Asbestos textile Industry*, ffhis material is attached for your information. Very truly yours. H. V. EEHDRICKS HVH/hp Bncll (l) WC Memorandum U/,30/51 (2) PHS Bulletin Ho. 241 cct Dr. C. M. Berry Dr. E. Hansen Dr. L. J. Hade EM003153 A6B1SI0S PPSt CmiSTHTl Asbestos is the c1o.be name for several different fibrous minerals, but commercial asbestos is mainly chrysotile, Chrysotile Is the fibrous form of serpentine and is a hydrous magnesium silicate, 3J,'-sO2S10s.2H20, or Kg^Si^E^O^, containing 44.1 per cent of combined silica, 4-3,0 per cent of magnesia, and 12,9 per cent of vater. Other types of asbestos often contain silicates of iron, calcium, and aluminum, as veil as magnesium, Chrycotlle represents approximately 95# of the asbestos used in this country. Other less common silicates which cen appear in fibrous form include! Anthcphyllite (Amoelte) - (Kg,Fe}ySigO^COK^ Tremalite - Cap!!ggS1^0?P (0H)> Actinollte - Trenolite in which Fe has replaced Kg in amounts greater than 2# Hornblende - Ca2Na(Kg,re11)/f (Al.re^.TU-jSi 5022(0,02)2 Enetatite - KgSiO-j Aeglrite - Kare1USi205 Jadelte - Ka A1 SigOg Vollastonite - CaSiOj Epldote - Ca2(Al,Fe)3 (SiO^ (OH) Silllnanite - Al2SiOj Itonortierite - AlgBSi^O^CQH) TOXICITY! The histological findings, particularly of early asbestoeis, doe* not indicate a chemical injury, Gardner, as a result of studies at Saranac Lab oratory, made the following statement! EM003154 - 2- *tfe have cone to the conclusion that inhaled asbestos fibers are Irritating, not because they are silicates but because they are stiff fibers which mechanically irritate the lungs, Dhlike the free silicas, these minerals vill not stimulate fibroblasts in any part of the body; only those In the lungs are affected. It was Inferred that these organs were affected because the more* sent s of respiration are so such more rapid and continuous than those of other viscera. Then it vas discovered that if asbestos was ground very finely so that few of the fibers were longer than 2 microns in length, the irritating property of the asbestos vas practically destroyed. Inhalation experiments with such fine chrysotile asbestos vere cerrled out over a period of several years. Ko fibrosis has developed in spite of the fact that an average atmospheric concentration of 125 million particles per cubic feet of air has been maintained. In contrast in a previously reported experiment, one-third this concentration of long-fiber asbestos duet produced veil marked fibrosis after about tvo years. * Only those silicates which are fibrous in structure have been defi nitely identified as pulmonary irritants. Sexpentlne vhich has the same chemical composition as chrysotile asbestos does not cause a pulmonary fibrosis end is considered as being physiologically Inert. Talc, a hydrous magnesium silicate, and dlatomaeeous earth, particularly calcined earth, have some clinical indices tions of having pathological significance other than benign, non-specific pneu moconiosis. The flndihg of asbestos bodies in the sputum is of considerable diagnostic Isportanoe. The identification of asbestos bodies in sputum can be done by the procedure given in "Industrial Dust", first edition, Drinker and Batch, pp. 165-166. English experience had indicated a chemical pathogenesis for asbes- 1*0 03155 3 tools, This is at direct variance with experience in this country and could pos sibly he partially accounted Tor by a difference in chenical or physical compost-- tion of the asbestos. This variance, however, indicates a need for further study of the pathogenesis* KAXIKOK ALLOWABLE COICCBITJttJICiHt The K&C of asbestos duet is 5 million particles per cubic foot of air, of a size from 2 microns long up* Because of the English experience, it is also advisable to hold the total count to 10 million particles per cubic foot of air, of a sice from 5 microns down. coLirerio" op act SAmat A Greeriburg-Smith or midget impinger flack is used with 25 isopro pyl alcohol as a collecting medium. The standard sampling rate of 1 c.f.m. or 0*1 c.f.au, respectively, is used. cocnniKo s/aspiat The counting technique is the light field method, as specified In either "The Determination and Control of Industrial Dust", Public Health Bulletin #217, PP* 40-43, or toisons, Hazards, Solvents", second edition, K. B. Jacobs, - ,pp. 144 147 with the following exception!- 'Two simultaneous counts are made -- total particles $ microns and less end asbestos fibers 2 microns end larger. Great care must.be exercised to obtain a good focus and a good light contrast during counting. Some asbestos fibers are extremely thin and consequently, hard to see and easily "burned out". aes n/30/51 EM003156 P. V, Church