Document wDrkvm3kJ5JzRYqGdVG2Gg4y4

urnoH :carbide corporation 1 t HARK AifH'Ji. N: W rvRS. *fV YORK 10017 '}. nr. J. A. Fiddle Mining and Metals Division <*'- King City, California o8. July .7, 1966 ' ongina,ma &.i Medical cv f ` ' Alivtriog Mr. L. D, >-nlet/C. E. Drown *&** Dr a. J. J. Veloh/II, S. Lane " 'Mr. L. Z. O'nourko dt ^ * Dear Mr. Riddle:. . . ' . The following are the results- of duct determinations at King City mine and mill June 22, 22, 19o6. I'm sure they have been reported to you before now by Mr. -Kanenc, however, they . 'are repeated here as a matter of record for our flie3. Location Mine -7.lte - 6/25/66 - Betide coerntor of front loader .(no cab) loading ore truck. Beside operator of r.ev: Michigan front leader f air-ccnc^I tioned cao) Area around truck during loauing. General area around gristly duri.nr truck loading MPPCV 2n.O ?. C Cj < > 15. ** 14.2 :U.ii - Q/.:,Vjumj I 1 :T ir\ -v * ' '* Betide bagger operator (Morning) Game location (Afternoon) Beside operator at discharge of bag conveyor 8.9 11.2 7.8 1*.3 14.0 Remarks Contractor operator. Gone dust came into cab through gear shift opening. Visible dust. Much loose, finely . divided material cn ground. Bagging open fiber Vicibie dust. Game Visible dust part of which was caused by hand shaping full.: bags. <; *> Kr. J. A. piddle .; -2- . ^ *'. - July 7, 1S66 Location. ' . - : Hill (contd) i './ .. t ' . . .' MPPCF1'2 Remarks .Press area - ' ~: ' Rook fiber circuit-general . . 9.7 .. ' 7.4 Beside front loader operator . ore pile . . - . . 20.2 Ground floor around offices and switch board at north cide . 4.3 of "building ` ... %L;f MPPCF - Millions of particles per cubic foot of air. 2. Samples were collected by impingement in distilled water. .... Dust counts were performed by the light-field microscope technique at a magnification of 100 diameters. - You will note that there wore only a few samples that . showed dust concentrations below the recommended limit of 5.0 MPPCF. At the mine sito the concentrations were influenced to a considerable extent by the presence of a large amount of loose, finely divided material in the haulage way for the front loaders. Loading operations kept the material etirreJ up enough that even in the general area varying from 20-50 feet from the griszly the counts were several times the limit. In view of the findings it is reccrrsnencled that the operator of the front loader that has no air-conditioned cab be supplied a res pirator. For operation with an air-conditioned cab it appears that adequate dust control can be achieved if the opening around the gear levers can be sealed. At the mill the principle source of dust still seems to be the bagging operation. Occasional bag ruptures and the loos of material from the bag valve when it is removed from the fil ling spout and when the bag drops to the conveyor ail combine to produce nore dust than the exhaust system can control. While wo supply the bagger operator with a respirator, in vlev; of the concentrations of dust that he may encounter, I believe it wise that we consider improvement in the dust control system. An additional reason for better dust control at .the bagger is pre vention of the spread of dust to other areas of the mill.* The high cotints in the area of the discharge from the bag conveyor ware* related in part to the practice of hand shaping the filled bags.- Each tine a bag was hit there was a visible loss of dust from the valve. With this operating practice, it  /' . t \.r I* \* .. \ \ Mr. J. A. Riddle-' -- "3-y VJuly 7, 1966 ,, . -- . -4 ,,' -.was difficult to determine-the effect of dust lose from the bagger at the conveyor discharge poinb.' I suggest that the ,practice be eliminated, if poscible., ^ * 1/ .?> The high dust concentration around the operator of the front loader while dressing the ore pile indicates that he .should wear a respirator while performing this and probably other operations involved in handling ore. I dont believe wo can rely on the moisture content of the, ore for adequate dust control. . ' ' V '. In inspecting the mill IInoted'the new sample bucking room - and the two hoods provided for duct control. I suggested that v olclrts of some type be provided for the sides and the backs l of, the hoods in- order to provide more air velocity at the ?,/ face. Mr. Cohan felt that the skirt3 could be made of canvas and not Interfere with operations.,;, . .. . - ? . ; . l ... As Mr. Kamcne gets further Inf{o the prac tict* of routine dv'.3t evaluation I believe that additional equipment will be "v needed-as follows: . -* ' * - . , - \ . ^' . ' ' - . ' .. - -.- -1. Carrying case for irapinger* campling tubes, sampling 't;. . apparatus and other accessories. Mr. Kamens felt ''V;- that ouch a case could be'made in the shop at the :iV ; ' pj.anv, . ' `, ' ' ' .r ~ 2. Additional impingers. The present number Is insuf- ; . ficlent to allow a complete survey of the mill without ' - interruption. I-have enclosed a catalog that may be v ' helpful in selecting a supplier. - ' 3. Additional counting cells. As With the impingers the number is insufficient for the most efficient U30 of time in dust counting. . : .'- 'h ;4. Stage micrometer for the microscope. Tills is desirable . .-7. as a means for calibrating the field of view. ,. ` 5. A dust count record book which I discussed with Mr. Kamens. During this visit Mr. Crow informed me- of the proposed study by the California Bureau of .`Occupational Health arid I had a chance to review the letter from the Chief of the Bureau, Thomas H. Kilby, M.D. As 1 understand it you will be contacted personally by a member of the Bureau in early July to make ar rangements for the study at a later date in the summer. If X^oscible I suggest wo made the date as late in the season as Mr.' J. A'.. Riddle -4- July 7, '19^6.; , possible. I. hope to bbtln' King City" lor at ieast part of y the study and the jn ter date- would be. better for me as .well t a3 for the plant. I aleojeuggcet the following action prior".." to the atudy. ' ' . v't-:y'"L ' ' \> Mill: r 1; C.iean-up the loos asbestos around the'outside and ' . . inside the plant. 'This, of course, lo action that ' ./ we would*wish to follow routinely but I believe it . especially inoortant before the study. - : : -:*<*< v-- :v 2, Ma'.ce- certain that "personnel are-well indoctrinated , in the use of respirators and also in the care of 'i . - respirators. For example, a respirator should fit * . well and. should do v:orn when conditions warrant. VJhen 5- not-'in use It chcrld be stored away-from dust. 3. Notify the plant physician of the impending visit. . I have discussed thin with Dr. K. S. Lane and he * agrees that this ;V3 acoirable because the State people may be- planning to contact xntr^phyrician. ' . '* * `/ * k . . '* 4'. Review the dust control cystcvn for the baggers so that even If we h'vre.'vb modified it by the date of , ' the visit wo can point to our plans for improvement. \ - .* *. - . ' 5.. Eliminate any visible dust leal-co in duct-work, et cetera. IhiE, too, is screening wo would normally do routinely but it is-important especially before the visit. . ' lilno: 1 Remove finely di dr.d. loose material from haulage way as'much'as r Tible.' '* . It is important that bo State investigators'Jrnovi that . ' we are aware of. the dust . iucing potential of this material -- and that : atsemet to el _r.atc it*. . .. As ycv. Into;;, vie have 'lovolcpcd a good deal of information . about the ehc.rasteri sties /-_ the* material we have been handling, '..'e have etui led the else rr.r.n'j cf the air-borne dust and know U* V osV-M* M eensidernbiy .'ram the usual asbestos, being much shorter*. Cur studios cf it- settling rates in water made i c necessary that v:e incru; the nettling time in counting colls lr. order to obtain v. xlucible results. Thus though - c we follow the United State: ublic Health Service dust collectioh . Hr. J. A. `Riddle ./ ; . ; -5-';. ; .... . July 7, 1966 and count procedures (a copy of v:hich is attached) we have found it necessary to modify the settling time. Our results . therefore tend to be on the. conservative.(safer) aide. . , .i We have also fcur.d from electron microscope and optical microscope studies of the dust that the fibrous material is difficult to identify at usual magnification (100-400X). Therefore, in our count procedures as a matter of increased safety we consider all visible particles to be fibrouo. We made it a practice, of course, to keep up with the - literature dealing'with the toxicity of asbestos. We are aware of the. developing beliefs that there is a relationship between exposure to dust and carcinoma. We make a special effort to stay abreact of experience v.dth short fiber asbestos. I feel, therefore, that we can demonstrate to the Scate investigators that we have respect for asbestos dust and are constantly reviewing methods for handling it effectively. - - Yours very truly, * ?WM/en ones. Paul W. McDaniel Industrial Hygiene Engineer .' - w i *.* t* :> t :