Document nmzxbpy7QQg7a0mLq7EweX1L8

FEB-14-00 IB 00 FROM-GERTLER VINCENT & PLOTKIN ' ^1 ID PAGE A\ h'ft J 4A-IHA rrn The Efficiency of Protective Hoods Used bv* Sandblasters to Reduce Silica Dust Exposure BE HZAD SAMIMI. Ph.D . ARTHUR NEILSON. B Sc., HAN'S WEILL, M.Dand MORTON' ZtSKIND, M.D. Department ii Mnjianc. Pulmonary Discoid 5<rc!im:. ur.c C ntveruiy ycimut oi Medicine. Sew Orleans, iOwu.ur.a Several types of respiratory protective hoods used by sandblasters were investigated in two steel fabrication yards. MSA Gravimetric Dust Samplers " ere used to collect recpirable dust samples outside and inside hoods during sandblasting. Colorimerric and x-ray diffraction techniques were applied to the samples for free-silica determina tion. The majority of the sandblastem, who wore various types of air-supplied hoods, were exposed Co an average level of silica dost several times higher ibaa the TLV. Sandblasters wearing non-air-supplied hoods were at the greatest risk. Modem well maintajrurd anal property woiti air-enpptied hoodi offered fair protection during sandblasting periods, hut the concentration of suspended respirable dust in ambient air during Don-blasting intervals exceeded the TLV by several times. Introduction Sandblasting was introduced INTO INDUSTRY in 1S04 and is widely used in shipbuilding, oil ng and platform manufacture and maintenance and in other metal industries. It is a method by which a 1 stream of silica sand is projected by com.' '`pressed air to prepare a clean surface suit ; able for subsequent treatment. Large quan tities of fine!;/ fragmented respirable particles of silica are created, which when inhaled, are responsible for accelerated silicosis in sandblasters and their associated workers. Exposure to respirable silica is intensified when blasting takes place in an enclosed area and is particularly dangerous for un protected individuals. 5iliccsis in sandblasters runs a rapidly TMi UjCv a'is SUDCOrtcL 'a rTf* Gy CSPHS T \i HE inyuitiicj of Hsaiih and by jruu Oh 'C)4?-03. Nauemi insutute for Occupationjl Sl/ecv -inti Hetaim and NW'L; SCOR tfrsm ? 17 HL RjcruCUi for nrsn.v.s Giduigl Ne iJJrc^scd! CO SforCrt \t Z;SjCj r.<l, MO, I-^rv Tulone A^ctiud. 'N'g.w Orleans. Louisiitia 7ni 12. Tract r.ansy NVIO ; rt t~iy -jpef f,r fur cerrjf iC3t iCO OQjv- an>2 do not dOrtStH'jftf either enOOriie.T.-n; or J.jappro'-al of the Jevtces progressive course in which the appearance of roeatgcuosraphic and functional abnor malities encountered in chronic forms of the disease is accelerated and evidence of auto immune disturbance is common. Superim posed infection by mycobacteria and fungi is a frequent occurrence. The average dura tion of exposure in fatal sandblaster's silico sis is ten years. Small series of cases and individual patients have been reported with duration of exposure prior to symptoms less than three years. This rapidly develop ing disease is often called acute silicosis. In the United Kingdom, the high morbidity and early fatality associated with, sandblast ing led to its prohibition in 1949.1 .Am additional danger in sandblasting is the impact of the abrasive materia! as it rebounds off the blasting surface. Strong helmets, which protect head and shoulders and adequate respiratory protection, arc needed to reduce the hazards of silica expo sure.- In this study, which has been car ried cut in two fabrication yards, (called Yard 1 and Yard 2) the efficiency of sev eral hoods used by sandblasters was exam ined. FEB-14-00 16:00 FROM:GERTLER VINCENT & PLOTKIN ID= PAGE 3 'American Industrial Hygiene Associafon Journal *, .. c A Materials and Methods ,:7\. Non-air-supplied hood. This is the socwled regular hood, which does not have an ^'lioe. It lacks underarm or shoulder straps (Figure ]) and the cape of the hood is loose. This hood was used mainly in Yard Le- We were informed that sandblasters wearing these hoods were supplied with Wilson Dust Respirators when they began to work in Yard I but in many instances did not wear them under the hoods. 2. Pulmosan air-supplied hood: This hood is equipped with an air line attached 1 .1 compressed air tank. It is made of a strong canvas fabric and is equipped with t* underarm straps. Three to four hoods are usually fed from a single air manifold. The'air flow through the bouk is significantly ^^ected by the number of hoods connected toy-thc air manifold, the size of the orifice be air valve (controlled by sandblaster) jt<he length and diameter of the air line. A^'air pressure gauge is connected to the 'manifold to indicate the air pressure t**tninea to the boons, but the air pres- within each hood is unknown. The m Pressure in the manifold is about lour Figure Z. A sandblaster wearing Bullard 7"-D (DHj Ah-Supplied Hood is. currying two grantoetnc samplers, one tor sampling inside and the other for sampling outside the hood- pounds per square inch. The underarm straps should be fastened while blasting, but during the summer of 1972. it was observed that tlie straps were left unfastened. This type of hood was mainly used in Yard 2. A dust respirator is usually not worn be neath Uiiv liuou. 3. 3idla.nl 77-D (also 77-OH) air-supplied noodsi This is a protective hood which was recently issued to sandblasters in Yard 2 (Figure 2> The upper part of the hood consists of a relatively large hard hat made of plastic with a front view window. The cape consists of an outer layer coated with nylon and an inner layer of stretchable cloth with comfortable knitted neck piece fast ened by a tippet to prevent the dust from enterute the hood. Air is supplied to the hood in the same manner as in Pulmosan hoods. Positive air pres stir" is maintained in the hoods by air flowing at a pressure of 3-4 p5i from the air manifold. Air flow in side the hood vanes from 6-15 cubic feet FROM = GERTLER VINCENT 8. PLOTKIN ID Figure 3 Aq old fashioned ami worn-out cir-suppiied hood woit. by asandblast::. i: '* V ' s f,'- t? < T? VifJ;* S>\ 5$ 'll ] per minute (cfm) with a noise level, inside the hood, of 72*76 decibels,5 (according to the company's manual). In Yard 1, the sandblasters complained of the intensity of noise inside die needs and tried to limit the noise by reducing air flow to the lowest rates possible. 4. Other types of hoods: A small num ber of other types cf air-supplied hoods were occasionally used iu Yard 1 by sandblasters (Figure 3). The hoods were older models and seme were worn-out. Information con cerning the manufacturer, mode! and other specifications was not available. A naiyucai Mahods To s'udy the efficiency of protective hoods. MSA Gravimetric Respirable Sam plers were employed. VJiilipcre 0 H p.m pore size hydrophobic biters with a 37 mm diame e" 'were used f or volicetine the sum- pies cf res.piracie dust The determination of the pc reenra^e oc Si'lica in the se mplc:; wus madi either by ;:he cc.erimetrtc rr.ccri- ,uj 3 3 or :<'.-to: Chirac UOl1 r!,; ' Fiftv-or!r* C-^nflirr^ 'f respirabie dus; col'ectec within the or;lathing' zone inside various -v pes of hooc N.neteen rssp irabl^ PAGE 4 February. 19\ dust samples were also collected with sac piers attached at the sandblaster's chest ou side the hood. For proper comparison, the samples wci classified into three operational categoric; hew, moderate and busy representing up t 2v'i hours, 2 b;-5 hours and over 5 hours t blasting respectively. For sampling outside the hoods, the w. clones were hooked to the sandblaster' chest. These samp!es were collected con tinuous'y during the working day. Jurin blasting and non-blasting intervals and rep resented the potential time-averaged con centration of respirable dust in ambient ai at the blasting site. . For sampling inside the heeds, the cy clones were hooked cither to the collar q the workers (in case of Pulmosan hoods) o: were attached in vertical position to the inner layer of the hood (in case of Bulian 77-D hoods) dose to sandblasters' mouth.'; Various procedures were used for dnsi sampling: I. For the study of Buiiard 77-D (DH) air-supplied hoods, two samplers were at tached within the sandblaster's breathing zone. Sampler No. 1, which was attached inside the hood, operated ooiy during ae| tual sandblasting periods. The cyclonevb| the other sampler (No. 2) was attached to the sandblaster's clothing near his breathing zone and sampled only curing the non- biasting periods- Each sandblaster wxs in structed to turn pump No. i on immediately after putting on his hood; at the same time pump No. 2 was turned off. When blasting ceased. He was to turn pump No. 1 off and activate pump No 7 before removing the hood- The some instructions were observed dur ing the entire sampling petted. The work ers were supervised by the investigators throughout the sampling period to assure the proper operation of the samplers. This pro cedure made It possible to ccilcct separate dust samples during sandblasting and non blasting periods. . la another sampling group, the cyclones were removed from the sampling line and the filter holders 'Acre attached inside the hoods. These samplers operated continuously during the working day collecting "total dust" during both the sandblasting (inside the hood) and non-blasting (ambient air) periods. 2. In the investigation of Pulmosan and other types of air-supplied hoods, the sam plers operated continuously during the en tire working period while sandblasters were engaged with blasting or other work. The samples collected measured the actual ex posure of saadblasteis to respirable stiica dust throughout the day. - 7* V Results Cphcentraiion of Respirable Dust Outside the Hoods ".^Nineteen gravimetric respirable dust sam ples were collected outside the hoods. Since the samples were collected continuously dur ing the working period in blasting and non blasting intervals, the results represent a time-averaged concentration of respirable dust in the ambient air at the blasting site. They do not indicate the concentrations during the actual blasting period which must have been much higher. "\>The results showed an average conccuuution of 2.0 (1.4-2.4), 6.9 (5.3-8.3) anc 37.2 (16.8-53.4) milligrams of respirable dost per cubic meter cf air (mg/na3) for slow, moderate and busy operations respec tively. The average percentage of irce-silica 'vas 67.4 (26.0-90*0), 54.5 (20.7-90.5) dnd,83.6 (65.2-100.0) for the three states of operational activity. The average concen tration of respirable dust outside the hoods exceeded the Threshold Limit Value1- (TLV) .bjk 20.0 (5.5-21.4) times in slow. 34.5 m0-59.2) times in moderate and 372.8 XS39.6-437.4) times in busy operations. 'These figures indicate a heavy concentration respirable dust created at the blasting site Concentration of Dust Inside the ofOn-Air-Supplied Hoods The tirne-veraped concentration of res pirable dusi w ithin non-air-supplied hoods (a;so c..:.cd regular hoods i was calculated ter 23 samples collected continuously during the working hours as described earlier. An average respirable dust concentration of 1.3 10-5-2 1). 2.S (2.3-3.5) and 11.0 (7.8 14 1) mg/m-1 was obtained for slow, moderate ana busy operations respectively. Toe sandblasters were supposed to wear an approved dust respirator when using non-airsupplied hoods, but during the study u was observed that 359c of them either did not observe this precaution, or did not have a dust respirator. The percentage of silica in these samples was 30.8 (6.0-68.0), 42.2 (13.4-64.0) and 70.3 (18.0-100.0) for slow, moderate and busy operations respectively. The average concentration of respirable dust samples exceeded the TLV bv 4.3 (0.4I0.-1) times in slow, 1-4.1 (3.6-23.3) rimes in moderate and 110.0 (15.5-119.7) times In busy operations. In only two of 23 sam ples was the respirable dust concentration lower than the TLV. These samples were obtained during a slow operation in which the blasting time was less than two and onehalf hours of the total working period of eight hours. Inva-ugation of Pulmosan AirSupplied Hoods During the summer of 1972, gravimetric respirable samples collected inside two Pul mosan air-supplied hoods showed concen trations of 0.3. 2.6 (2.0-3.3) and 4.4 mg/m3 for siow, moderate and busy operations re spectively. It should be noted that the sand blasters had not fastened the Underarm straps of their hoods, because of the hot weather and that the capes of the hoods were loose. Sampling was continuous during the working hours in blasting and non-biasting internals. The results therefore express the actual exposure of sandblasters to res pirable silica dust during the working day. Toe percentage of silica in these samples were 54.8, 77.2 (75.079.4) and 42.3 for FEB-14-00 16 03 FROM GERTLER VINCENT a PLOTKIN 144 ID' slew, moderate ar.ci busy operations. The average concentration o: respirable dust ex ceeded the TLV by 1.5 'jx.es in siow, 26.0 (16.4-25.2) times is moderate and 22.9 times la busy operations. ^Vh'jri -iuhr cimoit:; wacc'iiec'ed, d urine spring c: TT, inside Fu'.mesan air-supplied hoods, the sandblasters were instructed by the employe.- to tauten die underarm straps ot their hoods. These sampies were collect* cd ccrtt.nuousiy -4 jrtig the working hours as described above There was an average resptiaDic uust concentration ot 0.3 (0-2 0.5) m?/nr. Ail of these samples were in the "slow operation" category (less than 2!/c hours blasting time during the working day). The average percentage of free silica in the samples was ( 15 6-S7.5). Fifty percent of samples exceeded the calculated TLV i L 0); the range extended from 1.2 to 3.3 times the TLV'. The ratio of concentra tion to TLV in samples beiow the TLV var ied from 0.5 to 0.8. Although these results did not show dial the Pufmcsar. heeds were totally mffective m preventing the respirable dust from enter ing the hoods, they dearly indicated that even in. a slow operation (less than 2Vz hours blasting) a significant number of sandblast ers were exposed to amounts cf respirabic silica dust up to 3 3 times the TLV' during the working nay Both me number of work ers excessively exposed arte tho degree or exposure increased as the activity of the sandblasting operation was extended. The excessive ex secure of sar.dbiusiers to silica dust may nave rcett caused by any one or combination of the following factors: (a) Since T.e persona: gravimetric sam ples were collected continuously during the working hours : from inside the hoods dur ing blasting and Iron ambient air during non-biasting per.ods i a considerable por tion or the respireb-e oust rnisht have been pickey -.in ciTng ren-bl asking periods from the ambient air due to the presence rf sus pended dus: transmitted from nearby sand blasting sues PAGE G February, !f)7^ (b) Persistence of suspended dust in tht air at the blasting site after retrieval 0j hoods at the cessation of blasting. %) Defects (cracks, holes) and misfit of hoods. y ' d 1 Defects in air-supplying anti uu-ouri- tying equipment such as faulty filters. Investigation or Miscellaneous Hoods Calculations based upon samples collect ed continuously during working days from workers wearing air-supplied hoods other than PuimOsan and Bullard 77-D showed an average respirable dust concentration of 1.2 (1.5-1.0) and 7.4 (2.2-14.3) mg/m3 for stow and busy operations respectively; no samples ware collected in moderate op erations. Tlie average percentage of silica was 19.6 (12.5-26.6) and 63.0 (39.0-100.0) for slow and busy operations respectively. The concentration of respirable dust in these samples exceeded the calculated TLV in alfcases. The average dust concentration ex- cecded the average TLV (losing the average free silica pcrceut) by 2.4 (1.4-4.2) times in slew and 74.0 (22.3-60,6) times in busy operations. AH of the hoods, as mentioned^ earlier, were old fashioned and were usually^ wom-out and/or defective. | Examination of Bullard 77-D AirSupplied Hoods | - The samplers inside the Bullard 77-0: hoods operated only during sandblasting periods. Calculations based upon four sam ples showed an average dust concentration of 0.+ (0.2-0.6) mg/m-! The percentage of silica was quite low in these samples ranging from 1.0% to 15 0% with an average cf 5.-% and the concentration of respirable dust fell below the calculated XLVs. The ratio of concentration to TLV ranged from 0.05 to 0.70 with an average of 0.50. Al though the amounts of respirable dust col lected on the filters inside the Bullard 77-D hoods were reln/vely small (0.05 to 0-2 mg), :hc lew percentage of silica in these samples raises the question of the identity of the FEB-14-00 1E : 04 FROM = GERTLER VINCENT & PLOTKIN ID. PAGE 7 A 'nrriCitn industrial (iygttnc /tSscOeadon J&urnui non-silica portion of the samples. No addi tional analyses were performed on the sam ples to identttty the nen-sihea particulate matter, but we mav assume that the par ticulate matter was brought onto the filters from any one or combination of the follow ing sources. i) Penetration of rust, oil. grit, mist, fumes, and other particulate matter through the air compressing system because oE a defective filter or malfunction of air puri fying system. (b) Penetration of more submicronic aon-silica particles through the hood than silica particles. The latter are relatively larger in size and form a smaller fraction of particles within the submicronic size range; the percentage of silica in particles 0.4-0.6 fixa. size (stage #7 of Andersen NonViable Sampler) was 16.0% at the blasting site.11 (c) Droplets and nuclei produced by coughing and/or sneezing of the workers inside the hood. Exposure of Sandblasters to Silica Dus: During <Von-Blasting Period Personal gravimetric respirable sampies were collected in the breathing zone of the same sandblasters on the same days but .nlv during non-blasting periods after Bul lard 77-D hoods had been removed. An average respirable dust concentration of 0.8 (0.4-1.3) mg/m3 was computed fo: the ooQ-blasting periods The percentage of silica in the samples varied from 11.9 to 48.9% with an average of 32.0%. The concentration of respirable dust exceeded the TLV in three out of four cases (75% ) With an average ratio o 2.7 (0.8-4.3) times die TLV. These sandblasters were usually Engaged in related work such as painting in tbe vicinity of other blasting sites for most 0*.the non-blasting periods and wore no respiratory protective devices. Overall Exposure of Sandblasters Wearing Bullard 77-D Hoods to Silica Dust T The average respirable dust concentration 145 of 0.8 (0.3-1.3) mg,'m5 was obtained as the cwerail rtne-averaged exposure of sand blasters wearing Bullard 77-D hoods, to res pirable .'.lieu dust. The percentage of free silica m the .samples varied from 8 5% to 44,3% with an average of 25.5%-. The con centration of respirable dust exceeded the TLV with an average ratio of 2.2 (0.4-6.1) iimes the TLV. Of four workers studied, the concentration of respirable dust did not exceed the TLV m only one case in which the ratio of concentration to TLV was 0.4. Two total dust samples collected contin uously during working hours (from inside the hoods during blasting and from ambient air during non-blasting periods) showed to- tai dust concentrations of 3.5 and 3.3 (av erage = 3.4) tug/m.3 The percentage of free silica m these two samples was 80.9% -.li and 51.8% (average = 66.3%). The av erage concentration of total dust exceeded the corresponding TLV with a ratio of 7.9 times the TLV. The results of the various hood dust sam pling studies are summarized in Table I and Figures 4 and 5. '1 U Si Discussion and Conclusions The lochs of this study indicate that the protection of sandblasters exposed to high concentrations of respirable silica dust has not yet been satisfactorily achieved. Sand blasters wearing non-air-supplied bonds were a: the highest risk of exposure to silica dust. Thirty-five percent of these workers did not wear dust respirators under their hoods. The other 65% wore respirators but there was no regular maintenance and/or inspec tion of valves, filters and fitting of the respirators. Tnc Bullard 77-D air-supplied houd and the well maintained and properly worn Pulmosan air-supplied hood offered fair respira tor, protection curing the blasting period, but the average concentration of suspended dust in the ambient air inhaled by the same sandblasters during the unhooded non-oiasting period exceeded the TLV by several tunes . Tl FEB-14-00 160B FROM:GERTLER VINCENT & PLOTKIN ID PACE 9 12 3 ui/rsee xxe 12 3 12 1 I1 *5 <<* womio0'ui* hwcj*r \a*c4u4sM*en Figure a Comparison of mean ooncsntratioe of respirable dust in rag/m^ of air, fraction of free-silica and TLV in personal gravimetric samples collected outside hoods and inside various types of hoods. q-f ept^qtipn iup >c 2'/^ hrS &i35rir9 Un$*rvwr ftrgp* * lind^a^m' 4rvp roftA4 3-rtl Oflv ' &k- , j&t s fi ' v*>V t 5 57 8 9 Figure S. Comparison of meainc...o..n...c..e...n...t.r..a..t.i..o..n.._o_:....d..u...s..t....in......m... 9g../..m....'....<..?.f...s..i.r..,...f.r..a...c. tioft of free*siiica and TLV, m personal gravimetric samples collected 3t the breathing zone of sandblasters wearing various types cf protective boods. FEB-14-00 16 06 FROM = GERTLER VINCENT & PLOTKIN 143 ID: f It must be concluded that the majority of % sandblasters, wearing various types of air- ! supphed hoods, were exposed to ao average level of silica dust several times greater than the TLV. This was the result of wearing r: <V worn-out and defective hoods, faulty or care Eh - less operations and the presence of sus pended silica dust transmitted from adjacent blasting sites during the non-blasting periods when sandblasters were unhooded. Our observations demonstrate that the use of a modern air-suppikd hood alone cannot adequately protect the sandblaster from the hazard of silica dust unless he learns the proper use and maintenance of his hood, avoids careless or faulty opera tions and wears a dust respirator at all times while he is not blasting. Regular supervi sion of the workers, maintenance and repair of protective devices and effective dust sup pression measures are also required. Efforts should be made to substitute silica sand with other abrasive materials, low in free silica. Such silica substitutes as Saf-T Blast and Stan-BIast are currently used in many shipyards. Further research for better and safer methods of blasting ts accessary. References 1. Hunter, D.; Ihe Diseases of Occupation, 3rd Ed., p. '40, English Universities Press Ltd. PAGE 10 February. IP: London (1962). - 2. Patty. F. A.: industrial Hygiene and 7osier, ogy. Vol. 1, p. 349, Inter Science Publishei lnc. New York. (1948). 3. Bullard, E. D. Company; Respiratory Equij meat Catalog. 2680 Bridgeway, Sausaiito, Cal forma (April 1973). 4. Mine Safety Appliances Co.: Instructions ft MJA. Gravimetric Dust Sampling Kit. Vf.S.r Co., Pittsburgh. Pennsylvania (1970), 5. Lippman M: Respirable Dust Sampling. A me, lnd. Hyg. Assoc. J. 31:138 (MarcL-Apri1 197(j 6. Aerosol Technology Committee of America Industrial Hygiene Association: Guide fo Respirable Mass Sampling. Amer. Ind. Hy% Assoc. J. 31:133 (March-ApriL 1970). 7. Weidner. R. B.; Personal Respirable Mas Sampling Procedure. Occupational Health Pro gram. Cincinnati. Ohio (May 1968). 8. Carlson, A. B,, and C. V. Banks: Spectropbo temetric Determination Of Silicon. Anal Chem. 24:472 (1952). 9. TaiviUe. N. A., and F. Hyslop: Colorimetric Determination of Siliceous Atmospheric Contaminants. Amer. ind. Hyp. Assoc. J. 19:54 (Feb. 1958). 10. Bumstead, H. E.; The Determination of Alpha-Quartz in the Respirable Portion of Air-Borne Particulars by X-ray Diffraction, Amer. Ind. Hyg. Assoc. /. J4.T50 (1973). >. 11. SamimL B.: Silica Dust in Sandblasting Oper ation. A Ph.D- Dissertation, Department of Civil Engineering. Graduate School, Tuiane University of Louisiana, (Aug. 1973). 12. American Conference of Governmental Indus trial Hygienists: Threshold Limit Values for Chemical Substancee and Physical Agents Ox the Workroom Envirorunent vitft Intended'' Changes for 1973, Amer. Coni, of Govern.1 Ind. Hyg., Cincinnad, Ohio (1973), -C Supplemental Documentation of Threshold Limit Values The American Conference of Governmental Industrial Hygienists has announced that Supplemental Documentation to the Third Edition of the Documentation of Threshold Limit Values (1971) is now available. This supplement covers values adopted from the years 1971 through 1973. Copies, at a cost of 52.00 each, are available from the American Confer ence of Governmental Industrial Hygienists, P.O. Box 1937, Cincinnati, Ohio 45201.