heta 95-0318-2631 alcatel telecommunications cable roanoke

HETA 95-0318-2631Alcatel Telecommunications Cable

Roanoke, Virginia

Stan Salisbury, CIH

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports



This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.


applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

http://www.cdc.gov/niosh/hhe/reports



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PREFACEThe Hazard Evaluations and Technical Assistance Branch of NIOSH conducts field investigations of possiblehealth hazards in the workplace. These investigations are conducted under the authority of Section 20(a)(6)of the Occupational Safety and Health Act of 1970, 29 U.S.C. 669(a)(6) which authorizes the Secretary ofHealth and Human Services, following a written request from any employer or authorized representative ofemployees, to determine whether any substance normally found in the place of employment has potentiallytoxic effects in such concentrations as used or found.

The Hazard Evaluations and Technical Assistance Branch also provides, upon request, technical andconsultative assistance to Federal, State, and local agencies; labor; industry; and other groups or individualsto control occupational health hazards and to prevent related trauma and disease. Mention of company namesor products does not constitute endorsement by the National Institute for Occupational Safety and Health.

ACKNOWLEDGMENTS AND AVAILABILITY OF REPORTThis report was prepared by Stan Salisbury, CIH, from the Atlanta Field Office, of the Hazard Evaluationsand Technical Assistance Branch, Division of Surveillance, Hazard Evaluations and Field Studies(DSHEFS). Desktop publishing by Pat Lovell.

Copies of this report have been sent to employee and management representatives at Alcatle and the OSHARegional Office. This report is not copyrighted and may be freely reproduced. Single copies will beavailable for a period of three years from the date of this report. To expedite your request, include a self-addressed mailing label along with your written request to:

NIOSH Publications Office4676 Columbia ParkwayCincinnati, Ohio 45226

800-356-4674

After this time, copies may be purchased from the National Technical Information Service (NTIS) at5825 Port Royal Road, Springfield, Virginia 22161. Information regarding the NTIS stock number may beobtained from the NIOSH Publications Office at the Cincinnati address.

For the purpose of informing affected employees, copies of this report shall beposted by the employer in a prominent place accessible to the employees for aperiod of 30 calendar days.

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Health Hazard Evaluation Report 95-0318-2631Alcatel Telecommunications Cable

Roanoke, VirginiaMarch 1997

Stan Salisbury, CIH

SUMMARYIn July 1995, the National Institute for Occupational Safety and Health (NIOSH) received a request to evaluatepotential exposures to silica dust, hydrofluoric and nitric acids, isopropanol, and chlorine at the AlcatelTelecommunications Cable plant in Roanoke, Virginia. This facility manufactures fiber-optic telephone cable.The chief areas of concern included the “Chemical Vapor Deposition” (CVD) area where thin layers of high qualityglass are deposited inside quartz glass tubes mounted in glass-working lathes. Approximately 18 workers areassigned to CVD. Another area identified in the request was the “Chem-Clean Room” where spent or damagedquartz glass tubes are acid-cleaned and cut to shorter lengths for reuse in other parts of the fiber optic cablemanufacturing process. Work in the Chem-Clean Room only required one person working about four hours pershift.

On August 27-28, 1995, a NIOSH industrial hygiene investigator visited the facility to conduct a walk-through tourof the manufacturing process, to observe work practices and potential exposure risks, and to informally interviewemployees. On the second day of the visit, personal breathing zone samples were collected to evaluate employeeexposures to respirable airborne particulates and crystalline silica (quartz and cristobalite). Workers sampledincluded two CVD Operators and the Utility Glass Operator working in the Chem-Clean Room. General areasamples for airborne crystalline silica were also obtained near CVD lathe equipment, and above work tables in the“Measurements Area.” To characterize the composition of the airborne dusts sampled, bulk samples of settled dustwere taken from the top of a lathe compartment in the CVD area, and from the glass cutting saw waste receptaclein the Chem-Clean Room. High volume “bulk air” samples were also collected to estimate the percent ofcrystalline (free) silica contained in airborne dust samples.

Results from sampling found only trace amounts of airborne fused silica. The airborne silica collected in thesamples was identified as mostly amorphous (lacking the crystalline structure of quartz or cristobalite). However,because fused quartz glass is processed at this facility, the exposure limit for respirable amorphous fused silica(0.1 milligrams per cubic meter [mg/m3]), as recommended by the American Conference of GovernmentalHygienists (ACGIH), was selected to evaluate exposures during this survey. The highest personal exposure foundduring this survey, assuming all collected respirable particulate was amorphous fused silica, was 0.217 mg/m3.This six-hour sample was collected from the Utility Glass Operator cutting glass tubes in the Chem-Clean Room.

Optical examination of material taken from the saw waste receptacle found only amorphous silica (glass) andaluminum oxide. No crystalline silica (quartz or cristobalite) was found in this material when analyzed by x-raydiffraction (XRD). A sample of glass tubing processed in the CVD Department was also ground and

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microscopically analyzed by XRD. No crystalline forms of silica in the ground glass sample could be detected byXRD. Microscopic examination of the CVD tubing stock found the glass showing less than 5% crystallinity.Crystalline silica (quartz or cristobalite) was also not detectable by XRD analysis in the sample of settled dust takenfrom the top of a CVD compartment.

General impression from informal employee interviews found very few workers had specific health complaints,but many voiced lingering concern about the potential for exposure to silica.

Sampling results demonstrate that airborne silica exposures, either as fused, amorphous, or crystalline, arebelow all recommended exposure limits for workers assigned to the CVD, Clean Room, andMeasurements Departments. Based on this survey and previous environmental surveys of this process,Alcatel workers are not at risk from silica exposures in the routine manufacturer of optical fiber cable.However, any non-routine work practice involving cleanup or maintenance procedures that may releasefused silica (fused quartz) particles into a worker’s breathing zone should be evaluated. Cleanup ormaintenance workers potentially exposed to respirable particulate likely containing fused silica above0.1 mg/m3 should be adequately protected with effective engineering controls or required to wearappropriate respiratory protection. Local exhaust ventilation is recommended to better protect the UtilityGlass Operator when sawing quartz glass tubing. Other recommendations are offered concerning transportof CVD glass bubblers containing phosphorous oxychloride, and prevention of allergic skin reactions fromcontact with fiber coating materials.

Keywords: SIC 3357 (fiber optic cable) amorphous fused silica (CAS 60676-86-0), fused quartz tubing, silicontetrachloride, phosphorous oxychloride, germanium tetrachloride

TABLE OF CONTENTS

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Acknowledgments and Availability of Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Facility Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Process Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Chem-Clean Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Sample analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Evaluation Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Amorphous Fused Silica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6CVD and Sleeving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Chem-Clean Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Measurements Department . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Bulk Sample Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Attachment - Air Monitoring Results Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Health Hazard Evaluation Report No. 95-318

INTRODUCTIONOn July 7, 1995, NIOSH received a confidentialemployee request for a health hazard evaluation atthe Alcatel Telecommunications Cable plant inRoanoke, Virginia. A NIOSH industrial hygieneinvestigator conducted a site visit to evaluateemployee concerns over potential exposures torespirable crystalline silica during the operation ofthe “Chemical Vapor Deposition” (CVD) process,and when cleaning and cutting quartz glass tubes inthe “Chem-Clean Room.” On August 27-28, 1995,the NIOSH investigator visited the facility to:conduct a walk-through tour of the manufacturingprocess, observe work practices and potentialexposure risks, and informally interview employeesworking in the areas of concern. Personal breathingzone samples for two CVD Operators and the UtilityGlass Operator were collected to evaluate employeeexposures to respirable airborne particulates andcrystalline silica (quartz and cristobalite). Generalarea air samples were also obtained from glassworking lathes in the CVD and Clean Room(sleeving) areas. High volume “bulk air” sampleswere collected in the Chem-Clean Room andMeasurements Department to attempt identificationand content of crystalline silica (quartz orcristobalite) in airborne dusts.

BACKGROUND

Facility DescriptionThe Alcatel Telecommunications Cable facility inRoanoke, Virginia, was built in the 1960s and isowned by the ITT Corporation. The facility has186 employees, with 35-40 salaried employees, andabout 140 hourly workers. The plant operates withoverlapping 10 hour shifts Monday throughThursday, and overlapping 12 hour shifts on Fridaythrough Sunday. Approximately 35 workers per shiftoperate the facility. This company manufacturers125 micron optical fiber used in the fabrication offiber-optic telephone cable. The process used byAlcatel has been in operation at this facility since the

1970s.

Process DescriptionThe modified chemical-vapor deposition (MCVD)process used to manufacturer optical fiber at theAlcatel Telecommunications Cable plant wasinvented at the AT&T Bell Laboratories. TheMCVD process was the first of four processes nowbeing used by the optical fiber industry. The MCVDprocess involves:

(1) vaporizing and depositing high optical qualityglass on the inner surface of a quartz glass tube,

(2) collapsing the tube to form a preform rodcomprised of the core/clad structure needed forlight guidance, and

(3) drawing the preform into a controlled diameterlight-guide fiber.

Commercial application of the MCVD process beganin the early 1970s. Optical fibers produced aremainly silica (SIO2) with additions of 1%-25%germania (GEO2). The high purity comes from thevapor deposition of the starting materials, silicontetrachloride and germanium tetrachloride.1

Alcatel’s CVD Department has 22 CVD systems.Each system consists of a glass-working lathe, alarge gas train compartment, and a computer controlconsole. The gas train compartment contains thevalves, fittings, flowmeters, and chemicals neededfor the CVD process. Chemicals used in the gastrain include silicon tetrachloride, germaniumtetrachloride, phosphorous oxychloride, Zyron®(hexafluroethane), chlorine, oxygen, hydrogen,helium, and nitrogen.

To start the process, a CVD operator mounts a quartzglass tube, measuring about 2 inches in diameter and70 centimeters (cm) in length (known as the substratetube), in the lathe. Next a slightly smaller diameterglass tube (the exhaust tube) is inserted in theexhaust end of the substrate tube. The two tubes arejoined together by heating the joint with a handtorch. Both the inlet of the substrate and the outlet ofthe exhaust tube are connected to the lathe via rotary

Health Hazard Evaluation Report No. 95-318 Page 3

unions equipped with Teflon seals. Excess gassesand fumes flowing through the tubes are exhaustedthrough the “Tail Stock” side of the lathe into asealed flexible exhaust duct leading to a chemicalscrubber system.

To make a preform, thin layers of glass are depositedon the inside surface of the substrate tube. Thedeposits are mostly silicon dioxide (SIO2) formedfrom a reaction of silicon tetrachloride with oxygen.The layers of glass known as the “cladding” alsocontain small amounts of germanium, fluorine, andphosphorous that serve to reduce the optical index ofrefraction. Additional glass layers called the “core”are then deposited. The core layers are mostlygermanium-silicate. The core has a relatively higherindex of refraction from the cladding. Thisdifference serves to give the preform its ability toguide light. The deposition process requires heat toreact the starting materials flowing from the gas traincompartment. The hot zone is where the deposits ofsub-micron particles of optically pure glass collectonto the inside surface of the substrate tube. The hotzone is created with a oxyhydrogen fuel torch(2000°C) that traverses back and forth along thelength of the substrate tube. After deposition of thecore, the traversing torch is used to collapse the tubeinto a solid rod. About 25% of the outside portion ofthe substrate tube is milled off during the collapsephase of the process. The vaporized glass milled offis captured by a small local exhaust hood mounteddirectly above the traversing torch. A brilliant whitelight is generated from the hot zone. About 9 hoursare required to make what Alcatel calls their “stepone preform.”

From the CVD department the step one preform issent to the Clean Room. Here it is inspected foroptical and physical characteristics and sent to the“Sleeving” area where four other glass workinglathes are located. In Sleeving, the step one preformis inserted inside a second quartz glass tube and thetwo tubes are fused together with a traversingoxyhydrogen torch. Sleeving increases the preformdiameter to increase the amount of fiber that can beobtained from each preform. The rod, now called a“step two preform,” is further inspected and then sent

to the “Draw Room” where the rod is verticallymounted in a “draw tower” and heated to melt thebottom of the preform. The Draw Operator capturesthe “gob” of molten glass falling from the preformand manually threads this now relatively largediameter glass fiber stream down from the furnace toa capstan drive. The capstan drive temporarily feedsthe fiber stream into a vacuum hose until the fiberdiameter is reduced small enough to feed the fiberthrough the fiber coaters and curing fixtures. TheUV cured acrylic coating gives the fiber extrastrength and flexibility. After the fiber is at thespecified diameter, the fiber is threaded onto a “drawspool.” The lengths of fiber wound onto the drawspools vary according to customer specifications.The draw speed is computer regulated to pull themolten glass from the melting preform at a rate thatwill maintain a fiber diameter of 125 microns.Alcatel currently has eight draw towers at thisfacility.

From the Draw Room, the draw spools are sent to the“Measurements Department” for various tests. Aftertesting the draw spool is sent to the “Rewind Room”where the spools of fiber are rewound under zerotension onto “zero tension spools” so the fiber canagain undergo additional testing in theMeasurements Department. After final testing, thefiber is unwound from the zero tension spools ontothe spools used for shipping the finished product.

Chem-Clean Room

Although most quartz-glass tubes are acid washedwith hydrofluoric and nitric acid inside an enclosed(Polyflow) cabinet located in the “Clean Room”adjacent to the CVD Department, some out-of-tolerance or used quartz tubes are cleaned by hand inthe “Chem-Clean Room” by the “Utility Glass”operator. Working under a back-drafted localexhaust hood, the Utility Glass operator placesseveral tubes into a trough filled with a solution of48% hydrofluoric (HF) acid (3 gallons of HF to6 gallons of water). After soaking for severalminutes, the tubes are rinsed by lifting the tubes overto an adjacent trough (directly in front of the acidtrough) containing deionized water. This dual-


trough sink is about four feet long, with each troughbeing about 10 inches wide and about 6 inches deep.

After acid cleaning and rinsing, the tubes are placedonto a cart and moved next to a radial-arm glass sawwhere they are cut to specified lengths. A waterspray on the saw blade is used to control airbornedust, but no local exhaust system is available for thesaw. The Utility Glass operator normally works inthe Chem-Clean Room about four hours each shift.Personal protective equipment worn includes an acidresistant apron, safety glasses, face shield, protectivesleeves, and gloves. During the NIOSH site visit, a3M® 8710 disposable dust/mist respirator was wornwhen operating the glass saw. The face shield wasused only when acid washing tubes.

METHODS

SamplingBefore conducting the environmental evaluation,background information was requested by theNIOSH investigator concerning previousenvironmental surveys conducted at the facility. Themost recent monitoring data provided was for silicasampling done in 1985. The survey report foundcrystalline silica was below detectable limits for airsamples and less than 0.5% in bulk samples analyzedby x-ray diffraction.

Because of lingering employee concerns aboutpotential exposures to airborne free silica (quartz andcristobalite) in the CVD Department and Chem-Clean Room, two CVD Operators and the UtilityGlass Operator were asked to wear personalsampling devices. General area air samples forrespirable airborne particulates were also obtainedfrom CVD lathe equipment, and from above a lathemachine in the Sleeving area. To further identify thecomposition of airborne dusts being sampled, bulksamples of settled dust were taken from the top of alathe compartment in the CVD area, and from theglass cutting saw waste receptacle in the Chem-Clean Room. High volume “bulk air” samples werecollected to estimate the percent of crystalline (free)

silica contained in airborne dust samples. Toevaluate the crystallinity or amorphous nature of thefused quartz glass tubing processed by Alcatel, asample of glass tubing was analyzed using apolarizing light microscope with follow-up XRDanalysis.

Personal air sampling for respirable dust wasaccomplished using Gilian HFS 513 pre-calibratedair sampling pumps. A flow rate of 1.7 liters perminute (Lpm) was used to draw sample air throughan MSA cyclone fitted with a tared, 37 millimeter,5 micron pore size, polyvinyl chloride filter mountedin a 3-piece plastic cassette. The cyclone removesthe non-respirable particulates so the filter collectsonly that portion of the dust (<10 micrometers) thatpenetrates to the deeper areas of the lung.

Bulk air samples were also collected using a high-volume electric powered vacuum pump configuredto pull air at 9 Lpm through a pair of filter cassettesplaced side by side. Each filter in the pair wasconnected via plastic tubing to a “T” connectorattached to a plastic tube connected to the vacuumpump. Precise air flow was obtained through eachfilter by pulling air from the filter through a criticalorifice mounted inside the plastic tubing downstreamfrom the filter cassette and upstream from the “T”connector. One of the filters was configured with astainless steel cyclone to collect only respirable dust.The other filter had no cyclone and thereforecollected total airborne dust. Bulk air sampling isfrequently done when evaluating exposures toairborne free (crystalline) silica. Pulling a largervolume of air collects a greater quantity of respirabledust on the filter, thereby increasing the chance thatthe quantity of dust collected will contain sufficientfree silica to exceed the detection limit for x-raydiffraction (XRD) analysis. Bulk air samples wereobtained con-currently with personal samplescollected from the “Utility Glass” operator. Due toconcerns voiced by employees working in theMeasurements Depart-ment, high volume airsamples for total and respirable particulates werealso collected in that location.


Sample analysis

Airborne particulate concentrations were determinedby gravimetric analysis according to NIOSH Method0500.2 The total weight of each sample wasdetermined by weighing the sample plus the filter onan electrobalance and subtracting the previouslydetermined tare weight of the filter. Sample valuesless than the limit of detection were reported as notdetected (ND).

Filter samples were analyzed for quartz andcristobalite by x-ray diffraction (XRD) using NIOSHMethod 75003 with modifications that called fordissolving filters in tetrahydrofuran rather than beingashed in a furnace, running standards and samplesconcurrently, and using an external calibration curvefrom the integrated intensities rather than using thesuggested normalization procedure.

The bulk samples of material taken from the glasssaw and from the top of a CVD cabinet were alsoanalyzed for quartz and cristobalite using the XRDmethod noted previously. A two-milligram portionof each bulk was weighed onto an FWSB filter priorto analysis. Both samples were also opticallyexamined and described. To further evaluate thecrystallinity or amorphous nature of the fused quartzglass tubing processed by Alcatel, a sample of glasstubing was microscopicly examined with a polarizinglight microscope, and then further subjected to XRDanalysis to attempt identification of crystalline silica.

EVALUATION CRITERIAAs a guide to the evaluation of the hazards posed byworkplace exposures, NIOSH field staff employenvironmental evaluation criteria for the assessmentof a number of chemical and physical agents. Thesecriteria are intended to suggest levels of exposure towhich most workers may be exposed up to 10 hoursper day, 40 hours per week for a working lifetimewithout experiencing adverse health effects. It is,however, important to note that not all workers willbe protected from adverse health effects even though

their exposures are maintained below these levels. Asmall percentage may experience adverse healtheffects because of individual susceptibility, apre-existing medical condition, and/or ahypersensitivity (allergy). In addition, somehazardous substances may act in combination withother workplace exposures, the general environment,or with medications or personal habits of the workerto produce health effects even if the occupationalexposures are controlled at the level set by thecriterion. These combined effects are often notconsidered in the evaluation criteria. Also, somesubstances are absorbed by direct contact with theskin and mucous membranes, and thus potentiallyincrease the overall exposure. Finally, evaluationcriteria may change over the years as newinformation on the toxic effects of an agent becomeavailable.

The primary sources of environmental evaluationcriteria for the workplace are: (1) NIOSHRecommended Exposure Limits (RELs)4, (2) theAmerican Conference of Governmental IndustrialHygienists' (ACGIH) Threshold Limit Values(TLVs™)5 and (3) the U.S. Department of Labor,OSHA Permissible Exposure Limits (PELs).6In July 1992, the 11th Circuit Court of Appealsvacated the 1989 OSHA PEL Air ContaminantsStandard. OSHA is currently enforcing the 1971standards which are listed as transitional values inthe current Code of Federal Regulations; however,some states operating their own OSHA approved jobsafety and health programs continue to enforce the1989 limits. NIOSH encourages employers to followthe 1989 OSHA limits, the NIOSH RELs, theACGIH TLVs, or whichever are the more protectivecriterion. The OSHA PELs reflect the feasibility ofcontrolling exposures in various industries where theagents are used, whereas NIOSH RELs are basedprimarily on concerns relating to the prevention ofoccupational disease. It should be noted whenreviewing this report that employers are legallyrequired to meet those levels specified by an OSHAstandard and that the OSHA PELs included in thisreport reflect the 1971 values.

A time-weighted average (TWA) exposure refers to


the average airborne concentration of a substanceduring a normal 8-to-10-hour workday. Somesubstances have recommended short-term exposurelimits (STEL) or ceiling values which are intended tosupplement the TWA where there are recognizedtoxic effects from higher exposures over theshort-term.

Amorphous Fused SilicaSelection of the appropriate criteria for evaluatingexposures to silica in the CVD and Chem-Cleanareas was based on the assumption that the form ofsilica most likely encountered by Alcatel employeesis amorphous fused silica. Fused silica is a colorless,odorless solid that is a form of quartz. This materialis also know as quartz glass, identified by theChemical Abstract Service as (CAS) 60676-86-0.This CAS number appears on the Material SafetyData Sheet (MSDS) for the quartz tubing supplied toAlcatel by the General Electric (GE) Company. TheGE MSDS contains a statement that “when quartztubing is heated to working temperatures, the silicavapors given off condense as amorphous silica.” TheGE MSDS also indicates the OSHA eight-hourTWA PEL for amorphous silica is 6 mg/m3 and theACGIH TLV is 10 mg/m3. Although fused silica isstructurally non-crystalline (amorphous), there isconsiderable confusion in the toxicological literatureconcerning fused silica.7 The exposure limits citedin the GE MSDS, dated 1991, were for amorphoussilica, diatomaceous earth (CAS 61790-53-2), andare not appropriate for evaluating exposures toamorphous silica, fused.

The toxicology of fused silica, in spite of itsamorphous non-crystalline structure, has been foundto produce fibrosis and pulmonary lesions (althoughless severe than crystalline silica) in laboratoryanimals.7 Several studies have reported exposures tosilica fume can produce a unique form of acute andchronic respiratory symptoms that subside afterexposures ceases. Although condensed silica fumemay be amorphous,8 brief high exposures to silicafume have been associated with symptoms of metalfume fever persisting up to three months.9

Currently the ACGIH believes that fused quartz(amorphous fused silica) could be nearly asfibrogenic as crystalline quartz.7 Therefore theACGIH has adopted the TLV for quartz (0.1 mg/m3 -respirable particulates) as their TLV for amorphousfused silica. The NIOSH REL4 specified foramorphous fused silica is 0.05 mg/m3. However,determination of exposures based on the NIOSHREL requires the application of a more complexanalytical method10 (NIOSH Method 7501) that callsfor XRD analysis before and after heat treating thesample to 1500° C. This method has not been fullyvalidated for samples containing amorphous fusedsilica.

Fused silica is not specifically regulated by OSHAunder the “mineral dust exposure formula” as shownin Table Z3 of OSHA’s General Industry Standard.6Because X-ray diffraction cannot be used for directquantitative analysis of amorphous fused silica, asimple gravimetric analysis of a respirable dustsample is recommended by the ACGIH.7 Using thismethod, exposures to respirable dusts containingamorphous fused silica should be controlled tomaintain levels below 0.1 mg/m3.

RESULTS

CVD and SleevingAll air sampling results are shown in the attachedtable. As discussed in the Evaluation Criteria sectionof this report, the exposure assessment methodchosen for this survey was designed to monitorairborne respirable particulate concentrations. Allparticulates collected were assumed to consistentirely of amorphous fused silica. Analysis of airsamples collected found CVD operators (samples2007 and 2010) not exposed to respirable amorphousfused silica above concentrations detectable bygravimetric analysis (less than 0.02 mg/m3). Thisdetection limit shows that potential exposures forCVD operators to respirable amorphous fused silicaare well below the ACGIH TLV of 0.1 mg/m3 andalso below the NIOSH REL for respirable free silica(0.05 mg/m3). Area air samples collected directly


above the traversing torch of two glass-workinglathes, one in CVD (sample 1993), and one in theSleeving Area (sample 1998), also failed to collectrespirable particulates above the 0.02 mg/m3

detection limit. Each filter cassette was clipped tothe outside edge of the torch exhaust hood to captureany silica fumes escaping beyond the capture of theexhaust. These locations were selected to monitorwhat was believed to be a worse-case environmentfor quartz fume emissions.

Chem-Clean RoomSamples collected in the Chem-Clean Room diddetect measurable airborne respirable particulates.Using a conservative approach for evaluating fusedquartz exposure for the Utility Glass Operatorassumes all respirable particles collected wereamorphous fused silica. Based on gravimetricanalysis of the personal six-hour sample taken fromthe operator (sample 2008) the average airborneconcentration detected during the sampling periodwas 0.217 mg/m3. If no silica exposure is assumedfor the non-sampled portion of the 8-hour shift, thisresult is equivalent to 0.16 mg/m3 as an eight-hourTWA. This concentration was above the ACGIHTLV of 0.1 mg/m3 for an eight-hour TWA. A high-volume “bulk air” sample collected in an area aboveand in front of the glass saw detected an airbornerespirable particulate concentration of 0.135 mg/m3.An XRD analysis was performed on this sample andthe amount of free crystalline silica detected in thesamples was estimated at 4.8%. Based on thisestimate, an exposure to 0.2 mg/m3 of respirableparticulate would be equivalent to less than0.01 mg/m3 of respirable free (crystalline) silica.This concentration is well below the NIOSH REL of0.05 mg/m3. The actual amounts of amorphous fusedsilica in the samples were not determined.

Acid gases were not monitored during acid washingactivities, but the face velocity of the local exhausthood was checked with a calibrated air-flow meter.The average velocity, as determined from readingstaken at 15 points across the face of exhaust hood,was about 150 feet per minute. This flow waseffectively capturing HF vapors released from the

washing tank. No odor, eye, or respiratory irritationwas noted when standing next to the tank during thisactivity.

Measurements DepartmentThe “bulk air” sample collected in the MeasurementsDepartment did not detect respirable particulates ata concentration that would indicate an exposure riskfor silica. The sample (number 1243) detected only0.025 mg/m3 respirable particulates. Other airborneparticles are also likely within this sample, butassuming all particles were fuzed quartz, theconcentration was still well below the 0.1 mg/m3

TLV. No free crystalline silica was detected in thebulk air samples when analyzed by XRD.

Bulk Sample AnalysesThe bulk sample of light gray fibrous material takenfrom the top surface of a CVD cabinet (sample 6313)and wet gray mass of material (sample 6314) takenfrom inside the water spray collection receptacle ofthe glass saw used by the Utility Glass Operator wereoptically examined by the NIOSH contractlaboratory with the following observations: Sample6313 was mostly a gray fibrous mass with someloose particles trapped within the fibrous material.The particles were described as unidentified blackopaques of possible amorphous silica and otherparticles believed to be aluminum oxide. The wetsample (6314) was dried, and when examinedappeared to be very fine cream colored particles andsmall to medium shards of clear glass. No fiberswere present in this sample. The cream-coloredparticles appeared to be aluminum oxide. Nocrystalline quartz or cristobalite were observed ineither sample using X-ray diffraction (XRD)analysis. The glass shards were reported by thelaboratory to be “amorphous in nature,” with thefiner particles also thought to be to be amorphoussilica.

To further evaluate the crystallinity or amorphousnature of the fused quartz glass tubing processed byAlcatel, a sample of glass tubing was also analyzed.Portions of the tube were ground with a mortar and


pestle to obtain particles small enough to fit under amicroscope cover slip mounted on a glass slide. Theparticles were examined in 1.55 refractive indexliquid with a Leitz Dialux 20 polarizing lightmicroscope at 160X magnification. With the polarscrossed, less than 5% of the particles showedindistinct little patches of low birefringence (whitishareas on a black particle background). These littlepatches are where the silica has some crystallinity,whereas, the black parts are amorphous withoutdefinite crystalline lattice. A portion of the groundtubing was further ground to pass through a 38 :mscreen and analyzed by XRD to determine if

crystalline silica minerals could be detected. TheXRD scan (Figure 1) of the fused silica is overlayedwith index lines (noted with a Q or a C) to show thepositions for quartz and cristobalite peaks. The scanshows two broad peaks in the lower two-thetaregions which are indicative of amorphous silica.The primary cristobalite peak is hidden in the largeamorphous silica peak. There was no way to proveby XRD if cristobalite is present. The primary quartzpeak is on the right shoulder of the amorphous silicapeak and is also hidden. In this sample, quartz mustbe reported as not detected.

Figure 1 XRD Scan of fused quartz glass tubing

DISCUSSIONSampling results from this survey indicate thatinhalation exposures to respirable amorphous,crystalline, or fused silica are not likely for workersassigned to the CVD, Clean Room, andMeasurements Departments. The most conservativeapproach for evaluating this exposure risk was used.This survey method assumed that all collectedrespirable particulates were amorphous fused silica(fused quarts). Although laboratory analyses of bulksamples indicates the silica from the glass tubing is

technically non-crystalline (amorphous), toxicity datafor fused quartz suggests that use of the exposurelimit specified for amorphous silica is not applicable.Therefore, monitoring results were not compared tothe NIOSH REL4 for amorphous silica (6 mg/m3).The laboratory analysis of bulk samples collected inthis survey also indicates that subjecting samples toXRD analysis to identify the sample’s crystallinesilica (e.g. quartz or cristobalite) content is more thanlikely an exercise in futility.

Based on this survey and previous environmentalsurveys of this process, Alcatel workers are not at


risk from silica exposures in the routinemanufacturer of optical fiber cable. That is not tosay that precautions are not needed. Any non-routinework practice, cleanup, or maintenance proceduresthat might release fused quartz particles into aworker’s breathing zone should be evaluated.Maintenance or cleanup workers potentially exposedto airborne respirable particulates above0.1 mg/m3should be adequately protected witheffective engineering controls or required to wearappropriate respiratory protection. For example, aprocedure where excess exposures could occur mightinclude maintenance activity on containment orpollution control systems that receive excesschemical residue (soot) from CVD tail stockexhausts.

CONCLUSIONSBased on the assumption that all airborne respirableparticulates sampled were fused quartz, the onlyAlcatel employee found with potential exposuresabove the evaluation criteria of 0.1 mg/m3 was theUtility Glass Operator working in the Chem-CleanRoom. This person should continue to userespiratory protection designed and approved toprotect against exposure to fused silica. NIOSHrecommends11 the use of an air-purifying respiratorwith a high-efficiency particulate filter in work-settings where maximum concentration would notexceed 0.5 mg/m3.

RECOMMENDATIONS1. The MSDS supplied by the General ElectricCompany needs updating to reflect the exposurelimits applicable for fused quartz. This 1991 MSDSstates the TLV for amorphous silica is 10 mg/m3.This TLV is applicable to inhalable particles ofdiatomaceous earth (CAS 61790-53-2). Asdiscussed in the criteria section of this report, thecurrent TLV recommended by the ACGIH foramorphous fused silica (fuzed quartz) is 0.1 mg/m3.

2. Local exhaust ventilation is recommended forthe Chem-clean glass saw. The exhaust hood shouldbe designed to enclose the saw wheel and slide-tableas much as possible without interfering withvisibility or handling of the longer pieces being cut.The saw should be operated so that the flow of theabrasive fragments and glass dust coming off thecutting wheel is directed to the back of the enclosurehood. An example of this type of hood is shown inFigure 2.

3. The Utility Glass operator cutting quartz tubeswas wearing 3M 8710 (TC-21C-132) particulatedust/mist (DM) respirator. These respirators werecertified under old regulations (30 CFR 11) that havesince been revised and replaced with new respiratorcertification regulations (42 CFR 84). However,until they are phased out, respirators certified underthe old regulations will still be available on themarket until July 1998.

Research has shown that particles sized2 micrometers (2 µmd) or less can penetrate someDM filters certified under 30 CFR 11, and thesefilters should only be used if the particle size of theaerosol present in the workplace has beencharacterized, and the mass median aerodynamicdiameter (MMAD) is known to be greater than2 µmd.12 Under the new regulations, particulatefilters are tested under much more demandingconditions, using the most penetrating aerosols. Assuch, these filters are effective against any sizeaerosol.

Because the particle size of fused quartz glass dustgenerated from the saw is not known, until effectiveventilation controls are implemented, the glass sawoperator should use a DM respirator certified underthe new NIOSH respirator certification regulations.The minimum protective filter that should be used isN95. These respirators will have a certification labelwith the NIOSH and Department of Health andHuman Services (DHHS) emblem, with a numberingsequence of TC-84A-xxxx.

4. Draw Operators who work with uncured acryliccoating materials (Desolite®) should be aware of the


Figure 2 Glass saw exhaust hood recommendation

potential for allergic skin reactions from direct skincontact with these coatings. Chemical ingredientsfor both the primary (product code 3471U1-135) andsecondary (product code 3471-2-102) UV curedcoating materials are classified as “multifunctionalacrylates.” The specific chemical ingredients forthese compounds are designated as “Trade Secrets”by the coating’s supplier, DSM Desotech Inc., Elgin,IL. When contacted by NIOSH, DSM confirmedthat unreacted acrylics in these products are knownskin sensitizers. Although NIOSH was not given thespecific ingredients, based on a review of theliterature, and information provided by DSM,NIOSH offers the following comments:

C According to DSM Desotech, no solvents areused in the products. The MSDS for eachcoating material indicates the products containless that 1% volatiles. There is a low potentialfor exposure through inhalation.

C DSM recommends using acetone or butylalcohol as clean-up solvents.

C According to DSM Desotech, no skinsensitization or irritation is expected from thecoatings after curing. However, it appears thatonce a worker becomes sensitized it is possiblethat allergic skin reaction can occur, even tofinished fibers.13 Workers who handle thesecoating materials and who experience skin rash


1. Kirk, RE, Othmer DF, Grayson, M, Eckroth,D [1985]. Kirk-Othmer concise encyclopedia ofchemical technology. John Wiley & Sons, NewYork.

2. NIOSH [1994]. Particulates not otherwiseregulated, total; Method 0500. In: NIOSH manualof analytical methods, 4th ed. Eller, RM, ed.Cincinnati, OH: U.S. Department of Health andHuman Services, Public Health Service, Centersfor Disease Control, National Institute forOccupational Safety and Health, DHHS (NIOSH)Publication No. 94-113.

3. NIOSH [1994]. Silica, crystalline, by XRD;Method Number 7500. In: NIOSH manual ofanalytical methods, 4th ed. Eller, RM, ed.Cincinnati, OH: U.S. Department of Health andHuman Services, Public Health Service, Centersfor Disease Control, National Institute forOccupational Safety and Health, DHHS (NIOSH)Publication No. 94-113.

4. NIOSH [1992]. Recommendations foroccupational safety and health: compendium ofpolicy documents and statements. Cincinnati,OH: U.S. Department of Health and HumanServices, Public Health Service, Centers forDisease Control, National Institute forOccupational Safety and Health, DHHS (NIOSH)Publication No. 92-100.

5. ACGIH [1995]. 1995-1996 threshold limitvalues for chemical substances and physicalagents and biological exposure indices.Cincinnati, OH: American Conference ofGovernmental Industrial Hygienists.

6. Code of Federal Regulations [1993]. 29 CFR1910.1000. Washington, DC: U.S. GovernmentPrinting Office, Federal Register.

7. ACGIH [1991]. Documentation of thethreshold limit values and biological exposureindices, 6th Ed. Cincinnati, Ohio: AmericanConference of Governmental IndustrialHygienists.

8. Hampel GA and Hawley GG, eds. [1973].Structure of silica glass In: The encyclopedia ofchemistry, 3rd ed. Van Nostrand Reinhold Co.

9. Ratney RS. [1990]. Proceedings of the VIIthInternational Pneumoconioses Conference, Part II.Pittsburgh, Pennsylvania, August 23-26. NIOSHU.S. Department of Health and Human Services,DHHS (NIOSH), Publication No. 90-108 Part II,Pgs. 1134-1135.

10. NIOSH [1994]. Silica, amorphous; MethodNumber 7501. In: NIOSH manual of analyticalmethods, 4th ed. Eller, RM, ed. Cincinnati, OH:

should immediately be referred to adermatologist. Diagnosed sensitivity to thecoatings may require reassignment of sensitizedworkers. Workers who work with thesematerials on a daily basis must avoid all directskin contact and immediately wash the skin withsoap and water if contact does occur.

C The recommended protective glove material forthese products is nitrile rubber.

C A copy of the safe handling guide (availablefrom DSM Desotech) should be obtained andmade available to all Draw Operators and otherAlcatel employees who must work with thesecoatings.

5. The CVD operating procedures for fillingphosphorous oxychloride bubblers should bereviewed. The current practice of filling the bubblerat CVD system 35, and hand-carrying the glassbubbler container to the CVD gas train compartmentwhere it is to be used, is a dangerous practice. If aworker transporting this bubbler were to accidentallydrop and break a full container onto the floor of theCVD department, an extremely hazardousatmosphere could be created for workers near thespill. Any bubbler in transit should be carried in aprotective outer container that would preventbreakage of the bubbler if dropped to the floor.Special bottle carriers are commercially available.

REFERENCES


U.S. Department of Health and Human Services,Public Health Service, Centers for DiseaseControl, National Institute for OccupationalSafety and Health, DHHS (NIOSH) PublicationNo. 94-113.

11. NIOSH [1994]. NIOSH pocket guide tochemical hazards. Cincinnati, OH: U.S.Department of Health and Human Services, PublicHealth Service, Centers for Disease Control,National Institute for Occupational Safety andHealth, (DHHS) Publication No. 94-116.

12. NIOSH [1996]. NIOSH guide to theselection and use of particulate respiratorscertified under 42 CFR 84. Cincinnati, OH: U.S.Department of Health and Human Services, PublicHealth Service, Centers for Disease Control,National Institute for Occupational Safety andHealth, DHHS (NIOSH) Publication No. 96-101.

13. Maurice P, Rycroft R [1986]. Allergiccontact dermatitis from UV-curing acrylate in themanufacture of optical fibres. Contact Dermatitis,Vol. 15, No. 2 pgs 92-93.


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