facility. The layout of this facility is shown in Figure 5.

Preparatory to stripping, the parts and equipment that are not to be stripped
and that could be affected by the stripping compound are masked with aluminum
sheeting and aluminum tape.

Once the aircraft is masked, the building doors are closed and the exhaust
ventilation fans are turned on. Air enters the building from louver openings
in the door and in the side walls. Personnel then apply the paint stripping
compound to the various sections of the plane. The tail section, approximately
50' high, is sprayed from large, elevated, hydraulically-operated lifts. The
top and sides of the fuselage are sprayed by personnel working from two cages
suspended from overhead cranes. In addition to the personnel on the lifts and
in the overhead cages, there are persons applying stripper from the ground,
from elevated platforms, and from hydraulically operated stairs.

The stripping compound initially used is Intex 857 "mild" stripper, which con-
tains approximately 50% methylene chloride, 25% aliphatic and aromatic hydro-
carbons, 10% non-volatile hydrocarbons, and 15% water and ammonia. This compound
is supplied in large, 300-gallon containers which are positioned at appropriate
locations near the aircraft--two containers placed on either side of the tail
section, two others positioned on either side of the fuselage in front of the
wings.

Pneumatically-operated pumps in the containers force the stripping compound
through hoses to the spray handle. The stripper is sprayed onto the painted
surfaces in the form of a fine mist, in most cases from above with the spray
directed downward. For certain areas, such as the underside of the aircraft,

the spray was directed upwards, but by proper positioning of the lift and cages,
this upward spraying was kept to a minimum. Several coats of the "mild" stripper
are applied, with scraping and brushing of the surfaces between coats to assist
in loosening and removing the paint. A phenolic-based, "hot" stripper is
applied to stubborn areas. Table 2 lists several of the stripper solutions that
could be used for the stripping operation.

Tools used for the stripping and removal of the paint include a polypropylene
scrubbing brush, a rubber squeegee, aluminum wool on a mop handle, wire brush,
and a scraping tool. For applying the stripping compound to small areas, such
as around the windows of the cockpit, a bristle brush dipped in an open plastic
pail of stripper is generally used.

Approximately 1000 gallons of the non-phenolic, "mild" stripper is used for an
aircraft. Four to fifteen (an average of six) drums of "hot" phenolic stripper
are used.

As noted in Figure 5, one wall of the depainting building consists of over-
lapping sliding doors. These doors, which are electrically operated, open to
permit the aircraft to enter the bay and, during the stripping process, are
closed, and exhaust ventilation fans on the opposite wall are activated to
create an air flow across the building of between 25 and 50 linear feet per
minute. At the entrance to the exhaust plenum, directly in front of the filters,
the measured air velocity ranged from 100 fpm to as high as 625 fpm. These
velocities were attained with three of the four fans in an operating mode.

13


Table 6.

Job and work-shift TWA concentrations of methylene
chloride at Plant B, week of November 6, 1978.

TWA concentration

TWA concentration, all shifts

Job title Geometric Geometric
IBs/ Get (Gyan) 7 Mean Standard _ Range
Day Night Evening (ppm) Deviation" (ppm)
Process Operator 1.34 4.22 28.84 5.1 3.6 0.92-30.47
Extractor Operator 1.30 1.09 21.88 2.4 4.6 0.37-33.22
Evaporator Operator 1.69 2.28 _ Anal. a2) 1.05-4.95
Coffee Handler 0.95 0.78 18.28 1.8 5.5 0.32-18.28
General Laborer Zoe) ily) is} {05} 228 4.4 0.61-24.94
Caffeine Dryer 1.22 2.46 -- 2.0 5.39 0.48-12.64
Operator
All jobs:
Mean concen-
tration (ppm) iS Io? 20.9 2.9
Standard
deviation To) 32) 1.6 20)
Number 10 18 8 4.0
Range (> a (aye 7) (4)

¥

See footnote
+See footnote
(1) 0.92-3.53

(*), Table 5.
(+) and "Note," Table 4.
(2) 0.32-12.64; (3) 9.06-33.22; (4) 0.32-33.22.

34


Table 4.

Job and work-shift TWA concentrations of

methylene chloride at Plant A, May 16-17, 1979.

TWA concentration

TWA Concentrations, all shifts

Job title by shift (ppm) Geometric Geometric
a mean standard Range
Day Swing Night (ppm) deviation (ppm)
Patroler, Block I 69 315 = 147 2.93 69-315
Patroler, Block II 268 357 487 S158} 1.38 267-487
Doffer, Block I 344 441 135 307 1.76 135-490
Doffer, Block II 523 339-561 397 1.78 168-561
Jetwiper, Block I 286 307 504 335 1.42 227-504
Jetwiper, Block IL 197 177465 225 1.76 118-465
Bobbin Stores Op. 124 210 76 142 1.62 76-210
Creeler 162 93 57 90 a73, 56-162
Lacer 198 104 209 140 1.69 67-209
Coning Operator 63 40 - 46 3.66 31-63
Beaming Operator 237 258 68 181 1.92 68-278
Pressmen 319tt 264-375

*Except for the case of questionable value (see Table 3), this is a mean of two

samples, (shift sampled on two days)

+Geometric mean =

Geometric stnd. dev.

= antilog

= gs =
g

antilog

n

[ .

i log » |

r

)2

rus

‘1

isl

hs

n
Tosa xo ( = log x)”

++Mean of two samples, two pressmen monitored.

30

n (n-1)


10.

11.

12.

13.

14.

15.

REFERENCES

Criteria for a Recommended Standard...Occupational Exposure to Methylene
Chloride. National Institute for Occupational Safety and Health. U.S.
Department of Health, Education and Welfare, 1976.

Synthetic Organic Chemicals, U.S. Production and Sales, 1972, T.C. Publication
681, U.S. Tariff Commission, 1974.

SRI International, Chemical Industries Center, 1979.

Code of Federal Regulations, 29, 1910.1000.

American Conference of Governmental Industrial Hygienists. Threshold Limit
Values for Chemical Substances and Physical Agents in the Workroom Environment

with Intended Changes for 1979. Cincinnati, 1979.

Heppel, L.A., Neal, P.A., Perrium, T.L., et al. Toxicology of dichloroemthane-
I. Studies on effects of daily inhalation. J. Ind. Hyg. Toxicol. 26:8-16, 1944.

Stewart, R.D., et al. Carboxyhemoglobin evaluation after exposure to dichloro-
methane. Science 176:295, 1972.

Ratney, R.J., Wegman, D.H., Elkins, H.B. In vivo, conversion of methylene
chloride to carbon monoxide. Arch. Environ. Health. 28:223, 1974.

DiVencenzo, G.D., Hamilton, M.L. Fate and disposition of 14, methylene chloride
in the rat. Toxicol. Appl. Pharmacol. 32:385, 1975.

Vozovaja, M.A., et. al. Levels of methylene chloride in biological media in
pregnant or lactating female workers of an industrial rubber products factory.
Gig. Tr. J. Prof. Zabol, No. 4, 1974.

Progress in Genetic Toxicology, (Scott, D., ed.) Elsevier/North-Holland Bio-
medical Press, Amsterdam, The Netherlands, 1977.

Friedlander, B.R., Hearne, T.,Hall, S. Epidemiologic investigation of employees
chronically exposed to methylene chloride. J.O.M. 20(10):657, 1978.

SRI International. Hazard Process Index, 1974, p.530.

Manufacture of Chloromethanes from Methyl Alcohol and Chlorine (product
bulletin). Vulcan Materials Company, Wichita, Kansas, 1974.

Faith, W.L., et al. Industrial Chemicals, 4th Ed. John Wiley & Sons, New York,
1975, pp.530-538.
39


uv light

cl, 2 2cl-
methane CH, + 2Cl- + CH,C1 + HCL
methyl chloride CH,C1 + 2c CH,Cl, + HC1
methylene chloride CH,C1, + 2Cl+ + CcHC1, + HCL
chloroform CHC1, + 2Cl- + ecl, + HCL

carbon tetrachloride

Methylene chloride can also be produced by chlorinating methyl chloride that
results from the hydrochlorination of methanol, with the advantage that waste

hydrogen chloride is returned to the reactor for further methyl chloride pro-
duction.14,15 The reaction is as follows:

CH,OH + HCl + cH, ae 4,0

CH,CL + 2Cl- + CHCl, + HC1

A refinement in the process for producing methylene chloride involves using
finely divided sand, suspended in a fluidized bed, as a reaction medium and
maintaining the reaction temperature at 250-390°C. Hydrogen chloride liber-
ated during reaction is recycled to produce fresh methyl chloride from methanol.


Appendix C. Results of sampling for ammonia from the
paint stripping compounds used at Plant C

Concentrations of ammonia during an aircraft paint stripping operation at

Plant C are shown in the tabulation below. Concentrations were determined by
area samples using an impinger with absorbing reagent. They ranged from less than
1 ppm to 5.6 ppm. Average concentration for the workday was 2.6 ppm. The

current permissible exposure level (OSHA) for ammonia is 50 ppm, and the

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold

Limit Value (TLV) is currently at 25 ppm. The levels present in the depaining
facility were well below these standards and should not be considered an

exposure problem.

Sample number and location Ammonia concen-
(all front fuselage) tration (ppm)
1 Left side et)
2 Right side ioe)
3 Right side 1.8
4 Left side Sal
5 Left side 1.3
6 Right side 1.4
7 Left side 5.6
8 Blank ==

47

‘We oU.S. GOVERNMENT PRINTING OFFICE: 1980--657-147/1006


Table B-1 (Continued)

Sample number and location TWA concentration (ppm)
C-57 Operating level, Block II 28.0
between Metiers 62 and 63
C-58 Catwalk, Block II 86.6
between Metiers 58 and 59
C-59 Patroller, Block I 168.6
C-60 Jetwiper, Block I 128.4
C-61 Doffer, Block I ZENS)
C-62 Blank so

*This value is questionable; sample possibly adulterated or error in analysis.

45


Bobbin Stores

Bobbin Stores Operator--loads and unloads transports, readies bobbins to be
taken to the Textile Department. Also empties "shorts," which are recycled
back to the mixers.

Textile Department
Twisting Operators—

@ Creeler--doffs full packages (bobbins) after yarn had gone through
mechanical twisting to increase its strength.

e@ Lace-up Operator-—-laces or threads ends of full bobbins through the
twisting machine onto empty spools.

Coning Operators--doffs full cones, replaces empty bobbins, and laces up ends
of full bobbins for transfer to cones.

Service Operator--provides transport with full bobbins for the twisting and
coning operators; takes back empty bobbins. Not included in monitoring.

Conveyor Operator--operates conveyor "train" throughout all yarn-handling
departments. Collects full transports and returns empty transports to
Bobbin Stores. Not included in monitoring.

Beaming Operator--removes and replaces bobbins that transfer yarn onto
weaving section beams. Ties end together to maintain continuous feeding
and transfer of yarn.

In addition to the job categories mentioned above, there are plant maintenance,
quality control, and supervising personnel who may receive intermittent exposures
to methylene chloride.

The duration of exposure for these workers and the concentration of methylene
chloride exposure may vary with the job. However, the potential for exposure
is up to eight hours per day.

Plant B--Personnel

As many as 53-58 employees (salaried and hourly) work in the decaffeination area
at Plant B. Included in this group are general laborers (two per shift), mainte-

nance workers, and supervisors. The number of operators and their job titles
are listed below:

Job classification Workers per shift
Supervisor 1
Process Operator 2
Extractor Operator 3
Evaporator Operator ab
Coffee Handler 1

General Laborers 6-7 (two per shift)
(continued)

7


Personal samples taken from the General Laborers varied from 0.6 to 24.9 ppm,
with a mean concentration of 2.8 ppm. Extractor Operators had an 8-hour TWA
concentration that varied from 0.4 to 33.2 ppm, with a mean of 2.4 ppm. Evapora-
tor Operators had an average concentration of (nominally) 2 ppm, as did Caffeine
Dryer Operators. The lowest average concentration, 1.8 ppm, was recorded for
Coffee Handlers.

In terms of work shifts, the lowest 8-hour TWA mean concentration, 1.5 ppm, was
recorded during the day shift; the night shift was slightly higher at 1.7 ppm.
The system upset during the evening shift has already been noted. (There was a
mean concentration of 20.9 ppm during this shift.)

Short-term exposure sampling for methylene chloride was performed while personnel
were obtaining product samples for purposes of quality control. The Process
Operator was found to have the highest exposure level among the samples taken--

5 ppm, still well below the current TLVs.

Work-area samples for carbon monoxide and for total and respirable coffee dust
showed only trace amounts of carbon monoxide and negligible amounts--well below
1 mg per cubic meter--of dust.

RESULTS OF SURVEY--PLANT C

Results of sampling for methylene chloride during paint stripping operations at
Plant C, which were limited to those from a single shift due to aircraft scheduling
difficulties, are presented in Table 7. (The results of area sampling for the
presence of ammonia from the paint stripping compounds are given in Appendix Cc.)
Time-weighted-average exposures for personnel working in the depainting facility
were well below the OSHA permissible exposure limit of 500 ppm, and with one
exception (Sample R-10), were below the American Conference of Governmental
Industrial Hygienists recommended Threshold Limit Value of 200 ppm. The range

of methylene chloride exposure concentrations was 15.7 to 268 ppm, with an

average concentration of 64 ppm.

The highest exposure concentration of methylene chloride, 268 ppm, was to the
paint stripper personnel who worked on the wheel well of the aircraft. This is
an area where airflow is probably disrupted, creating pockets of stagnant air
in which the vapor content is higher. Concentrations of methylene chloride at
other locations around the aircraft were less than 100 ppm, indicating that the
exhaust system in this new facility was functioning well.

During the preliminary, walk-through survey conducted in the previous year, the
stripping operation was carried out in a facility that had no exhaust ventilation
system, but that relied instead upon natutal ventilation through open doors to
dilute and disperse the vapors. The movement of wind was, however, apparently
sufficient to maintain low levels of methylene chloride, since the results of
sampling done at that time are similar to those of the recent survey. However,
operations in the new facility do not have to be exposed to inclement weather.

35


ABSTRACT

Following preliminary, walk-through, industrial hygiene surveys of seven U.S.
plants in which methylene chloride is used, three facilities were selected for
further surveying of human exposures to the chemical. Ninety-four full-shift
personal samples for methylene chloride covering workers in 19 job classifica-
tions, and area samples of 19 different sites at these three facilities were
collected and analyzed. The findings were reported separately for the three
plants. This report consolidates the findings for the individual plant surveys.

The report includes—-in addition to background information on production and

uses, toxicity and human exposure standards, and production processes--descrip-—
tions of operations and jobs, exposure control efforts, health and safety programs,
air sampling data collected, summary tables of worker exposure levels to methylene
chloride and associated substances (acetone, methanol, coffee dust, and ammonia),
sampling and analytical procedures and methods, evaluation of findings, and
recommendations.

Results of the survey showed time-weighted-average personal exposures for
normal operations ranging from 0.3 to 561 ppm--four samples, at one plant, above
500 ppm and one sample, at another plant, above 200 ppm. Exposures to the
other substances surveyed were all below current permissible levels.

This report was submitted in partial fulfillment of Contract No. 210-76-0158

by SRI International under the sponsorship of the National Institute for
Occupational Safety and Health.

iv


Table 3.

(continued)

Job title/location and sample number

TWA concentration

(ppm)
Personal samples
Creeler c-8 55.5
C-18 SS/o8)
C-32 162.0
c-49 128.9
Lacer c-9 66.6
c-19 208.9
c-31 198.0
c-48 140.4
Coning Operator c-10 20.5)
c-16 572.1%
C-33 62.9
C-50 48.8
Beaming Operator c-11 236.5
C-17 68.0
C-34 237.4
C-51 27fe>
Pressman Block II C-42 374.6
C-43 264.1
Area Samples
Operating level, Block II C-12 659.4
between metiers 58 and 59 C-28 409.6
C-39 547.9
C-56 587.4
Operating level, Block II c-13 828.1
between metiers 62 and 63 C-29 679.0
c-40 950.5
C-57 730.8
(continued)

28


vas

ROLL-UP DOOR

i

STORAGE AREA

OO OO

TTT Tt TaTcaatetatetat.

OFFICES

LUNCH
ROOM

OO

Mitetatatatatatatetaty
EXHAUST PLENUM

(CEILING:

70 FT HIGH)

‘AUT

160°

240"

IRETRACTABLE DOORS

FIGURE 5 LAYOUT OF THE AIRCRAFT PAINT STRIPPING FACILITY AT PLANT C


departments that have been designated as high-noise areas, hearing protection

is required. Other operations sometimes may require protective clothing, safety
glasses or chemical goggles, safety shoes, respirators, aprons, or gloves, and
these are provided to the employee.

Plant B--Health and Safety

At Plant B, the health and safety program is under the direction of a Safety
Coordinator. The coordinator's responsibilities include conducting safety
meetings with department supervisors, providing safety information, performing
safety audits, and conducting formal meetings between representatives of manage-
ment and labor. A corporate industrial hygienist/toxicologist (located at
corporate headquarters, in another state) is available to provide technical
support for the Safety Coordinator. It was reported that personal sampling for
methylene chloride, four times per year per operator, and routine area monitoring
are performed using charcoal tubes and bags or syringes.

The medical department is staffed by one consulting physician and three full-
time nurses. Medical assistance is augmented by the department supervisors,

who are all trained in first aid. In addition, nine employees have been trained
as Emergency Medical Technicians. A nearby hospital has facilities for emergency
care.

Pre-employment physical examinations are required by Plant B for all of its
employees. Periodic physical examinations are performed on a one- to three-
year cycle (depending on the employee's job and age). Methylene chloride
workers are required to have annual physicals. These physicals include a
blood profile, EKG (if over the age of 40), urinalysis, hearing test, and pul-
monary function test. Methylene chloride workers also receive a (SMA20) series
of laboratory blood-evaluations.

The plant requires that every employee working in the production areas wear
company-supplied work clothing. Bump hats, safety glasses, and safety shoes

are optional but are made available to every production worker. During specialized
operations, additional safety equipment is available (and/or required), including
several different types of respirators such as nuisance-dust masks, cannister
respirators, and self-contained breathing apparatus (Scott Air Pacs®). Gloves

and safety shields are also provided, and emergency safety showers, eyewash
facilities, change rooms, lockers, and showers are available.

Plant C--Health and Safety

The safety, medical, and industrial hygiene programs at the Base in which Plant
C is located are the responsibility of the Safety Officer, Occupational Medical
Services, and Bioenvironmental Engineering Services, respectively. The safety
function at the Base, staffed by 19 persons, is responsible for flying, ground,
explosive ordnance, and missile safety programs, as well as for safety in the
paint stripping and other ground maintenance activities.

Occupational Medical Services comprises three physicians, four nurses, several
technicians, and ancillary staff. This group operates a dispensary, which is
open from 7:30 a.m. to 4:00 p.m. A hospital on the Base supplements the services
of the dispensary.

20


Additional air removal is accomplished by pulling vapors through gratings into
a trough in the floor.

The aircraft being stripped during the survey was a C-130 Hercules cargo plane.
Work on the plane was to continue for approximately nine full shifts before the
entire stripping job was completed.

PERSONNEL AND THEIR ACTIVITY
Plant A--Personnel

Of the approximately 1950 employees at Plant A, some 920 are potentially exposed
to methylene chloride. However, all of these personnel may not be working with
the triacetate fibers continuously throughout the entire work shift. The 920
employees potentially exposed are, roughly, equally divided over four rotating
shifts, although there are fewer personnel in the work areas during the after-
noon and night shifts.

There are 20 employees in the preparation area, where the "dope (liquid polymer)
for the fiber is mixed and filtered. In the extrusion areas, there are approx-
imately 260 operators in Block I, where acetate fibers are primarily produced
(some triacetate yarn is also produced) and some 80 employees in Block II, where
most of the triacetate yarm is manufactured. There are approximately 100
employees in the Bobbin Stores area; and in the Textile Department, twisting
employs approximately 130; coning has 140; and beaming has approximately 190
persons. As mentioned previously, not all of these personnel are continuously
exposed to methylene chloride. (Extent of potential exposure depends primarily
on whether acetate or triacetate fibers are being run.)

Job titles and description of the personnel in the fibers production areas are:

Preparation Area

Control Operators--charge and monitor the mixing of the triacetate flake and
methylene chloride and methanol in the mixers. These persons are located
in a remote control room and were not included in the detailed monitoring.

Pressmen—-prepare the filter presses for filtration of the dope. They remove
and replace filter elements and also operate the recovery system for
reclamation of dope from the elements.

Extrusion Area

Jet Wiper--operates and maintains the extrusion equipment to ensure an even
and continuous flow of the dope.

Doffer--removes and replaces bobbins on the metiers. Loads bobbins onto the
transport, observes the operation of the individual cabinets.

Patroler--assists the Doffers. Removes "shorts," bobbins that do not have

a full amount of yarn. Also observes the operation of the individual
cabinets.

16


Table 3. (continued)

Job title/location and sample number TWA concentration
(ppm)

Area Samples

Catwalk, Block II c-14 786.9
between metiers 58 and 59 C-27 645.1
C-41 975.1
c-58 482.5
(Blank) c-15 =
c-30 et
C-47 =
C-62 =

*These values are questionable; sample possibly adulterated or error in analysis.

29


TI

PREPARATION

TRIACETATE
POLYMER
FLAKE

METHYLENE CHLORIDE
AND METHANOL

EXTRUSION

5)

|_.—CABINET
FILTRATION
BOBBIN
=
TEXTILE DEPT
ened [| BOBBIN TWISTING
a p> H
TRANSPORT STORAGE CONING IBREROURE
BEAMING

FIGURE 3 A SCHEMATIC DIAGRAM OF THE PROCESS FOR MAKING TRIACETATE FIBERS


BACKGROUND

Methylene chloride, also known as methylene dichloride, methylene bichloride,
and dichloromethane, is a colorless, heavy, mobile, and volatile liquid with
a pleasant odor. The chemical formula and chemical and physical properties
of the compound are given in Table 1.

PRODUCTION AND USES

The substance is widely used for a variety of purposes, including paint strip-
ping, manufacturing of photographic film, propelling aerosols, manufacturing

of triacetate fibers, metal degreasing, extraction in the food products industry,
fumigation, and fire extinguishing. Paint removing accounts for the chemical's
greatest use (30% of total consumption in 1977).!.4 Tt has been estimated that
eS metric tons of methylene chloride were produced in the United States in
1977.

TOXICITY AND HUMAN EXPOSURE STANDARDS

The current Occupational Safety and Health Administration (OSHA) standard for
methylene chloride is 500 ppm for an eight-hour time-weighted average (TWA)
exposure.’ A Threshold Limit Value (TLV) of 200 ppm, adopted by the American
Conference of Governmental Industrial Hygienists (ACGIH) is currently in effect,
but there is a proposal to lower the TLV to 100 ppm.5 In March of 1976, a
National Institute for Occupational Safety and Health (NIOSH) criteria document
on methylene chloride was released in which a still lower TWA of 75 ppm is
recommended .1

The current OSHA standard of 500 ppm is based on work published in 1944 by
Heppel and others, who demonstrated through animal experimentation that
methylene chloride is a narcotic and irritant at high airborne concentrations
(5,500-10,000 ppm) .& Several reports and studies indicate that methylene
chloride can produce stupor, headache, irritability, giddiness, and other cen-
tral nervous system effects among exposed workers. At levels well above those
normally found in the occupational environment, the compound can cause damage
to lungs, liver and kidneys.!

Studies in the 1970s demonstrated that methylene chloride is metabolized in
the poy to carbon monoxide, ultimately causing an elevation in carboxyhemo-
globin, 27,859 and it is on the basis of these studies that NIOSH has recom-
mended a TWA of 75 ppm. As part of this recommendation, as well as to account
for the concomitant effects of methylene chloride and carbon monoxide, NIOSH
recommends that the exposure to methylene chloride be limited so that the com-
bined exposure of methylene chloride and carbon monoxide (when levels of carbon
monoxide exceed 9 ppm) follow this equation:

acy) ., Ue) 1
L(CO) (GH,C1,)

3


RESULTS AND RECOMMENDATIONS

Results of the in-depth exposure surveys carried out at Plants A, B, and C,
together with summaries and recommendations, are presented in this chapter.

RESULTS OF SURVEY--PLANT A

Concentrations of methylene chloride (as well as of acetone) during yarn produc-
tion and processing operations at Plant A were calculated following analysis of
the collected personal and area samples, and the results for methylene chloride
are shown in Table 3. (See Appendix B for acetone results.) The results of area
sampling for the presence of methanol in the filter press area of the Preparation
Department at Plant A are presented in Appendix B. (The time-weighted average
(TWA) exposures for acetone were determined to be below the current OSHA standard
of 1000 parts per million, and concentrations of methanol were well below the
OSHA standard of 200 ppm.)

Personal TWA exposures for methylene chloride were determined to range from 31
ppm for a Coning Operator to 561 ppm for a Doffer in Block II. Area samples
taken in the vicinity of the extrusion cabinets in Block II showed concentrations
in the range of 409-950 ppm on the operating level and from 488 to 975 ppm on the
catwalk area of Block II. During the survey period, ten metiers in Block II
were producing triacetate yarn, and the remaining two were producing acetate
staple.

The full-shift personal sampling data are shown in Table 4 in the form of con-
centrations for each job classification, by shift, together with geometric means,
the geometric standard deviation, and the concentration range for each shift.
The geometric standard deviation (GSD) is used as an indicator of variability.
Variability can be caused by such factors as:

1) Small changes in ambient solvent concentration and operational
differences; for example, start-ups and shut-downs of metiers generally
take place on the day shift, and such activities can have a slight effect
on concentrations in the immediate area of the metier.

2) Different operators do the same task in different ways--some get closer
to the equipment, some take longer or shorter times to complete a
task, etc.

As used here, a GSD < 1.0 indicates little variability in the results, while a
GSD > 2.0 indicates relatively high variability.

It can be seen in Table 4 that two job classifications have GSDs greater than
2.0: Patroler, Block I, and Coning Operator. For Block I Patrolers, there was

a great variability between samples, and three of the sample results were excluded
from the computation (see Table 3). The 69 ppm concentration for the Patroler

26


sampling was limited to a single shift because of difficulties in scheduling air-
craft for the operation. (Area sampling for the presence of ammonia from the
stripping compounds, also carried out, is discussed separately in this chapter.)

PERSONAL SAMPLING AND ANALYSES

Personal sampling employed MDA Accuhaler” pumps, at Plant A and Plant C, or Ben-
dix BDX-44 pumps, at Plant B, attached to belts or clothing worn by the workers.
Each pump was connected by Tygon tubing to the sampling medium, which was com-
posed of two SKC charcoal tubes in series--a large one, 600 mg of charcoal, in
front (upstream) and a Standard one, 150 mg of charcoal, in back (downstream) .
All tubes were from SKC Lot 106, with the exception of the Standard (backup)
tubes in the assemblies at Plant B, which were from Lot 28. The tubes in the
assemblies were connected by Tygou® tubing, which was kept at a minimum. Two
tubes were used to keep completed methylene chloride samples from migrating due
to the compound's high vapor pressure; also, use of two tubes would detect over-
loading, or pulling through, of methylene chloride during the sampling operation.
The entire charcoal content (600 mg) of the front, or upstream, tube was combined
(the charcoal in the tubes is divided into two-thirds and one-third sections) to
yeild the primary sample, while the smaller (150 mg) tube located behind con-
stituted backup (and was analyzed separately) .

The sampling pumps were used to draw air through the charcoal tubes at a nominal
rate of 20 milliliters per minute at Plant A and Plant C, 50 ml/min at Plant B.
The pumps were calibrated (and rechecked after use) using a bubblemeter (inverted
buret).

Personal sampling of workers on full-shift jobs was conducted over the total
working shift at Plant B. At Plants A and C, while sampling was performed for
less than eight hours, the nature of the operations are such that the exposure
for the individuals would not be expected to vary. Hence, a time-weighted
average (TWA) was calculated for every person on an eight-hour basis. The
calculation was:

24,450 x mg per liter

TWA (ppm) = Mu

ppm = parts of methylene chloride vapor per million
parts of air

Mw molecular weight (methylene chloride = 84.93)
mg per liter = milligrams of methylene chloride in
one liter of air sample collected.

At Plant B, because of the nature of the operation, each job type was sampled
separately. When a task was to be performed that would expose a worker to a
potentially higher than normal concentration (e.g., quality control sampling),
an additional sample was taken during the full length of time of the task to
determine ceiling concentrations.

The methylene chloride samples were analyzed at an SRI International laboratory
(accredited by the American Industrial Hygiene Association) using the NIOSH-

23;


5. Individual personal and area TWA concen-
trations of methylene chloride at
Plant B, week of November 6, 1979

6. Job and work-shift TWA concentrations
of methylene chloride at Plant B,
week of November 6, 1978 ........ ~- 34

7. Personal TWA concentrations of
methylene chloride at various
locations during an aircraft
paint stripping operation
at Plant C, May 15, 1979 .......-.- - 36

+ » 32

vi


CONTENTS

Preface: ~ 2 3. « sheqeu thee pYorsueumss © + « Lad.
Abstract) 2 = 7 = » -an?imemes-ssr-0s 8- el . LV
Introduction . . . 6 «ss 0 2 ee ee ew ww iL
Background . . p00 500 9050 Ff
Facilities and Resco “uA go009 00095 8
Survey Procedures and Methods .......... 22
Results and Recommendations ........... 26
References . 2... eee ee ee ee ee ee ee FD
Appendices .. ee ~. 46

A. Residual mavtilen chloride ev “the
decaffeinated coffee beans and crude
coffee, as reported by Plant B,

November 1978 ........ oe. 40
B. Results of sampling for aware
and methanol at Plant A ........ 41

C. Results of sampling for ammonia
from the paint stripping compounds

used at Plant C ..........4.. 47
FIGURES
1. A schematic diagram of producing methylene
chloride by chlorination of methane .... 6
2. A schematic diagram of producing methylene
chloride by hydrochlorination of methanol . 6
3. A schematic diagram of the process
of making triacetate fibers ........ 11
4. A schematic diagram of the process
for producing decaffeinated coffee .... 12
5. Layout of the aircraft paint
Stripping at Plant © =. 2-2... >. . 14
TABLES

1. Chemical and physical data

for methylene chloride ....... - &
2. Principal ingredients of compounds used iin

paint stripping operations at Plant C... 15
3. Individual personal and area TWA

concentrations of methylene chloride

at Plant A, May 16-17, 1979 ........ 27
4. Job and work-shift TWA concentrations

of methylene chloride at Plant A

ew dail, IE) 5 ooo 6 oe oo 8 SM)

v


green beans ———__>

water extraction

<< _water solution

beans separation water extract
washing methylene methylene chloride
contactor columns
chloride sos
water
drying
solvent & caffeine extraction
finishing
condensation | fractionation
and
ean evaporation
methylene “|
chloride
methylene
caffeine “chioride

Figure 4.

a)

A schematic diagram of the process
for producting decaffeinated coffee.



a highly unusual exposure situation during a sampling period of several shifts
was remote; therefore, the resulting exposure measurements can be considered to
represent only those exposures that are associated with the usual and normal
operating conditions.


(continued)

Job classification Workers per shift
Maintenance (for all areas) 5
Maintenance Supervisor 1

Job descriptions of each of the operators, as furnished by the company, are as
follows:

Evaporator Operator: This operator is responsible for the methylene chloride
evaporation system, the clean-solvent storage system, and caffeine recovery
system. He maintains records on all of those systems and is continuously
monitoring and adjusting the equipment to maintain proper levels in all of
the tankage. This worker spends the majority of time on the second and
third levels of the decaffeination facility.

Coffee Handler: This operator is responsible for the decaffeinated coffee
from the time it enters the bean drying system, through the storage silos,
to the user area. He controls bean moisture; maintains the identity of
beans, by batch and silo location, and is also responsible for taking
inventories of beans. This worker spends most of his time on the second and
third levels of the process facility.

Extractor Operators: These operators are responsible for the extractors and
their storage tankage. They maintain records of the operation and adjust,
control, and maintain proper levels in their vessels. ‘These operators
spend the majority of their time on the second level.

Process Operators: These operators are responsible for the rotating disc
columns, the extract solvent stripper, the wastewater stripper, and the
carbon adsorption system. They maintain records on their systems and
adjust, control, and maintain proper operating conditions and levels.
These operators spend the majority of their time throughout the facility
or in the control room.

Although not included in this list of workers, the caffeine dryer operator was
included in the study since he spends most of his time on the first level of
the extraction process and could be exposed to methylene chloride vapor.

The exposure duration for these workers is quite variable; however, the potential
exposure to methylene chloride in the decaffeinating facility is up to eight
hours per day.

Plant C--Personnel

There are 106 persons who work in the aircraft stripping operation at Plant C.
They are all designated as Paint Strippers (with a job grade of WG-5). They
work on a three-shift, five-day-per-week schedule. At the time of the survey
made for this study, 22 Paint Strippers were working an aircraft, each stripper
responsible for an assigned area of the plane. General area assignments are:

18


WeEGIeINUG/NE l= lage

Extent-of-Exposure Survey
of Methylene Chloride

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service

Center for Disease Control

National Institute for Occupational Safety and Health


Appendix B. Results of sampling for acetone
and methanol at Plant A

Results of sampling for acetone at Plant A are shown in Table B-1. Since the
purpose of this study was to determine the exposure of personnel to methylene
chloride, the personnel monitored in Block I were those involved with production
of triacetate yarn, and not with the acetate. Disregarding the one questionable
sample, the range of exposure values were from 4 ppm for a Pressman working in
the Preparation Area of Block II to 574 ppm for a patroler in the Extrusion
Area of Block I. (Two results from company-collected samples indicated concen-
trations of 768 ppm and 747 ppm for the Patroler and the Jetwiper, respectively,

in Block I.)

At the recent meeting of the Threshold Limit Value (TLV) Committee of the American
Conference of Governmental Industrial Hygienists (ACGIH) (in May 1979), an
intended change was proposed for acetone, lowering the TLV from the current 1000
ppm to 750 ppm. This intended change will remain as a notice for at least two

years, after which it may become adopted as a recommended TLV by the ACGIH.

Results of area sampling for the presence of methanol in the filter press area of

the Preparation Department at Plant A are shown in Table B-2.

41


where:

c(cO) = TWA carbon monoxide, ppm

L(CO) = recommended TWA carbon monoxide, ppm
C(CH,C1,) = TWA methylene chloride, ppm
L(CH,C1,) = recommended TWA methylene chloride, ppm

Several other effects have been attributed to methylene chloride exposure.
A study published in the Soviet Union reported that methylene chloride was
found to cross the placenta in pregnant workers;10 some teratogenic effects,
including cleft palate and rotated kidneys, were observed in experimental
animals;! and the chemical has also been found to be mutagenic in salmonella
typhimurium and E. coli that were exposed for 6-8 hours in a desiccator to
concentrations as low as 11 ppm. il

The Eastman Kodak Company recently reported on the results of an epidemiologic
study of a large working population exposed continuously to relatively low
levels of methylene chloride for up to 30 years. 12 The purpose of the study

was to determine whether employees exposed to methylene chloride exhibited an
increased risk for specific causes of mortality, specifically ischemic heart
disease, that could be attributed to the work environment. Air sampling re-
sults based on each sample obtained in the work area revealed a methylene
chloride concentration range of 0-350 ppm with a mean value of less than 100 ppm.
Continuous personal monitoring showed a time-weighted average concentration of
33 ppm.

While the results were not reported in complete detail, those that were pub-
lished indicate no excess mortality for ischemic heart disease in the produc-
tion workers exposed to methylene chloride. It would be helpful, however, to
have a detailed presentation of standardized mortality ratios for ischemic
heart disease, to know more about the selection procedure for hiring production
workers; to see if the results change when the 7% of employees who have termi-
nated are also included; and to learn whether the results are supported by an-
other mortality study being performed by Dow Chemical and Celanese Corporation.

PROCESSES FOR PRODUCING METHYLENE CHLORIDE

Methylene chloride is commercially produced by two major processes: one
beginning with the chlorination of methane, the other with the hydrochlori-
nation of methanol. (See Figures 1 and 2.)

In the production of methylene chloride as a second step in the chlorination

of methane, pre-heated gaseous methane and chlorine are forced into a reactor,
where ultraviolet light from mercury-arc lamps promote the reaction. The
temperature within the reactor is maintained at about 360°C (although some
plants use temperatures at 450°-500°C to obtain particularly high yields of
methylene chloride). It has been found that a ratio of 1.7 moles methane to

1 mole chlorine yields about 30% methylene chloride in the resultant chloro-
methane product mixture. If, however, the feed gas contains two volumes methane
to one volume each of chlorine and (probably recycled) methyl chloride, the
yield of methylene chloride may be as much as 80% of the total product mixture.

The basic chlorination reactions involved are as follows:

5


Table 1. Chemical and physical data for methylene chloride.

Chemical formula: CHCl,

Some chemical and physical properties:

Freezing point -97°C
Boiling point (760 mm HG) 40.4°C
Specific gravity (20°C) 1.320
Density (20°C) 1315.7 kg/m3
Molecular weight 84.93
Vapor density (Air = 1.02) 2.93
Diffusivity in air:25°C, latm 9x 10> a fice
Refractive index (20°C) 1.4244
Auto-ignition temp. 640°C
Flash point none
Explosive limits: (25°C,

vol. in air) 14-25%
Solubility (H,0, 20°C) 13.2 g/kg
Vapor pressure (0°C) 147 mm Hg

at 20°C 349

at 30°C 511

Source: Compiled from Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Ed.,
Vol. 5. New York, Wiley-Interscience, 1979, p. 687.


SUMMARY AND RECOMMENDATIONS

From the data collected during this exposure-level survey, the following summaries
and recommendations are made:

TWA personal exposures of workers at Plant A to methylene chloride were
found in some instances to exceed the current Federal OSHA standard of
500 ppm, although long-term Plant A data and State OSHA data show the
facility to be in compliance with the Federal OSHA standard. Continued
and careful monitoring and evaluation of the work-exposure situations
should be performed in an effort to minimize exposure of personnel to
methylene chloride.

The Dow Chemical-Celanese epidemiologic study referred to under "Toxicity
and Human Exposure Standards" in the "Background" chapter of this report
should be reviewed by NIOSH to determine whether it meets the NIOSH re-
quirements of this type of study.

The 8-hour TWA exposures of workers to methylene chloride during normal
operations at Plant B, averaging 2.9 ppm, were found to be well below
the current OSHA standard and the American Conference of Governmental
Industrial Hygienists (ACGIH) recommended Threshold Limit Value (TLV) of
200 ppm. This is due principally to the fact that the decaffeination
process is in a closed system that is rarely opened. Levels of methylene
chloride in the atmosphere at the Plant are highest during quality-control
sampling of the product or during a system failure. (During the failure
that occurred in the course of this survey, concentrations of methylene
chloride were higher than usual, but even then they were still below

the OSHA standard and the TLV of the ACGIH.

The analytical method used by the Plant B company for determining the
presence of methylene chloride from long-term sampling with charcoal
tubes proved to be highly reliable and effective, especially at concen-
trations below the OSHA standard. NIOSH method $329 may not have the
sensitivity necessary for precise determinations at such lower concen-
trations.

Time-weighted-average personal exposures to methylene chloride in the
work-area atmosphere at Plant C, ranging from 15.7 to 268 ppm and
averaging 64 ppm, were below the current OSHA standard of 500 ppm and,
with one exception, were below the ACGIH recommended TLV of 200 ppm.
The single sample in which 200 ppm was exceeded (268 ppm) was for a
worker in the wheel well of the aircraft, indicating less ventilation
at this location than at other locations around the aircraft. The
installation of an auxiliary fan at the wheel.well location should be
considered to dissipate the build-up of paint stripping vapors.

The new facility for depainting of aircraft appears to be well designed
and equipped to maintain potential worker exposure within the current
OSHA standard.

A reassessment by NIOSH of methylene chloride toxicity has resulted in
a recommendation that the OSHA standard for the substance be lowered to
75 ppm, and it can be seen in the survey results in this report that a

EY:


Carbon monoxide samples were taken with Draeger short-term and long-term indi-
cator tubes. The short-term tube samples were taken with a Draeger hand-held
bellows pump; the long-term tube samples were taken with an MDA Accuhaler®
pump. (In the presence of carbon monoxide, an indicating layer in the tubes
discolors from white to brownish-green, and the length of the discoloration
corresponds to the carbon monoxide concentration in parts per million.)

Plant C--Other Substances

Several area samples of air at Plant C were collected to detect the presence

of ammonia from the stripping compounds used. In this sampling, both stationary
and hand-held apparatus were used. The stationary samplers consisted of Draeger
indicator tubes, a dilute (10 ml) solution of sulfuric acid, midget impinger,
and a Bendix BDX-44 pump that drew air through the absorbing solution at the
rate of 1 liter per minute. Flow rate was determined by calibration with a
bubblemeter and was checked periodically during the sampling period. These
samplers were attached to the railing of the elevated platform in the stripping
facility, and samples were collected for periods of one hour at several inter-
vals during the day.

Following collection of the samples, the absorbing solution was transferred
into glass vials and capped. Analysis was performed using NIOSH Method No.
P&CAM 205, in which Nessler reagent is added to the collected sample to produce
a yellow-brown complex. (The absorbance of the yellow-brown solution at 440
nonameter is read on a spectrophotometer and compared with a standard curve

to determine the ammonia concentration.)

Ammonia concentrations were also measured with a Draeger indicator tube and a
Draeger hand-held bellows pump, a procedure in which air is drawn through the
indicating packing in the glass tube. In the presence of ammonia, the packing
turns from a yellow color to black, the length of stain or discoloration corres—
ponding to the concentration of ammonia present. In several locations, the
detector tube indicated the short-term concentration to be approximately 1 ppm;
and in one instance, the level detected was approximately 5 ppm.

cS)


Table B-1. Results of personal sampling for
acetone at Plant A, May 16-17, 1979.

Sample number and location

TWA concen-
tration (ppm)

Patroler, Block I
Doffer, Block I
Jetwiper, Block I
Patroler-Doffer, Block II
Doffer, Block II
Jetwiper, Block II
Bobbin Stores Operator
Creeler, Textiles
Lacer, Textiles
Coning Operator
Beamer, Line 3

Operating level, Block II
between Metiers 58 and 59

Operating level, Block II
between Metiers 62 and 63

Catwalk, Block II
between Metiers 58 and 59

Blank
Coning Operator
Beaming, Gauging Operator

Creeler

(continued)
42

91.1

340.2

54.9

44.4
21.6
86.5
113.9
27)
yaleal

HS) 5 f3)

96.5

a)

SY / oF!

585.6%

63.2

137.0


approved analytical method $329, with minor adjustments in technique: the NIOSH
method calls for desorption of the charcoal sample using 1 ml of carbon disulfide;
however, since 600 mg of charcoal were used in the primary adsorbing tube, 2 ml
of carbon disulfide were used to desorb. A desorption time of at least 30 minutes
was used. Following desorption, a portion of the sample was injected into a gas-
liquid chromatograph equpped with a flame ionization detector. The area under
the sample peak was measured and integrated, and the results were read directly
from a standard curve that was prepared earlier from injections of known quanti-
ties of methylene chloride.

In the case of Plant B, the decaffeination facility, the samples were also anal-
yzed using a method developed by the company that operates that facility. This
method calls for desorption of the charcoal using 2 ml of toluene. Like the
method described above (NIOSH $329), the Plant B method requires desorption for
at least 30 minutes, but electron capture, rather than flame ionization detection,
is used. Desorption efficiency (DE) tests that were made for the NIOSH-approved
analytical method indicated good precision. The average DE was 0.97 + 0.02
(from 18 samples), and recovery was also very good, with an average recovery

of 0.95 + 0.03 for 17 samples (approximately three in each of six test levels--
one-half, one, and two times the OSHA TWA and ceiling permissible contentrations) .
Desorption efficiency tests of the Plant B method also indicated good precision:
the average DE was found to be 0.85 + 0.02 (from four samples). The company
reports an average DE of 0.96 from its tests of desorption efficiency. Both

DEs were performed within the range of methylene chloride found in the company's
plants.

SAMPLING FOR OTHER SUBSTANCES

As noted previously in this chapter, sampling was carried out for several poten-
tially toxic substances, other than methylene chloride, that might be expected
to be found in conjuction with methylene chloride. This sampling is discussed
below.

Plant A--Other Substances

Sampling for methanol at Plant A was performed using silica gel tubes and Bendix
BDX-44 pumps. The samplers were positioned close to the filter presses when they
were being dismantled and were allowed to operate for approximately four and one-
half hours at the rate of 50 ml per minutes. (Flow rates were calibrated with a
bubblemeter). Following collection of the sample, the tubes were capped, refrig-
erated, and sumitted to the analytical laboratory for analysis using NIOSH-
approved method S59.

Plant B--Other Substances

Area sampling for coffee dust and for carbon monoxide (which is a metabolic
product of methylene chloride) was carried out at Plant B.

Both total and respirable coffee dust samples were collected on preweighed, 37-
mm-diameter, 0.8-ym-pore-size polyvinyl chloride filters in a three-piece
cassette filter holder. Respirable dust samples were also taken on the same
filter media preceded by a Bendix BDX-99 10 mm cyclone assembly. Samples were
taken for 8 hours at a nominal flow of 2 liters per minute for the total coffee
dust sample and 1.7 liters per minute for the respirable dust samples.

24


INTRODUCTION

Under the terms of the authority and responsibility given to the National Insti-
tute for Occupational Safety and Health (NIOSH) to develop needed information
regarding potentially toxic substances in industry (see Preface), NIOSH contrac-
ted with SRI International to conduct an industrial hygiene study to assess
exposure to four chlorinated hydrocarbons. Chlorinated hydrocarbons were selec-
ted as an area for study because vinyl chloride has been shown to be a human
carcinogen and because a growing number of the compounds have been shown by re-
search to be known animal carcinogens and suspected human carcinogens. The four
compounds selected for study-~benzyl chloride, monochlorobenzene, methylene
chloride, and methyl chloride--were chosen on the bases of: the industry in
which the compound is produced or used; history of production and use; processes
and related new materials involved; and number of workers potentially exposed.
The report that follows concerns industry exposures to methylene chloride.

OBJECTIVES AND SCOPE OF THIS STUDY

The objectives of this industrial hygiene study were to:
e@ Review and summarize the toxic effects of methylene chloride.

@ Document and describe selected workplaces, including information on the
production and use of methylene chloride.

e@ Identify job types and describe specific jobs.

© Describe current industrial hygiene and safety practices, including engi-
neering controls, work practices, administrative controls, and biological
and environmental sampling and control procedures.

@ Document (1) job-function exposures to methylene chloride and (2) relevant
process or production changes occurring during the survey that could affect
the evaluation of job-function exposures.

©@ Describe analytical procedures for collection and analysis of methylene
chloride.

Detailed industrial hygiene surveys reflecting these objectives were made at
three U.S. facilities where methylene chloride is used. These detailed surveys,
which had been preceded by preliminary surveys of seven facilities, were con-
ducted during the period November 1978-May 1979.

LIMITATIONS OF STUDY

The industrial hygiene surveys represent singular evaluations of worker expo-
sures to methylene chloride and do not reflect possible variations in exposure
due to seasonal or operational changes. An attempt was made to evaluate expo-
sures for each job type as encountered during all work shifts. These studies
were made during, periods of normal production. The possibility of encountering

1


Table 2.

Principal ingredients of compounds used
in paint stripping operations at Plant C.

Ingredient
Product
Substance Percent*
Turco 5351 Thin Phenols 24
Methylene chloride 48
Caustic soda 1
Water, soaps, and corrosion inhibitors
Turco 5873 Methylene chloride 58
Water 18
Ammonia 2
Xylene 3
Pine oil 6
Chromate as total Cr. (2000 ppm)
Pennwalt 739-A Methylene chloride aD
(hot strip) Sodium chromate 1
Phenols Als}
Eldorado PR-3400 Methylene chloride 7P)
Tetrahydrofuran 2
Ethanol 4
Ammonium hydroxide 6
Potassium hydroxide hs
Inland Chem. Co. AP-599 Methylene chloride 75
Perchloroethylene 2
Petronate HL 6.7
Ammonium hydroxide ipl
Methanol 8.8
Sodium chromate 0.5
Intex 857 Methylene chloride 50
Aliphatic and aromatic hydrocarbons 25
Nonvolatile aliphatic and aromatics 11
Water and ammonia ls)
Chromates 0.16

Pennwlat 768-A*

Alodine

Chromate salts

Nitric acid
(Ph--1.5-2.0)

Inert ingredients

1/2-3 oz/gal
8-12 mg/gal

a
Except where noted.

4
Data not readily available (phenolic-type paint remover) .

15


Table 5. Individual personal and area TWA
concentrations of methylene chloride
at Plant B, week of November 6, 1978.

TWA concen-

Job title/location and sample number cearisionn (ges)

Personal samples

Process Operator

Extractor Operator

Evaporator Operator

Coffee Handler

General Laborer

6C

11c*
UbYere
21C
26C
38C
41¢

8c
126%
27C
36C

2c
13¢c*
16c*
22¢
23¢
37¢

(continued)

32

Nw
NNONNSOOU

NOE
SCOCHPREPUBANFSEN
SCHOLOWADY

Or RUWORNAULD

BRU
HNO

DO e
CrRwWS RY CFO
WOwwo

DAnUFON


Table 5. (continued)

TWA concen-

Job title/location and sample number canon (eps)

Caffeine Dryer Cperator 4c 12.6
25C ea
43C 0.5

Short-term sampling--
during quality control

Coffee Handler 33¢ 0.3
Extractor Operator 34C 0.9
Process Operator 35C Sal
Area samples
5th floor
Above S5 burp tank 44C 0.50
Between #3 & #4 sludge tanks 45C Tas
RDC’ draw off 28C .
Between Swing &
#1 fractionator 47C 2.08
2nd floor +
S6 #1 column, RDC area 30C 0.52
S6 control room 32¢ 0.05
1st floor--caffeine
dryer operator desk 31¢ 1.46
(Blanks) Bp't

ences the evening shift (first day of sampling), a relief valve began to lift
and pressurize in the wastewater recovery system, causing amounts of wastewater
containing solvent to back up into the drain system for an undetermined length
of time. Under this upset condition, concentrations of methylene chloride
determined on these workers may be higher than normal.

+Rotating disc contactor (colum).
t+tBelow detectable limits.

88


DEPARTMENT OF HEALTH AND HUMAN SERVICES
PUBLIC HEALTH SERVICE
CENTER FOR DISEASE CONTROL,
NATIONAL INSTITUTE FOR OCCUPATIONAL SAFETY AND HEALTH
ROBERT A. TAFT LABORATORIES
4676 COLUMBIA PARKWAY, CINCINNATI, OHIO 45226

OFFICIAL BUSINESS
PENALTY FOR PRIVATE USE. $300

Third Class Mail

POSTAGE AND FEES PA
U.S. DEPARTMENT OF t
HHS 396

DHHS (NIOSH) Publication No.80-131


The Bioenvironmental Engineering Services Division consists of four military
officers, one civilian industrial hygienist, two civilian industrial hygiene
technicians, and five military industrial hygiene technicians. An annual,
routine sampling survey, in which charcoal tubes are utilized, is made for
methylene chloride, ammonia, and phenols. This survey is augmented by sampling
that is conducted when a problem arises, when special projects are undertaken,
or when new materials are tested.

Pre-employment physical examinations are required of all Air Force personnel
(except those in clerical positions). These physicals include medical history,
audiograms, chest X-ray, EKG (if over the age of 40), vision tests, serology,

and urinalysis. Annual examinations are required for certain jobs (paint stripping
is a required job group) and are tailored to the exposure. Annual physicals are
similar to the pre-employment examination. Those workers who perform paint
stripping receive annually, in addition to the tests already mentioned, SGOT,
audiometric examination, total blood count, and urinalysis. Exit physicals are
required in certain jobs, such as those that expose workers to high levels of
noise.

Personnel working in the depainting areas are required to wear protective
clothing, which includes coveralls, monogoggles, rubber gloves, and safety shoes
or rubberized boots. Organic-vapor-cartridge, half-mask respirators had been
required for the stripping operation when it was carried out in a building used
prior to the construction of the facility referred to previously; however, with
the exhaust ventilation system in the new facility, respirators are no longer
required. Workers are able to change from their work clothing in the locker
room of the new facility, and the clothing may be left to be laundered by a
private contractor.

2


PREFACE

NIOSH has been granted the authority and responsibility under the "Occupational
Safety and Health Act of 1970" to conduct field research studies in industry,
evaluate findings, and report on these findings. Section 20(a)7 of this Act
states that NIOSH shall conduct and publish industrywide studies of the effects
of chronic or low-level exposure to industrial materials, processes, and stresses
on the potential for illness, disease, or loss of functional capacity in aging
adults. Section 22(e) provides the authority to enter into contracts, agreements,
or other arrangements with appropriate public agencies or private organizations
for the purpose of conducting studies relating to responsibilities under the Act.
For this purpose NIOSH established a contractual agreement with SRI International
to perform an extent of exposure study of methylene chloride. The funding for
this work was provided by the Division of Cancer Cause and Prevention, National
Cancer Institute, through the Interagency Agreement on Research on Occupational
Carcinogens (Y-01-CP-60605).

iii


Appendix A. Residual methylene chloride found in
decaffeinated coffee beans and crude
caffeine, as reported by Plant B,
November 1978

Decaffeinated beans

Sample date Average methylene Number of
(month/year) chloride (ppm) samples
5-78 0.35 295
6-78 0.35 115
7-78 0.42 208
8-78 0.36 230
9-78 One 174

Crude caffeine

Sample date Methylene
(1978) chloride (ppm)
10-17 0.14
10-26 0.10
11-1 0.24
a3) 0.13

40


number of personal exposure levels exceed such a figure, particularly
ones at Plant A (two at Plant C). It would appear that compliance with
a 75 ppm standard could present a significant problem in connection with
production operations of the type carried out at Plant A (see "Facilities
and Personnel Surveyed" in this report). At Plant C, it would appear
that utilization of the full capacity of the facility's exhaust system,
augmented if necessary, with an auxiliary fan at the aircraft wheel well
location as noted above, could provide the necessary ventilation.

With regard to sampling that was conducted for substances other than
methylene chloride: airborne concentrations of acetone (Plant A) were
well below the OSHA standard of 1000 ppm; concentrations of methanol
(Plant A) were well below the OSHA standard of 200 ppm; and sampling
for carbon monoxide and coffee dust (Plant B) revealed only trace and
neglible amounts.

38


FACILITIES AND PERSONNEL SURVEYED

Three facilities at which methylene chloride is used were surveyed for this
report: a plant that manufactures acetate and triacetate fibers; a coffee
processing plant; and a U.S. Air Force base at which one of the principal
missions is maintenance of aircraft and other equipment. In an attempt to
provide as much of an exposure cross-section. as possible, the plants were
selected on the basis of such criteria as number of persons potentially exposed;
level of substance concentrations as determined by preliminary area sampling;
continuous operations and therefore relatively constant exposure levels; expo-
sure situations limited primarily to the target chemical; unique use of the
substance; and process representative of a major use of the.substance.

The facilities are designated as Plants A, B, and C in this report. They are
briefly described below, followed by descriptions of their process and control
operations, personnel and jobs in which potential exposure to methylene chloride
occurs, and health and safety programs that have been established.

DESCRIPTION OF FACILITIES
Following are brief overviews of the three facilities surveyed for this report.
Plant A--Overview

At this facility, located in the Southeast, methylene chloride is used in the
conversion of cellulose acetate and triacetate flake into fibers. Production
of fibers, which began in 1948, is carried out in four major buildings, desig-
nated as: (1) Cellulose Acetate, (2) Block I Extrusion, (3) Block II Extrusion,
and (4) Textile. The plant operates continuously--24 hours per day, 7 days

per week.

Plant B--Overview

Principal operations at Plant B, located in the Southwest, have been concerned
since 1947 with the processing and packaging of coffee. A decaffeinating
facility, in which methylene chloride is used as a solvent, began operations
in the early 1950s. The company reports that this decaffeinating facility is
the largest of two that it operates in the United States. Prior to mid-1975,
the solvent that had been used in decaffeination (for some 20 years) was tri-
chloroethylene.

Plant C--Overview

Plant C, one of several installations of the U.S. Air Force Logistics Command,
began operations in 1941. About one third of the installation's operations, as
measured in terms of persons, is concerned with the maintenance of Air Force
aircraft and other equipment. A part of this maintenance activity, in turn, is

8


The operations involved in producing triacetate fiber are illustrated in Figure 3.
Plant B--Process and Control

Methylene chloride is used at Plant B in the extraction of caffeine from green
coffee beans. The extraction process is carried out throughout eight levels of
a 14-level, partially enclosed structure.

The method of removing caffeine from the coffee beans is called solvent extrac-
tion (the leaching of a soluble substance from a solid using a liquid solvent).
In this continuous process, caffeine is first extracted from green coffee beans
in an extractor colum. The now caffeine-rich extract is then fed to a rotating
disc contactor (RDC) column in which a countercurrent liquid/liquid process re-
moves the caffeine, using methylene chloride as the single solvent. Following
this step, the water is stripped of its residual solvent by fractionation and
recycled to the process; also, the solvent from the RDC is purified by distilla-
tion and is recycled. The entire process is illustrated in Figure 4. There are
negligible amounts of solvent residue in the decaffeinated beans and in the crude
caffeine, according to data collected by the company (see Appendix A).

The process was reported to be operating at about two-thirds capacity during the
time of this survey. Each month, the process uses approximately 5100 gallons of
methylene chloride, most of which leaves the facility in the wastewater or through
a carbon bed vent system.

Two sets of quality-control product samples are taken by two different operators
once each shift. In one set, an operator collects decaffeinated beans, prior

to the drying stage, with a cup attached to a long handle. This worker removes
a cover, opens a port to where beans are flowing through a four-inch pipe, lowers
the cup into the port opening, and draws out a sample, which he places in a
plastic bag. The port is then closed. The operator's exposure to methylene
chloride during the collection of these samples is negligible.

Another worker obtains samples of the solvent extract from the top of the rotating
disc colum, where the solvent is flowing through a series of water-chilled
sampling loops. For this set of samples, the worker opens a series of valves

and places a glass jar under a spout, which is then opened until the jar is
filled. During this sampling the operator wears protective gloves. Although a
small amount of the extract drips onto the floor, the sampler's exposure to
methylene chloride is negligible.

The company reports that the in-plant air is routinely monitored for methylene
chloride and that bag or syringe grab sampling and also sampling using charcoal
tubes are performed. Syringe grab sampling using 1 cc plastic disposable syringes
was observed by the survey team. Samples are taken to a laboratory on the plant
site where they are analyzed by gas chromatography with a flame ionization
detector. A 5 ppm standard is injected into the gas chromatograph before and
after each set of samples is analyzed.

Plant C--Process and Control

Methylene chloride is used at Plant C as the major constituent in stripping
compounds for removing paint from the outer skin of aircraft. The bulk of the
paint stripping operations are conducted in a newly-constructed depainting

10


DISCLAIMER

The contents of this report are reproduced herein as
received from the contractor.

The opinions, findings, and conclusions expressed
herein are not necessarily those of the National
Institute for Occupational Safety and Health, nor
does mention of the company names or products consti-
tute endorsement by the National Institute for Occu-
pational Safety and Health

NIOSH Project Officer: Michael S. Crandall

SRI International Project Leader: Masao Koketsu

DHHS (NIOSH) Publication No.80-131

dei


on the day shift is also somewhat suspect but was not excluded. There was also
a high variability in data for Coning Operators, and one sample, collected during
the night shift and showing a concentration of 572 ppm, was excluded from the
computation. (Ambient concentrations of methylene chloride in this area have
been determined by Plant A monitoring personnel to be less than 200 ppm.)

For all the job classifications, some variability in the exposure levels occurs
from shift to shift, even though the operations are continuous and constant.
Week-to-week variations may also occur, due to changes in the size of yarn being
produced--i.e., smaller-denier giving off less vapor than the larger—denier
filaments--and changes in the production rate.

In several cases, the survey results indicate that the OSHA standard of 500 ppm
for an 8-hour TWA exposure was exceeded. However, only one duplicate sample
made by Plant A monitoring personnel exceeded 500 ppm; also, long-term sampling
and analyses by the Plant, and confirmed by a recent State OSHA industrial hy-
giene survey, show that the facility has been, and continues to be, in compliance
with the current Federal OSHA standard.

Almost all of the samples from the Patrolers, Doffers, Jetwipers, and Pressmen
exceeded the Threshold Limit Value (TLV) of 200 currently recommended by the
American Conference of Governmental Industrial Hygienists (ACGIH), and some of
the samples collected for Bobbin Stores Operator, Lacer, and Beaming Operator
were also above the 200 ppm level. Samples for Creeler and Coning Operator did
not exceed the 200 ppm TLV.

RESULTS OF SURVEY--PLANT B

Time-weighted average personal and area concentrations of methylene chloride
during decaffeination operations at Plant B are shown in Table 5. The personal
sampling data are shown in Table 6 in the form of concentrations for each job
classification, together with geometric means, the geometric standard deviation,
and the concentration range for each shift. (See "Plant A," above, for more
information on use of the geometric means and deviations.)

All of the concentrations are well below the OSHA permissible exposure limit of
500 ppm, and the ACGIH recommended TLV of 200 ppm. The range of 8-hour expo-
sure concentrations varied from 0.3 to 33.2 ppm, with an average concentration
of 2.9 ppm.

As noted in Table 5, higher personal sample concentrations recorded during the
evening shift are most likely from a system upset that occurred; moreover,
residual quantities of methylene chloride from that upset most likely caused an
elevation in samples of area concentrations, which were taken during the shift
following the system upset. Full-shift area samples obtained by the survey team
during the second day varied from 0.05 to 2.08 ppm (see Table 5).

The highest exposure concentration of methylene chloride was recorded in the
Process Operator job category, which had a mean exposure of 5.1 ppm. ‘The
company reports an average exposure of 5.7 ppm from the sampling it performed
over the past year for this job category. The range of values recorded for
Process Operator varied from 0.9 to 30.6 ppm, with the highest levels recorded
during the evening shift. (See above and footnote in Table 5 for this shift.)

31


Location _ Number of Workers

Nose

Fuselage, front
Fuselage, center
Fuselage, top
Wing, engine
Wing

Wheel Well

Tail Section

PwWWNNNNSE

Each worker masks off, applies stripper to, and washes down his or her assigned
area. In addition to the personnel identified above, there are supervisory
personnel, drivers, maintenance personnel, and other "depainter" personnel who
may be exposed intermittently to methylene chloride. The exposure duration for
these workers is quite variable; however, for most of the paint stripping crew,
the exposure to methylene chloride may be up to eight hours per day.

HEALTH AND SAFETY PROGRAMS

Each of the facilities surveyed has a formal health and safety program, which
are described below.

Plant A--Health and Safety

The health and safety program of Plant A is under the direction of an Environ-
mental Superintendent, whose responsibilities include directing the efforts of
the plant safety committee, comprised of both management and hourly employees.
This committee conducts department inspections and assists in resolving problems
relating to safety and health. The Environmental Superintendent has direct
responsibility for the plant safety and environmental program and has a staff
of eight persons.

There is an environmental technician at the plant who performs periodic measure-
ments and monitoring of work operations for assessing employee exposure to various
chemicals, including methylene chloride (using charcoal tubes and a direct—
reading portable gas chromatograph). Also available for technical assistance

are industrial hygienists from the corporate staff located in New York City.

The medical needs of Plant A are handled by a nurse on each shift and by a
physician employed part-time. They conduct pre-employment physical examinations
and periodic examinations, as well as handling injury and illness cases. Some
85 persons throughout the plant have been trained in first aid and are able to
provide immediate care in the event of an accident.

Medical monitoring is being provided to employees exposed to certain hazardous
or toxic chemicals, including asbestos (insulation), chromic acid, and benzene.
Also, periodic audiometric examinations are given to employees working in areas
designated as high-noise exposure areas. Exempt salaried personnel are given
biannual or annual physical examinations depending on age.

Personal protective equipment in general is not required in most areas of the
plant. However, for persons working in areas of the Textile and Extrusion

19


EXTENT-OF-EXPOSURE SURVEY OF METHYLENE CHLORIDE

Joel M. Cohen
Robert Dawson
Masao Koketsu
SRI International
Menlo Park, CA 94025

Contract No. 210-76-0158

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service
Center for Disease Control
National Institute for Occupational Safety and Health
Division of Surveillance, Hazard Evaluations, and Field Studies
Cincinnati, Ohio 45226

August 1980

For sale by the Superintendent of Documents, U.S, Government
Printing Office, Washington, D.C. 20402


Table B-1 (continued)

Sample number and location TWA concentration (ppm)

C-19 Lace-up Operator 479.5
C-20 Bobbin Stores Operator 69.6
C-21 Patroler, Block II 117.6
C-22 Jetwiper, Block IT 63.5
C-23 Doffer, Block II 24.0
C-24 Doffer, Block I 61.5
C-25 Jetwiper, Block I 401.1
C-26 Patroler, Block I By/sisf)
C-27 Catwalk, Block II 124.7

between Metiers 58 and 59
C-28 Operating level, Block II 21.9

between Metiers 58 and 59
C-29 Operating level, Block II 37.7

between Metiers 62 and 63
c-30 Blank oS
C-31 Lacer 29.6
C-32 Creeler 202.6
C-33 Coning Operator 101.3
C-34 Beaming Operator 191.7
C-35 Bobbin Stores Operator 193.6
C-36 Doffer, Block IT 164.6
C-37 Patroller, Block II 15.5

(continued)
43


Table 3. Individual personal and area TWA
concentrations of methylene chloride
at Plant A, May 16-17, 1979.

Job title/location and sample number TWA concentration
(ppm)

Personal samples

Patroler, Block I C-1 31.7*
C-26 1911.8*
Cc-45 68.8
C-59 314.8
Patroler, Block II c-4 266.8
c-21 486.7
c-37 268.4
c-53 445.5
Doffer, Block I c-2 490.0
C-24 135.3
C-44 343.8
c-61 392.0
Doffer, Block II c-5 168.4
(CHAS) 561.4
C-36 522.9
C-55 509.3
Jetwiper, Block I c-3 Sys}
Cc-25 504.0
C-46 286.0
c-60 227.0
Jetwiper, Block II C-6 117.7
CP 464.5
C-38 196.6
C-54 236.4
Bobbin Stores Operator C-7 209.9)
c-20 75.8
(G=8}3) 123.6
C-52 208.9
(continued)

27


Table 7. Personal TWA concentrations of methylene chloride
at various locations during an aircraft paint
stripping operation at Plant C, May 15, 1979.

TWA concen-

Location* and number tration (ppm)
Tail section, right side R-1 28.7
Fuselage, right side R-2 21.4
Fuselage, right front side R-3 40.1
Wing R-4 SSeds
Fuselage and top R-5 ble
Wing R-6 91.7
Wing, engine R-7 PANS
Fuselage, Center R-8 88.6
Tail section, left side R-9 33.6
Wheel well R-10 268.0
Wheel well, tail R-11 84.2
Tail section, right side R-12 28.0
Blank R+13 np’

*
Area of aircraft worked primarily.

tNone detected. Detection limit: 10 micrograms.

36


SURVEY PROCEDURES AND METHODS

The procedures and sampling and analytical methods employed in this survey of
exposure to methylene chloride are described in this chapter of the report. At
all three plants, sampling for other potentially toxic substances that might be
expected to be found in conjunction with methylene chloride exposure also were
made--for acetone and methanol at Plant A, coffee dust and carbon monoxide at
Plant B, and ammonia at Plant C--and this sampling is also discussed, separately
in those instances where it differed from the sampling for methylene chloride.
The detailed surveys at each of the three plants had all been preceded by pre-
liminary walk-through surveys, the purpose of which was to identify suitable
facilities for in-depth study.

GENERAL SURVEY PROCEDURES

At Plant A, personal (breathing zone) samples were collected on representative
workers in each of the following work areas:

@ Production

e@ Extrusion

@ Bobbin stores
e Textiles

The breathing zone samples were for detection of methylene chloride and acetone
using charcoal tube/sampling pump assemblies. (Area samples for detection of
methanol in the filter press room were also made, using silica gel tube/sampling
pump assemblies--see subsequent section in this chapter.) All personal samples
were collected for at least two hours--most of them for more than six hours. The
samples were collected during four successive work shifts, beginning with the after-
noon shift of one day and ending with the afternoon shift of the following day.

At Plant B, the survey team sampled every operator working in the decaffeinating
facility except for mantenance personnel. Breathing zone samples were taken with
charcoal tube/sampling pump assemblies for approximately eight hours on all shifts,
with additional samples taken for short durations during selected operations. In
addition, area monitoring was performed, using a Century Systems Total Organic
Vapor Analyzer (OVA) as well as charcoal tubes/sampling pumps. The Century OVA
was used in a portable fashion to measure the presence of total hydrocarbons at
several locations throughout the facility where there would seem to be a chance
for exposure to methylene chloride--locations such as valves, flanges, pumps and
quality-control sampling ports. The analyzer proved to be especially helpful in
pinpointing areas of potential exposure. (Area sampling for coffee dust and
carbon monoxide, which was also conducted, is discussed separately in this chapter.)

At Plant C, the survey team sampled for methylene chloride on 12 of the 22 members

of the aircraft paint stripping crew as they were conducting a stripping operation,
These breathing zone samples were collected with charcoal tube/sampling pump assem-
blies. Sampling time for the personal samples ranged from 6.5 to 7 hours. Personal

22


Caustic

soga
Methane and HCL

(lo separation)

Meinane 3 7” E
sionne | Reactor B 58 3
Chlorine a = é :
HC! solution Waste
Methylene Methyl Sullune
chloride chloride are)

Hl

column

5 8

Waste

Figute 1. A schematic diagram of producing methylene
chloride by chlorination of methane.13

Underchiorinated Hecycle

Methylene Chioride
een —*} Chlorination Product crnatonrn
Reactor Recovery
Carbon Tetrachloride
t
Hydrogen Chloride Losses
Process
i" } Water
vdeo: Acid
Methanol 4 chionination Hydrochloric Acid
System AOU Hydrogen Chioride
Water
Methyl Chloride Water
Losses

Figure 2. A schematic diagram of producing methylene
chloride by hydrochlorination of methanol .14



Table B-1 (continued)

Sample number and location

TWA concentration (ppm)

C-38

c-39

c-40

c-41

C-42
C-43
C-44
C-45
C-46
C-47
C-48
c-49
c-50
C-51
c-52
c-53
c-54
C-55

C-56

Jetwiper, Block II

Operating level, Block II
between Metiers 58 and 59

Operating level, Block II
between Metiers 62 and 63

Catwalk, Block IT
between Metiers 58 and 59

Pressman, Block II
Pressman, Block II
Doffer, Block I
Patroler, Block I
Jetwiper, Block I
Blank
Creeler-Lacer
Creeler

Coning Operator
Beaming Operator
Bobbin Stores Operator
Patroler, Block II
Jetwiper, Block II
Doffer, Block II

Operating level, Block II
between Metiers 58 and 59

(continued)
44

10.6

Bon)

40.6

109.7

63-3)

185.2
144.0
96.4
ISS) oe)
168.6
21.4
Be)
18.1

28.0


Table B-2 Results of area sampling for methanol in the
filter press area at Plant A, May 17, 1979.

Sample number and location Concentration
(ppm)
CM-1 Between presses 104-A and 105A 38.3

maintenance on press 105-A

CM-2 Between presses 108-A and 109-A 4323)
maintenance on press 109-A

46


the stripping of paint from aircraft, and methylene chloride is the major
constituent in the stripping compounds used.

PROCESS AND CONTROL OPERATIONS
Plant A--Process and Control

Methylene chloride is used at Plant A to dissolve triacetate polymer flake,
thereby converting this solid material into a liquid medium that is suitable
for extruding fibers. The liquid form of the polymer is referred to as "dope."

The triacetate flake and other dry ingredients are added, automatically, to a
batch mixer through a weigh hopper. A solution of methylene chloride and methanol
is then fed into the mixer via a closed piping system and slowly mixed with the
solids until they are completely dissolved. Following the mixing, the dope is
filtered to ensure that it is absolutely free of materials that could block the
holes in the jets, or "spinnerettes", through which the liquid polymer will be
subsequently extruded.

During the mixing and filtration processes, the solution is maintained in an
enclosed system, and there are no exposures under normal operating conditions.
However, the filter presses require periodic stripping and replacement of the
filter elements. Approximately 10-12 filter presses are stripped each week, and
the elements are replaced with fresh cloth filters. The removed filters are
permitted to partially dry before being processed to recover the solvent and
polymer. To remove and replace the filter elements in each press takes two men
approximately 45 minutes. A local exhaust system has been installed in the
filter press rooms of Block I and Block II to aid in the removal of solvent
vapors when the filters are dismantled.

Following filtration, the triacetate dope is pumped to the extrusion area, where
it is preheated, filtered through a candle filter, and forced through an extru-
sion head (spinnerette or jet). The extruded fibers travel down through a drying
cabinet in which air removes the solvent and dries the fibers. The fibers are
brought together at the base of the cabinet, and the resulting triacetate yarn

is spun onto a carrier package known as a bobbin. A number of individual cabi-
nets are grouped together in a long row (called a metier).

The principal control of the solvent vapors--in addition to general ventilation--
is the individual cabinet, through which air is constantly pulled from its
openings to the work area. This air passes through the cabinet, collecting
vapors from the drying filament, and finally passes through a charcoal recovery
system to reclaim the solvent. There is a slight negative pressure inside the
cabinet to prevent the solvent-laden air from escaping back into the work area.
However, the fiber filaments continue to release some methylene chloride vapor
while being spun onto the bobbin and throughout other operations which the yarn
undergoes. These other operations include: twisting, which is mechanically
performed to strengthen the yarn; coning, which transfers the yarn from a supply
bobbin to a cone for use in the textile industry; and beaming, which is the
transfer of filament from several hundred bobbins onto a large spool known as a
weaving or section beam. All of these operations are conducted in the Textile
Department of the plant.