Badger Operator--Responsible for maintaining equilibrium conditions in the con-
tinuous fractionating columns and associated equipment. Monitors all pro-
cess control equipment and adjusts process variables as necessary.

Transfer Man--Responsible for unloading trucks and rail tank cars of raw mater-
ials for the process and for loading rail tank cars with the finished
product for shipment. This includes taking quality control samples of
both incoming and outgoing shipments.

HEALTH AND SAFETY PROGRAMS

Plant A--Health and Safety

Plant A has a formalized safety program, which includes an environmental health
group composed of health and safety professionals. Medical assistance is avail-
able on the plant site from a physician, and there is a fulltime nurse on each
shift. Pre-employment and annual physicals are required by Plant A for all of
its employees.

The company requires that each employee in the manufacturing areas wear overalls,
safety shoes, hard hat, and safety glasses at all times. All employees also have
at their disposal additional safety equipment, which includes respirators

(fitted with chemical cannisters suitable for organic vapors and acid gases),
Scott Air-Paks®, gloves, goggles, boots, rubber aprons, face shields, and

other safety equipment. In the monochlorobenzene facility, all personnel are
required to wear rubber work shoes or overshoes and to carry respirators at

all times. Written procedures have been established for proper protection of
employees who execute potentially high-exposure tasks, such as opening process
lines or other equipment.

Biological monitoring has been performed at the Plant for phenols in urine.

Plant B--Health and Safety

Pre-employment physicals are required for each employee at Plant B. These
physicals include job and family medical history, chest x-ray, audiograms,

and blood and urine analysis. Complete blood tests are also performed annually
by a nearby clinic.

The Plant has a formalized safety program, directed by one of its salaried
employees who has received some training in industrial hygiene technology.
Industrial hygiene functions at the plant are augmented by a regional industrial
hygienist. Each foreman is required to be trained in first aid. A hospital,
about one-half mile away, is available in case of emergencies.

14


Table C-2. Individual personal and area TWA concentrations of benzene
(Cont'd) and dichlorobenzene at Plant C, June 1979.

TWA concentration (ppm)

Dichloro-—

Job title and sample number Benzene Benzene
Area samples

Badger #2--N.E. corner 953 0.15 D533)

974 0.11 0.75

MCB tank car loading rack-- 957% 0.07 --

West end 1048 0.09 -

Interim benzene unloading 1oit 0.20 --

station

Py
Below detection limit--0.001 for benzene; 0.01 for dichlorobenzene.

‘Sampling pump stopped working--results questionable.
30,000 gal. MCB loaded (day 1 of survey).
$40,000 gal. MCB loaded (day 2 of survey).

35,

Ye U.S. GOVERNMENT PRINTING OFFICE

1981--757-074/1061


Table B-2. Individual personal and area TWA concentrations of benzene
and ortho-dichlorobenzene at Plant B, January 1979.

TWA concentration (ppm)

0-dichloro-
Job title/location and sample number Benzene Benzene
Personal samples
Senior Operator 2C 0.3 (tae
5C 0.8 0.8
10c 0.1 0.1
13¢ 0.8 0.2
Distillation Operator 1c 0.2 (eal
0.1 0.1
0.3 One
ahr (eal
Material Handler 3¢ 3.5 0.1
3.0 Onl
1.4 Ova
Area samples
Boilermaker--replacing MCB 4C 0.1 0.1
primary condenser and re-
moval of drums
Distillation Operation--QC 15C 1.6 0.1
sampling at Azeo #1, MCB
receiving
Blank 6C --* =—*
Area--near colum "B" at 14C 5.5 0.6
bottoms sampling portt
Area--near colum '"D" 16C 0.6 0.4
bottoms pump
Area--walkway between MCB 17C 1.3% 0.3%

and BZ sampling ports

* Below detectable limit (less than 10 micrograms).
+ Colum B was not operating.
+ Sampling pump stopped operating--results are questionable.

31


produced from this reaction. The mixture is then separated into acid and
organics in two separators. The acid is concentrated and recycled. The
organic fraction is washed with caustic to remove any residual acid. The
washed organics are then introduced to a dehydrator, where entrained water
from the washing sequence is removed.

The crude nitrochlorobenzene is stripped of excess monochlorobenzene in a
distillation colum. The botton of the stripper contains the finished crude
product; the overhead contains MCB, which is pumped back to the surge tank.

Plant B--Process Control

The manufacturing of MCB at Plant B is a part batch, part continuous operation.
The process begins with the introduction of vaporized chlorine and dry benzene
into one of two batch-operated chlorinators, which contain the catalyst. Water
runs continuously onto the reaction vessels, reportedly for cooling the system.
Hydrogen chloride gas created during chlorination is separated from the other
reaction products and is transferred to an area where it is recovered as a
usable product.

The crude reaction mixture is pumped to storage tanks, from which it is drawn
for refining in the continuously operated refining unit. Plant B has two sets
of fractionization (stripping) columns, only one set of which is used at a time,
the other set being reserved as a backup (such as during general maintenance).
After the benzene is stripped from the monochlorobenzene, the MCB is pumped

to intermediate storage tanks (and the benzene is pumped to a storage tank for
recycling to the chlorinators). Crude MCB from the intermediate storage tank
is pumped to a second stripping colum, where it is further refined by the
removal of dichlorobenzenes and other polychlorobenzenes. The refined MCB then
leaves the stripper for storage.

A potential for exposure to MCB exists during quality-control sampling or when
system maintenance is required. At the time of this survey, open-spout sampling
ports were in the process of being changed to a closed-system type. At the
open-spout ports, spillage or drips were caught in buckets beneath the ports.
This effluent would contain quantities of MCB or a combination of MCB and other
chlorobenzenes. Gloves are worn by the operators during sampling, and operators
are instructed to wear respirators equipped with organic vapor/acid gas cannist-
ers. The survey team observed, however, that some of the operators were not
wearing respirators during the collection of samples.

In early 1978, Plant B began a program of engineering and process changes in the
MCB unit to reduce airborne benzene levels to 1 ppm as an eight-hour time-weighted
average. At the time of this survey, most of these changes had been completed.
They include:

@ Installation of improved condensers for the fractionating columns
to achieve better condensing and cooling;

® Repositioning and manifolding of vents to reduce total emissions
and installation of refrigerated cooling-water units on certain
vents to increase condensing capacity; and


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

Time-weighted average exposures of workers at Plant A to monochlorobenzene are
shown in Table 2 in the form of concentrations for each job classification, by
work shift, together with geometric means* for the job categories. Individual
personal sample results, together with results of long-term area sampling, are
shown in Appendix Table A-1.

Variations among personal samples can be caused by such factors as: (1) small
operational changes, and (2) different operators doing the same task in differ-
ent ways--some get closer to the equipment, some take longer or shorter times
to complete a task, etc. For all job classifications, there is inevitably
some variation in exposure levels from shift to shift, even though the opera-
tions are nominally continuous and constant overall.

Personal exposures to concentrations of MCB in both the monochlorobenzene and
nitrochlorobenzene work areas ranged from less than 0.1 ppm to 4 ppm, a range
that is well below the OSHA standard and ACGIH recommended Threshold Limit Value
(both 75 ppm). The mean MCB exposure concentration for all jobs in MCB manu-
facturing was 0.19 ppm. The actual highest mean concentration was for MCB Oper-
ator (0.24 ppm). As can be seen in Table 2, the difference between average
exposures for jobs in the MCB production area were very small. The highest
concentration of MCB for a job category in the nitrochlorobenzene manufactur-
ing area was 4 ppm (Day Operator). The mean concentration for all jobs in

this area was 0.46 ppm. As compared with the monochlorobenzene manufacturing
area, somewhat higher mean concentrations of MCB were recorded for all job
categories in the nitrochlorobenzene area, except for the Washing Operator.

The difference in mean MCB exposures between the three work shifts was not
great.

The MCB found in long-term area samples in the monochloro- and nitrochlorobenzene
work areas ranged from 0.2 to 2.4 ppm (Appendix Table A-1).

Personal exposure (TWA) and area concentrations of benzene and o-dichlorobenzene
are shown in Appendix Table A-2. The TWA personal concentrations of benzene
taken in the MCB production area ranged from 0.8 to 21 ppm, with 2 out of 15

* 1,2
Geometric mean = antilog > (= log x; »)
i-1

18


DEPARTMENT OF HEALTH AND HUMAN SERVICES
PUBLIC HEALTH SERVICE
CENTERS 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

t

=
US.MAIL
——s

Third Class Mail

POSTAGE AND FEES PAID
U.S. DEPARTMENT OF HHS
HHS 396

DHHS (NIOSH) Publication No. 81-105


ABSTRACT

Following preliminary, walk-through, industrial hygiene surveys of U.S. plants
in which monochlorobenzene is used and produced, three facilities were selected
for further surveying of human exposures to the chemical. Fifty-eight full-
shift personal samples for monochlorobenzene covering workers in 20 job classi-
fications, and area samples of 30 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—-des-
criptions of operations and jobs, exposure control efforts, health and safety
programs, air sampling data collected, summary tables of worker exposure levels
to monochlorobenzene and associated substances (benzene, dichlorobenzene, and
nitrochlorobenzene), sampling and analytical procedures and methods, evaluation
of findings, and recommendations.

Results of the survey showed time-weighted-average personal exposures to mono-
chlorobenzene for normal operations ranging from below the detectable limit to
4 ppm--all well below current permissible levels of 75 parts per million. All
but two of personal samples for other substances were well below permissible
limits. (Two benzene samples at one plant showed concentrations of 15.7 and
21.1 ppm, above the OSHA standard and ACGIH recommended level of 10 ppm).

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 A-4. Results of side-by-side personal sampling for monochloro-

henzene and benzene conducted by Plant A and SRI International,
November, 1978.

Monochlorobenzene Benzene
g Sg N Xe Sg N
*
SRI 0.2 ppm 3.8 27 1.8 ppm 2.8 15
Plant A* 0.2 ppm 2.5 18 1.5 ppm 2.8 14

*
Charcoal tubes used as collection medium.

*the collection medium was a 3M passive sampler. All samples (SRI and Plant
A) were analyzed using desorption with carbon disulfide and analysis by gas
chromatography with flame ionization detection.

29


Every employee is required to wear Plant-supplied work clothing, safety hat,
safety shoes, safety glasses, and NIOSH-certified respirators equipped with
organic vapor/acid gas cannister. Gloves, face shields, and rubber boots are
supplied when a specific task warrants extra personal protection, and air-
supplied respirators are also available for high-risk exposures. Locker rooms
with showers are available for the employees.

Plant C--Health and Safety

Health and safety programs at Plant C are provided by the corporation that
operates the monochlorobenzene operation at the chemical complex. The Medical
Department, directed by a physician, has a staff of six physicians and 20
registered nurses who handle problems 24 hours a day, seven days a week. The
Safety Department has a staff of 15, including the manager. The Industrial
Hygiene program is conducted by a manager and a staff of 25 hygienists.

Emergency medical personnel on every shift respond with a radio-dispatched van
to requests for medical assistance. An Occupational Health Team consisting of
a medical doctor, safety engineer, and industrial hygienist has been assigned
to each area of the chemical facility where exposures to chemicals might occur.
Industrial hygienists have access to a wide array of sampling and analytical
equipment that includes a computerized system of continuous air monitoring, gas
chromatographs, and mass spectrometers.

Safety showers are strategically located within the site. Employee safety
equipment provided by Plant C includes coveralls, shoes, hard hats, safety
glasses, respirators, and gloves. Plastic monogoggles are also required in
the chlorobenzol area. Showers, a locker room, and an isolated eating area
are provided for employees.

tls}


a geometric mean concentration of 0.6 ppm. This is below the current OSHA
standard and ACGIH recommended TLV of 10 ppm. Material handlers received
the greatest exposure to benzene, a geometric mean concentration of 2.4
ppm. Concentrations of dichlorobenzene were below 10 ppm for all personal
samples.

RESULTS OF SURVEY--PLANT C

Time-weighted-average exposures of workers at Plant C to monochlorobenzene,
by job classification and work shift, are presented in Table 4. Individual
personal sample results, and results of area sampling, are shown in Appendix
Table C-1. All of the sample results at Plant C were well below the current
OSHA standard and ACGIH recommended Threshold Limit Value.

Table 4. Job and work-shift concentration of
monochlorobenzene at Plant C, June 1979.

TWA Concentration (ppm)

Day Evening Night Geometric

Job Title Shift Shift Shift Mean
Chlorobenzol area

Operator --}-- —-,-- --,-- --

Mechanic --

Maintenance Worker

(adjacent area) --,--

Construction Worker ——
Badger area

Operator 0.42,0.59 0.36 0.25 O589.

Transfer Man ft: 9 7 ed O) 1.84

*Below detection limit (less than 10 micrograms).

Of the 18 personal samples taken, only 6 showed detectable levels of MCB.
All six were collected in the Badger (recovery) area on the Operators and
the Transfer Man; no MCB was detected for workers in the chlorobenzol
(reactor) area. Concentrations of MCB for four Badger Operators ranged
from 0.25 ppm to 0.59 ppm, with a mean (geometric) of 0.39 ppm. The two
Transfer-Man samples in the Badger area showed concentrations of 1.79 ppm
and 1.90 ppm (mean, 1.84).

Results of area sampling for MCB (20 samples) presented in Appendix Table
C-1 are similar in level to the personal results. The eeas monitored in
the chlorobenzol area yielded no detectable MCB. In the Badger area, both
the control room and GC room yielded detectable levels of MCB--0.21 ppm and
0.22 ppm in the control room, and 0.40 ppm in the one sample in the GC room.
Five area samples for MCB at Badgers 2 and 3 yielded detectable levels
ranging from 0.62 ppm to 2.35 ppm (mean, 1.02). Two samples at the tank
car loading truck showed 3.15 ppm and 10.5 ppm MCB.

21


SAMPLING AND ANALYSES

Personal sampling employed charcoal tubes and monitoring pumps--Bendix
BDX-44 at Plants A and B, MDA Accuhaler® at Plant C--which were attached
to the clothing and belts of the workers. The pumps were connected to
the sampling media by Tygon® tubing.

At Plants A and B, the sampling medium was a large-size charcoal tube
(600 mg) containing a 400-milligram adsorbing section backed up by a
200-mg section to determine breakthrough of the substances being sampled.
The sections are separated by a portion of urethane foam and are analyzed
separately. The charcoal tubes used at Plant C were standard-size, 150
mg (100 mg adsorbing section and 50 mg backup section). The sampling
pumps drew air through the tubes at nominal rates of 100 milliliters per
minute at Plants A and B and 20 milliliters per minute at Plant C.

While sampling was performed for somewhat less than the full eight-hour
shift for most of the workers surveyed, the nature of the operations are
such that the exposure for individuals would not be expected to vary.
Hence, the TWA calculated was on an eight-hour basis. The calculation for
MCB concentration was as follows:

C = (24,450) x (W)
(Mw) x (V)
where: C = Concentration of MCB, ppm
W = Mass of MCB collected, mg
MW = Molecular weight of MCB, 112.56 g/gmol
V = Volume of air sampled, L

The Plant A and B samples were analyzed for monochlorobenzene, benzene,

and dichlorobenzene according to NIOSH-approved analytical technique $133
with a minor adjustment in technique: The NIOSH method calls for desorption
of the charcoal using 1 ml of carbon disulfide: however, since large char-
coal tubes were used, 2 ml of carbon disulfide were used to desorb.

Samples collected at Plant C were analyzed for MCB, dichlorobenzene, and
benzene according to NIOSH method P & CAM 127 (modified)?, All samples
were analyzed by gas-liquid chromatography with flame ionization detection.
Four area samples that were taken at Plant A for nitrochlorobenzene were
analyzed according to NIOSH method S218”.

17


Table B-1. Individual personal and area TWA concentrations of

monochlorobenzene at Plant B, January 1979.

Job title/location and sample number

TWA concen-
tration (ppm)

Personal samples

Senior Operator

Distillation Operator

Material Handler

Boilermaker--replacing MCB primary
condenser and removal of drums

Distillation Operator--QC sampling
at Azeo #1, MCB receiving

Blank

Area Samples

Near column "B" at bottoms sampling
port?

Near column "D" bottoms pump

Walkway between MCB and benzene
sampling ports

2c
5c
10¢
13¢

ic

3¢

4c

15¢

6C

14¢

16¢
17¢

SC SCOO HFNOO NONO
UND BORN NEROUW

Nn
ce)

*

14.2

4.6
34>

IH +

Column B was not operating

30

Below detectable limit (less than 10 micrograms).

Sampling pump stopped operating--results are questionable.


operating area, and clean equipment for maintenance work.

Utility Day Operator--Unloads from tank truck or tank car (or receives by pipe-
line) the raw materials used, which include sulfuric acid, nitric acid, and
monochlorobenzene. Loads tank trucks and tank cars, and then transfers
by pipeline the finished products made in the department (p-nitrochloro-
benzene and o-nitrochlorobenzene). Also makes up batches of mixed nitric
and sulfuric acids for another department at the plant site.

Repairman--Performs repairs throughout the department and performs other opera-
tion assistance such as inserting and pulling blanks, installing pressure
gauges, disconnecting lines for clean-out, opening equipment for inspection
or clean-out, and making minor modifications. Repairs steam traps and
tracing, applies temporary insulation to lines, patches small leaks in lines
and vessels, replaces small lines, etc.

Porter Helper--Performs typical porter duties in the control rooms, offices, and
toilet areas in the department; also performs some pickup and cleanup in
the process area.

Plant B--Personnel

Twelve employees work within the monochlorobenzene manufacturing area at Plant
B, and an additional 16 employees handle MCB on an intermittent basis. The
job titles and number of workers that work in the MCB manufacturing unit are
as follows:

Number per Total

Job Title Shift Force
Senior Operator 1
Distillation Operator

*

Process Helper al 4
Material Handler--Loading
(on day or swing shift only) 1 2

*
This employee works in the MCB manufacturing area on the average of 25% of
the time.

12


DDT 7
Other 6

100%

HUMAN EXPOSURE STANDARDS AND TOXICITY

The current Occupational Safety and Health Administration permissible limit

of exposure to MCB is 75 parts per million (ppm) as a time-weighted average
(IWA) for eight hours. The Threshold Limit Value recommended by the American
Conference of Governmental Industrial Hygienists is also 75 ppm,” "... [in the
belief hoe this limit is low enough to prevent narcotic effects or chronic
poisoning."+ The American Industrial Hygiene Association, in a 1971 publication,
indicated that, based on unpublished data, a "...somewhat lower concentration
may be more appropriate."5

Monochlorobenzene can enter the body through inhalation of its vapor and by
percutaneous absorption of the liquid. Typically, as a chlorinated benzene,
MCB is irritating to the skin, conjunctiva, and mucous membranes of the upper
respiratory tract, and prolonged or repeated contact with the liquid may cause
skin burns. An acute exposure to the compound can cause drowsiness, incoordin-
ation, and unconsciousness. Animal experiments have indicated histological
changes in the liver, kidneys, and lungs after chronic exposure. © In one such
experiment, for example, animals were exposed to inhalation doses of 0, 75, or
250 ppm of MCB for seven hours, 5 days per week, for 24 weeks, and subtle hema-
tological and histological changes, together with a decrease in food utilization,
were observed at the 75 ppm and 250 ppm exposure levels. No such changes were
observed among controls.

BASIC PROCESS FOR PRODUCING MCB

The 12 chlorinated benzenes, including monochlorobenzene, are formed by replac-

ing the hydrogens of benzene with chlorine atoms. Monochlorobenzene is produced
by chlorinating benzene in the presence of a catalyst, usually ferric chloride.

The chemical reaction involved is:

catalyst
Ce He ae cl, Ce He CL + HCL
(benzene) (chlorine) (MCB) (hydrogen-
chloride)

The ferric chloride catalyst is either added as such or generated during the 1.8
reaction by exposing a large surface of iron to the liquid being chlorinated.’
Two major isomers of dichlorobenzene, ortho- and para are also formed, as is

a small amount of the meta- isomer. As chlorination continues, tri-, tetra-
penta-, and hexachlorobenzenes are formed. The degree of chlorination can be
controlled by the catalyst used, temperature, and ratio of benzene to chlorine,
but since each of the previous compounds, except hexachlorobenzene, can be
further chlorinated, those compounds are always a mixture of chlorinated benzenes.
Pure compounds are obtained by distillation and crystallization. A simplified,
block, diagram of the basic process for manufacturing MCB is shown as Figure 1.


Table A~2. Individual personal and area TWA concentrations of
benzene and ortho-dichlorobenzene at Plant A, November 1978.

TWA concentration (ppm)
Job Title/location and sample number o-dichloro-
Benzene benzene

Personal samples--monochlorobenzene

production
*
MCB Operator 100c, 3 -
112¢ ZA gah --
120¢ ie? =
126C 2.0 ==
HCl Operator 101¢ 1.0 —
111¢ ee =
121¢ dhedl =
122¢ 1.4
128C 1.4
Day Operator 104¢ Peal ==
11oc® bay --
127¢ 25 0.3
134¢ 1.3 =
Repairman 109C¢ 0.8 —
130C 1300) --
Blank 129¢ BD BD
Area samples--monochlorobenzene and
nitrochlorobenzene production areas
MCB Storage--Day tanks, on stairway 114¢ ils} _
Grade level--#3 chlorinator 116C is --
Grade level--below benzene stripper 115C (3) =
Grade level--crude liquor transfer 118¢ 0.9 --
Grade level--near chlorinator cooler 125¢ 0.5 --
1st level--between #2 & #3 chlorinators 133C 3.0 --

alley 0.1 ppm.

A trainee--was wearing an organic-vapor-cartridge respirator while
gathering quality-control product samples.

‘Operator was preparing equipment for maintenance.

Note: BD = Below Detection.

27


REFERENCES

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.

American Conference of Governmental Industrial Hygienists. Documentation
of the Threshold Limit Values for Substances in Workroom Air, 3rd Ed.
Cincinnati, 1971.

American Industrial Hygiene Association. Chlorobenzene (dated 1964).
In Hygienic Guide Series. Detroit, 1971.

Key, MM, et al. (eds.): Occupational Diseases--A Guide to Their
Recognition. Washington, D.C., U.S. Dept. of Health, Educ. & Welfare
DHEW (NIOSH) Publication No. 77-181, 1977.

Dilley, JV: Toxic evaluation of inhaled chlorobenzene (monochloro-
benzene). In Final Report of Division of Biomedication and Behavioral
Sciences, National Institute for Occupational Safety and Health. NIOSH,
Contract No. 210-76-0126, 1977.

Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Ed., Vol. 5.
New York, Wiley-Interscience, 1979, pp. 797-798.

National Institute for Occupational Safety and Health. NIOSH Manual of
Analytical Methods, 2nd Ed., Vols. 1,2, and 3. Washington, U.S. Dept.

of Health, Educ. and Welfare DHEW (NIOSH) Publication Nos. 77-157-A,B,

and C, 1977.

24


INTRODUCTION

Under the terms of the authority and responsibility given to the National
Institute for Occupational Safety and Health (NIOSH) to develop needed infor-
mation regarding potentially toxic substances in industry (see Preface), NIOSH
contracted with SRI International to conduct an industrial hygiene study of
exposure to four chlorinated hydrocarbons. Chlorinated hydrocarbons were
selected 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 research 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 numbers of workers potentially exposed.
The report that follows concerns industry exposures to monochlorobenzene.

OBJECTIVES AND SCOPE OF THIS STUDY
The objectives of this industrial hygiene study were to:

Review and summarize the toxic effects of monochlorobenzene.

Document and describe selected workplaces, including information on
the production and use of monochlorobenzene.

@ Identify job types and describe specific jobs.

@ Describe current industrial hygiene and safety practices, including
engineering controls, work practices, administrative controls, and bio-
logical and environmental sampling and control procedures.

© Document (1) job-function exposures to monochlorobenzene 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 mono-
chlorobenzene.

Detailed industrial hygiene surveys reflecting these objectives were made at
three U.S. facilities where monochlorobenzene is produced and/or used. The
detailed surveys, all of which had been preceded by preliminary surveys, were

conducted during the period November 1978 to June 1979 by the contractor and
by NIOSH.

LIMITATIONS OF STUDY

The industrial hygiene surveys represent singular evaluations of worker exposures
to monochlorobenzene which do not reflect possible variations in exposure due


CONTENTS

Preface......+- ereiejele es elerviv ie s'sisrerececole
Abstract...... C8 bees eewess ben ee enone
Introduction........+++6 SEO DO RUE NOU OIG

Background. . we cece

Facilities and Personnel Surveyed

Description of Facilities...

Process and Control Operations..

Personnel and Their Activity........
Health and Safety Programs........++++++e+%
Survey Procedures and Methods........... Glelelaletersistereatei sof 16
Results and Recommendations.........+ ee eeeee seen eeenen 18
Results of Survey - - Plant A..........-++ eerie sie aLO:
Results of Survey - — Plant B......eeeee cece eeeee 20.
Results of Survey - - Plant C........ pocunoncassd Rodi
Summary and Recommendations.......- poeeoacdcUoj0o 22

References....

Appendix (Tables)....... care



In addition to the employees just mentioned, there are an additional 40 me-
chanics, laboratory technicians, and supervisory staff who may be exposed to
MCB intermittently. Senior Operator and the Distillation Operator are the
principal job classifications that are directly involved with the MCB process
area and that receive a continuous exposure to MCB. The duties of these two
operators are as follows:

Senior Operator--Responsible for operating the chemical processing equipment
to produce chlorinated benzene, nitric acid, and purified polychloro-
benzene. Directs the other operators, material handlers, and the process
helper. Checks all gauges and meters and adjusts flows of material as
needed. Also takes samples as required and assists the maintenance crew
during repairs.

Distillation Operator--Maintains equilibrium conditions in the continuous
fractionating columns and in the drying system. Checks all temperature
and pressure instruments, flowmeters, and operating pumps and valves.
Also takes samples and assists the maintenance crew during repairs.

Plant C--Personnel

At Plant C, 12 hourly employees are assigned to work each day in the mono—
chlorobenzene manufacturing unit, which comprises two major areas--Clorinator
(reactor) and Badger (recovery). Hourly employees work eight-hour shifts on

a standard (four-shift rotation) schedule. The job titles and number of workers
in the MCB unit are as follows:

Per
Job title shift Total
Chlorobenzol Operator 2 6
Alternate (day shift only) 1 ‘il
Badger Operator at 5}
Plant Mechanic (day shift only) it i
Transfer Man i i

The process-operator and transfer-man job classifications are directly involved
with the MCB process and receive the most continuous exposure to the chemical.
Other mechanics, as well as laboratory technicians and supervisory staff, may
be exposed intermittently. The duties of the Operators and Transfer Men are
as follows:

Clorobenzol Operator--Responsible for operating the chemical processing equip-
ment to produce chlorinated benzene. Monitors all process control equip-

ment and makes necessary adjustments. Also takes process samples as

required.

13)


BACKGROUND
Monochlorobenzene, or MCB, is a colorless liquid with a penetrating odor of

almonds. The chemical formula, synonyms, and some chemical and physical proper-
ties of MCB are given in Table 1.

Table 1. Chemical and physical data for monochlorobenzene

Synonyms: chlorobenzene, chlorobenzol, phenylchloride, benzene monochloride

Chemical formula: CgH<Cl

Some chemical and physical properties:

Molecular weight 112.56
Saturated vapor concentration (vol., 20°C) 11,900 ppm
Melting point -45°C
Boiling point (101.3 kPa) 132°¢
Critical temperature 359. 29°C
Liquid density 1.10118 kg/L
Explosive limits (vol. in air, 101.3 kPa) 1.3-7.1%
Flash point (closed cup) 28°C

Heat of vaporization 333.1 J/g

Source: Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Ed., Vol. 5.
New York, Wiley-Interscience, 1979, p. 799.

PRODUCTION AND USES

Large quantities of monochlorobenzene were once used in the production of DDT
insecticide and phenol; however, because of a restriction on the use of DDT,
and because MCB was replaced by cumene in the manufacture of phenol, the
production and use of MCB in the United States has declined. Estimated produc—
tion volumes for the latest three years for which data are available were 170
million kilograms in 1976, 148 million kg in 1977, and 134 million kg in 1978.1

Monochlorobenzene is currently used mainly as a solvent, (e.g., in the manu-
facture of pesticides and for degreasing) and in the production of nitrochloro—
benzenes (used as intermediates for dyes, herbicides, and insecticides). The
U.S. consumption pattern for MCB, based on data for 1976, is approximately as
follows :1

Solvent (e.g., pesticides, degreasing) 49%
Manufacture of nitrochlorobenzene 30
Diphenyloxide 8


Table 2. Job and work-shift TWA concentrations of monochlorobenzene
at Plant A, November 1978.

TWA concentration (ppm)

Job title Day Evening Night Geometric
Shift Shift Shift Mean
Monochlorobenzene production
MCB Operator 0.9,0.2 0.1 0.2 0.24
HCl Operator (0) Sa a OnE 052 0.1 OmaL9
Day Operator 0.1,0.2
0.1,0.1 0.12
Repairman 0.5,0.1 0.22
Nitrochlorobenzene production
Nitration Operator 25 Or) 0.2 0.9 0.50
Washing Operator 0.5,0.1 @oal a8} 0.20
Day Operator 4.0
Porter O55)
Repairman 1550.0) O95

19


Nish

TECHNICAL REPORT

Extent-of-Exposure Survey of
Monochlorobenzene

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

Centers for Disease Control

National Institute for Occupational Safety and Health


FACILITIES AND PERSONNEL SURVEYED

Three facilities at which monochlorobenzene is produced and/or used in further
chemical production were surveyed. In an attempt to provide as much of an
exposure cross-section as possible, the following criteria were used for plant
selection: the number of persons potentially exposed; level of exposure exper-
ienced, as determined by preliminary area sampling; type of operation (continu-
ous or batch); exposure situations limited primarily to the target chemical;
and a process representative of a major use of the substance.

The facilities are designated as Plants A, B, and C. They are briefly described
below, followed by discussions of their process and control operations, descrip-
tions of personnel and jobs in which potential exposure to MCB occurs, and des-
ceriptions of health and safety programs that have been established.

DESCRIPTION OF FACILITIES

The following are brief overviews of the three facilities at which in-depth expo-
sure surveys were made for purposes of this report.

Plant A--Overview

Both monochlorobenzene and nitrochlorobenzene (derived from MCB) are manufac-
tured at this facility. The facility is one production unit of a plant that
produces a number of different chemical compounds. Both the MCB and nitrochloro-
benzene manufacturing operations were surveyed in this study.

Plant B--Overview

Plant B is a long-time (over 30 years) producer of MCB in a part batch, part
continuous, operation. The plant, which also manufactures several other chemi-
cal compounds, is located on the site of a larger chemical manufacturing facility.

Plant C--Overview

The chlorobenzene production unit is located in a large Midwest, chemical-prod-
ucing and -using facility. The MCB production unit, which covers 23 acres, has
been in operation since 1922, and most plant additions and technology changes
have been continuous and relatively minor over the years since that date. An
exception is in the chlorinator technology; a new chlorinator unit was recently
installed and the old unit put on standby.


Chlorine

Reactor

Dry Benzene
HC1
Cooling
Catalyst
Removal
HCL
Wet
Benzene
Benzene ; Benzene
Drying a Refining

MCB >

Dichlorobenzene isomers

Refining

Abstracted from: Dylewski, SW: Emission Control Options for
the Synthetic Organic Chemicals Manufacturing Industry: Chloro-
benzenes Product Report (Draft). Prepared for Environmental
Protection Agency, Research Triangle Park, N.C., August 1978.

Figure 1. A simplified, block, diagram of the basic process for manufacturing
monochlorobenzene.


Table A-1. (continued)

TWA concentra-

Job title/location and sample number tion (ppm)
Grade level--below benzene stripper 114C 0.9
Grade level--crude liquor transfer 118¢ 1.1
Grade level--near chlorinator cooler 125C 0.2
1st level--between #2 & #3 chlorin-
ators 133¢ 1.4
1st level NCB--acid dehydrator 113¢ 0.2

*
A trainee--was wearing an organic-vapor-cartridge respirator while
gathering quality-control product samples.

ay
Operator was preparing equipment for maintenance.

-
“Operator was transferring MCB.

26


Table A-l. Individual personal and area TWA concentrations of mono-
chlorobenzene at Plant A, November 1978.

TWA concentra-
Job title/location and sample number tion (ppm)

Personal samples

Monochlorobenzene production

MCB Operator 100C 02
112c* 0.9
120¢ 0.1
126C 0.2

HCl Operator 101¢ 0.1
111¢ Ou
121¢ 0.1
122C 0.2
128C¢ tical

Day Operator 104C Onn
11oct 0.2
127¢ 0.1
134C 0.1

Repairman 109¢ 0.5
130C 0.1

Blank 129¢ ==

Nitrochlorobenzene production

Nitration Operator 102¢ Dol!
107C dhe #2
117¢ 0.2
132¢ Ons

Washing Operator 103C Dos!
105¢ OnS
119¢ 0.1
123¢ 0.1

+

Day Operator 131¢~ 4.0

Porter 108C 0.5

Repairman 106C 15
124C 0.6

Area samples

MCB storage--day tanks

on stairway 114¢ 0.9

Grade level--#3 chlorinator 116C 2.4

(continued)

25


to seasonal or operational changes. An attempt was made to evaluate exposures
for each job type as encountered during all work shifts. These studies were
made during periods of normal production. No abnormal exposure situations
were encountered during the sampling periods; therefore, the reported exposure
measurements are considered to represent only those exposures associated with

normal operating conditions.


SURVEY PROCEDURES AND METHODS

The procedures and sampling and analytical methods employed in this survey of
exposure to monochlorobenzene are described in this chapter of the report. Per-
sonal samples taken at all three plants were analyzed for benzene and dichloro-
benzene, in addition to monochlorobenzene, and area sampling was performed at
Plant A for the presence of nitrochlorobenzene. The detailed surveys at each
of the three plants had all been preceded by walk-through surveys to identify
suitable facilities for more in-depth study. In-depth sampling at Plants A

and B was conducted by the contractor, Plant C by NIOSH industrial hygiene
personnel without the assistance of SRI.

GENERAL SURVEY PROCEDURES

At Plant A, the survey team sampled every operator working in the monochloro-—
benzene and nitrochlorobenzene manufacturing units for the presence of MCB,
benzene, and dichlorobenzene. Breathing zone samples were taken with charcoal
tube/sampling pump assemblies for approximately eight hours on all shifts. Area
monitoring was performed with charcoal tube/sampling pump assemblies and a
Century Systems Total Organic Vapor Analyzer. The Century analyzer was used

at several locations throughout the MCB facility where there seemed to be a
chance for exposure, such as near valves, flanges, pumps, and quality-control
sampling ports.

Area samples for nitrochlorobenzene were also taken around the nitrochlorobenzene
manufacturing unit. These samples were collected in large-size silica gel tubes
using a Bendix monitoring pump. Sampling times were approximately eight hours.

At Plant B, every operator working in the monochlorobenzene manufacturing unit
was monitored for the presence of MCB, as well as benzene and dichlorobenzenes.
Eight-hour TWA breathing zone, charcoal-tube samples were collected. Personal
samples were also taken to determine ceiling concentrations during those opera-
tions where there was a potential for short-term, high-level exposure to MCB,
benzene, or dichlorobenzene.

Area charcoal-tube samples were collected at locations with potential higher-
than-normal MCB exposure, such as near quality-control sampling ports.

Most of the regular-shift employees at Plant C were monitored for MCB, dichloro-
benzene, and benzene. A new recovery unit was being constructed in an area
adjacent to the Plant's chlorinator, and two of the construction workers were
also monitored for MCB exposure. Charcoal tubes were used for the personal
sampling, as well as for the area samples that were taken.

16


Table C-1. Individual personal and area TWA concentrations
(Cont'd) of monochlorobenzene at Plant C, June 1979.

TWA concen-
Job title/location and sample number tration (ppm)

Area Samples

MCB tank car loading rack--West end 9577 Bells)
1048 10.50
Interim benzene unloading station 1017 =

*nelow detectable limit (less than 10 micrograms)
tsampling pump stopped working--results questionable.
#30 ,000 gal. MCB loaded (day 1 of survey).

540,000 gal. MCB loaded (day 2 of survey).

33


Table C-2. Individual personal and area TWA concentrations of benzene
and dichlorobenzene at Plant C, June 1979.

TWA concentration (ppm)

Dichloro-
Job title and sample number Benzene Benzene
Personal samples
Operator 964 0.17 0.54
966 0.09 --
982 -- =
987 0.03 --
989 0.03 --
980 -- a
9o2 0.05 =
999 -- —
Mechanic 951 oo —
Maintenance Worker (adjacent 956 — 2.28
area) 996 -- 1.30
Construction Worker (new 105 -- -
construction around chlorinator)
Badger Operator 961 0.30 =
975 0.36 7
985 0125: --
994 0.28 =
Transfer Man 960 0.82 0.23
108 0.24 --
Area samples
Chlorinator--control room 950 0.04 =
976 _ =
109 = oo
Chlorinator--north end 952 0.08 --
972 ==
102 --
Badger--control room 963 O21:
973 0.34
997 0.33 --
Badger--GC room 962 0.23 --
970 0.30 =—
991 0,08 =
Badger #3--N.E. corner 967 O}vil --
O77 0.34 0.33
1007 0.15 --
(continued)

34


As noted on Table C-1, 30,000 gallons of MCB were being loaded during
the sampling period on day one, and 40,00 gallons were loaded during
the sampling period on the second day.

Results of analyzing samples for benzene and dichlorobenzene at Plant C
are shown in Appendix Table C-2. In the 18 personal samples, detectable
levels of benzene were found in 11, the highest of which was 0.82 ppm (well
below the current OSHA standard of 10 ppm). Levels of benzene in area
samples, and levels of dichlorobenzene in personal and area samples, were
also well below the OSHA standard and the ACGIH Threshold Limit Value.

The ranges of mean exposures to MCB for job categories at Plants A, B, and
C, together with the mean personal exposure for all jobs at each plant, are
shown in the following tabulation (figures are parts per million):

Plant A Plant B Plant C
Range of mean job-category 0.12-0.95 0.57-1.11 €detect.-1.84
exposures to MCB
Mean personal exposure for all 0.27 0.74 0.11

job categories

SUMMARY AND RECOMMENDATIONS

From the data collected during this survey, the following summaries and recommen-—
dations are made:

e fEight-hour TWA concentrations of monochlorobenzene from personal
monitoring at all of the three facilities included in this survey
were well below the current OSHA permissible level and ACGIH Thres-
hold Limit Value (see Chapter II--"Background"). Low concentrations
are due to combinations, according to each plant, of the following
factors: the processes are performed in closed systems that minimize
the possibility of MCB release into the work atmosphere; the process-
es are highly automated, demanding little time of operators in the
process area; and processes in relatively open structures.

@ Personal, eight-hour-TWA concentrations of monochlorobenzene at
Plant A ranged from 0.1 ppm to 4 ppm in the two manufacturing areas
surveyed—-monochlorobenzene production and nitrochlorobenzene produc-
tion. The geometric mean concentration of MCB for all job categories
in the monochlorobenzene facility was 0.1 ppm; for job categories
in the nitrochlorobenzene facility the average was <0.5 ppm. Eight—
hour-TWA personal concentrations of MCB at Plant B ranged from 0.1
to 2.9 ppm, with a mean concentration of 0.8 ppm for all job classi-
fications. Plant B was operating at a low capacity during the
survey, and it is not known if personal exposures would remain
below the current permissible (or ACGIH recommended) level during

22)


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, agree-
ments, or other arrangements with appropriate public agencies or private organi-
zations 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 monochlorobenzene.

The funding for this work was provided by the Division for Cancer Cause and
Prevention, National Cancer Institute, through the Interagency Agreement on
Research on Occupational Carcinogens (Y-01-CP-60605) .

iii


e@ A process change for removing benzene contaminant during the
neutralization of crude product that will reduce corrosion and
the consequent need to open lines and vessels for maintenance.

Plant C--Process and Control

Monochlorobenzene is manufactured at Plant C by a continuous, closed, process in
fundamentally the same way as previously described in this report. The manu-
facturing facility includes two buildings--one, containing a control room, in
the Chlorinator (reactor) area and one in the Badger (recovery) area containing
a control room and a gas chromatograph (GC) room. All other structures and
equipment involved with MCB production are open to the air. The Plant C lay-
out is shown in Figure 2,

The production area offers potential exposure to benzene, chlorine, sodium
hydroxide, hydrogen chloride, and hydrochloric acid, and to mono-, di-, tri-,
and tetra-chlorobenzenes. However, since the production process is closed and
continuous, exposures should be minimal around most equipment under normal
operating conditions. During start-up, maintenance, or if system leaks occur,
exposures would be expected to be greater. (Data supplied by Plant C dating
back to 1972 show no samples exceeding the 75 ppm TWA standard for MCB.)

PERSONNEL AND THEIR ACTIVITY

Plant A--Personnel

There are 14 persons at Plant A who are involved in the production of monochloro-
benzene; 15 persons work in nitrochlorobenzene production. (This workforce is
supplemented by contract maintenance laborers who, in general, are not assigned
to a fixed work area but work in a number of areas, including the production
facilities. These workers assist with the maintenance of the facilities and

are not directly involved in the operation of chemical production equipment.)

Monochlorobenzene Personnel--

There are four principal job classifications involved with monochlorobenzene
production:

e@ Premium Operators

e@ Day Operators

e@ Repairmen

e Porters
Most of the time, these individuals are indoors, in a control-room blockhouse
located at grade level in the middle of the monochlorobenzene facility. Those

workers whose duties include checking the operation, cleanup, and maintenance
of the equipment make frequent, short-duration, trips outdoors to various


reactors, chlorinators, storage tanks, and associated equipment.

The duties of the four job classifications associated with the production of
monochlorobenzene are as follows:

Premium Operator--Responsible for operating the department, process equipment,
and auxiliaries. Controls inventories of raw materials, finished goods,
intermediates, and products in storage tanks and processing equipment.
Disposes of the waste material and adds oil to the refrigeration systems
as necessary.

Day Operator--Initiates the transfer of wet benzene by pipeline to the process
area and also receives benzene from terminal storage. Responsible for
loading and unloading of monochlorobenzene, ortho-dichlorobenzene, para-
dichlorobenzene, and benzene from tank cars and trailer trucks; this in-
cludes the connecting and disconnecting of loading, unloading, or steam
lines to tank-car or trailer-truck coils. Responsible for drumming of
products and assists the Premium Operator in the disposal of waste material.
Also drains water from wet benzene and cleans equipment. Assists Repair-
men in the cleaning of reboilers, heat exchangers, and condensers (or any
other equipment normally cleaned by two Repairmen) on the day when only
one Repairman is present. Often assists Repairmen in their duties.

Repairman--Responsible for cleaning reboilers, heat exchangers, condensers,
and water jets; also performs general repair work as directed by the
supervisor.

Porter--Performs custodial services in control room offices and repair area.

Nitrochlorobenzene Personnel--

The nitrochlorobenzene manufacturing area employs a nitration operator, washer
operator, utility day operator, repairmen, porters, and an hourly foreman (on
day shift). Descriptions of these job classifications follows:

Nitration Operator—--Monitors and controls continuous nitration of monochloro—
benzene, separation of crude nitrochlorobenzene from spent acid, and de-
hydration of the spent acid. Performs most of these tasks from the con-
trol room. Makes periodic trips to the process area to sample, check
equipment, clear lines, clean up operation area, and clean equipment for
maintenance work.

Washing Operator——Monitors and controls the continuous neutralization, washing,
dehydrating, and MCB stripping of the new MCB crude generated in nitration
process. Performs most tasks from the control room. Makes periodic trips
to the process area to sample, check equipment, clear lines, clean up

11


DISCLAIMER

Mention of company names or products does not constitute endorsement
by the National Institute for Occupational Safety and Health.

NIOSH Project Officer: Michael S. Crandall
SRI International Project Leader: Masao Koketsu

DHHS (NIOSH) Publication No. 81-105


Table C-1. Individual personal and area TWA concentrations

of monochlorobenzene at Plant C, June 1979.

Job title/location and sample number

TWA concen-
tration (ppm)

Personal samples

Operator (chlorobenzol)

Mechanic (chlorobenzol)

Maintenance Worker (adjacent
area)

Construction Worker (new construction
around chlorinator)

Badger Operator

Transfer Man (Badger area)

Area samples

Chlorinator--control room

Chlorinator--north end

Badger--control room

Badger--GC room

Badger #3--N.E. corner

Badger #2--N.E. corner

(continued)

32

964
966
982
987
989
980
oo
999

951

956
996

105

961
975
985
994

960
108

950

109

952
972
102

963
973
997

962
970

991
967

1007

953
974


samples registering above the OSHA and ACGIH standards (10 ppm). The geometric
mean for the benzene personal samples was 1.9 ppm,and the seven area samples
ranged from 0.3 to 3 ppm. Three out of 15 personal samples for o-dichloro-
benzene showed concentrations above the limit of detection (they were 0.1,

0.1, and 0.3 ppm). However, all area samples were at or below the detection
limit.

Four long-term area samples for nitrochlorobenzene were taken in the nitrochloro-
benzene manufacturing unit, all four of which were determined upon analysis to
be below the level of detection for the substance (Appendix Table A-3).

Simultaneously with the SRI survey team, Plant A conducted personal sampling
for MCB and for benzene using a 3M passive sampler as the collection medium for
the samples. As with the SRI charcoal-tube samples, the Plant A samples were
analyzed using desorption with carbon disulfide and analysis by gas chromato-
graphy with flame ionization detection. The results of this side-by-side
sampling are shown in Appendix Table A-4.

RESULTS OF SURVEY--Plant B

Time-weighted-average exposures of workers at Plant B to monochlorobenzene are
shown in Table 3, where concentrations and geometric means for each job classi-
fication, by shift,are given. Individual personal sample results, and the
results of long-term area sampling, are shown in Appendix Table B-1.

Personal MCB exposure concentrations ranged from 0.1 to 2.9 ppm, which is well
below the current OSHA standard and ACGIH recommended Threshold Limit Value.
The highest concentration, for a Distillation Operator, was 2.9 ppm. (The
mean concentration of MCB for all jobs was 0.8 ppm.) The Senior Operator job
classification received the highest mean concentration, which was 1.1 ppm.
(See Table 3.)

Long-term area samples for MCB were taken during the day shift on the second
day of the survey. The concentrations of MCB found in these samples ranged from
3.1 to 14.2 ppm (Appendix Table B-1).

Table 3. Job and work-shift TWA concentrations of monochlorobenzene
at Plant B, January 1979.

TWA concentration (ppm)

Job title Day Evening Night Geometric
Shift Shift Shift Mean
Senior Operator 221059 2.8 0.4 deal
Distillation Operator On2 yo: 0.1 2.9 0.57
Material Handler Or8,055 0.7 0.65

Personal and area concentrations of benzene and o-dichlorobenzene at Plant B
also were determined, and the sampling results are presented in Appendix
Table B-2. Personal TWA benzene levels ranged from 0.1 to 3.5 ppm, with

20


EXTENT-OF-EXPOSURE SURVEY OF MONOCHLOROBENZENE

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
Centers for Disease Control
National Institute for Occupational Safety and Health
Division of Surveillance, Hazard Evaluations, and Field Studies
Cincinnati, Ohio 45226

February 1981


Table A-3, Area concentrations of para-nitrochlorobenzene at
Plant A, November 1978.

*
Time Volume Concentration

Location and sample number (min) (liter) (ppm)

Above underground PNCB

storage tank Sl 415 70%5 --*

Below #1 Nitrator

(on OC booth) S2 406 TNs 7 ad

Between #1 and #2 separators 83 401 77.7

Grade level, near NCB pumps S4 375) 62.2 --

¥
All were below detectable limit (less than 10 micrograms).

28


full-capacity operating conditions. At Plant C, personal
TWA exposures to MCB were well below current exposure
standards, ranging from below-detectable (12 of 18 samples)
to 1.90 ppm. Long-term area samples for MCB at the three
plants were also low (the highest level was a 14.2 ppm
concentration at Plant B).

Personal concentrations of benzene and dichlorobenzene
were also determined from air samples taken during the
survey. Forty-two of the 44 benzene personal samples at
the three plants ranged from 0.02 ppm to 3.5 ppm. The
remaining two samples (2 of 15 at Plant A) showed concen-
trations of 15.7 ppm and 21.1 ppm. (The current OSHA
standard and ACGIH recommended Threshold Limit Value is
10 ppm). Personal concentrations of o-dichlorobenzene
ranged from below-detectable to 2.28 ppm (well below the
current OSHA standard of 50 ppm). Four samples for para-
nitrochlorobenzene, taken at Plant A, yielded concentrations
that were below the detectable limit.

The plants should maintain their vigilance on exposures

of personnel to monochlorobenzene (and other toxic sub-
stances). This should include maintaining ventilation

and other physical control measures and a personnel expos-
ure monitoring program. Also, instruction of employees,
particularly new employees, in the toxic nature of the
substances with which they work, and work practices that
are in consort with process operations and production rates
that exist at any given time should be implemented or
continued.

23:


PROCESS AND CONTROL OPERATIONS

All three of the plants surveyed used the fundamental process for producing
monochlorobenzene as described briefly in the preceding chapter ("Background"),
including the use of ferric chloride as a catalyst. The nature of the process

is such that the structures utilized are not enclosed. Comments and observations
on the process operation at each of the three plants are given below as approp~
riate.

Plant A--Process and Control

As noted previously, both monochlorobenzene and nitrochlorobenzene are produced
at Plant A, and production of both was included in this survey. The process/
control operations involved in their production are discussed below.

Monochlorobenzene Manufacturing--

Monochlorobenzene is produced at Plant A by the continuous chlorination of
benzene. Benzene for the process is pumped by pipeline from a reception terminal
to in-plant bulk storage, from which it is then pumped to the manufacturing area.
Chlorine is vaporized and pumped to the manufacturing area from another depart—
ment at the plant site.

The benzene (both unreacted and recycled) is dried and passed into a series of
three chlorinators, where it reacts with vaporized chlorine and the ferric
chloride catalyst. The catalyst is added to the system once each day by an
operator who manually empties the needed amount into a slurry tank. Hydrogen
chloride gas created during chlorination is separated from the other reaction
products, cooled, and passed to an absorber from which it is recovered as a
usable byproduct.

The crude chlorinated benzene and the unreacted benzene pass from the chlorin-
ator to the first of three separatory stages. The first stage removes the
catalyst; in the second stage, unreacted benzene is separated by distillation
(and returned for reintroduction to the process); in the third stage, MCB and
residual amounts of dichlorobenzene are passed into a uit, called the mono-
column, where the final MCB product is separated. (The dichlorobenzene is
pumped to another department for recovery.)

Nitrochlorobenzene Manufacturing--

Nitrochlorobenzene is manufactured by the reaction of monochlorobenzene and
nitric acid in the presence of sulfuric acid. Monochlorobenzene for the manu-
facturing process is received by pipeline from the MCB manufacturing unit at
Plant A. Nitric acid is received by rail car.

The MCB is pumped, from underground storage, to a surge tank, then to the first
of three nitrators, to which nitric acid and sulfuric acid are also added.

The three nitrators agitate the material as it cascades through them, and para-
nitrochlorobenzene, ortho-nitrochlorobenzene, hiboilers, and sulfuric acid are


Ho [ti oO o jit

® Tank car loading and unloading
Storage Storage
MCB MCB
®
Badger Badger
#3 Badger Area A!
Control Room
3)
® Toll
Badger © R
GC undown
a Room Receiver

Safety Shower

Neutralizer Area

me

Cott

JEL,

Chlorinator Area
Control Room

Water Cooling
Tower

3)

[Chlorinaton
Area

rea sampling points
A pling poi

Figure 2. Layout of the MCB manufacturing facility at Plant C.

10