TSCA SECTION 4
HUMAN EXPOSURE ASSESSMENT
CYCLOHEXANONE
Final Report
Prepared by:
John Carpenter
Robert Hall, Ph.D.
Virginia Hodge
Henry Nelson, Ph.D.
William Perry
Arlan Shochet
Fred Zafran
Contract No. 68-01-4839
DOW #11
JRB Associates
8400 Westpark Drive
McLean, Virginia 22102
December 9, 1981
-------
TABLE OF CONTENTS
Page
1. INTRODUCTION 1-1
2. IDENTITY, PHYSICAL PROPERTIES, AND CHEMICAL BEHAVIOR 2- 1
2.1 MOLECULAR STRUCTURE, FORMULA, AND CAS NUMBER 2- 1
2.1.1 Identity of Cyclohexanone 2- 1
2.1.2 Description of Technical Grades and Contaminants....2- 1
2.2 PHYSICAL PROPERTIES 2-2
2. 3 CHEMICAL PROPERTIES 2-2
3. SOURCES OF RELEASE 3- 1
3.1 MANUFACTURING 3- 1
3.1.1 Releases from Manufacturing Processes 3- 1
3.1.2 Location of Facilities 3- 5
3.1.3 Production, Import and Trends 3- 5
3.2 PROCESSING 3-3
3.3 DISTRIBUTION IN COMMERCE 3- 9
3.3.1 Releases During Transport 3- 9
3.3.2 Releases from Storage 3-10
3.4 CONSUMPTION 3-10
3.4.1 Releases Due to Industrial and Commercial Use 3-12
3.4.2 Releases from Consumer Uses 3-13
3.4.3 Export Quantities 3-14
3. 5 DISPOSAL 3-14
3.6 NATURAL AND INADVERTENT PRODUCTION 3-14
3.7 SUMMARY OF ENVIRONMENTAL RELEASES 3-14
4. ENVIRONMENTAL FATE 4-1
4.1 CHEMICAL TRANSFORMATIONS 4- 1
4.1.1 Hydrolysis, Oxidation, and Reduction. 4- 1
4.1.2 Photochemical Oxidation and Photolysis 4- 1
4. 2 BIOTRANSFORMATION 4-5
4. 3 ENVIRONMENTAL TRANSPORT 4-6
4. 3.1 Volatili ty 4-7
4.3.2 Adsorption 4-9
4.4 BIOCONCENTRATION/BIOMAGNIFICATION 4- 9
5. MONITORING
5.1 METHODOLOGY 5-1
5.1.1 Sampling 5- 1
5.1.2 Analysis 5- 2
5.2 DETECTION AND MEASUREMENT RELATED TO
INDUSTRIAL PROCESSES AND WASTE DISPOSAL 5- 2
5.3 DETECTION AND MEASUREMENT RELATED TO
COMMODITIES AND CONSUMER PRODUCTS 5- 3
5.4 DETECTION AND MEASUREMENT IN THE ENVIRONMENT 5- 3
6. HUMAN EXPOSURE
6.1 OCCUPATIONAL EXPOSURE 6-1
6. 2 CONSUMER EXPOSURE 6-2
6.3 GENERAL POPULATION EXPOSURE 6- 4
REFERENCES R- 1
-------
1. INTRODUCTION
In April 1979, the Interagency Testing Committee, created under Section
4(e) of the Toxic Substances Control Act (TSCA), recommended that cyclohexa-
none be considered by EPA for testing under Section 4 of TSCA. This report
presents an assessment of human exposure to cyclohexanone. Its purpose is to
provide the Test Rules Development Branch of EPA's Office of Pesticides and
Toxic Substances with human exposure information to evaluate the need for a
test rule on cyclohexanone.
1-1
-------
2. IDENTITY, PHYSICAL PROPERTIES, AND CHEMICAL BEHAVIOR
2.1 MOLECULAR STRUCTURE, FORMULA, AND CAS NUMBER
2.1.1 Jdentitv of Cvclohexanone
Cyclohexanone is a six carbon, saturated, cyclic ketone. The only func-
tional group present is the carbonyl group (C=0). Cyclohexanone is the name
approved by the International Union for Pure and Applied Chemistry (IUPAC) and
is derived by replacing the -e of the corresponding alkane with -one. Common
names include cyclohexyl ketone, ketohexaraethylene, and pimelic ketone.
Table 2-1 lists the IUPAC and common names, Chemical Abstract Service
(CAS) number, molecular formula, and structural formula for Cyclohexanone.
Table 2-1. Identity Data for Cyclohexanone
IUPAC Name Cyclohexanone
Common Names Cyclohexyl Ketone
Ketohexamethylene
Piraelic Ketone
CAS Number 108-94-1
Molecular Formula CgH-QO
Molecular Structure 0
C
Sources: Fisher (1978)
Union Carbide (1975)
2.1.2 Description of Technical Grades and Contaminants
Cyclohexanone is commercially available in several grades. Table 2-2
shows the specifications of a typical low-purity grade and a typical high-
purity grade. Water (0.2$ maximum) is the only contaminant that has been
specifically identified in either grade.
2-1
-------
Table 2-2. Specifications of a Typical
Low-Purity and High-Purity Grade of Cyclohexanone
Property
Low Purity
High Purity
Appearance
Ketone Content (% Min)
Water Content (% Max)
Specific Gravity
Distillation Range (1 Atm)
Ash (% Max)
Acidity ($ Max)
Colorless Liquid
89$
0.2$
20/20°C, 0.910-0.950
152-157°C
0.01
Colorless Liquid
99.5$
0.2$
15.5/15.5°C, 0.950-0.951
152-157°C
0.01
0.03$
Source: Fisher (1978)
2.2 PHYSICAL PROPERTIES
Cyclohexanone is a colorless liquid with an odor resembling peppermint
and acetone. Table 2-3 lists some of the physical properties of
Cyclohexanone. The spectrum of Cyclohexanone in methanol is given in Figure
2-1.
2.3 CHEMICAL PROPERTIES
The carbonyl group of Cyclohexanone is responsible for most of the
compound's chemical reactivity. This group is partially polarized because
oxygen is much more electronegative than carbon (Morrison and Boyd 1973):
{ C = 0
\ /6+ 5-
The carbonyl carbon has a positive partial charge, which makes it susceptible
to nucleophilic addition. The hydrogens that are ot to the carbonyl group are
slightly acidic and are therefore susceptible to abstraction in alkaline
solutions. This may be due to the resonance stabilization of the resultant
carbanion by the carbonyl group.
2-2
-------
Table 2-3« Physical Properties of Cyclohexanone
Molecular Weight 98.15*
Boiling Point, °C (1 Atm) 155.8a
Freezing Point, °C -31.2a
Specific Gravity, 20/20°C 0.9U82a
Refractive Index, nD20 1.4512a
Flash Point, °F, Tag Open Cup, Tag Closed Cup 116b(TOC), l43b(TCC)
Vapor Pressure, torr (20°C) 2a, 4°
Heat of Vaporization (BTU/lb under 1 Atm) 174b
Absolute Viscosity, cp (20°C) 2.2b
Surface Tension, dynes/cm (20°C) 27.7b
Solubility in Water, g/liter 25a, 23°
Solubility in Ethyl Alcohol, Diethyl Ether,
Acetone, Benzene, Chloroform Soluble
a Union Carbide 1975
b SRC 1976
0 Verschueren 1977
d Weast 1972
2-3
-------
1.0
0.8
, (U
c OJ
j» 0.4
<
0.2
I 1
220 240 260 280 300 320 340 360
Nanometers
Source: Sadtler Index 1966 in SRC 1976.
Figure 2-1. Spectrum of Cyclohexanone
(0.50 g/L in methanol)
2-4
-------
The chemical properties of cyclohexanone are similar to those of
saturated noncyclic ketones. Cyclohexanone undergoes several major types of
reactions including oxidatlve cleavage at the carbonyl group, catalytic reduc-
tion to cyclohexanol and/or oyclohexane, various types of nucleophilic addi-
tions to the carbonyl carbon, and various photolytic reactions. The cyclo-
hexanone carbanion formed by the abstraction of an a hydrogen from cyclo-
hexanone is a nucleophile; therefore, it will add to the carbonyl carbon of
various aldehydes and ketones.
The reactions that appear to be important commercially or environmentally
will be discussed below.
Approximately 95$ of the cyclohexanone currently produced is used to
synthesize two precursors of nylon: adipic acid and e -caprolactam. Most of
the remaining cyclohexanone is used as a solvent (see Section 3). Adipic acid
can be produced by the oxidative cleavage of cyclohexanone by nitric acid (SRC
1976):
0
II
0
V2°5
HMO
100°C
HO
CH CH CH
)H
150 psi
Oxidative cleavage of cyclohexanone by microorganisms has been reported (see
Section 1). e-Caprolactam can be produced by the nucleophilic addition of
hydroxylamine (NH-OH) to the carbonyl carbon of cyclohexanone followed by a
Beckman rearrangement (SRC 1976):
0
II
0
HO NHOH
intermediate
N-OH
0
(Beckman
rearrangraent)
ON-H
-caprolactam
The photolysis of cyclohexanone by radiation with wavelengths above
290 nm may be an important transformation process for cyclohexanone in the
2-5
-------
troposphere, in water or on soil. The photolysis of cyclohexanone at 313 nm
gives high quantum yields of cyclopentane, 1-pentene, and carbon monoxide
(Blacet and Miller 1957):
8
o
hi/ (313nm)
+ H2C=CH(CH2)2CH3 + CO
2-6
-------
3. SOURCES OF RELEASE
3.1 MANUFACTURING
3.1.1 Releases from Manufacturing Processes
About 80$ of the annual production volume of cyclohexanone is synthesized
by oxidizing cyclohexane (RTI 1977):
OH
120-250°C /x^ ^
'2
0 OH
6 • 6
pressure
catalyst
(cyclohexane) (cyclohexanone) (cyclohexanol)
The two products, cyclohexanone and cyclohexanol, can be separated with
vacuum-fractionating techniques, but the usual procedure is to use the mixture
captlvely as feedstock for subsequent synthesis of caprolactam and adipic
acid.
Figure 3-1 shows a process flow diagram for air oxidation of cyclohexane
to cyclohexanone (Pervier et al. 1974).
Pervier et al. (1974) have inventoried environmental releases during
cyclohexanone production. According to their report, which was based on
information supplied by producers, the single largest source of releases
during the oxidation process is the venting of spent air via the oxidizer
vent. The overall emission factor for hydrocarbons was 0.039 kg/kg product.
Of these hydrocarbon emissions, three manufacturers estimated that cyclo-
hexanone contributed 5$, 10$, and 28$. Using the average value of 14$, the
estimated emission factor for cyclohexanone is 0.0055 kg/kg product. (The
extreme values of 5$ and 28$ yield an emission factor range of 0.0020-0.011
kg/kg product.) When the average factor is applied to 80$ of the estimated
1979 cyclohexanone production, i.e., the amount produced by cyclohexane
oxidation (see Section 3-1.3). the estimated annual releases to the air are
1.8 x 106 kg (range: 6.4 x 105 kg - 3-5 x 106 kg).
Releases to water are possible because of the washing and ester hydro-
lysis steps during product purification. The solubility of cyclohexanone in
water is 2.5 kg/100 kg solution (Union Carbide 1975). Pervier et al. (1974)
3-1
-------
NJ
Cyclohexane
HstartJ
Air
.J
Compression
Source: Pervier et al. 1974
Recycle Cyclohexane
Water Caustic
Vent
("Spent" Air)
Distillation and
Purification
Heavy Light Aqueous
Ends Ends Waste
Hydrogen,^
Figure 3-1. Flow Diagram for Cyclohexanone Production from Cyclohexane
-------
estimated a wastewater volume of 175 gal/min (665 liters/min) for a plant with
a capacity of 31.000 tons (14,270 kg) cyclohexanorfe per year. Assuming that
production is 80$ of capacity, the volume of wastewater released can be calcu-
lated from the factor 12.4 kg wastewater/kg cyclohexanone. Applying this
factor to 80$ of the 1979 cyclohexanone production volume (see Section 3-1.3)
yields 3.94 x 10° kg wastewater/year. If the wastewater were saturated with
cyclohexanone, the maximum amount released would be 2.5$ of the wastewater
discharged annually, or 9.9 x 10^ kg/year. This estimate represents 31$ of
annual production, and is clearly unrealistically high.
Using the estimate of Pervier et al. (1974), which states that the 175
gal/min (665 liters/min) discharge releases 2,000 Ib/hr (908 kg/hr) of
organics, a concentration of 0.023 kg organics/kg wastewater was calculated.
Since cyclohexanol is 1.44 times as water-soluble as cyclohexanone (Stecher
1968), and since the primary product of the oxidation reaction is cyclohexanol
(Pervier et al. 1974 report a 9:1 cyclohexanol/cyclohexanone ratio using a
boric acid catalyst), the actual concentration of cyclohexanone was estimated
to be about 10$ of the total, or 0.0023 kg cyclohexanone/kg wastewater. Using
the value of 3.94 x 10° kg wastewater/year (calculated above), the annual
release of cyclohexanone to aqueous waste was estimated to be 9.0 x 10 kg, or
2.9$ of production.
Unlike the estimate of atmospheric emissions, which was based on indus-
trial data after emission controls, the water release estimates do not take
into account subsequent treatment or disposal.
Solid wastes from cyclohexanol/cyclohexanone synthesis would probably be
derived from catalyst regeneration and from heavy ends and sludges after
distillations. In both cases, residual cyclohexanone is expected to be
minimal.
In addition to the cyclohexane oxidation process for cyclohexanone
production, approximately 20$ is synthesized by hydrogenation of phenol (RTI
1977):
OH 0
100-200
1-4 Atra
Pd cat.
o
Figure 3-2 is a process flow diagram for phenol hydrogenation.
3-3
-------
. Solvent,-.
Phenol
Preheater
Reactor
Condenser
Catalyst
Gas
LO
-p-
Adapted from SRC 1976.
_BJ[nert gases
Scrubber
Distillation
Recycle
Phenol
Cyclohexanone
Figure 3-2. Flow Diagram for the Production of Cyclohexanone from Phenol
-------
Air emissions are possible at the reactor vent (after the scrubber) and
at the distillation vents (RTI 1977). In the absence of monitoring or indus-
trial data, it is estimated that the air emission factor for the phenol reduc-
tion process would be similar to that for the cyclohexane oxidation process:
0.0055 kg/kg cyclohexanone. This order-of-magnitude estimate was based on the
general similarities of the respective process conditions, especially tempera-
ture. It is consistent with an industrial process that is 90$ efficient in
collecting cyclohexanone product, and 95$ efficient in removing or destroying
the remaining 10$ of potential emissions. These are reasonable values for an
average industrial process. Applying this estimated release factor to 20$ of
the 1979 cyclohexanone production volume yielded estimated air emissions of
approximately 4 x 10 kg cyclohexanone.
Although no data were available on cyclohexanone releases to wastewater
during phenol reduction, these releases should be smaller than those from
cyclohexane oxidation because aqueous extraction is not used as part of the
process; only scrubber water would contain cyclohexanone. Furthermore, if
scrubber water were stripped by distillation, wastewater streams should
contain very little cyclohexanone. Based on these considerations, phenol
reduction would produce only 10$ of the water releases/kg of product that
cyclohexane oxidation produced. The release factor would thus be 0.003 kg/kg
produced, and the estimated annual release would be 2 x 10^ kg cyclohexa-
none. Because of the lack of data, this estimate involves a substantial
degree of uncertainty. Also, the estimate does not take into account subse-
quent water treatment or waste disposal.
Releases of cyclohexanone in solid waste could not be estimated due to
lack of information on waste sources, waste composition, and treatment
processes.
3.1.2 Location of Facilities •
Figure 3-3 shows the locations of the eight plants identified as cyclo-
hexanone producers in 1979.
3•1«3 Production. Import and Trends
USITC reports that the 1979 production volume of cyclohexanone was
Q
3.968 x 10 kg (personal communication between USITC statistics clerk to
3-5
-------
Hopewell
NORTH DAKOTA (MINNESOTA
aft, LA
Freeport (m)t located)
ictoria
Figure 3.3 Locations of Cyclohexanone Producers, 1979
-------
R. L. Hall, JRB Associates, December 17, 1980). Table 3-1 summarizes produc-
tion for 1979 and previous years, and distributes 1979 production among the
plants in proportion to their estimated capacities. Cyclohexanone production
has grown by an average of about 15% per year since 1975.
Cyclohexanone imports for 1975-1979 are summarized in Table 3-2.
Table 3-1. Production of Cyclohexanone by Year
Company & Plant
Location3
Allied Chemical
Hopewell, VA
Celanese Chemical
Bay City, TX
Nipro, Inc.
Augusta, GA
Badische Co.
Freeport, TX
DuPont
Orange, TX
Victoria, TX
Monsanto Co.
Pensacola, FL
1979
Capacity3
190.0
45.0
156.0
141.0
122.0
231.0
227.0
Production (106 kg)
1979 1978 1976 1977 1975
67.3
15.9
55.2
49.9
43.2
81.8
80.4
Process
and Use
Phenol reduction;
captive use
Cyclohexane oxi-
dation; captive
use
Cyclohexane oxi-
dation; captive
and merchant use
Cyclohexane oxi-
dation; captive
use
Cyclohexane oxi-
dation; captive
use
Cyclohexane oxi-
dation; captive
use
Union Carbide
Taft, LA
Phenol reduction
9.1
3.2
TOTAL'
1,121.0 396.9 527
338
291
251
3SRI 1980
Production totals from USITC 1977-1979 and 1980 personal communication with USITC.
3-7
-------
Table 3-2. Imports of Cyclohexanone by Year
Amount Imported
Year (kg)*
1975 24,086b
1976 2,000
1977 47,592
1978
1979 21,580°
aUSITC 1977a-1979a
"Includes unknown fraction of cyclohexanol
in cyclohexanone/cyclohexanol mixture.
CUSITC, personal communication between
Mrs. Gessner and R.L. Hall, JRB Associates,
December 18, 1980
3.2 PROCESSING
Processing of cyclohexanone could entail preparing cyclohexanone for
distribution in commerce, e.g., by adding a stabilizer or by freezing, and/or
formulating products that contain cyclohexanone, e.g., a paint or a pesticide
mixture.
Environmental releases from the preparation of cyclohexanone for distri-
bution are estimated to be very small, based on the fact that only about
2.3 x 10? kg (about 6$ of 1979 production) were shipped to buyers. The
remainder was reported to have been used captively (see Table 3-1). No infor-
mation was available on procedures used by Nipro, Inc., in preparing cyclo-
hexanone for shipment. Presumably the procedure would be carried out in the
plant, and emissions would be included in estimates of emissions due to
production.
According to EPA pesticide registration files, 20 pesticide products
containing cyclohexanone are registered. Because the amount of cyclohexanone
used in formulating these products is unknown, releases due to formulating
could not be estimated. However, pesticides must comprise a small fraction of
cyclohexanone use (see Section 3.4); therefore, releases would be expected to
be small and localized at the respective plants.
3-8
-------
3.3 DISTRIBUTION IN COMMERCE
3.3.1 Releases During Transport
As noted in Section 3.2, only 6% of the cyclohexanone produced is avail-
able for sale and transport. The remainder is used captively within the pro-
•T
duction plant complex. The maximum amount transported would be 2.3 x 10' kg.
Releases from transporting this product can be divided into loading losses and
transport losses.
Releases due to truck loading have been estimated in two publications.
Table 3-3 summarizes the estimated release factors and the resulting emis-
sions. The release factor cited in SRC (1976) (1 x 10~^ kg/kg) was based on
the assumption that the product of vapor pressure and molecular weight is
proportional to the release factor for an evaporative process; the uncer-
tainties introduced by this assumption were not discussed. The second esti-
mate was derived from an EPA publication (EPA 1979), which lists emission
factors for gasoline and other petroleum liquids. The emission factor for
gasoline (6.3 x 10 kg/kg for normal submerged filling) was adjusted by the
vapor pressure ratios at 20°C — cyclohexanone:gasoline = 2 mm:320 mm; this
provided the emission factor of 4 x 10 kg/kg cyolohexanone loaded. The two
estimates differ by a factor of about two.
Table 3-3 Emission Factors and Estimated Releases
from Cyclohexanone Loading and Transport
Process
Truck/Railcar
Loading
Truck/Railcar
Loading
Truck/Railcar
Transport
Emission Factor
1 x 10~5 kg/kg
4 x 10~6 kg/kg
0-6 x 10~9 kg/kg
Estimated Emissions (kg)
200
90
0-0.1
Reference
Lande et al.
1976
EPA 1979
EPA 1979
The release factor for tank transport of cyclohexanone was derived from
the published value for gasoline transport (1 x 10~° kg/kg transported, EPA
1979), corrected for the vapor pressure ratio at 20°C (2 mm/320 mm). The
emissions estimated by this method are negligible.
3-9
-------
3.3.2 Releases Purina Storage and During Filling/Withdrawal from Storage
Tanks
EPA (1977) calculated emission factors for several petroleum derivatives
for losses during storage, in filling of and withdrawal from fixed-roof,
floating-roof, and variable-vapor-space storage tanks. The emission factors
were calculated from empirical equations presented in the EPA (1977) docu-
ment. JRB calculated emission factors for cyclohexanone by substituting
physical parameters of cyclohexanone such as vapor pressure and molecular
weight into the empirical equations presented in the EPA (1977) document.
Table 3-4 lists the estimated emission factors for and emissions of
cyclohexanone associated with each type of storage tank. The estimates were
based on the following assumptions:
• The 95$ of cyclohexanone production which is used as a chemical pre-
cursor is stored.
• Average storage time is 28 days.
• The amount of cyclohexanone stored is divided equally among the five
types of storage tanks considered: new and old fixed roof, new and
old floating roof and variable vapor space.
• Ambient conditions: storage temperatures of 15.6°C, daily ambient
temperature change of 8.3°C, wind velocity 10 mi/hr.
• Various other assumptions detailed in EPA (1977) about tank dimen-
sions, volume, and dimensionless factors used in the equations.
The total estimate of cyclohexanone release during storage, filling of
storage tanks, and withdrawal from storage tanks for 1979 based on the esti-
mated releases listed in Table 3-4 was 8,500 kg.
3.4 CONSUMPTION
Consumption includes not only the commercial processes that remove cyclo-
hexanone from the materials balance (conversion to another chemical and expor-
tation), but also its direct use as a solvent. The destruction of cyclo-
hexanone during waste disposal processes is discussed in Section 3.5.
Cyclohexanone is used almost entirely as an intermediate in producing
caprolactam and adipic acid, monomers used for the synthesis of nylon. In
1974, 95$ of the cyclohexanone produced was consumed as a chemical interme-
diate, with the remaining 5$ being used as a solvent (Patterson et al.
1976). This same distribution is assumed to apply to 1979 production.
3-10
-------
Table 3-4. Cyclohexanone Emissions from Storage
OJ
i
Tank Type and
Conditions
Fixed Roof Tanks
Breathing Loss
"New" Tanks
"Old" Tanks
Working Loss
Floating Roof Tanks
Standing Storage Loss
"New" Tanks
"Old" tanks
Variable Vapor
Space Tanks
Filling Loss
Derived
Cyclohexanone
Release Factor
1.1 x 10~6 kg
day kg
1.3 x 10~6 kg
day kg
1.1 x 10~5 _kg_
kg throughput
1.5 x 10~7 kg
day kg
3.4 x 10~7 kg
day kg
1.1 x 10~5 _kg
kg throughput
Weighting
Factor
0.2
0.2
0.4
0.2
0.2
0.2
0.2
Assumed
Days of kg kg
Storage3 Stored Emissions
28 7.5 x 107 2,300
28 7. 5 x 107 2,700
15 x 107 1,700
28 7.5 x 107 300
28 7. 5 x 107 700
7. 5 x 107 800
8,500
aEPA 1977
Fraction of stored Cyclohexanone using respective tank type. These are estimates and are not
tank census data.
Corresponds to the 95% of Cyclohexanone production used captively for further manufacturing.
on
-------
3.4.1 Releases Due to Industrial and Commercial Use
Assuming that the percentage breakdown of cyclohexanone use in 1979 was
the same as that reported for 1974 production (Patterson et al. 1976), 43% of
o
the cyclohexanone (1.7 x 10 kg) was used for caprolactam synthesis and 52%
(2.1 x 108 kg) in adipic acid.
Basdekis (1979) estimated the emission factor for volatile organic
compounds (VOC) during caprolactan synthesis to be 1.17 g VOC released/kg
caprolactaca produced. This estimate was based on engineering judgments and on
visits to two plants. A 90% yield for the cyclohexanone-to-caprolactam
conversion can be assumed, based on the high efficiencies usually obtainable
in large-scale continuous industrial processes. The release factor is there-
fore equivalent to 1.21 g VOC/kg cyclohexanone used. When this release factor
is applied to the estimated amount of cyclohexanone used for caprolactam
synthesis (see above), an estimate of 2.1 x 10 kg VOC releases is obtained.
Although no composition data on VOC were available, it is unlikely that more
than 10% of this is cyclohexanone. This judgement is based on the fact that
emission of a significant fraction of the feedstock unreacted would be
economically unsound and it would be preferable to recycle the vent gas.
Thus, the estimated air emissions of cyclohexanone from caprolactam synthesis
were approximately 2 x 10 kg.
Basdekis (1979) reported that cyclohexanone was qualitatively identified
in caprolactam plant wastewater. He estimated a typical wastewater flow rate
of 550,000 kg/hr for a 70 x 10" kg caprolactarn/year model plant, or 69 kg
wastewater/kg caprolactam. Using the method outlined above, the wastewater
flow is 72 kg/kg cyclohexanone used. The total wastewater flow for utiliza-
Q 1 f\
tion of 1.7 x 10 kg cyclohexanone would be 1.2 x 10 kg. The total organic
carbon composition of this stream was estimated to be 480 ppm (Basdekis
1979). Cyclohexanone would contribute about 10% of the organic content, since
it is not present in significant amounts after the first step in caprolactam
synthesis. Using 50 ppm as an estimate of cyclohexanone content in the waste-
water stream yields an estimate of 60,000 kg cyclohexanone in wastewater
streams before treatment. This is 0.4% of the cyclohexanone input. In-plant
treatment of wastewater streams probably removes 58% of the cyclohexanone
(Patel and Patel 1977), leaving a discharge to receiving waters of 25,000 kg
cyclohexanone annually. This estimate involves a large degree of uncertainty.
3-12
-------
Potential air emissions due to synthesis of adipic acid from cyclohexa-
none were estimated by Bruce et al. (1979). Based on visits to adipic acid
plants and industry responses to a questionnaire, Bruce et al. estimated an
emission rate for VOC of 45.2 kg/hr for an annual production volume of
Q
8.546 x 10 kg adipic acid. The release factor derived from this estimate was
4.6 x 10 kg cyclohexanone/kg adipic acid produced, based on an 8,760-hour
year. By assuming a 90? yield in the conversion of cyclohexanone to adipic
acid, the estimated air emission factor is 6.2 x 10 kg cyclohexanone
released/kg cyclohexanone used. Applying this factor to cyclohexanone usage
for adipic acid production yielded 1.3 x 10 kg cyclohexanone released to air
annually.
Bruce et al. (1979) estimated that releases of volatile organic compounds
to wastewater would be negligible compared to air emissions.
The locations of the releases estimated above would be the production
plants, since in most cases the cyclohexanone produced is used captively for
either caprolactam or adipic acid synthesis. A breakdown showing which plants
produce which product(s) is available in Stanford Research Institute's
Chemical Economics Handbook, but the information cannot be included in the
present report.
An estimated 5% of the cyclohexanone produced is used as an industrial
solvent. The compound is used as a solvent for inks, pesticides, textile
dyes, and sludge; as a degreaser for metal and leather; as a spot remover; and
as a paint remover (SRC 1976). The amount used in 1975 was 1.98 x 10 kg;
this would represent a maximum estimate for air emissions. However, in the
absence of specific data from industry on recycling procedures or emission
controls, it is not possible to estimate actual annual releases of cyclohexa-
none due to solvent evaporation. According to Patterson et al. (1976), the
major source of cyclohexanone emissions to the atmosphere is its use as an
industrial solvent (see also Section 6.3).
3.4.2 Releases from Consumer Uses
Since almost all cyclohexanone is used industrially, releases from
consumer products that contain cyclohexanone are expected to be very small.
The only direct source of releases appears to be the application of pesticides
that contain cyclohexanone to the air and soil. Cyclohexanone is used as a
solvent for lindane, an anti-borer insecticide applied to food crops.
3-13
-------
3.1.3 Export Quantities
The export of cyclohexanone in 1979 was not tabulated separately by the
Bureau of the Census (personal communication between Mrs. Gessner, U.S. Bureau
of the Census, and R. L. Hall, JRB Associates, December 18, 1980). Cyclohexa-
none may be included in the category that includes ethers and ketones. A
special search would have to be requested by EPA to obtain export data. No
exports of cyclohexanone were listed for the years 196M-1973 (SRC 1976).
3.5 DISPOSAL
Data were not available on cyclohexanone releases from disposal of solid
wastes. These wastes would include both industrial sludges and discarded
consumer products. It would be necessary to analyze landfill leachates and
information on industrial disposal methods to estimate releases from these
sources.
3.6 NATURAL AND INADVERTENT PRODUCTION
Cyclohexanone is not known to be a product of metabolism or other natural
processes.
Emissions from automobile exhausts are a possible source of inadvertent
production. The sources cited in SRC (1976) do not list cyclohexanone as one
of the exhaust components that have been measured. For ketones that were
measured, concentrations ranged from undetectable to 1.5 parts per million
(ppm). The authors pointed out that previous reports had estimated annual
automotive hydrocarbon emissions to be 2.5 x 10^ kg and that, if cyclohexa-
none contributed an average of 0.1 ppm (a hypothetical value), then cyclohexa-
none emissions would be 2,500 kg. The amount of unburned hydrocarbon emis-
sions will be greatly reduced as more cars use catalytic converters, so this
estimate can be taken as a maximum.
3.7 SUMMARY OF ENVIRONMENTAL RELEASES
The major source of cyclohexanone releases is estimated to be water
releases from cyclohexanone production. Air emissions from production are
also an important source. It is possible that evaporation of industrial
cyclohexanone solvent contributes more than all other sources combined, but
3-14
-------
emission control devices probably reduce the actual emissions considerably.
The main data gap appears to be the lack of information on disposal and/or
treatment of industrial wastes — solid sludges, wastewaters, and vent gases.
Table 3.5 summarizes the environmental releases estimated in this
chapter.
3-15
-------
Table 3.5 Estimated Annual Releases of Cyclohexanone
Process
Cyclohexanone production
Cyclohexanone processing
Cyclohexanone transport
Cyclohexanone loading
Cyclohexanone storage
Industrial consumption
Caprolactam
Adipic acid
Solvent
Consumer Use
Export
Disposal
Natural/Inadvertent
Production
Estimated Releases (kg) to
Air Land Water
2.2 x 106
0
0-0.1
90-200
8.5 x 103
2 x 104
1.3 x 105
_<1.98 x 107
0
NK
NK
NK
NK 9.2 x 106a
0 0
0 0
0 0
NK NK
NK 2.5 x 104
NK 0
NK 0
0 0
NK NK
NK NK
0 0
Disposal
0
0
0
0
NK
NK
NK
NK
NK
NK
NK
0
aThis value reflects releases to wastewater, not emissions to surface water
(see Section 3.1.1).
NK - Not known
3-16
-------
4. ENVIRONMENTAL FATE
4.1 CHEMICAL TRANSFORMATIONS
Ketones undergo four major types of reactions: nucleophilic addition to
the carbonyl carbon (e.g., hydrolysis); oxidation; reduction of the carbonyl
carbon; and various reactions involving the initial abstraction of an
at hydrogen.
1.1.1 Hydrolysis, Oxidation, and Reduction
The carbonyl carbon of a saturated ketone is not as susceptible to
nucleophilic attack as that of an aldehyde (Morrison and Boyd 1973). There-
fore, many aldehydes hydrolyze readily, but saturated ketones such as cyclo-
hexanone generally do not hydrolyze at significant rates in the environment
(SRC 1976). Oxidation or reduction of ketones requires somewhat more severe
conditions than those normally encountered in the environment (Morrison and
Boyd 1973). Therefore, significant rates of chemical oxidation or reduction
of cyclohexanone in the environment are unlikely. For example, most ketones
are stable in the presence of oxygen at ambient temperatures (SRC 1976).
4.1.2 Photochemical Oxidation and Photolysis
In smog chamber studies cyclohexanone was somewhat less chemically
reactive than many compounds tested, including several other ketones (Levy et
al. 1969, Levy 1973, and Laity et al. 1973). Levy (1973) performed individual
smog chamber studies on 45 commonly used solvents, including alkyl amines,
alkenes, aromatics, alcohols, and ketones. Each solvent was rated as having
high, intermediate, or low reactivity with respect to a number of measured
parameters that were used to estimate chemical reactivity in smog. Although
the investigators did not report the actual rates of solvent degradation, they
reported the time required to obtain a nitrogen dioxide (NOp) maximum in the
smog chamber after a given compound was introduced (NOp is generated during
smog degradation of hydrocarbons). Cyclohexanone was ranked 37th out of 45
solvents and had a low reactivity in terms of the amount of time required to
obtain an NOp maximum.
Laity et al. (1973) performed individual smog chamber studies on 39
commonly used solvents, including alkanes, alkyl acetates, alkenes, aromatics,
4-1
-------
alcohols, and ketones. Their studies also indicated that cyclohexanone has a
low chemical reactivity in smog. The investigators measured a number of para-
meters used to estimate chemical reactivity in smog, including the rate of
solvent disappearance. Since there were occasional variations in smog chamber
conditions, results were expressed in terms of the rate of disappearance of
toluene, a standard solvent. Because some of the 39 solvents had approxi-
mately the same disappearance rate, there were only 23 rankings among the 39
solvents. The maximum rate of cyclohexanone disappearance in relation to
toluene (1.0) was 0.5, which corresponded to the 18th fastest ranking.
Although cyclohexanone appears to have a low chemical reactivity in smog
with respect to many other compounds, it probably undergoes significant rates
of photodecomposition in smog and urban atmospheres. No rates of photodecom-
position for cyclohexanone could be found in the literature; however, photo-
decomposition rates of cyclohexanone can be estimated. Several studies have
shown a good correlation between the experimental rates of organic photodecom-
position and hydroxyl radical (»OH) rate constants for many organics (Winer et
al. 1976 and Darnall et al. 1976). As a result of these studies, the photo-
oxidation of organics by hydroxyl radicals has been postulated to be the
primary rate-determining step for the photodecomposition of many organics in
smog and urban atmospheres (Winer et al. 1976 and Darnall et al. 1976). Since
photolysis may also be involved in the photodecomposition of ketones, Winer et
al. (1976) have postulated that the photodecomposition rate of ketones can be
approximated by the following equation:
^ - k <
dt KOH v
where
kQjj = rate constant for reaction with hydroxyl radicals
(•OH) = hydroxyl radical concentration
khv = Pn°tolysis rate constant
(C) = concentration of the ketone
Assuming that the hydroxyl radical concentration remains constant during
photodecomposition, the photodecomposition rate can be represented as a pseudo
first order equation:
4-2
-------
dfi. = k (C)
dt p
where
V - lr (DHl -k V
p ~ OH *un' hf
Therefore, the half-life for photodecomposition is given by:
t i. = In 2/k
'/2 P
Winer et al. (1976) determined the values of kQjj and khj/ to be 9.0 x 10'
liters mol~1 sec and 3.9 x 10 sec~1, respectively, for methyl isobutyl
ketone (MIBK), and 2.0 x 10^ liters raol"1 see"1 and 1.9 x 10 sec"1, respec-
tively, for methyl ethyl ketone (MEK). Assuming an average urban concentra-
7 3
tion of 10 hydroxyl radicals/cm-3 (Darnall et al. 1976), the estimated photo-
decomposition half-lives for MIBK and MEK are 1.2 and 5.4 hours, respec-
tively. Laity et al. (1973) measured the photodecomposition rates of MIBK,
MEK, and cyclohexanone in relation to that of toluene (1.0) in a smog chamber.
The rates were 0.8, 0.3f and 0.5, respectively. Assuming that the smog
chamber studies approximated urban atmospheric conditions and that the esti-
mated photodecomposition rates for MIBK and MEK in urban atmospheres are
accurate, the photodecomposition half-life for cyclohexanone in urban atmos-
pheres should be between 1.9 and 3.2 hours:
1.2 ' = 1.9 hours and 5-4 ' = 3.2 hours
0.5 0.5
The photodecoraposition half-life of cyclohexanone in rural atmospheres
will depend, in part, upon the relative importance of photochemical oxidation
and photolysis. Since the photolysis rates of MIBK and MEK appear to be
negligible compared to the compounds' photochemical oxidation rates in urban
atmospheres (e.g., KQU(OH) > > Khl/) the photodecoraposition rates of MIBK and
MEK in nonurban atmospheres with low concentrations of hydroxyl radicals and
other oxidants would be expected to be much slower than in urban atmos-
pheres. The relative importance of photolysis and photochemical oxidation in
determining the overall photodecomposition of cyclohexanone is unknown,
although photolysis appears to be more important for cyclohexanone than it is
4-3
-------
for MIBK or MEK. Therefore, the decrease in the photodecomposition rate of
cyolohexanone in going from urban to nonurban atmospheres may not be as great
as that postulated for MEK and MIBK.
The photolysis rate of cyclohexanone in the troposphere, in water, or on
soil will depend primarily on the intensity of solar radiation and on the
extinction coefficients and quantum yields at wavelengths above 290 nm (Mill
1980). Cyclohexanone absorbs substantial amounts of radiation at wavelengths
above 290 nm (Serat and Mead 1959) and high quantum yields at 313 nm for the
breakdown to carbon monoxide, cyclopentane, and 1-pentene (Blacet and Miller
1957). Somewhat lower quantum yields were observed for ethylene and
propylene. Blacet and Miller (1957) proposed the following mechanism to
account for the observed products of cyclohexanone photolysis:
CH.CH.C CH0CH.CH. CH,(CHJ J3H.CO
• 2 2.U 2 c • £ • £ 2 3 2 •
CH
H2C ^ CH2
ethylene cyclopentane 1-pentene
CO CO
carbon
propylene
H?C=CHCH_ carbon monoxide carbon monoxide
4-4
-------
4.2 BIOTRANSFORMATION
Biological transformation refers to those enzymatically mediated reac-
tions carried out by microorganisms that are commonly found in soil and water
(i.e., bacteria, fungi, protozoa, and algae). These reactions include oxida-
tion, reduction, hydrolysis, and in some instances, rearrangements. The term
also applies to the metabolic transformation of compounds by higher organisms,
such as macroinvertebrates, fish, and mammals.
From the limited literature available for review it is evident that
cyclohexanone is biodegradable by waste treatment microorganisms. Pure cul-
tures of bacteria and fungi, isolated from several different sources, also
have been shown to utilize cyclohexanone as a carbon and energy source to
various degrees.
Fitter (1976) demonstrated a 96$ chemical oxygen demand (COD) for cyolo-
hexanone by adapted activated sludge that was incubated in open beakers and
stirred constantly. The initial cyclohexanone concentration of 200 mg/liter
as COD was biodegraded at a rate of 30 mg COD/g dry inoculum per hour, over a
5-day period.
In 5-day biochemical oxygen demand (BOD,-) tests with acclimated seed from
a laboratory scale activated sludge unit, Patel and Patel (1977) found that
for cyclohexanone, 58.3$ of the theoretical oxygen demand (ThOD) was elimi-
nated. These investigators also reported the biodegradability of caprolactam
wastewater, which contains cyclohexanone, cyclohexanol, cyclohexanone oxime,
and caprolactam (the monomer for Nylon-6) as main constituents. In a model
activated sludge reactor, adapted sludge reduced 98-99$ of the wastewater BOD
at an organic loading of 0.50 kg BOD/day per kg mixed-liquor suspended
solids. Additionally, Verschueren (1977) cited BOD,- values of 32$ and 46$
ThOD, and a BOD2Q of 77$ ThOD.
Norris and Trudgill (1971) isolated a soil bacterium, Nocardia globerula.
(culture enriched with cyclohexanol) that oxidized cyclohexanone as its sole
carbon source. Stirling et al. (1977) isolated a Nocardia sp. (tentative
identification) from estuarine mud flats by enrichment with cyclohexane, that
also was capable of cyclohexanone oxidation. From these studies the following
metabolic sequence was postulated: sequence cyclohexane—»-cyclohexanol »>
cyclohexanone —»-epsilon-caprolactone —»-6-hydroxycaproate—»-adipate.
4-5
-------
Murray et al. (197*0 also isolated a soil bacterium (a strain of Nooardia
madurae strain) that utilized cyclohexanone as its sole carbon source. •
Optimum growth of the Nocardia sp. occurred at a cyclohexanone concentration
of 0.1$ (v/v). Contrary to the results reported above, these authors proposed
a metabolic pathway that involves formation of 2-hydroxycyclohexane-1-one.
This metabolite was identified in the Nooardia culture extract, whereas
epsilon-caprolactone was not found.
The growth of a Pseudomonas sp. isolated from activated sludge was
enhanced by adding cyclohexanone, cyclohexanol, or cyclohexylaraine to a basal
salts growth medium (Bisz-Konarzewska 1978). Other gram-negative bacteria
common to activated sludge were inhibited by these compounds. Lowery et al.
(1968) found that of eight yeasts capable of growth on n-alkanes, only two
strains of Rhodotorula glutinis showed limited growth on cyclohexanone.
Matthews (1976) investigated the characteristics of a "sewer slime" that was
growing in sewage that contained cyclohexane derivatives from industrial
processes. The slime consisted primarily of the bacterium Zooaloea
filipendula and the yeast-like fungus Rhodotorula glutinis. as well as other
bacterial species and mold fungi. With cyclohexane derivatives as the sole
carbon source, the growth of the sewer slime on agar plates was enhanced by
these compounds in the following order: cyclohexanol > methycyclohexanone >
cyclohexanone > methycyclohexene > n-butanol = methylcyclohexanol >
cyclohexene. Cyclohexanone was especially active in promoting the growth of
molds (e.g.. Penicillium cephalosporium and Pennicillium trichothecium types).
4.3 ENVIRONMENTAL TRANSPORT
The vapor pressure of cyclohexanone is approximately 2 mm Hg at 20°C
compared to 17 mm for water. Therefore, unbound molecules of cyclohexanone
should evaporate fairly slowly into the atmosphere (Union Carbide 1975). The
aqueous solubility of cyclohexanone is approximately 25 g/liter at 20°C (Union
Carbide 1975). Thus, substantial quantities of cyclohexanone can be dissolved
in water. Interphase transport depends primarily on volatility and adsorption
characteristics.
4-6
-------
4.3.1 Volatility
Mackay and Leinonen (1975) and Dilling (1977) used the following equation
to estimate the evaporative half-lives of slightly to moderately soluble
organics from water as a function of depth:
t i = d 1n 2/K.
'/2 L
where
t = evaporative half-life from water
d = depth (in meters)
K, = liquid mass transfer coefficient (in m/hr)
The liquid mass transfer coefficient is related to the diraensionless Henry's
Constant by the following equation (Dilling 1977):
H K k.
K. = g-L-
L " H k + k.
g 1
where
H = dimensionless Henry's constant
k1 = liquid exchange constant (in m/hr)
k = gas exchange constant (in m/hr)
o
The above equation is based on the two-film transport model described by Liss
and Slater (1974). Dilling (1977) calculated the dimensionless Henry's
Constant using the following equation:
u 16.04 PM
H = TS
where
H = dimensionless Henry's Constant
P = vapor pressure in mm Hg
M = molecular weight in g/mol
T = temperature in degrees Kelvin
S = aqueous solubility in mg/liter
4-7
-------
Dilling (1977) and Mackay and Leinonen (1975) used the following equa-
tions taken from Liss and Slater (197^) to calcula'te liquid and gas exchange
constants, respectively:
ki = kico2
kg = kgH20 <
where
klC02 = liquid exchange constant for C02
gH20 = gas exchange constant for H20
MC02 = molecular weight of C02
MH20 = molecular weight of H20
M = molecular weight of substance
Dilling (1977) estimated the evaporative half-lives of 28 chlorinated
hydrocarbons of low to moderate aqueous solubility. He reported good correla-
tion between estimated and experimentally determined evaporative half-lives.
Mackay and Leinonen (1975) also estimated the theoretical evaporative half-
lives of 18 organics of low to moderate aqueous solubility.
The dimensionless Henry's Constant and the evaporative half-life from
water as a function of depth can be calculated for cyclohexanone using the
method suggested by Dilling (1977). The calculated value for the dimension-
less Henry's Constant is U.3 x 10" , and the calculated evaporative half-life
in hours for cyclohexanone from water as a function of depth (d) in meters is
130d. For example, the estimated evaporative half-life for cyclohexanone from
a body of water 2 meters deep is 390 hours, or a little more than 16 days.
The magnitude of the exchange constants is dependent on the extent of
turbulence (Southworth 1979 and Thibodeaux 1979). Therefore, evaporation
rates would be greater for streams and lakes with turbulent atmospheric condi-
tions than for ponds and lakes with relatively calm atmospheric conditions.
The values of the exchange constants for carbon dioxide and water used to
calculate the exchange constant for cyclohexanone were average values deter-
4-8
-------
mined for the sea-atmospheric interface, which is generally turbulent (Liss
and Slater 1974).
Although the above estimate of the evaporative half-life of cyclohexanone
from water may be qualitatively useful, it may not be quantitatively accu-
rate. This is because the aqueous solubility of cyclohexanone may be too
great to accurately estimate Henry's constant from the ratio of vapor pressure
to aqueous solubility. The aqueous solubility of cyclohexanone is much
greater than most values (of the aqueous solubilities of organic compounds)
reported by Dilling (1977) to exhibit good correlation between experimental
and estimated evaporative half-lives.
The rate of evaporation of cyclohexanone from soils will depend upon both
its vapor pressure and its affinity for soils. Adsorption to soils and sedi-
ments is discussed in the next section.
4.3.2 Adsorption
No specific information on soil/air or sediment/water partitioning could
be found in the literature. Equilibrium partition coefficients for sediment/
water can sometimes be used to qualitatively estimate sediment/water
partitioning in natural aquatic systems (Mill 1980). However, estimates of
sediment/water equilibrium partition coefficients appear to be currently
restricted to hydrophobia, chemically unreactive compounds (Karickhoff
1979). Therefore, estimates of sediment/water partitioning for cyclohexanone
which is not hydrophobia and which may be subject to chemical adsorption,
cannot be made.
4.4 BIOCONCENTRATION/BIOMAGNIFICATION
Bioconcentration by an organism is the direct concentration of a compound
from the surrounding environment through absorption and/or ingestion. A
bioconcentration factor is usually defined as the ratio of the concentration
of the compound in the test organism to the concentration of the compound in
the environment (usually water). Bioraagnification is the indirect concentra-
tion of a compound in higher food chain species resulting from the consumption
of lower organisms, with a net increase in tissue concentrations in the higher
species.
4-9
-------
No pertinent studies were available on the bioconcentration/biomag-
nification of cyclohexanone'. SRC (1976) predicted a very low bioconcentration
factor (about 4) and no biomagnification of cyclohexanone. Considering the
high aqueous solubility (23,000 mg/liter, as cited in Verschueren 1977) and
the low octanol/water partition coefficient of this compound (log PpH = 0.81,
Leo et al. 1971), there is little potential for bioconcentration of cyclo-
hexanone .
4-10
-------
5. MONITORING
5.1 METHODOLOGY
Environmental samples of cyclohexanone may take the form of solids,
liquids or gases. Although cyclohexanone evaporates moderately slowly, most
sampling and analytical protocols focus on vapor phase samples. Gas chromato-
graphy (GC) is the preferred method for analyzing cyclohexanone in environ-
mental samples. However, there are some colorimetric or spectrophotometric
methods that are specific for detecting cyclohexanone in samples of mixed
ketones.
5.1.1 Sampling
Liquid or solid samples containing cyclohexanone can be treated by
solvent extraction to quantitatively recover the analyte. The resulting
solution is either analyzed directly by GC or concentrated by evaporation
prior to GC determination. Vapor stripping of cyclohexanone from liquid
samples is probably inefficient due to the compound's relatively high boiling
point (156°C).
The vapor sampling method involves collection and concentration of the
sample in sorbent-packed columns. This is accomplished by pumping a known
volume of atmospheric sample through an adsorption tube, which is then sealed
and stored until analysis. The sorbed material is removed by thermal
stripping or solvent extraction depending upon the reactivity of cyclohexanone
with the adsorbent and the efficiency of the adsorbent to collect and subse-
quently desorb the analyte. NIOSH (1978) reported that the amount of cyclo-
hexanone on charcoal tubes decreases as storage time increases.
The method specified by NIOSH (1978) entails packing activated charcoal
derived from coconut shells into two separate sections of an adsorber tube.
The first section contains 100 mg and the second (back-up) section, which
serves as a control to determine if the analyte has broken through the first
section, contains 50 mg. If the back-up section contains 25$ or more of the
total cyclohexanone collected, the sample is considered to be invalid because
of the strong possibility that some material has passed through the collection
apparatus. For extraction from the charcoal adsorbent, NIOSH recommends
0.5 ml carbon disulfide.
5-1
-------
Other solid, polymeric adsorbents have been studied for use as possible
replacements for, or in conjunction with, activated charcoal. Holzer et al.
(1977) used Tenax, Carbopack, and Ambersorb, and Parkes et al. (1976) reported
better sorption characteristics for ketones with Chromosorb than with
charcoal.
5.1.2 Analysis
NIOSH (1978) specifies GC analysis for environmental samples in the parts
per million (ppm) range. The method utilizes a stainless steel column (10'ft
x 1/8 in) containing 10$ FFAP on diraethylchlorosilated Chromosorb W at a
temperature of 110°C and a flame ionization detector at 255°C. The validated
concentration range for the NIOSH method is 98-392 mg/m^ (25-100 ppm v/v) with
a standard deviation of 7.4 mg/m^ (1.85 ppm).
Methods other than the GC method specified by NIOSH (1978), have been
reported in the literature. Parkes et al. (1976) obtained a detection level
of 0.3 ppb (4 (u)g/m^) for cyclohexanone using heat desorption from a
Chromosorb adsorbent rather than solvent extraction. Andrew et al. (1971)
developed a colorimetric test to detect alicyclic ketones from field samples
of mixed ketones; however, other alicyclic compounds may interfere with this
process.
5.2 DETECTION AND MEASUREMENT RELATED TO INDUSTRIAL PROCESSES
AND WASTE DISPOSAL
The literature contains very little information pertaining to the detec-
tion and measurement of cyclohexanone related to, or identified with, indus-
trial processes, production, or waste disposal. A NIOSH study on health
hazard evaluation revealed concentrations of <1 ppm (v/v) of cyclohexanone in
both worker and general area samplers at a plant engaged in vinyl paint
spraying (Ruhe 1974).
Cyclohexanone was found but was not quantified in an EPA survey analysis
of the effluent of various chemical plants (Shackleford and Keith 1976).
These include a latex plant in Calvert City, Kentucky, unspecified chemical
plants in Kingsport, Tennessee, and Louisville, Kentucky and an unspecified
textile plant.
5-2
-------
5.3 DETECTION AND MEASUREMENT RELATED TO COMMODITIES AND CONSUMER PRODUCTS
No information could be found in the literature on the detection or
measurement of cyclohexanone in consumer products or commodities.
5,4 DETECTION AND MEASUREMENT IN THE ENVIRONMENT
In the Talladega National Forest, located approximately 35 miles from
Tuscaloosa, Alabama, ambient air samples were taken during the late fall of
1976 and the spring of 1977. Cyclohexanone was not present in the winter
sample; it was detected but not quantified in the spring sample (Holzer et al,
1977). No data on cyclohexanone in water samples were available from the
STORET data base. However, an EPA compilation of survey analyses of organic
compounds in water lists five samples of finished drinking water (4 samples,
EPA Lab, Cincinnati, OH; 1 sample Ottumwa, Iowa) that contained cyclohexa-
none. The compilation did not provide sampling points or measured levels
(Shackleford & Keith 1976).
5-3
-------
6. HUMAN EXPOSURE
6.1 OCCUPATIONAL EXPOSURE
Cyclohexanone is a colorless liquid used primarily as a chemical inter-
mediate in manufacturing adipic acid (NIOSH 1978 — see Chapter 3). It is
also used widely as a solvent in lacquers, paint removers, metal degreasers,
and adhesives. The greatest potential for occupational exposure occurs when
cyclohexanone is used as a solvent in open processes. There is probably
little exposure potential associated with its use as a chemical intermediate,
since the manufacturing process is an automated, closed system. However,
intermittent exposures may occur in the latter case during cleaning operations
or following accidental spills.
Although cyclohexanone has a low vapor pressure at 25°C (4.5 mm Hg), it
has an evaporation rate 41 times that of ether (NIOSH 1978). The potential
for exposure by inhalation is therefore quite large; a significant amount may
be inhaled in a short period of time. Little information was available on the
ability of cyclohexanone to be absorbed through intact human skin. The com-
pound is known to defat the skin (Rowe and Wolf 1963), thus decreasing the
effectiveness of the skin barrier and enhancing the absorption of cyclohexa-
none or other substances.
Nelson et al. (1943) reported on the sensory thresholds for irritation by
cyclohexanone in a group of 10 men and women exposed for 3-5 minutes. They
reported that a concentration of 75 parts per million (ppm) was irritating to
the subjects' eyes and upper respiratory tracts. The highest concentration
that could be tolerated for 8 hours was estimated to be 25 ppm. Because of
the irritating properties of cyclohexanone, it is unlikely that workers could
tolerate prolonged exposure to cyclohexanone vapor at concentrations above of
25 ppm.
The only information available on the extent of occupational exposure to
cyclohexanone is from NIOSH (1978). Surveys were performed at three indus-
trial sites where cyclohexanone was known to be used as a solvent. In all
three surveys, air samples were collected in charcoal tubes and analyzed by
gas chromatography (GC). The results of these surveys are listed in Table
6-1.
6-1
-------
Table 6-1. Results of NIOSH Health Hazard
Evaluation Studies on Cyclohexanone
Job
Description
Spray painting
and laoquering
Preparation of
nylon cord
Paint stripping and
spray painting
Number of
Samples
4 personal
4 area
4 personal
13 personal
Concentration
<1 ppm
<1 ppm
2-21 ppm
0.7-5.7 ppm
Reference
NIOSH 197U
NIOSH 1975
NIOSH 1977
The American Conference of Governmental Industrial Hygienists (ACGIH) has
recommended a maximum 8-hour time-weighted average for workplace air of 50 ppm
cyclohexanone (ACGIH 1980). The ACGIH intends to reduce the standard to 25
ppm (ACGIH 1980), as originally proposed by NIOSH in 1978. NIOSH (1980) esti-
mated that 839,200 persons are potentially exposed to cyclohexanone.
6.2 CONSUMER EXPOSURE
Cyclohexanone is used to a limited extent as a solvent in several con-
sumer products; however, little information is available that specifically
addresses exposure to cyclohexanone through the use of consumer products.
Lee et al. (1979) evaluated the various uses of 31* solvents. They
reported that cyclohexanone is used as a solvent in the following consumer
products: spot removers for leather and textiles, metal degreasers used in
repair work, lacquers and other protective coatings (e.g., wood stains), and
paint removers used in furniture repairing and refinishing. Consumer exposure
indices were estimated using the EPA exposure index designed by Auerbach
Associates, Inc. The exposure indices were estimated to be 2.71* for spot
removers and 3«08 for each of the three remaining uses.
Lee et al. made numerous comparisons to determine which of the 31* sol-
vents presented the highest potential risk for humans and for the environ-
ment. Their comparisons included production quantities, annual consumption,
exposure indices, and toxicity. Cyclohexanone was among the 12 high-risk
6-2
-------
solvents based on the evaluations and comparisons in this study. Using the
exposure indices derived for consumer applications, cyclohexanone ranked sixth
based on the maximum exposure score and third based on the median exposure
score. Cyclohexanone also had a high ranking when toxicity and consumer
exposure were compared for the various solvents.
Ulsaker and Korsnes (1977) reported that cyclohexanone was present in
several intravenous solutions that had been stored in polyvinyl chloride (PVC)
bags. Table 6-2 summarizes the investigators' findings. The solutions ranged
in age from 6 months to 3«5 years. The cyclohexanone content varied consider-
ably — from <1 mg/liter to 15.9 mg/liter. The PVC bags containing the intra-
venous solutions were labeled with written declarations. No cyclohexanone was
detected in the ink used for printing these declarations. The authors sug-
gested that the cyclohexanone in stored intravenous solutions may result from
its use as a solvent during production of the PVC bags.
Table 6-2. Cyclohexanone Content in Stored Intravenous Solutions
Sample
a
b
c
d
e
f
g
h
Solution3
500 ml saline
500 ml saline
500 ml saline
500 ml saline
500 ml 5% glucose
500 ml Ringer's
76.5 ml ACD
63 ml CPD
Age
(years)
2.5
2.5
3.5
3.5
3.5
2.0
1.5
0.5
Cyclohexanone
(mg/liter)b
2.9,
8.0,
U.8,
7.2,
6.2,
15.5,
<
<:
2.9
8.8
4.8
6.7
6.7
15.9
1
1
aSamples a and b and samples c and d had the same batch numbers.
'Duplicate analyses were performed i
Source: Ulsaker and Korsnes (1977)
Duplicate analyses were performed for samples a-f.
6-3
-------
Cyclohexanone may also be present in tobacco and tobacco smoke. Pilotti
et al. (1975) studied the compounds present in tobacco and tobacco smoke to
determine inhibitory effects on cell growth. Compounds chemically related to
those found in tobacco and tobacco smoke were also tested for inhibitory
effects. The authors noted that most of these related compounds are also
found in tobacco and tobacco smoke; they did not specify which ones were and
which were not. Cyclohexanone was among the 250 compounds tested. At the
maximum concentration used (1 mM), Cyclohexanone had no effect (0$ inhibition)
on cell growth. Thus, it is not clear from this study whether Cyclohexanone
is actually a component of tobacco and tobacco smoke, or is just chemically
related to such a compound.
6.3 GENERAL POPULATION EXPOSURE
There is only one study available that examines the relationship between
releases of Cyclohexanone to the environment and ambient exposure levels
affecting the general population. Patterson et al. (1976) calculated ground
level Cyclohexanone concentrations at a distance of 500 meters from the major
Cyclohexanone manufacturing facility. As of 1974, this was DuPont Chemical in
Belle, West Virginia; the plant had a capacity of 240 million Ibs/year).
According to Patterson et al., the primary source of emissions of cyclohexa-
none results from the use of solvents, followed by losses from production
facilities. Although emissions from solvent usage are believed to be of
greatest magnitude, the authors noted that these sources tend to be small and
geographically scattered. On the other hand, Cyclohexanone is produced at a
few locations for which the emission characteristics can be reasonably well
defined. Thus, the authors chose to examine the impact of ketone losses from
a major manufacturing facility. In developing their estimate, the investi-
gators made the following assumptions:
1. The manufacturing facility had a capacity of 240 million Ibs/year.
2. The emission rate was 1% of the above value, or 34.5 g/sec of cyclo-
hexanone. Data were not available on emissions from cyolohexanone
manufacture and processing. Because of this, Patterson and
coworkers based their estimate of release to the environment from
Cyclohexanone production on data from similar chemical processes
(EPA 1973 and EPA 1975 from Patterson et al. 1976).
6-4
-------
3. Releases to the atmosphere did not come from one location at the
plant site, but from a number of points of varying heights. Emis-
sions were thus characterized as coming from an area source
100 meters on a side, and a height of 10 meters.
4. Meteorologic conditions were neutral stability (Pasquill-Gifford
Stability Class D) and a wind speed of 2 m/sec.
Thus, ground level concentrations (K in g/m^) were calculated for a
distance 500 meters from source of release using simple diffusion modeling:
,2
x = a e *• z
U 7T(7
y a z
where:
Q = source strength (emission rate) in g/sec
u = average wind speed in m/sec
ery'o- z = diffusion coefficients in y and z directions in meters
H = effective height of source of emission in meters.
Substituting in the equation:
„ 3U.5 -V2( 10/18.5)2
X = (2) TT (36)(18.5) 6
= 7.124 x 10 g/m for a 10-minute average concentration
Over a period of an hour this value becomes 5.129 x 10~^ g/nr or 1.3 ppm
average concentration. For a 21-hour period, the average concentration was
roughly 1.0 ppm.
Other than the information presented above, there are no studies that
address the issue of general population exposure to ambient levels of cyclo-
hexanone. From the limited data available on sources of release, environ-
mental occurrence, transport and transformation, it is possible to present a
qualitative estimate of the exposure potential.
Patterson et al. (1976) noted that a major source of release of cyclo-
hexanone to the atmosphere is the venting of off-gases from the production
process. Based on 1979 production figures JRB estimates that approximately
2.2 x 10° kg cyclohexanone are released annually (see Section 3.1.1 and Table
3-5). The industrial use of cyclohexanone in the manufacture of adipic acid
6-5
-------
and caprolactam is an additional source of emissions, releasing an estimated
annual amount of 1.3 x 10 kg and 2 x 10 kg of cyclohexanone, respectively
(see table 3.5). Finally, storage and loading of the ketone are associated
with the following estimated annual releases to the atmosphere (respec-
tively): 4.2 x 10 kg and 90-200 kg. Note that in their use as solvents,
virtually all ketones will evaporate to the surrounding air. Generally,
industrial control methods include collection under hoods and incineration
(SRC 1976, Patterson et al. 1976). However, such methods are not 100$ effi-
cient. Furthermore, they are not used equally in the control of all ketones
(i.e., emissions of highly photoreactive ketones such as MIBK are more
strictly regulated — see below). Thus, in the absence of specific industrial
data, it was not possible to estimate the release levels of cyclohexanone.
Once released to the atmosphere, cyclohexanone is susceptible to photo-
chemical transformation. Compared with other ketones such as methyl ethyl or
methyl isobutyl ketone, cyclohexanone has a relatively low chemical reactivity
in smog. However, the compound still undergoes significant photodecomposition
(in smog and urban atmospheres) with an estimated half-life in the range 1.9-
3.2 hours (see Section 4.1.2).
There were no monitoring data available on levels of cyclohexanone in the
atmosphere. Therefore, it is difficult to draw conclusions as to the poten-
tial for general population exposure to the compound in the ambient air.
However, from the information presented above, it appears that outside of the
industrial setting, exposure through inhalation would be very limited, with
increased risk associated only with the closest proximity to industrial
emraitters.
Cyclohexanone has been shown to be degraded by microorganisms common to
both natural water and waste treatment systems (see Section 4.2). Bench-scale
activated sludge systems, once acclimated, easily degraded cyclohexanone as
well as the more complex mixture of wastewater from the caprolactam manufac-
turing process (containing cyclohexanone, cyclohexanol, cyclohexanone oxime,
and caprolactam). However, wastewater from manufacturing and from industrial
use of cyclohexanone has been reported to contain significant quantities of
waste ketone (see Section 3.4.1 and Table 3-5). Although the information
available on treatment or disposal is insufficient for estimating annual
levels released to the environment, it is clear from existing monitoring data
6-6
-------
that the compound is present in aqueous discharges to surface waters.
Shackelford and Keith (1976) report the detection of cyclohexanone (no levels
given) in the effluent from chemical plants (Kingsport, Tennessee and
Louisville, Kentucky), latex plants (Calvert City, Kentucky), and textile
plants (location unspecified).
Cyclohexanone has been detected in finished drinking waters (Shakelford
and Keith 1976: 1 listing, EPA Cincinnati, Ohio; 1 listing Ottumwa, Iowa-no
concentrations given), but there is not sufficient information available to
quantitatively estimate levels of exposure or even to clearly characterize the
circumstances of exposure. However, it is likely that increased risk of
exposure is associated with the use of surface waters (as input to municipal
treatment systems) that receive effluents from industrial facilities that
manufacture, process, or use cyclohexanone.
6-7
-------
REFERENCES
American Conference of Governmental Industrial Hygienists. 1980. TLVs —
Threshold limit values for chemical substances in workroom air adopted by
ACGIH for 1980. Cincinnati, OH: American Conference of Governmental
Industrial Hygienists.
Andrew P, Smith AF, Wood R. 1971. Simple field test for the determination of
cyclohexanone and methylcyclohexanone vapors in air. Analyst (London)
96(1144) .-528-534.
Basdekis, HS. 1979. Emission control options for the synthetic organic
chemicals manufacturing industry: Caprolactam abbreviated product report
(draft). U.S. Environmental Protection Agency, Research Triangle Park, NC
(Contract No. 68-02-2577).
Bisz-Konarzewska A. 1978. The effects of cyclohexane derivatives on
selection of bacterial groups forming activated sludge microflora. Acta
Microbiol. Pol. 27(2):155-160.
Blacet FE, Miller A. 1957. Photochemical decomposition of cyclohexanone,
cyclopentanone and cyclobutanone. J. Am. Chem. Soc. 79:4327-4329.
Bruce WD, Blackburn JR, Basdekis HS. 1979. Emissions control options for the
synthetic organic chemicals manufacturing industry: Adipic acid product
report (draft). U.S. Environmental Protection Agency, Research Triangle Park,
NC (Contract No. 68-02-2577).
Darnall KR, Lloyd AC, Winer AM, Pitts JN Jr. 1976. Reactivity scale for
atmospheric hydrocarbons based on reaction wih hydroxyl radical. Environ.
Sci. Technol. 10(7):692-696.
Billing WL. 1977. Interphaae transport process. II: Evaporation rates of
chloro- methanes, ethanes, ethylenes, propanes, and propylenes from dilute
aqueous solutions. Comparisons with theoretical predictions. Environ. Sci.
Technol. 11(4):405-409.
Fisher WB. 1978. Cyclohexanol and cyclohexanone. In: Kirk-Othmer
Encyclopedia of chemical technology, 3rd ed. NY: Interscience Publishers.
7:411-416.
Gunter BJ, Lucas JB. 1975. Health hazard evaluation report no. 74-61-232 —
Gates Rubber company, Denver, CO. Cincinnati OH: U.S. Department of Health,
Education and Welfare, National Institute for Occupational Safety and Health.
Holzer G, Shanfield H, Zlatkis, A, Bertsch W, Juarez P, Mayfield H, Liebich
HM. 1977. Collection and analysis of trace organic emissions from natural
sources. J. Chromatogr. 142:755-764.
Karickhoff SW, Brown DS, Scott TA. 1979. Sorption of hydrophilic pollutants
on natural sediments. Water Res. 13:241-248.
R-1
-------
Laity JL, Burs tain IG, Appel BR. 1973. Photochemical smog and the
atmospheric reactions of solvents. 7:96-112. In: less RW (ed.), Solvents,
theory and practice. Advances in Chemistry, Series 124. Washington, DC:
American Chemical Society.
Lee BB, Wilkins GE, Nichols EM. 1979. Organic solvent use study.
Cincinnati, OH: Industrial Environmental Research Laboratory (EPA
560/12-79-002).
Leo A, Hansch C, Elkins D. 1971. Partitions coefficients and their uses.
Chem. Reviews 71(6):525-616.
Levy A, Miller SE, Scofield F. 1969. Photochemical smog: An appraisal of
ketone reactivity. Amer. Chem. Soc. Div. Org. Coatings Plast. 29(2):427-440.
Levy A. 1973. The photochemical smog reactivity of organic solvents. In:
Tess RW (ed.), Solvents, theory and practice. 6:71-93. Advances in
Chemistry, Series 124. Washington DC: American Chemical Society.
Liss PS, Slater PG. 1974. Flux of gases across the air-sea interface.
Nature 247:181-183.
Lowery CE Jr., Foster FW, Jrertshuk P. 1968. The growth of various
filamentous fungi and yeasts on n-alkanes and ketones. I. Studies on
substrate specificity. Arch. Mikrobiol. 60:246-254.
MacKay D, Leinonen PH. 1975. Rate of evaporation of low-solubility
contaminants from water bodies to atmosphere. Environ. Sci. Technol.
9(13):1178-1180.
Matthews PJ. 1976. Growth characteristics of a sewer slime. Environ.
Pollut. 10(2):79-88.
Mill T. 1980. Data needed to predict the environmental fate of organic
chemicals. In: Hague (ed.), Dynamics, exposure and hazard assessment of
toxic chemicals. Ann Arbor, MI: Ann Arbor Science Publishers, Inc.
21:297-322.
Murray JR, Scheikowski TA, MacRae 1C. 1974. Utilization of cyclohexanone and
related substances by a Nocardia sp. Antione van Leeuwenhoek 40(1):17-24.
Morrison RT, Boyd RN. 1973. Organic chemistry, 3rd ed. Boston, MA: Allyn
and Bacon.
National Institute for Occupational Safety and Health (NIOSH). 1978.
Criteria for a recommended standard . . . occupational exposure to ketones.
Washington, DC: U.S. Government Printing Office (NIOSH Pub. No. 78-173).
National Institute for Occupational Safety and Health (NIOSH). 1980.
Cyclohexanone. In: The national occupational hazard summary report.
Cincinnati OH: National Institute for Occupational Safety and Health.
Nelson KW, Ege JF Jr, Ross M, Woodman LE, Silverman L. 1943. Sensory
response to certain industrial solvent vapors. J. Ind. Hyg. Tox.
25(7):282-285.
R-2
-------
Morris DB, Trudgill PW. 1971. Metabolism of cyclohexanol by Nocardia
globerula CL1. Biochem. J. 121(3):363-370.
Okawa MT, Keith W. 1977. Health hazard evaluation determination report no.
75-195-396 — United Airlines Maintenance Base, San Francisco International
Airport, Burlingame, CA. Cincinnati, OH: U.S. Department of Health,
Education and Welfare, National Institute for Occupational Safety and Health.
Parkes DG, Ganz CR, Polinsky A, Schulze J. 1976. A simple gas
chromatographic method for the analysis of trace organics in ambient air. J.
Am. Ind. Hyg. Assoc. 37(3):165-173-
Patel MD, Patel DR. 1977. Biodegradability and treatability of caprolactam
waste. Indian J. Environ. Health 19(4):310-318.
Patterson RM, Bronstein MI, Garshiek E. 1976. Assessment of cyclohexanone as
a potential air pollution problem, Volume III. U.S. Environmental Protection
Agency, Research Triangle Park, NC (Contract No. 68-02-1337, NTIS No.
PB258-359).
Pervier JW, Barley RC, Field DE, Friedman BM, Morris RB, Schwartz WA. 1974.
Survey reports on atmospheric emissions from the petrochemical industry,
Volume II (final report). U.S. Environmental Protection Agency, Office of Air
and Water Programs (EPA 450/3-73-005b).
Pilotti A. 1975. Effects of tobacco and tobacco smoke constituents on cell
multiplication in vitro. Toxicology 5(1):49-62.
Pitter P. 1976. Determination of biological degradability of organic
substances. Water Res. 10(3):231-235.
Research Triangle Institute (RTI). 1977. Industrial process profiles for
environmental use: Chapter 6. The industrial organic chemicals industry.
Cincinnati, OH: U.S. Environmental Protection Agency (EPA 600/2-77-023f,
Contract No. 68-02-1325, NTIS No. PB281478).
Rowe VK, Wolf MA. 1963- Cyclohexanone. In: Patty FA (ed.), Industrial
Hygiene and Toxicology, Vol. II, 2nd revised edition. NY: Interscience
Publishers.
Ruhe RL. 1974. Health hazard evaluation/toxicity determination report no.
73-72-155 — Inland Manufacturing Division, Vandalia, OH. Cincinnati, OH:
U.S. Department of Health, Education and Welfare, National Institute for
Occupational Safety and Health (NTIS Pub. No. PB246449).
Serat WF, Mead JF. 1959. The irradiation chemistry of dilute aqueous
solutions of cyclohexanone. Radiat. Res. 11(3):370-382.
Shackleford W, Keith LH. 1976. Frequency of organic compounds identified in
water. Athens, GA: U.S. Environmental Protection Agency, Environmental
Research Laboratory (EPA 600/1-76-062).
Southworth GR. 1979. The role of volatilization in removing polycyclic
aromatic hydrocarbons from aquatic environments. Bull. Environ. Contarn.
Toxicol. 21:507-514.
R-3
-------
Stanford Research Institute (SRI). 1980. 1980 Directory of chemical
producers, USA. Menlo Park, CA: Stanford Research Institute International.
Stecher PG (ed.). 1968. The Merck Index, 8th edition. Rahway, NY: Merck
and Co., Inc.
Stirling LA, Watkinson RJ, Higgins MJ. 1977. Microbial metabolism of
alioyclic hydrocarbons: Isolation and properties of a cyclohexanane degrading
bacterium. J. Gen. Microbiol. (Eng.) 99(1):119-125.
Syracuse Research Corporation (SRC). 1976. Investigation of selected
potential environmental contaminants: ketonic solvents. Washington, DC:
Office of Toxic Substances, U.S. Environmental Protection Agency (EPA
560/2-76-003, NTIS PB 252 970).
Thibodeaux LJ. 1979. Chemodynamics: Environmental movement of chemicals in
air, water and soil. New York, NY: John Wiley and Sons, Inc.
Ulsaker GA, Korsnes RM. 1977. Determination of cyclohexanone in intravenous
solutions stored in PVC bags by gas chromatography. Analyst 102(1220):882-
883.
Union Carbide Corporation. 1975. Ketones. New York, NY: Union Carbide
Corporation.
/
U.S. Environmental Protection Agency. 1977. Compilation of air pollutant
emission factors, 3rd edition. U.S. Environmental Protection Agency, Research
Triangle Park, NC. Publication AP-42, Part A. August 1977.
U.S. Environmental Protection Agency. 1979. Supplement No. 9 for compilation
of air pollutant emission factors, 3rd edition. U.S. Environmental Protection
Agency, Research Triangle Park, NC. Publication AP-42. March 1979.
U.S. International Trade Commission (USITC). 1977. Synthetic organic
chemicals: United States production and sales, 1975. (USITC 804).
U.S. International Trade Commission (USITC). 1977c. Synthetic organic
chemicals: United States production and sales, 1976. (USITC 833).
U.S. International Trade Commission (USITC). 1978. Synthetic organic
chemicals: United States production and sales, 1977. (USITC 920).
U.S. International Trade Commission (USITC). 1979. Synthetic organic
chemicals: United States production and sales, 1978. (USITC 1001).
U.S. International Trade Commission (USITC). 1977a. Imports of benzenoid
chemicals and products, 1975. (USITC 806).
U.S. International Trade Commission (USITC). 1977b. Imports of benzenoid
chemicals and products, 1976. (USITC 828).
U.S. International Trade Commission (USITC). 1978a. Imports of benzenoid
chemicals and products, 1977. (USITC 900).
R-J»
-------
U.S. International Trade Commission (USITC). 1979a. Imports of benzenoid
chemicals and products, 1978. (USITC 990).
Verschueren K. 1977. Handbook of environmental data on organic chemicals.
New York: Van Nostrand Reinhold Co.
Weast RC, ed. 1972. CRC handbook of chemistry and physics, 1972-1973- 53rd
ed. Cleveland, OH: The Chemical Rubber Company.
Winer AM, Lloyd AC, Darnall KR, Pitts JN Jr. 1976. Relative rate constants
for the reaction of the hydroxyl radical with selected ketones, chloroethenes
an monoterpene hydrocarbons. J. Phys. Chera. 80(14):1635-1639.
R-5
------- |