INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 93
CHLOROPHENOLS OTHER THAN PENTACHLOROPHENOL
This report contains the collective views of an international group of
experts and does not necessarily represent the decisions or the stated
policy of the United Nations Environment Programme, the International
Labour Organisation, or the World Health Organization
Published under the joint sponsorship of
the United Nations Environment Programme,
the International Labour Organisation,
and the World Health Organization
World Health Organization
Geneva, 1989
The International Programme on Chemical Safety (IPCS) is a joint
venture of the United Nations Environment Programme, the International
Labour Organization, and the World Health Organization. The main
objective of the IPCS is to carry out and disseminate evaluations of
the effects of chemicals on human health and the quality of the
environment. Supporting activities include the development of
epidemiological, experimental laboratory, and risk-assessment methods
that could produce internationally comparable results, and the
development of manpower in the field of toxicology. Other activities
carried out by the IPCS include the development of know-how for coping
with chemical accidents, coordination of laboratory testing and
epidemiological studies, and promotion of research on the mechanisms
of the biological action of chemicals.
WHO Library Cataloguing in Publication Data
Chlorophenols other than pentachlorophenol
(Environmental health criteria; 93)
1. Chlorophenols I. Series
ISBN 92 4 154293 4 (NLM Classification: QV 223)
ISSN 0250-863X
(c) World Health Organization 1989
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CONTENTS
1. SUMMARY
1.1. Identity, physical and chemical properties,
analytical methods
1.2. Sources of human and environmental exposure
1.2.1. Production figures
1.2.2. Manufacturing processes
1.2.3. Uses
1.2.4. Waste disposal
1.2.5. Release of chlorophenols into the environment
1.2.6. Natural sources
1.3. Environmental transport, distribution, and transformation
1.3.1. Degradation
1.3.2. Bioaccumulation
1.3.3. Effects of physical chemical and biological
factors on degradation
1.4. Environmental levels and human exposure
1.4.1. Chlorophenol levels in the environment
1.4.2. Chlorophenol levels in food, drinking-water, and
treated wood
1.5. Kinetics and metabolism
1.6. Effects on organisms in the environment
1.7. Effects on experimental animals and in vitro systems
1.8. Effects on man
1.8.1. Non-occupational exposure
1.8.2. Occupational exposure
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1. Identity
2.2. Physical and chemical properties
2.3. Conversion factors
2.4. Analytical methods
2.4.1. Sample collection and storage
2.4.2. Sample preparation and analysis
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1. Natural occurrence
3.2. Man-made sources
3.2.1. Production levels and processes
3.2.1.1 World production figures
3.2.1.2 Manufacturing processes
3.2.2. Uses
3.2.2.1 Wood treatment
3.2.2.2 Agriculture
3.2.2.3 Domestic
3.2.2.4 Water treatment
3.2.2.5 Additives
3.2.2.6 Intermediates in industrial syntheses
3.2.3. Other sources
3.3. Waste disposal
3.4. Losses of chlorophenols into the environment
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION
4.1. Transport and distribution
4.1.1. Atmospheric movement
4.1.1.1 Volatilization
4.1.2. Soil movement
4.1.2.1 Adsorption
4.1.2.2 Leaching
4.1.3. Transport in aquatic environments
4.2. Degradation and bioaccumulation
4.2.1. Degradation
4.2.1.1 Abiotic degradation
4.2.1.2 Degradation by microorganisms
4.2.2. Bioaccumulation
4.3. Effects of other physical, chemical, or biological factors
4.3.1. pH
4.3.2. Lack of oxygen
4.3.3. Inorganic nutrients
4.3.4. Organic matter
4.3.5. Temperature
4.4. Persistence
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1. Environmental levels
5.1.1. Air
5.1.2. Water
5.1.2.1 Sediments
5.1.3. Soil
5.1.4. Food and feed, drinking-water
5.1.4.1 Food
5.1.4.2 Livestock feed
5.1.4.3 Drinking-water
5.1.5. Treated wood
5.1.6. Terrestrial and aquatic organisms
5.1.6.1 Invertebrates
5.1.6.2 Fish
5.1.6.3 Other non-human vertebrates
5.2. General population exposure
5.3. Occupational exposure
6. KINETICS AND METABOLISM
6.1. Absorption
6.2. Distribution
6.2.1. Tissue distribution following chlorophenol
exposure
6.2.2. Tissue distribution following exposure to
chemicals metabolized to chlorophenols
6.3. Metabolic transformation
6.4. Elimination and excretion
7. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
7.1. Laboratory toxicity studies
7.1.1. Acute toxicity
7.1.2. Long-term toxicity
7.1.3. Organoleptic effects
7.2. Toxicity studies under natural environment conditions
7.2.1. Bacteria
7.2.2. Phytoplankton
7.2.3. Zooplankton
7.2.4. Fish
7.2.5. Effects on physical and chemical variables
7.3. Treatment levels
8. EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO SYSTEMS
8.1. Acute studies
8.2. Skin and eye irritation; sensitization
8.3. Short-term exposure
8.4. Long-term exposure
8.5. Reproduction, embryotoxicity, and teratogenicity
8.6. Mutagenicity and related end-points
8.7. Carcinogenicity
8.8. Factors modifying toxicity; metabolism
8.9. Mechanisms of toxicity, mode of action
9. EFFECTS ON MAN
9.1. Acute toxicity
9.2. Long-term exposure
9.2.1. Effects on skin and mucous membranes
9.2.2. Systemic effects
9.2.3. Psychological and neurological effects
9.2.4. Reproductive effects
9.2.5. Carcinogenicity
9.2.5.1 Case-control studies reviewed by IARC
9.2.5.2 Cohort studies reviewed by IAC
9.2.5.3 More recent studies
10. EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE ENVIRONMENT
10.1. Evaluation of human health risks
10.1.1. Exposure levels
10.1.1.1 Non-occupational exposure
10.1.1.2 Occupational exposure
10.1.2. Toxic effects
10.1.3. Risk evaluation
10.2. Evaluation of effects on the environment
10.2.1. Levels of exposure
10.2.2. Transport
10.2.3. Degradation
10.2.4. Bioaccumulation
10.2.5. Persistence
10.2.6. Toxic effects on environmental organisms
10.2.7. Risk evaluation
11. RECOMMENDATIONS
11.1. Production
11.2. Disposal
11.3. Occupational exposure
11.4. General population exposure
11.5. Recommendations for future research
11.5.1. Environmental Aspects
11.5.2. Toxicology
11.5.3. Epidemiology
12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES
REFERENCES
WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR CHLOROPHENOLS
OTHER THAN PENTACHLOROPHENOL
Members
Dr U.G. Ahlborg, Unit of Toxicology, National Institute of
Environmental Medicine, Stockholm, Sweden
Dr L.A. Albert, Division of Studies on Environmental Pollution,
National Institute for Research on Biotic Resources, Vera Cruz,
Mexico (Vice-Chairman)
Dr F.A. Chandra, Toxicology and Environmental Health, Department of
Health and Social Security, London, United Kingdom
Dr A. Gilman, Industrial Chemicals and Product Safety Section, Bureau
of Chemical Hazards, Environmental Health Directorate, Department
of National Health and Welfare, Tunney's Pasture, Ottawa, Canada
Dr I. Gut, Biotransformation, Institute for Hygiene and Epidemiology,
Prague, Czechoslovakia (Chairman)
Dr R. Jones, Health and Safety Executive, Bootie, Merseyside, United
Kingdom
Dr J. Kangas, Kuopio Regional Institute of Occupational Health,
Kuopio, Finland
Dr E. Lynge, Danish Cancer Registry, Institute of Cancer Epidemiology,
Copenhagen, Denmark
Dr U.G. Oleru, Department of Community Health, College of Medicine,
University of Lagos, Lagos, Nigeria
Dr J.K. Selkirk, Division of Toxicology Research and Testing,
Carcinogenesis and Toxicological Evaluation Branch, National
Institute of Environmental Health Sciences, Research Triangle
Park, NC, USA
Dr A. van der Gen, Leiden University, Leiden, Netherlands
Observer
Dr S. Lambert (European Chemical Industry Ecology and Toxicology
Centre), Rhône Poulenc, Décines Charpieu, France
Secretariat
Dr G.C. Becking, Team Leader, International Programme on Chemical
Safety, Interregional Research Unit, World Health Organization,
Research Triangle Park, NC, USA (Secretary)
Dr T. Kauppinen, International Agency for Research on Cancer, Lyons,
France
Mr R. Newhook, Bureau of Chemical Hazards, Environmental Health
Directorate, Department of National Health and Welfare, Tunney's
Pasture, Ottawa, Canada (Temporary Adviser, Rapporteur)
NOTE TO READERS OF THE CRITERIA DOCUMENTS
Every effort has been made to present information in the criteria
documents as accurately as possible without unduly delaying their
publication. In the interest of all users of the Environmental Health
Criteria documents, readers are kindly requested to communicate any
errors that may have occurred to the Manager of the International
Programme on Chemical Safety, World Health Organization, Geneva,
Switzerland, in order that they may be included in corrigenda, which
will appear in subsequent volumes.
***
A detailed data profile and a legal file can be obtained from the
International Register of Potentially Toxic Chemicals, Palais des
Nations, 1211 Geneva 10, Switzerland (Telephone no. 7988400-7985850).
ENVIRONMENTAL HEALTH CRITERIA FOR CHLOROPHENOLS OTHER THAN
PENTACHLOROPHENOL
A WHO Task Group on Environmental Health Criteria for
Chlorophenols other than Pentachlorophenol met at the Monitoring and
Assessment Research Centre, London, United Kingdom, on 21-25 March,
1988. Dr M. Hutton opened the meeting and welcomed the members on
behalf of the host institute and on behalf of the United Kingdom
Department of Health and Social Security, who sponsored the meeting.
Dr G.C. Becking addressed the meeting on behalf of the three
Cooperating Organizations of the IPCS (UNEP, ILO, and WHO). The Task
Group reviewed and revised the draft criteria document and made an
evaluation of the risks for human health and the environment from
exposure to chlorophenols other than pentachlorophenol.
The drafts of this document were prepared by Mr R. NEWHOOK and
Dr A. GILMAN, Health Protection Branch, Ottawa, Canada. Dr G. BECKING,
IPCS Interregional Research Unit, was responsible for the overall
scientific content of the document and Mrs M.O. HEAD, Oxford, England,
for the editing.
The efforts of all who helped in the preparation and finalization
of the document are gratefully acknowledged.
***
Partial financial support for the publication of this criteria
document was kindly provided by the United States Department of Health
and Human Services, through a contract from the National Institute of
Environmental Health Sciences, Research Triangle Park, North Carolina,
USA -- a WHO Collaborating Centre for Environmental Health Effects.
The United Kingdom Department of Health and Social Security generously
supported the costs of printing.
1. SUMMARY
1.1 Identity, Physical and Chemical Properties, Analytical Methods
Chlorophenols (CPs) are organic chemicals formed from phenol
(1-hydroxybenzene) by substitution in the phenol ring with one or more
atoms of chlorine. Nineteen congeners are possible, ranging from
monochlorophenols to the fully chlorinated pentachlorophenol (PCB).
Chlorophenols, particularly trichlorophenols (T3CP), tetrachloro-
phenols (T4CP), and PCP, are also available as sodium or potassium
salts.
Chlorophenols are solids at room temperature, except for 2-MCP,
which is a liquid. The aqueous solubility of chlorophenols is low, but
the sodium or potassium salts of chlorophenols are up to four orders
of magnitude more soluble in water than the parent compounds. The
acidity of chlorophenols increases as the number of chlorine sub-
stitutions increases. The n-octanol/water partition coefficients
of chlorophenols increase with chlorination, indicating a propensity
for the higher chlorophenols to bioaccumulate. Taste and odour
thresholds are quite low.
Technical grade chlorophenol products are heterogeneous mixtures
of chlorophenols, unreacted precursors, and a variety of dimeric
microcontaminants. As a result of the semiquantitative nature of the
reaction of chlorine with molten phenol, commercial formulations of
chlorophenols contain substantial quantities of other chlorophenols.
When the alkaline hydrolysis of chlorobenzenes is used to manufacture
chlorophenols, the technical product can contain unreacted
chlorobenzene.
A number of other compounds are present as microcontaminants in
technical tri- and tetrachlorophenol preparations, as a result of the
elevated reaction temperatures used. These include the polychlorinated
dibenzo- p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs),
polychlorinated phenoxyphenols ("predioxins"), polychlorinated
diphenyl ethers, polychlorinated benzenes, and polychlorinated
biphenyls. Lower chlorophenol preparations do not contain detectable
levels of dioxins, presumably because their manufacture does not occur
at sufficiently high temperatures. Tri- and tetrachloro-dibenzo-
p-dioxins predominate in T3CP formulations, while the hexa, hepta,
and octa congeners are the major PCDD contaminants in technical T4CP
and PCP. 2,3,7,8-Tetra-chlorodibenzo- p-dioxin (2,3,7,8-TCDD) occurs
primarily as a contaminant of 2,4,5,-T3CP, though it is present at
low µg/litre concentrations in T4CP, PCP, and Na-PCP. Chlorophenol
formulations contain a similar array of PCDFs. Phenoxyphenols may
comprise as much as 1-5% of the formulation.
A large number of sampling and analytical methods have been
developed for the determination of chlorophenols in different media.
Sensitive methods, such as gas chromatography, high-performance liquid
chromatography, and mass spectrometry are increasingly used.
1.2 Sources of Human and Environmental Exposure
1.2.1 Production figures
Recent data on production levels of chlorophenols other than PCP
are not readily available. Around 1975, the combined global production
of all chlorophenols approached 200 million kg; slightly more than
half of this quantity consisted of non-PCP chlorophenols, primarily
2,4-dichlorophenol (2,4-DCP), 2,4,5-trichlorophenol (2,4,5-T3CP),
and 2,3,4,6-tetrachlorophenol (2,3,4,6-T4CP). Consumption has since
declined in some countries as a consequence of health-based concerns
(particularly for 2,4,5-T3CP), and the use of alternative wood
preservatives. Some European countries and the USA are major producers
and consumers of chlorophenols.
1.2.2 Manufacturing processes
The compounds 2-MCP, 4-MCP, 2,4-DCP, 2,3,4-T3CP, 2,4,6-T3CP,
2,3,4,6-T4CP, and PCP have been made by direct stepwise chlorination
of phenol or lower chlorinated phenols at a high temperature; a
catalyst is necessary if the last two chlorophenols are being
produced. Alternatively, some chlorophenols (2,5-DCP, 3,4-DCP,
2,4,5-T3CP, 2,3,4,5-T4CP and PCP) can be produced by the alkaline
hydrolysis of the appropriate chlorobenzene.
Both methods yield contaminants that are themselves potential
health hazards, including polychlorinated dibenzo- p-dioxins (PCDDs),
polychlorinated dibenzofurans (PCDFs), and 2-phenoxyphenols.
1.2.3 Uses
Chlorophenols are toxic for a wide range of organisms, a property
that accounts for many of their uses. Large quantities of higher
chlorophenols are used in pressure treatment in the wood preservation
industry; in addition, substantial amounts of the sodium salts of
T4CP, PCP, and T3CP are used to surface-treat fresh-cut logs and
lumber against sapstain fungi and surface mould. Large quantities of
lower chlorophenols serve as intermediates in the production of
pesticides, such as T4CP, PCP, 2,4-D, and 2,4,5-T. The use of 2,4,5-T
has been discontinued in a number of countries. Lesser amounts of
chlorophenols are used as wood preservatives in agricultural and
domestic applications, and as additives to inhibit microbial growth in
a wide array of products, such as adhesives, oils, textiles, and
pharmaceutical products.
1.2.4 Waste disposal
As a result of process design, the quantities of chlorophenolic
wastes generated are reportedly small. Available treatment methods for
such waste should prove satisfactory, if they are carefully applied.
Gravity separation is the primary treatment method most often used to
recover oil and the associated chlorophenol for recycling and
treatment. Organisms during secondary treatment degrade roughly 90% of
most chlorophenol waste, provided that they are acclimated to the
waste, and precautions are taken against shock loadings. Adsorption
onactivated carbon as a final clean-up step removes almost 100% of
remaining waste chlorophenols in waste-streams. Incineration appears
to be an effective means of disposal, if the temperatures are high
enough and residence times long enough to ensure complete combustion
and prevent the formation of PCDDs and PCDFs in the incinerator.
1.2.5 Release of chlorophenols into the environment
Patterns of losses to the environment appear similar in most
industrialized countries. The majority of chlorophenol wastes are
released in spills and leaching from treated lumber (PCP, NaPCP,
NaT4CP), and as contaminants or breakdown products of agricultural
pesticides (2,4-DCP, 2,4,5-T3CP). Substantial amounts of
chlorophenol wastes (NaT4CP, NaPCP) are released from sawmills,
planer mills, and the incineration of wood wastes. Significant amounts
of chlorophenols can be formed and subsequently released into the
environment from the chlorine bleaching process in pulp and
paper-mills, the chlorination of waste-water and drinking-water, and
the incineration of municipal waste. A significant amount of wastes is
discharged from manufacturing sites. Losses during storage and
transport are negligible. No estimates are available of the quantities
of chlorophenols released as a result of the disinfection of
waste-waters with chlorine, volatilization, or domestic uses of
products containing these compounds.
1.2.6 Natural sources
While some chlorophenols and related organohalogens occur
naturally, as metabolites of certain flora and fauna, these sources
are thought to make a negligible contribution to overall environmental
levels.
1.3 Environmental Transport, Distribution, and Transformation
Chlorophenols adsorb strongly on acidic soils, and those with a
high organic content. Leaching is more significant in basic and
mineral soils. Studies to date have not addressed the quantitative
contribution of these processes to the transport of chlorophenols
in situ.
Adsorption appears to play an important role in surface waters.
Chlorophenols that are not degraded in the water body are incorporated
into the sediments, most likely because they adsorb on sediment
particulates. They may persist in sediments for years. However, it is
not known how important this process is for lower chlorophenols, since
they should be adsorbed to a lesser extent than the T4CPs and PCP
studied to date.
While a large part of the chlorophenols entering natural waters is
probably degraded, they are nonetheless fairly persistent and, thus,
may be transported considerable distances by water.
Although chlorophenols are principally water and soil
contaminants, some atmospheric movement occurs, and low levels of PCP
have been found in rain, snow, and outdoor air. No corresponding
measurements have been made for other chlorophenols, but it is highly
probable that they too are transported in this manner.
1.3.1 Degradation
Chlorophenol residues are removed from the environment by both
biological and non-biological degradation. Laboratory studies have
shown that ultraviolet radiation can break down chlorophenols in a
matter of hours to days, and the shifts in the ratio of PCP to some of
its breakdown products in situ suggest that this process is
important in exposed habitats.
A large number of bacteria and fungi from different habitats are
able to degrade chlorophenols in the laboratory, sometimes eliminating
tens of mg/litre in a matter of hours or days. Degradation is
generally slowest for the higher chlorinated phenols, and for those
with a chlorine in the "meta" position. Previous exposure to a given
chlorophenol or a related compound enables a microorganism to
metabolize it immediately and/or at a faster rate, presumably by
inducing the necessary enzymes. In general, anaerobic biodegradation
of these compounds is much slower than aerobic metabolism.
Considerable overlap appears to exist in the rates of biodegradation
of the compounds in different habitats.
But chlorophenols should only persist in environments where the
rates of these transformations are minor. The persistence of
chlorophenols other than PCP has not been studied under controlled
conditions, but spills and applications of PCP as a herbicide
reportedly disappear in a matter of weeks or months.
1.3.2 Bioaccumulation
Bioaccumulation of chlorophenols appears to be moderate, and most
bioconcentration factors (BCFs) fall roughly between 100 and 1000. The
biocentration factor is usually a positive function of the chlorine
number, and there are no obvious relationships between it and the type
of organism (algae, plants, invertebrates, fish). Once exposure is
discontinued, chlorophenols clear rapidly from biota, indicating that
the bioaccumulation observed in field studies is the result of
long-term exposure rather than persistence.
1.3.3 Effects of physical, chemical, and biological factors on
degradation
Both the rate of evaporation and the extent of adsorption of PCP
(and undoubtedly other chlorophenols) are inversely related to pH. In
contrast, the rates of photolysis of 4-MCP and 2,4-DCP both increase
with pH, and shortage of oxygen, inorganic nutrients, or organic
matter may all influence the biodegradation rate of various lower
chlorophenols. Higher temperatures increase the rates of evaporation,
photolysis, and microbial degradation of chlorophenols, although the
last process obviously has an upper limit.
1.4 Environmental Levels and Human Exposure
1.4.1 Chlorophenol levels in the environment
Data on levels of chlorophenols other than PCP in the environment
are not available for air. Levels of PCP in outdoor air range from 1
to several ng/m3. Work-place air concentrations of chlorophenols are
much higher. Facilities in which chlorophenols are used, such as
sawmills, often have air levels of several tens of µg/m3, while in
manufacturing facilities, concentrations may be in the mg/m3 range.
Residues of all chlorophenol isomers have been found in fresh and
marine waters. In relatively undeveloped areas, levels are often
undetectable in receiving waters, and only occasionally exceed
1 µg/litre close to industrial sources of chlorophenols. In receiving
waters from heavily industrialized regions, ambient levels are
somewhat higher, but still median concentrations do not exceed
1 µg/litre, while the maximum concentrations in surface waters and
ground waters can reach several µg/litre. As a result of spills,
isolated levels as high as 61 000 µg/litre of chlorophenols (T4CP +
PCP) in ground water, and 18 090 µg/litre in surface waters have been
reported.
Levels of some chlorophenols in effluents from chemical and wood
preservation industries may reach several thousand µg/litre, though
typical levels are in the low µg/litre range, and dilution apparently
reduces these to the observed low ambient levels.
Chlorophenol concentrations in sediments are generally higher than
those in the overlying water. Levels in sediments from waters not
receiving large chlorophenol inputs generally contain less than 1 µg
of the individual chlorophenols/kg dry sediment. The maximum levels of
all chlorophenol isomers in fresh-water sediments in industrialized
regions seldom exceed 50 µg/kg. However, in some instances, thousands
of µg chlorophenols/kg have been detected in fresh-water sediments
adjacent to point sources (spillage sites and effluent discharges).
In waters receiving chlorophenolic wastes, invertebrates generally
contain from trace levels to 20 µg of chlorophenols from the
surrounding environments/kg wet tissue, though levels approaching
200 µg/kg have been observed in some instances. Fish can contain
similar whole-body levels of chlorophenols, usually concentrated in
the liver and viscera. For example, liver tissues from sculpins
inhabiting polluted waters contained up to 1600 µg/kg wet weight. In
birds, muscle tissues exhibited only trace to moderate (50 µg/kg wet
weight) levels of chlorophenols, however, higher concentrations have
been found in single samples of liver, brain, kidney, and eggs. For
instance, a level of 1017 µg 2,4-DCP/kg (fresh weight) was found in
the kidney of an eagle.
1.4.2 Chlorophenol levels in food, drinking-water, and treated wood
Quantities of T4CP range from trace to several µg/kg in carrots,
potatoes (also 2,4-DCP), turnips, cabbages, beets, and raw milk,
though contamination from treated wood storage containers can elevate
these levels considerably. Recent restrictions on the agricultural use
of chlorophenols have reduced this contamination. T4CP has been
detected in poultry, but no reports of residues in other meat have
been found.
Drinking-water supplies are characterized by relatively low
concentrations of chlorophenols. While a variety of congeners have
been detected, these are usually present in the range of 10-3 to
10-1 µg/litre.
Concentrations of PCP or T4CP in treated wood are predictably
high, and can reach several hundred mg/kg of wood dust or shavings.
1.5 Kinetics and Metabolism
The lower chlorophenols are readily absorbed across the skin of
both laboratory animals and human beings. The results of studies on
rats further suggest that absorption via the skin is greater for the
sodium salts than for the parent molecules (2,3,5,6-T4CP and its salt
were used). Ingested chlorophenols are also readily taken up from the
gastrointestinal tract. The absorption of inhaled lower chlorophenols
by experimental animals has not been studied.
Experimental animals accumulate chlorophenols mostly in the liver
and kidney, and to a lesser extent in the brain, muscle, and fat
tissues. The higher levels in the liver and kidney may reflect their
greater circulating blood volume, as well as the role these organs
play in the detoxification and elimination of these compounds. Related
compounds, such as trichlorophenyl acetate, 2,4-D, Nemacide, Silvex,
2,4,5-T, and lindane, yield similar tissue distributions of
chlorophenol metabolites.
In the animals studied to date, most chlorophenols were rapidly
conjugated to glucuronates or sulfates in the liver. This binding, and
also dechlorination and methylation, serve to detoxify these
compounds. At present, the only chlorinated phenol that is known to be
metabolized to a more toxic substance is 2,3,5,6,-T4CP, which gives
rise to tetrachloro- p-hydroquinone. The corresponding quinone has
been shown to bind covalently to protein and DNA.
Chlorophenols are eliminated by test mammals primarily through the
urine (roughly 80-90%), in both free and bound forms. Smaller amounts
are eliminated in faecal matter. A single dose of chlorophenols is
virtually eliminated within one to several days. Elimination rates
appear to be even more rapid for some tissues.
1.6 Effects on Organisms in the Environment
The available information on the effects of chlorophenols in the
environment centres primarily on aquatic organisms. Considerable
overlap exists in the concentrations that are toxic for bacteria,
phytoplankton, plants, invertebrates, and fish, most of the EC50 and
LC50 values falling in the several mg/litre range. Toxicity generally
increases with the degree of chlorination of the phenol ring. However,
chlorophenols with chlorine in the 3 and 5 positions ("meta"
chlorophenols) are often more toxic than expected solely on the basis
of their chlorine number. Species-specific sensitivity can override
these general patterns. Furthermore, particularly in the case of the
higher chlorophenols, acute toxicity is a strong inverse function of
pH, reflecting the degree of ionization of the chemical. In long-term
studies, sublethal levels of 2,4-DCP reduced both growth and survival
of fathead minnows. In one study, exposure to a concentration of only
0.5 µg 2,4,6-T3CP/litre was fetotoxic in trout.
Fish kills have resulted from PCP spills, some of which have also
involved T4CP. In controlled field studies, exposure to large
quantities (100-5000 µg/litre) of chlorophenols (4-MCP, 2,4-DCP,
2,4,6-T3CP) generally impaired algal primary production and
reproduction, altered algal species composition dramatically, and
reduced zooplankton biomass and production. These studies shed little
light on the hazard, if any, presented by the low-level contamination
observed in most environments. The low concentrations of several
chlorophenols typically found in moderately contaminated waters have
been reported to impair the flavour of fish.
1.7 Effects on Experimental Animals and In Vitro Systems
In rats, lethal doses of lower chlorinated phenols resulted in
tremors and convulsions (except for T4CP and some T3CPs), hypotonia,
and, after death, a rapid onset of rigor mortis. Acute LD50s for rats
for all lower chlorophenols and routes of administration ranged from
130 to 4000 mg/kg body weight. The range of toxicity of the compounds
generally occurred in the following order: T4CPs > MCP > DCPs >
T3CPs, when the toxicant was administered either orally or by
subcutaneous injection. When injected intraperitoneally, the
toxicities of MCP, DCPs, and T3CPs were similar, while T4CP was 2-3
times more toxic. In studies on dermal exposure, 2,3,5,6-T4CP was the
most toxic of the T4CP isomers. These variations according to route
of administration may reflect differences in the rate of absorption of
the compounds. Acute effects are attributable to the parent
chlorophenol itself rather than to the microcontaminants.
Some reports have indicated that lower chlorinated phenols cause
mild irritation of the eye in rats. This effect increases with the
number of chlorine atoms on the phenol ring. Skin sensitization has
not been shown for the chlorophenols.
Short-term exposures of rats and mice to 2,4-DCP at hundreds of
mg/kg have been consistently associated with increased spleen and
liver weights and, in some instances, with haematological or
immunological effects. The very few studies concerning exposure to
various tri- and tetrachlorophenols have also identified
exposure-related changes in the weight or histology of the liver and,
in some instances, of the spleen or kidney. In one study, combined
pre- and postnatal exposure to 2-MCP and 2,4-DCP resulted in
haematological changes in exposed rats, but only 2,4-DCP elicited
immune responses.
Several lower chlorophenols appear to be mildly fetotoxic, though
the data are inconsistent in this regard. While female rats exposed to
2-MCP, 2,4-DCP, or 2,4,6-T3CP in the drinking-water produced smaller
litters with an increased frequency of stillborn offspring in one
study, similar or higher exposures in other studies did not have any
effects on these and other reproductive parameters. A dose of 30 mg/kg
body weight per day of pure or technical 2,3,4,6-T4CP delayed
ossification of fetal skull bones, but was not embryolethal.
Birth defects did not arise as a result of daily exposure of rats
to concentrations of up to 500 mg 2-MCP/litre, 300 mg 2,4-DCP/litre
(both in the drinking-water), 1000 mg 2,4,6-T3CP/kg body weight and
30 mg 2,3,4,6-T4CP/kg body weight (both by gavage).
Limited information indicates that 2,4,6-T3CP (in yeast and
mammalian test systems) and 2,3,4,6-T4CP (Chinese hamster cell
cultures) elicited weak mutagenic responses, but were not clastogenic.
Most of the other chlorophenols that have been tested have been found
to be non-mutagenic in the few test systems used (primarily
bacterial).
Exposure of rats and mice (both sexes) to 2,4-DCP for 2 years at
doses as high as 440 and 1300 mg/kg body weight per day, respectively,
proved negative with respect to carcinogenicity. In a test with a
similar design, 2,4,6-T3CP at doses of up to 10 000 mg/kg body
weight per day caused cancer in mice (hepatocellular carcinomas or
adenomas) and male rats (lymphomas, leukaemia). The 2,4,6-T3CP used
was commercial grade and was not analysed for impurities, such as
PCDDs and PCDFs.
Studies on rats on the carcinogenicity of 2-MCP or 2,4-DCP
(500 µg/litre and 300 µg/litre, respectively, for 15-24 months) were
inadequate. Some chlorophenols appeared to be promoters (MCPs,
2,4-DCP, and 2,4,5-T3CP); others did not.
Exposure of female rats to 2,4-DCP in the drinking-water, at
0-300 mg/litre, altered the major immune function in offspring exposed
prenatally and postnatally, but not in rats exposed only in utero.
In contrast, in a similar study, a concentration of 2-MCP as high as
500 mg/litre did not have any adverse effects on the immune systems of
rats.
The major effects observed with lethal exposures to chlorophenols
indicated a general effect on the nervous system. Long-term studies
implicated the liver and kidney as organs that accumulate high
concentrations of chlorophenols and are often adversely affected by
exposure to chlorophenols, perhaps reflecting their roles in the
detoxification and elimination of xenobiotics. On the basis of the
suppression of cell-mediated immunity in rats exposed to 2,4-DCP, it
can be assumed that the thymus and spleen may be target organs.
The toxicology of chlorophenols is complicated by the presence of
PCDD and PCDF microcontaminants in technical grade products.
Assessment of toxicity studies with chlorophenols requires a knowledge
of the types, levels, and effects of the microcontaminants that are
present in the formulation studied, because some PCDDs and PCDFs are
extremely toxic.
The major mode of action in the acute toxicity of chlorophenols
involves the uncoupling of oxidative phosphorylation and the
inhibition of the electron transport system. These effects are related
to the number of chlorine atoms on the molecule and to a lesser extent
by their positions on the molecule. PCP is 40 times more potent than
2,4-DCP as an uncoupler. The chlorophenate ion is evidently
responsible for the uncoupling reaction, while the undissociated
molecule causes convulsions.
Other enzyme systems are also inhibited by exposure to
chlorophenols in vitro, though, in some instances, such inhibition
is not observed with in vivo exposures.
1.8 Effects on Man
1.8.1 Non-occupational exposure
Low (usually 10 mg/kg) levels of the lower chlorinated phenols are
found in the serum, urine, and adipose tissues of the general
population. The major identifiable sources of these chlorophenols are
food and drinking-water. Chlorophenol levels in the ambient atmosphere
have not been measured.
In the only instance of acute exposure of the general population
to chlorophenols, an explosion at a manufacturing plant contaminated
an area, with a population of 37 000 persons, with sodium hydroxide,
2,4,5-T3CP, and TCDD. However, the effects, if any, of the released
2,4,5-T3CP were masked by those of TCDD. Clinical symptoms
attributed to TCDD were recorded in the exposed individuals. No toxic
effects have been attributed to the low concentrations of
chlorophenols typical of most non-occupational exposures. However,
undesirable organoleptic effects are produced by chlorophenols at very
low concentrations.
1.8.2 Occupational exposure
Worker exposure is a major concern in industries in which
chlorophenols are used extensively, as respiratory and dermal
absorption of these compounds results in measurable levels in the
blood and urine of exposed workers. In the manufacture of
chlorophenols, clinical symptoms associated with exposure include eye,
nose, and airway irritation, dermatitis, chloracne, and porphyria.
Abnormal liver function tests, changes in brain wave activity, and
slowed visual reaction time have been reported in association with
high-level exposure.
In sawmill workers, Na-T4CP exposures have caused numerous cases
of dermatitis and respiratory irritation. Eye, nose, and airway
irritation from exposure to T3CP have been reported by gas mask
testers.
Conflicting results have come from epidemiological studies
relating cancer incidence and mortality to chlorophenol exposure in
the work place. Associations between soft-tissue sarcoma, malignant
lymphoma, and nasal and nasopharyngeal cancer, have been shown in some
epidemiological studies, but not in others. Exposure levels have not
been accurately determined in these studies, and the conflicting
results remain unresolved, at present.
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1 Identity
Chlorophenols are organic chemicals formed from phenol
(1-hydroxybenzene) by substitution in the phenol ring with one or more
atoms of chlorine. Nineteen congeners are possible, ranging from
mono-chlorophenols to the fully substituted pentachlorophenol.a
However, this document does not deal with pentachlorophenol, which has
been evaluated previously (WHO, 1987b). The chlorophenols
(particularly trichlorophenols and tetrachlorophenols) are also used
in the form of sodium or potassium salts. The CAS number, name,
chemical (molecular) formula, commercial uses, and common synonyms and
trade names for each chlorophenol congener, are presented in Table 1.
The general chemical structure for the chlorophenol congeners is shown
below.
a The chlorophenol congeners are designated as follows:
monochlorophenols (MCP); dichlorophenols (DCP); trichlorophenols
(T3CP); tetrachlorophenols (T4CP); pentachlorophenol (PCP).
Chlorine substitution is also indicated: 2,4-dichlorophenol
(2,4-DCP); 2,4,6-trichlorophenol (2,4,6-T3CP), etc.
Table 1. Information on the identity of chlorophenol congenersa
CAS numberb Common name Abbreviation Molecular Common synonymsc Common trade
formula names
95-57-8 2-monochlorophenol 2-MCP C6H5ClO o-chlorophenol;
ortho-chlorophenol;
1-chloro-2-hydroxybenzene
108-43-0 3-monochlorophenol 3-MCP C6H5ClO m-chlorophenol;
meta-chlorophenol;
1-chloro-3-hydroxybenzene
106-48-9 4-monochlorophenol 4-MCP C6H5ClO p-chlorophenol;
para-chlorophenol;
1-chloro-4-hydroxybenzene
576-24-9 2,3-dichlorophenol 2,3-DCP C6H4Cl20
120-83-2 2,4-dichlorophenol 2,4-DCP C6H4Cl20 NCl-C55345
583-78-8 2,5-dichlorophenol 2,5-DCP C6H4Cl20
87-65-0 2,6-dichlorophenol 2,6-DCP C6H4Cl20
95-77-2 3,4-dichlorophenol 3,4.DCP C6H4Cl20
591-35-5 3,5-dichlorophenol 3,5-DCP C6H4Cl20
15950-66-0 2,3,4-trichlorophenol 2,3,4-T3CP C6H3Cl30
933-78-8 2,3,5-trichlorophenol 2,3,5-T3CP C6H3Cl30
933-75-5 2,3,6-trichlorophenol 2,3,6-T3CP C6H3Cl30
95-95-4 2,4,5-trichlorophenol 2,4,5-T3CP C6H3Cl30 NCl-C61187 Collunosol;
Dowicide 2;
Dowicide B;
Nurelle;
Preventol 1
Table 1. (contd).
CAS numberb Common name Abbreviation Molecular Common synonymsc Common trade
formula names
88-06-2 2,4,6-trichlorophenol 2,4,6-T3CP C6H3Cl30 NCl-C02904 Dowicide 2; Omal;
Phenachlor
609-19-8 3,4,5-trichlorophenol 3,4,5-T3CP C6H3Cl30
4901-51-3 2,3,4,5-tetrachlorophenol 2,3,4,5-T4CP C6H2Cl40
58-90-2 2,3,4,6-tetrachlorophenol 2,3,4,6-T4CP C6H2Cl40 Dowicide 6
935-95-5 2,3,5,6-tetrachlorophenol 2,3,5,6-T4CP C6H2Cl40
a From: Jones (1981).
b Chemical Abstracts Service Registry number.
c From: NIOSH (1983) and Verschueren (1983).
Note: Owing to the planar nature of the phenol ring, other congeners (e.g., 2,4,5,6-T4CP) are possible, but these are
identical in structure to the listed congeners.
Technical grade chlorophenols are heterogeneous mixtures of
chlorophenol congeners, unreacted precursors, and a variety of dimeric
microcontaminants. For example, Cochrane et al. (1983) found that
technical 2,4-DCP contained on average, 92.24% 2,4-DCP, 4.48% 2,6-DCP,
1.24% 2,4,6-T3CP, 1.09% 2-MCP, and 0.46% 4-MCP.
Similarly, Levin et al. (1976) examined the composition of 3
commercial chlorophenol formulations used to control fungi in Swedish
sawmills and found that Na-2,4,6-T3CP contained approximately 5%
T4CP, Na-2,3,4,6-T4CP included 5% T3CP and 10% PCP, and technical
NaPCP contained 5% T4CP.
Kleinman et al. (1986) determined that commercial Na-T4CP, used
in the USA, contained 3.1% PCP, 20.7% 2,3,4,6-T4CP, and less than
0.4% of other chlorophenol congeners. These results are typical,
showing that roughly 2-12% T4CP congeners occur in technical PCP
formulations, together with trace quantities of several lower
chlorophenols (Jones, 1981; Lanouette et al., 1984).
Contamination of technical chlorophenols varies according to the
production process used. Because of the elevated reaction temperatures
used to produce chlorophenols, a number of compounds are present as
microcontaminants in technical chlorophenol preparations prepared by
this procedure. These include the polychlorinated dibenzo- p-dioxins
(PCDDs) polychlorinated dibenzofurans (PCDFs), polychlorinated
diphenyl ethers, polychlorinated phenoxyphenols, polychlorinated
benzenes, and polychlorinated biphenyls. Where the alkaline hydrolysis
of chlorobenzenes is used to manufacture chlorophenols, the technical
product also contains the unreacted chlorobenzene. Technical
chlorophenol salts usually also contain an excess of sodium or
potassium hydroxide.
While commercial MCP and DCP contain little or no detectable PCDDs
and PCDFs, presumably because their manufacture does not involve high
enough temperatures, other chlorophenols may contain up to many mg/kg
of particular PCDDs, and PCDFs (Firestone et al., 1972; Woolson et
al., 1972; Levin et al., 1976; Levin & Nilsson, 1977; Rappe et al.,
1979; Cedar, 1984; Kleinman et al., 1986). Concentrations of PCDDs and
PCDFs in some American and European chlorophenols are provided in
Table 2. Tri- and tetrachloro-dibenzoxo-dioxins predominate in T3CP
formulations, while the hexa, hepta, and octa congeners are the major
PCDD contaminants in technical T4CP and PCP (Firestone et al., 1972;
Rappe et al., 1978a). 2,3,7,8-Tetrachloro-dibenzo- p-dioxin
(2,3,7,8-TCDD) occurs primarily as a contaminant of 2,4,5-T3CP
(Table 2), though it is present at low µg/kg concentrations in T4CP,
PCP, and NaPCP (Hagenmaier, 1986; Hagenmaier & Brunner, 1987).
Predioxins (chlorinated phenoxyphenols) may comprise as much as 5% of
technical CP preparations (Levin et al., 1976; Levin & Nilsson, 1977).
Most of the data in Table 2 concern chlorophenol formulations from
the 1970s. As a result of modifications in production chemistry, it is
likely that the levels of microcontaminants in current formulations
are somewhat lower. Indeed, all of the 1986 tetrachlorophenol products
assayed by Agriculture Canada (1987) contained levels of H6CDD that
were several times lower than those in the earlier reports (Table 2).
2.2 Physical and Chemical Properties
Data on some physical and chemical properties of chlorophenols are
summarized in Table 3. All of the CPs are solids at room temperature,
except for 2-MCP, which is a liquid. They have strong odours that have
been described as pungent or medicinal, particularly those of
2-monochlorophenol (2-MCP) and 2,4-dichlorophenol (2,4-DCP). Taste and
odour thresholds are so low that Maximum Acceptable Concentrations of
chlorophenols in drinking-water are based on organoleptic rather than
toxicological criteria (US EPA, 1980c; WHO, 1984).
Although the solubility in water of all chlorophenols is poor,
varying from 2.1 × 10-1 mol/litre for 2-MCP t o 7.9 × 10-4 mol/litre
for 2,3,4,6-T4CP (US EPA 1980c) they readily dissolve in a number of
organic solvents. In contrast, the sodium or potassium salts of
chloropenols (most commonly NaT3CP, NaT4CP, and NaPCP) are up to
four orders of magnitude more soluble in water than the parent
compounds. The acidity of chlorophenols increases as the number of
chlorine substitutions increases. Thus, ionization of the higher
chlorophenols begins at a lower pH than that of the lower
chlorophenols (pH approximately 3.5 versus 7 for PCP and 2-MCP,
respectively), with important implications for the interactions
between pH and chlorophenol sorption (section 4.1.2.1), or toxicity
(section 6.1.1). The n-octanol-water partition coefficient of
chlorophenols also increases with chlorination, indicating a
propensity on the part of the higher chlorophenols to bioaccumulate.
2.3 Conversion Factors
MCP 1 mg/m3 = 0.190 ppm; 1 ppm = 5.258 mg/m3
DCP 1 mg/m3 = 0.150 ppm; 1 ppm = 6.667 mg/m3
T3CP 1 mg/m3 = 0.124 ppm; 1 ppm = 8.076 mg/m3
T4CP 1 mg/m3 = 0.105 ppm; 1 ppm = 9.488 mg/m3
Table 2. Polychlorodibenzo-p-dioxins (PCDDs) and polychtorodibenzofurans (PCDFs) in some American and European
mono-, di-, tri-, and tetrachlorophenolsa
Formulation PCDD Concentration PCDF Concentration Year
(mg/kg) (mg/kg) sample
received
2-MCP ND T4CDF presentb 1967
2,4-DCP ND ND 1970
2,6-DCP ND ND 1970d
Na-2,4,5-T3CP ND ND 1967
Na-2,4,5-T3CP 2,7-D2CDD 0.72 ND 1969
2,3,7,8-T4CDDc 1.4
2,4,5-T3CP 1,3,6,8-T4CDD 0.30 ND 1969
2,3,7,8-T4CDc 6.2
2,4,5-T3CP P5CDD 1.5 ND 1970
2,4,5-T3CP ND T3CDF presentb 1970
2,4,5-T3CP 2,3,7,8-T4CDD 0.07 ND 1970
2,4,6-T3CPf 2,3,7-T3CDD 93 T4CDF 1.5 1970d
1,3,6,8-T4CDD 49 P5CDF 17.5
H6CDF 36
H7CDF 4.8
O8DF
Table 2. (contd.)
Formulation PCDD Concentration PCDF Concentration Year
(mg/kg) (mg/kg) sample
received
2,3,4,6-T4CP H6CDDc 15 H6CDF presentb 1970d
H6CDDc 14 H7CDF present
H6CDDc 5.1 O8CDF
O8CDD 0.17
2,3,4,6-T4CP H6CDc 4.1 T4CDF < 0.5 1967
P5CDF 10 (PCDDs);
H6CDF 70 1967d
H7CDF 70 (PCDFs)
O8CDF 10
2,3,4,6-T4CPf ND T4CDF presentb 1967d
H6CDF present
2,3,4,6-T4CPe T4CDD 0.7 T4CDF ca.10 1970d
P5CDD 5.2 P5CDF ca.10
H6CDD 9.5 H6CDF ca.60-70
H7CDD 5.6 H7CDF ca.60-70
O8CDD 0.7 O8CDF ca.10
2,3,4,6-T4CPe T4CDD 0.4 T4CDF ca.10 1970d
P5CDD 3.5 P5CDF ca.10
H6CDD 5.3 H6CDF ca.60-70
H7CDD 2.1 H7CDF ca.60-70
O8CDD 0.3 O8CDF ca.10
Table 2. (contd.)
Formulation PCDD Concentration PCDF Concentration Year
(mg/kg) (mg/kg) sample
received
TCP/PCPg H6CDD 1-4 (n = 6) not reported 1986
H7CDD 40-102 (n = 6) not reported
O8CDD 27-55 (n = 6) not reported
Na-T4CP/PCPg H6CDD N.D.-4 (n = 13) not reported 1986
H7CDD 10-119 (n = 13) not reported
O8CDD 5-330 (n = 13) not reported
a Reports of PCDDs from Firestone et al (1972), except where otherwise indicated; quantitative data on
PCDF concentrations from Rappe et al. (1978a).
b Unquantified. See Firestone et al. (1972).
c Confirmed by combined gas chromatography-mass spectrometry,
d Not reported.
e Rappe et al. (1979).
f Rappe et al. (1978b).
g Agriculture Canada (1987).
ND: No congener detected; limit of detection from Firestone et al. (1972) is approximately 0.02 ppm for PCDDs,
that from Rappe et al. (1978a) is roughly 0.01-0.04 mg/kg (Buser & Bosshardt, 1976).
Table 3. Physical and chemical properties of chlorophenols other than pentachlorophenola
Compound Relative Density Boiling point Melting point Flash Vapour log
molecular (°C at 760 mm) (°C at 760 mm) point pressure n-octanol/
mass (°C) (mm) water
(temperature) partition
coefficient
2-MCP 128.56 1.2634 (20/4) 174.9 9 63.9 1 (12.1 °C) 2.15b
3-MCP 128.56 1.268 (25/4) 214 33 1 (44.2 °C) 2.50b
4-MCP 128.56 1.2651 (30/4) 219.75 43.2-43.7 121.1 1 (49.8 °C) 2.39b
2,3-DCP 163 206 57-59
2,4-DCP 163 1.38 (60/7) 210 45 62 1 (76.5 °C) 3.06c
2,5-DCP 163 211 (744 mm) 59 3.20c
2,6-DCP 163 219-220 (740 mm) 68-69 1 (59.5 °C)d
3,4-DCP 163 253.5 (767 mm) 68
3,5-DCP 163 253 (757 mm) 68
2,3,4-T3CP 197.45 sublimes 83.5
2,3,5-T3CP 197.45 248.5-249.5 62
2,3,6-T3CP 197.45 272 58
2,4,5-T3CP 197.45 1.68 (25/25)e sublimes 68-70.5 1 (72 °C) 3.72f
(275 mm) 1 (53 °C) 3.62c
1 (76.5 °C)
Table 3. (contd).
Compound Relative Density Boiling point Melting point Flash Vapour log
molecular (°C at 760 mm) (°C at 760 mm) point pressure n-octanol/
mass (°C) (mm) water
(temperature) partition
coefficient
2,4,6-T3CP 197.45 1.49 (75/4)e 246 69.5 113.9
3,4,5-T3CP 197.45 271-277 (746 mm) 101
2,3,4,5-T4CP 231.98 1.67d sublimes 116-117
2,3,4,6-T4CP 231.98 1.6 (60/4)g 150 (15 mm) 70 1 (100 °C) 4.10c
2,3,5,6-T4CP 231.98 115
a Principal source: Jones (1981).
b From: Fujita et al. (1964).
c From: Stockdale & Selwyn (1971).
d From: US EPA (1980a).
e From: Kozak et al. (1979).
f From: Leo et al. (1971).
g From: Verschueren (1983).
2.4 Analytical Methods
2.4.1 Sample collection and storage
Proper sampling and sample storage are essential prerequisites for
residue determinations, particularly as picogram or nanogram
quantities are often encountered in environmental samples. It is,
therefore, important to minimize contamination, and to collect
representative samples.
Chlorophenols in the air have been collected by drawing air
through an absorbent liquid at a given rate for a given period, using
absorbents such as potassium carbonate (Dahms & Metzher, 1979) or
ethylene glycol (Wyllie et al., 1975). If a significant proportion of
the chlorophenols present is likely to bind to container walls, as
occurs with water samples, glass containers are preferable to plastic
ones (Kozak et al., 1979).
To avoid erroneous determinations, samples should be processed
immediately or appropriate steps taken to avoid losses through
degradation. If samples are to be stored for an extended length of
time after collection, major losses of chlorophenols may occur as a
result of photodecomposition, oxidation, biodegradation, or
evaporation (section 4). If it is necessary to store samples, changes
in residue levels can be reduced by refrigeration or freezing. The
American Public Health Association (Greenberg et al., 1985) recommends
preserving waste-water samples containing phenolic compounds by
acidification with phosphoric acid and treatment with copper sulfate,
prior to refrigeration.
2.4.2 Sample preparation and analysis
The early procedures used to analyse for chlorophenols were
reviewed by Bevenue & Beckman (1967). Most were colorimetric
techniques, the most popular being the 4-aminoantipyrine method; none
of the methods was either very specific or sensitive. They are no
longer widely used, and are not discussed here. Instead, more
sophisticated analytical techniques are being increasingly used,
including thin-layer chromatography (TLC), gas chromatography (GC),
high-performance liquid chromatography (HPLC), ion exchange
chromatography, infrared (IR) and ultraviolet (uv) spectroscopy, mass
spectrometry (MS), and mass fragmentography. Table 4 includes examples
of the techniques available for the sampling and determination of
chlorophenols other than pentachlorophenols. An indication of the
sensitivity of each method is given, when available.
Table 4. Analytical methods for chlorophenols other than PCPa
Matrix Chlorophenol Sampling, extraction Analytical method Detection limit/ Reference
recovery
Air T4CP Bubbler collection; Derivatization with 0.05 µg/m3 Dahms & Metzner
absorption in acetyl chloride; GC (1979)
potassium carbonate analysis, EC detector
solution; hexane
extraction
Air 3-MCP Polyether-type HPLC analysis, EC 5 ng US EPA (1980d)
4-MCP polyurethane foam; detector
2,4-DCP Soxhlet extraction
2,4,5-T3CP with diethyl ether/
2,4,6-T3CP hexane; evaporation;
extraction with NaOH,
buffered with phosphoric
acid
Water 2-MCP Adsorption on Florisil column Eichelberger
2,4-DCP activated carbon; with anhydrous et al. (1970)
2,4,5-T3CP adsorbates extracted sodium sulfate for
2,4,6-T3CP with chloroform then clean-up; GC analysis
sodium hydroxide
followed by ethyl ether
Table 4. (cont'd).
Matrix Chlorophenol Sampling, extraction Analytical method Detection limit/ Reference
recovery
Surface 2-MCP Adsorption on Form pentafluorobenzyl Kawahara (1971)
water 2,4-DCP activated carbon; ether derivatives;
adsorbates extracted GC analysis
with chloroform then
partitioned into acetone
Water 2-MCP Methylene chloride HPLC analysis, 4.2-12.6 ng; Realini (1981)
2,4-DCP extraction of acidified UV254 detector 93-97%
2,4,6-T3CP sample, followed
by ion-pair extraction
of basic sample with
acetonitrile
Air T4CP Collection in 0.1 N GC analysis, 0.5 µg/m3 Kleinman et al.
sodium hydroxide in EC detector (1986)
impingers, acidification,
extraction with toluene
Air T3CP Collection in Acetylation and 2-5 µg/m3 Kauppinen &
T4CP toluene in impingers, extraction with Lindroos (1985)
extraction into basic hexane; GC analysis,
borax solution EC detector
Table 4. (cont'd).
Matrix Chlorophenol Sampling, extraction Analytical method Detection limit/ Reference
recovery
Water 4-MCP Adsorb basic sample GC analysis, Fl 80-102% Chriswell et al.
2,4,6-T3CP on anion exchange detector; confirmation (1975)
resin; extraction by GC-MS
of hydrochloric acid
and acetone-water
eluates with methylene
chloride
Water T3CP Adsorb on XAD-4 Derivatization with T3CP: 1 µg/litre, Woodrow et al.
T4CP resin; extract with diazomethane; 74.8-77.7%; (1976)
acetone, hydrochloric dissolve in hexane; T4CP: 0.5 µg/litre,
acid; concentrate, HPLC clean-up on 46.7-61.4%;
then dilute with Partisil silica PCP: 0.5 µg/litre,
water; partition column; GC analysis 72.5-85.1%
with sodium sulfate, with EC detector
dry over
dichloromethane
Surface 2,4-DCP Addition of sodium Extract & derivatize 1-2 ng/litre, Abrahamsson & Xie
waste, or 2,6-DCP phosphate buffer by adding 98-105% (1983)
drinking- 2,4,6-T3CP solution, for acid hexane containing
water 2,3,4,6-T4CP waste-water pH internal standard
adjustment to 7 (2,6-dibromophenol)
with sodium and acetic anhydride
hydroxide directly to sample;
GC analysis, EC
detector
Table 4. (cont'd).
Matrix Chlorophenol Sampling, extraction Analytical method Detection limit/ Reference
recovery
Urine 2,4-DCP Partitioned into Purified by TLC; GC Kurihara & Nakajima
(mouse) 2,4,5-T3CP ethanol or benzene, analysis thermal (1974)
2,4,6-T3CP and water, both conductivity detector;
phases analysed; confirmation by MS
enzyme hydrolysis
of water soluble CP
conjugates
Urine T3CP Benzene extraction Der. with diazom 1 µg/litre, Edgerton et al.
(human, T4CP from acidified, ethane; separation on 89.3-97.0% (1979)
rat) hydrolysed solution acid alumina column;
GC analysis, EC detector;
GC-MS confirmation
Urine T4CP Acidic hydrolysis; LC analysis column: 23 µg/litre, Pekari & Aitio
(human) hexane/isopropanol Spherisorb ODS; 54.6% (1982)
extraction; mobile phase:
evaporation and methanol +
redistillation in ammonium carbonate;
methanol-water UV254 detector
Table 4. (cont'd).
Matrix Chlorophenol Sampling, extraction Analytical method Detection limit/ Reference
recovery
Urine 2-MCP Hydrolyse conjugates Der. with sodium Hargesheimer & Courts
(human) 4-MCP in acidified sample bicarbonate then (1983)
2,4-DCP by boiling; make acetic anhydride
2,6-DCP basic with sodium extraction methylene
2,4,5-T3CP hydroxide extract chloride; GC analysis,
2,4,6-T3CP with methylene EC and FI detectors;
chloride; neutralize, confirmation by MS
dry with sodium
sulfate
Blood 3-MCP Hydrolysis with HPLC analysis, 5 ng, US EPA (1980d)
(human) 4-MCP hydrochloric acid EC detector 80-100%
2,4-DCP extraction with hexane
2,4,5-T3CP ethyl ether;
extraction with sodium
hydroxide, buffered
with phosphoric acid
Table 4. (cont'd).
Matrix Chlorophenol Sampling, extraction Analytical method Detection limit/ Reference
recovery
Animal 2,4-DCP Optional alkaline Der. to trimethylsilyl 0.02 mg/kg Clark et al. (1975)
tissue 2,4,5-T3CP digestion; acid ether; GC analysis (2,4-DCP);
(sheep hydrolysis; 0.01 mg/kg, > 95%
cattle) distillation with water; (2,4,5-T3CP)
methylene chloride
Sediment T4CP Homogenization; toluene Derivatization 0.5-25 µg/kg, Butte et al. (1983)
and clams extraction from pyrolytic ethylation 76.7-98.8%
acidified sample with triethylsulfonium
2,4,6-tribromophenol iodide; GC analysis,
as internal standard EC detector;
Confirmation by MS
Fish 2-MCP Gel permeation Derivatization with 2-MCP-47% Stalling et al.
tissue 2,4-DCP chromatography to remove pentafluorobenzyl 2,4-DCP-78% (1979)
2,4,6-T3CP lipids, free fatty bromide; silica 2,4,6-T3CP-86%
acids; acid-base gel chromatography PCP-63%
extraction clean-up; GC analysis,
EC detector
Meat and 2,4-DCP Alkaline digestion; Derivatization 10 µg/kg, Sackmauerova-Veningerova
poultry 2,3,4-T3CP steam distillation of with methyl iodide; 92-98% et al. (1981)
livers 2,4,5-T3CP acidified sample; GC analysis;
2,4,6-T3CP toluene extraction EC detector
dry sodium sulfate,
evaporate
Table 4. (cont'd).
Matrix Chlorophenol Sampling, extraction Analytical method Detection limit/ Reference
recovery
Muscle 2,4-DCP Blended in GC analysis, Sherman et al. (1972)
(hen) hexane-sulfuric acid; EC detector
extraction with
NaOH, then hexane
Liver 2,4-DCP Ground; dried with Florisil column Sherman et al. (1972)
(hen) sodium sulfate eluted for clean-up; GC
with hexane; analysis, EC detector
extraction of eluate
with acetonitrile,
then hexane; dried
with sodium sulfate
Soil 2-MCP Steam distillation of GC analysis, EC < 0.1 mg/kg Narang et al. (1983)
2,4-DCP acidified sample; detector 2-MCP-59%;
2,4,6-T3CP extraction with 2,4-DCP-64%;
toluene dichloromethane 2,4,6-T3CP-70%
eluted through anhydrous
sodium sulfate
extraction with
hexane
Table 4. (cont'd).
Matrix Chlorophenol Sampling, extraction Analytical method Detection limit/ Reference
recovery
Wood 2,3,4,6-T4CP Extraction with diethyl Elution from TLC 200 mg/kg dust Levin & Nilsson (1977)
dust ether; evaporation; with n-hexane; 70%
dissolve in acetone derivatization
and TLC (silica gel) with diazomethane;
GC with Ni63
EC detector
Wood 2,4,6-T3CP Pumped through GC analysis, EC Kauppinen & Lindroos
dust 2,3,4,6-T4CP membrane filter; detector (1985)
Soxhlet extraction
with diethyl ether;
evaporate; dissolved
in hexane
a GC = gas chromatography.
TLC = thin-layer chromatography.
HPLC = high-performance liquid chromatography.
MS = mass spectrometry.
EC = electron capture detection.
FID = flame ionization detection.
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1 Natural Occurrence
Some chlorophenols are present in the environment independent of
man-made input. Dichlorophenols have been detected in a variety of
organisms (Siuda, 1980). 2,4-Dichlorophenol occurs naturally in a
Penicillium sp., while 2,6-DCP serves as a sex pheromone for several
species of tick. A number of related organohalogens are also found in
flora and fauna (Arsenault, 1976; Siuda, 1980). However, these sources
cannot account for the significant amounts of chlorophenols,
particularly the higher chlorinated phenols, found in the environment.
3.2 Man-made Sources
3.2.1 Production levels and processes
3.2.1.1 World production figures
Reliable data on production levels of chlorophenols other than PCP
are not readily available. In 1975, the combined global production of
all chlorophenols approached 200 million kilograms (Table 5). Slightly
more than half consisted of chlorophenols other than PCP, with
2,4-DCP, 2,4,5-T3CP, and 2,3,4,6-T4CP predominating. Where
commercial use data are available, recent figures indicate that
consumption has declined (IARC, 1986). Chlorophenols are used in
countries other than those shown in Table 5, but the quantities used
are not known. Information on PCP production is presented in WHO
(1987b).
3.2.1.2 Manufacturing processes
While most chlorophenols can be produced by several different
procedures, only a few methods are actually used in commercial
manufacture (Doedens, 1963; Freiter, 1979). Most chlorophenols are
made by the direct stepwise chlorination of phenol or lower
chlorinated phenols at an elevated temperature. The compounds 2-MCP,
4-MCP, 2,4-DCP, 2,6-DCP, 2,4,6-T3CP, 2,3,4,6-T4CP, and PCP are
manufactured by this means. The manufacture of T4CP or PCP requires
the use of a catalyst, such as iodine, aluminium chloride (AlCl3),
ferric chloride (FeCl3), or antimony chloride (SbCl3). The process
is not quantitative, with the result that batches of one chlorophenol
will usually contain substantial amounts of other CPs (section 2.1).
Table 5. Production/consumption of chlorophenols other than PCP
Country Compound Year Production/ Reference
consumption
(kg/year)
Global total chlorophenols 1975 1.8 × 108 (P)a Levin & Nilsson
(1977)
non-PCP 1978 0.98 × 108 (P) Ahlborg &
chlorophenolsb Thunberg
(1980)
Canada total chlorophenols 1976 3.4 × 106 (C) Jones (1981)
non-PCP chlorophenols 1.5 × 106 (C)b
total chlorophenols 1981 > 5.266 × 106 (C) Jones (1984)
1981 4.000 × 106 (P)
non-PCP chlorophenols 1981 > 3.730 × 106 (C)
tetrachlorophenol 1981 7.86 × 105 (C) Jones (1984)
and Na-T4CP 12.44 × 105 (P)
Na-T3CP 1981 3.0 × 103 (C) Jones (1984)
1.0 × 103 (P)
2,4-dichlorophenol 1981 3.700 × 106 (C) Jones (1984)
1.850 × 106 (P)
total chlorophenols 1984 3.89 × 106 (S) Environment
non-PCP chlorophenols 1984 4.91 × 105 (S)b Canada
(1986)
tetrachlorophenol 1984 4.9 × 105 (S) Environment
and Na-T4CP Canada
(1986)
2,4,5-trichlorophenol 1984 < 1.0 × 103 (S) Environment
and Na-2,4,5-T3CP Canada
(1986)
Europe monochlorophenols 4.5 × 106 (P) Krijgsheld &
van der Gen
2,4-dichlorophenol 9.1 × 106 (P) (1986)
Table 5. (contd).
Country Compound Year Production/ Reference
consumption
(kg/year)
United total chlorophenols 1972 > 1.14 × 106 (C)d Ahlborg &
Kingdom Thunberg
(1980)
USA total chlorophenols 1976 > 2.421 × Buikema et al.
107 (S,P)c,d (1979)
non-PCP chlorophenols 1976 > 1.995 × Buikema et al.
106 (S,P)b (1979)
2,4-Dichlorophenol 1976 1.995 × 106 (S)
a P = production, C = consumption, S = sales volume.
b By difference, from data presented in reference.
c Sales approximate consumption, since most use is domestic (Jones, 1981).
d A conservative estimate, derived by adding figures for major chlorophenols.
Alternatively, some chlorophenols are produced by the alkaline
hydrolysis of hexachlorobenzene (HCB) or other chlorobenzenes in
methanol, ethylene glycol, and other solvents. The compounds 2,5-DCP,
3,4-DCP, 2,4,5-T3CP, 2,3,4,5-T4CP, 2,3,5,6-T4CP, and PCP can be
synthesized by this type of reaction (Doedens, 1963; Freiter, 1979).
Both methods may yield contaminants that are themselves potential
health hazards, specifically PCDDs, PCDFs, and 2-phenoxyphenols
(section 2.1), especially if optimum reaction conditions are not
maintained (particularly temperature and pressure) in the production
of higher chlorophenols. In addition, chlorophenols derived from the
hydrolysis of chlorobenzenes may include substantial amounts of the
initial isomer in the final product.
3.2.2 Uses
The uses of commercial chlorophenols are summarized in Table 6.
These compounds are biocides, a property that accounts for many of
their uses. Chlorophenols, particularly tetra-, and to a lesser
extent, trichlorophenols, have been used as bactericides, algicides,
molluscicides, acaricides, fungicities, and mould inhibitors, and for
less specific uses, such as general antiseptics and disinfectants.
Chlorophenols are also used as intermediates in the production of
certain herbicides, dyes, and drugs.
At present, use patterns are more restricted than is indicated in
Table 6. For example, revisions to Canadian standards for chlorophenol
in 1980 resulted in a sharp reduction in use in domestic interiors,
agriculture, the leather industry, and as slimicides in the pulp and
paper industries. Both the quantities and patterns of use are even
more restricted in some countries. For example, in Sweden and Finland,
chlorophenols are no longer used, or use is severely restricted in the
wood preservation or pulp and paper industries (Ahlborg & Thunberg,
1980; Lindroos et al., 1987).
Most chlorophenols are applied in the form of a chlorophenol-oil
mixture, but some are dissolved in a "clean" carrier that can be
recovered, such as methylene chloride (Jones, 1981). In contrast, the
sodium salts of higher chlorophenols (particularly T3CP, T4CP, and
PCP) are readily soluble in water.
3.2.2.1 Wood treatment
Large quantities of higher chlorophenols are used in wood
preservation (Table 6). In Canada in 1981, most chlorophenol-treated
wood was preserved by pressure treatment with pentachlorophenol
(Table 7). This compound has been evaluated previously (WHO, 1987b),
and will not be covered here.
Substantial amounts of the sodium salts of T4CP (ca. 13% of total
1981 chlorophenol consumption: Table 7), and lesser amounts of NaT3CP
and NaPCP have been used to protect fresh-cut logs and lumber. These
compounds, which are readily soluble in water, are used to surface-
treat lumber by dipping or spraying to protect against sapstain or
mould. Some plywood mills also use T4CP to reduce decay and mould,
and insect attack. The preservative is usually added to the glue.
3.2.2.2 Agriculture
At one time, chlorophenol-treatment was widely used in
agriculture, to prevent wood decay in buildings, food containers, and
horticultural timbers. Recently, such chlorophenol applications have
been considerably restricted in some countries (section 3.2.2), and as
a result, the quantities of non-PCP chlorophenols used in agriculture
are minor (Jones, 1981).
Table 6. Principal uses and reactions of selected chlorophenols other than PCPa
Compound Principal uses Other uses
2-chlorophenol Intermediate for Polymer intermediate for
further chlorination to fire-retardant varnishes;
2,4-dichlorophenol, cotton fabric treatment
2,4,6-trichlorophenol, to provide rot resistance;
and pentachlorophenol ingredient in coal
processing
4-chlorophenolb Intermediate for
higher chlorophenols;
intermediate dyes,
fungicides, and drugs
2,4-dichlorophenol Intermediate for Intermediate for
production of 2,4-D and production of Sesone,
other herbicides; Nitrofen, Nemacide,
ingredient of Genite-EM-923; raw
antiseptics; starting material for polyester
material for higher films; mothproofing;
chlorophenols miticide
2,4,5-trichlorophenol Intermediate in Germicides and
manufacture of 2,4,5-T ingredients of
and related herbicides; germicidal soaps
fungicide, bactericide,
algicide
2,4,6-trichloropenol Precursor for higher CPs;
germicide, particularly for
preservation of wood,
leather, glue, and textiles;
intermediate in preparation
of insecticides and soap
germicides
2,3,4,6- Fungicide and bactericide Preservative for latex
tetrachlorophenol, for wood preservation; and leather; preservative
and its sodium salt sodium salt is sapstain in glue for plywood
inhibitor; pesticide
a From: US EPA (1979).
b From: US EPA (1980c).
3.2.2.3 Domestic
T4CP is an active ingredient in formulations of PCP used as wood
preservatives for homes, and as an additive to paints and stains
(Table 6). Sales in Canada for these purposes contribute only a small
fraction to the total PCP market (Jones, 1981) (Table 7) as a result
of recent government restrictions on their use (section 3.2.2). T3CP
is used as a general-purpose home antiseptic and as the active
ingredient in some throat lozenges. At one time, 4-MCP was found in
disinfectants for home, farm, dental, hospital, and veterinary uses,
but has been largely replaced by other chemicals (Exon, 1984).
Table 7. Canadian use patterns for chlorophenols and their sodium
salts in 1981a
Use Product Consumptionb % of Total
(kg × 103/year)
Wood preservation PCP 1536 25.2
(pressure treatment)
Wood protection Na-PCP 32 0.5
(surface treatment) Na-T4CP 786 12.9
Na-T3CPc 1 0.02
Intermediates for 2,4-DCPd 3700 60.7
phenoxy herbicides
Additives in products NaPCP 38 0.6
listed in footnote e NaT3CPc 2 0.03
Total 6095
a From: Jones (1984).
b Includes chlorophenols present in exports (13.6% of total
consumption), principally treated wood products.
c Chlorophenols are no longer registered for use in Canada.
d 2,4-D is no longer produced domestically, though considerable
quantities continue to be imported.
e Adhesives, construction materials, fabrics, fibreboard
products, finished paper, leather, paper machine felts,
photographic solutions, pulp and paper process solutions,
rayon emulsions, rubber, rubber gaskets.
3.2.2.4 Water treatment
Information is lacking on the use of non-PCP chlorophenols in
water-treatment applications (Jones, 1981).
3.2.2.5 Additives
Sodium salts of T3CP and T4CP have been used to inhibit
microbial growth in a diverse array of products (Tables 6 & 7). These
applications make up only a small fraction of the total consumption of
chlorophenols (Jones, 1981).
3.2.2.6 Intermediates in industrial syntheses
Production of chlorophenols is stepwise and not quantitative,
hence lower chlorophenols are generally recycled within a reactor
system, or recycled from other manufacturing processes in the
production of the higher chlorinated phenols. The lower chlorophenols
also serve as intermediates in the production of other pesticides
(Table 6). Large amounts of 2,4-DCP are consumed in the manufacture of
the phenoxy herbicide 2,4-D (Table 7), and also as a precursor for the
production of the pesticides Sesone, Nitrofen, Nemacide, and
Genite-EM-923. 2,4,5-T3CP is used in the manufacture Ronnel(R),
2,4,5-T, and related herbicides, while 4-MCP is used in the production
of the germicide 4-chlorophenol- o-cresol. Small amounts of lower
chlorinated phenols have been used in the manufacture of some dyes and
drugs.
3.2.3 Other sources
Chlorophenols are also generated by human activity via several
indirect routes. They are formed as by-products of chlorine bleaching
in paper-mills, and subsequently released into the environment
(Ahlborg & Thunberg, 1980; Xie et al., 1986) (section 5.1.2.1). The
chlorination of municipal and industrial wastes, and municipal
drinking-water can give rise to mono-, di-, and trichlorophenols in
the µg/litre range (NRCC, 1978). At these levels, the taste and odour
of water may be affected locally, though the chlorophenol
concentrations are well below those that produce any observable toxic
effect in test organisms (section 6.1). The incomplete incineration of
chlorophenol wastes can release substantial quantities of these
compounds into the environment (section 3.4). The lower chlorinated
phenols are also formed as a result of the bioconversion of lower
chlorinated benzenes and related compounds (Ballschmiter & Scholz,
1980). The contributions of these sources to environmental release or
human exposures to chlorophenols are generally not well-defined, and
are not considered in subsequent sections.
3.3 Waste Disposal
Waste-waters containing chlorophenols arise from three sources,
i.e., the manufacture of chlorophenols, the manufacture of compounds
in which chlorophenols are used as intermediates, and wood-treatment
facilities. Both manufacturers and regulatory agencies have emphasized
appropriate process design, in order to minimize the volume of waste
generated, particularly in the treatment of lumber (Richardson, 1978).
Information on the handling of chlorophenol-containing wastes in
Canada is limited. In the past, some industries disposed of
2,3,4,6-T4CP and PCP-contaminated wastes as raw effluent into deep
wells, or into lagoons, prior to discharge into the North Saskatchewan
River (Jones, 1981). However, most Canadian wood-treatment plants
report that they do not have any discharge and are able to dispose of
their minimal wastes by incineration, or containment and evaporation
in lagoons. Data to confirm the adequacy of such treatments are
generally not collected (Richardson, 1978), but they are probably
adequate, if applied correctly.
While waste-water treatment plants have been used in only a few
large wood-preserving plants and by some chemical manufacturers (US
EPA, 1979), their use is increasing in response to environmental
concerns. Such methods and their efficiency have been described (US
EPA, 1979).
Usually primary treatment is applied only in instances where the
chlorophenol in question is dissolved in a carrier oil, when gravity
separation tanks are used to recover the oil and associated
chlorophenol for subsequent recycling or waste treatment. A few plants
also use hay or sand filtration to remove some oil droplets and wood
particles (Richardson, 1978). Flocculation is not widely used, because
flocculents have proved ineffective or inconsistent in removing
chlorophenols (US EPA, 1979).
Chlorophenols are effectively removed by secondary treatment under
favourable conditions. Roughly 90% of total phenols were removed from
waters containing wastes from the manufacture of phenoxy herbicides in
aerated lagoons (US EPA, 1971) or by trickling filter/activated sludge
treatments (Mills, 1959). Several laboratory and treatment-plant
studies have shown that PCP can be degraded by activated sludge (Dust
& Thompson, 1973; Kirsch & Etzel, 1973; Etzel & Kirsch, 1974; Moos et
al., 1983; Guthrie et al., 1984; Hickman & Novak, 1984), a fluidized
bed reactor (Hakulinen & Salkinoja-Salonen, 1982), and a biofilm
reactor (Salkinoja-Salonen et al., 1984). However, of 14 municipal
treatment plants surveyed by the US EPA, 8 did not remove any of the
PCP load, while the remainder were considered to remove PCP (6-87%)
primarily by adsorption on solids (Hickman & Novak, 1984).
Furthermore, degradation by microorganisms is sharply reduced, when
chlorophenol concentrations are excessive (Broecker & Zahn, 1977;
Reiner et al., 1978; El-Gohary & Nasr, 1984; Salkinoja-Salonen et al.,
1984). If secondary treatment facilities are to remove chlorophenols
reliably, they must include acclimated organisms, and chlorophenol
concentrations must be dilute and fairly stable (Hickman & Novak,
1984). These considerations suggest that such wastes are best handled
by a facility designed specifically to treat them, rather than being
treated at general-purpose sewage-treatment plants.
Chemical oxidation, using such chemicals as chlorine or potassium
permanganate, may also be effective in treating
chlorophenol-contaminated wastes. While chlorination of municipal
wastes can actually produce mono-, di-, and tri- chlorophenols, they
are subsequently oxidized together with higher chlorophenols to
compounds that are less toxic and/or more biodegradable (US EPA, 1979;
Sithole & Williams, 1986).
Adsorption of chlorophenols on activated carbon is sometimes used
as a final clean-up step for waste-waters, though this is feasible
only when waste treatment is handled in the same plant from start to
finish. Removal of 2,4-DCP (Aly & Faust, 1964) and PCP (Richardson,
1978) approaches 100% using this method.
Incineration has also been used to dispose of chlorophenol wastes,
but the available information deals mainly with PCP. A controlled air
incinerator destroyed more than 99.99% of PCP in treated wood at
combustion temperatures of between 916 and 1032°C, and yielded no
measurable T4CDD or T4CDF in the off-gas (Stretz & Vawuska, 1984).
However, incinerator temperatures must be high enough and residence
times long enough to ensure complete combustion. Rappe et al. (1978b)
demonstrated that burning technical T4CP at low temperatures
increased the content of PCDDs. Similarly, low-temperature destruction
in hog-fuel or "wigwam" burners fed chlorophenol-contaminated sawdust
and wood shavings can lead to the formation of PCDDs and PCDFs (Crosby
et al., 1981).
3.4 Losses of Chlorophenols into the Environment
In the absence of information from other countries, releases of
chlorophenols into the Canadian environment for 1981 (Jones, 1984) are
presented in Table 8 by way of an example. Of the 5.27 × 106 kg of
chlorophenols consumed in Canada in 1984, 1.37 × 106 kg (26%) were
eventually released into the environment. A large proportion (less
than 28%) of these releases would have been as PCP and NaPCP, but the
data compiled in the table do not distinguish these from T4CP and
Na-T4CP.
Table 8. Chlorophenol releases into the Canadian environment in 1981a
Source Quantity (kg × 103/year)
1. Releases in wastes from production sites
emissions 3
effluents 70
solids -
sub-total > 73
2. Releases in other wastes
(a) Industrial
(i) Wood preservation sites
liquid 2
solids -
incineration (hog-fuel) -
landfill 1 (PCP, T4CP)
sub-total > 3
(ii) Saw-mill/planer mill
liquid 21
solids -
(ii) Incineration (hog-fuel) 272
Pulp mills/landfill -
sub-total >293 (NaPCP, NaT4CP)
(b) Agricultural
solids (livestock litter)
landfill
(c) Domestic
solids
incineration (mun.)
landfill
3. Releases during storage and transport
(solids and liquids)
(a) Industrial 3.5
(b) Agricultural 3.4
(c) Domestic 0.1
sub-total 7.0
Table 8. (cont'd).
Source Quantity (kg × 103/year)
4. Releases in situ from treated products
(solids and liquids)
(a) Industrial 618
(b) Agricultural 370 (2,4-DCP)
(c) Domestic 1
sub-total 989
Grand total > 1365
a From: Jones (1984).
In 1981, a significant amount (ca. 5%) of the total releases of
chlorophenols in Canada occurred from production sites. Following this
estimate, production of all chlorophenols ceased in Canada. However,
this route could be a significant source of chlorophenol contamination
in countries where they are still manufactured. Releases from plants
will include a variety of chlorophenols from the manufacture of
chlorophenols and chlorophenol-derived products. A small proportion of
these materials reaches the environment after incineration (Table 8),
but the bulk of the chlorophenols released from production sites in
Canada is diluted and released as untreated effluent.
Losses into the environment during the storage and transport of
chlorophenols are small (Table 8), comprising less than 1% of the
total production.
The majority (>70%) of the chlorophenols released into the
Canadian environment arose from treated products (Table 8). About
two-thirds of these came from industrial sources, which were not
identified by Jones (1984). Petrochemical drilling fluids contain
large amounts of chlorophenols (from 700 to 1400 mg NaPCP/kg), to
prevent fermentation of polysaccharides, starch, and polymers (Jones,
1981). Once used, the drilling waste is stored on site, in sumps that
are often subject to flooding and washing out. In-service treatment
with wood preservatives, principally PCP and its salts, also results
in some spillage. Large spills have been responsible for fish kills in
waters contaminated in this fashion (Jones, 1981). In addition,
unknown, but presumably large, quantities of PCP and T4CP are leached
from treated lumber in storage or in service. The remaining third of
the environmental releases, which Jones (1984) identifies as primarily
2,4-DCP, is from agricultural sources. Commercial preparations of
pesticides, particularly 2,4-D, 2,4,5-T, and Lindane, contain
chlorophenols as contaminants. Furthermore, chlorophenols are among
the early degradation products of these widely-used chemicals.
Chlorophenols from these sources contaminate soils treated with the
pesticides, and runoff from these soils finds its way into adjacent
water bodies and ground water.
Much of the remaining input of chlorophenols into the environment
occurs in the form of industrial wastes. These comprise roughly 22% of
the total chlorophenol releases, primarily as NaT4CP and NaPCP. Most
of these are released in liquid wastes from pulp-mills (where they are
by-produc