OECD SIDSHYDROQUINONEFOREWORDINTRODUCTIONHYDRQUINONECAS N°: 123-31-9

UNEP PUBLICATIONSOECD SIDSHYDROQUINONESIDS INITIAL ASSESSMENT PROFILE
123-31-9

CAS Nr.
Chemical Name
Structural formulaHydroquinone (1,4-Benzenediol)

HO

OH

CONCLUSIONS AND RECOMMENDATIONS
It was reported that the chemical was of low international concern, but processing sites such as inindustrial photography, may present local environmental concern based on default modelling.
It is currently considered of low priority for further work.
SHORT SUMMARY WHICH SUPPORTS THE REASONS FOR THE CONCLUSIONSAND RECOMMENDATIONS
Virtually all the uses of hydroquinone are industrial. Approximately 25% of the hydroquinone
manufactured is used as an intermediate for synthesis of antioxidants and antiozonants for use inrubber. Another 25% is used as an intermediate for chemical conversion to inhibitors used tostabilize monomers. An additional 33% is used in the photographic industry including black-andwhite photographic film, lithography, and hospital x-ray film. Other uses (11-12%) include
chemical conversion to stabilizers for paints, varnishes, motor oils, and fuels, and for antioxidants
for industrial fats and oils. Hydroquinone has been used in water cooling towers as a rust inhibitor.
Hydroquinone is considered to be readily biodegrable and photodegradable.
The aquatic toxicity of hydroquinone to fresh water fish, Daphnia, and algae was between 0.0500.335 mg/l; the predicted chronic values for these fresh water taxa were calculated to be < 0.100.
The 84 hr LC50 for the salt water shrimp, C. septemspinosa, was selected as the only salt water
species for analysis. Based on these data and on the predicted aquatic toxicity values, the USEPA
identified concern concentrations or predicted no effect concentrations (PNECs) at 1.0 µg/l for
fresh water species and 8.0 µg/l for salt water species. Alternatively, a PNEC can be derived using
the assessment factors recommended in the SIDS Manual. As only acute effect data for fish anddaphnids are available, an assessment factor of 100-1000 would be appropriate. Due to the large
available database, a factor of 100 would be acceptable. Applied to the lowest experimental valueof 0.044 mg/l (fathead minnow), a PNEC of 0.44 µg/l can be derived.
The PNECs are compared to the maximum annual estimated water concentrations based on the
1992 TRI release levels and the "what-if scenarios" for manufacturing, processing, and use sites
which were considered to be conservative estimates of PECs.
All but one of the direct discharge sites have PECs less than 0.07 µg/l and, therefore, the
PEC/PNEC ratios range from 8.2x10-5 to 6.8x10-2 using a PNEC of 1.0 µg/l. One direct discharger
has a predicted surface water concentration of 180 µg/l which would indicate a PEC/PNEC ratio ofgreater than one. However, in investigating site specific information for this discharger, it became
apparent that the plant PEC/PNEC ratio was significantly less than 1 as no hydroquinone was
2

UNEP Publications

OECD SIDSHYDROQUINONE

detected from its NPDES-regulated outfall prior to discharge.
Use of the alternative PNEC of 0.44 µg/l causes an additional four indirect discharges to exceed a
PEC/PNEC ratio of one (PEC/PNEC ratios of 1.5-2.0); however, considering that there are
estimated to be 16,000 to 66,000 processor/users of hydroquinone in the USA, the number ofpredicted PEC/PNEC ratios > 1 are small. Since all of the direct and indirect discharges identified
in the exposure assessment have NPDES regulated discharges, it is very unlikely that they actually
have discharges with PEC/PNEC ratios > 1. It is much more likely that the "what-if scenario" hasoverestimated the actual PEC.
The frequency of exceeding a PEC/NPEC of 1 can be calculated using the Probabilistic Dilution
Model (PDM 3) program. Using this model, a concern concentration of 1 µg/l is predicted to be
exceeded 0.5 days/yr (0.14% of the year) and a concern level of 0.044 µg/l is predicted to be
exceeded 3 days/yr (0.81% of the year).
While toxicity to mammalian species is associated with high doses of hydroquinone, these effects
are either species- and strain-specific or minimized in humans through reduced exposure. Dermal
effects in humans who use hydroquinone-containing skin products appear to be limited toindividuals who misuse the products or to products which contain other active ingredients. Similar
dermal effects have not been demonstrated in animals treated with similar or higher concentrationsof hydroquinone. Potential hazards from dermal exposure to aqueous solutions of hydroquinone
are also low based on dermal absorption rates. Exposure information provided indicates that
exposure potential for hydroquinone is low. Because no human health concerns have been
identified and exposure potential is low, this substance has a low priority for further work.

IF FURTHER WORK IS RECOMMENDED, SUMMARISE ITS NATURE
Depending on the extent of use, national action to avoid risk to the aquatic environment could be
warranted on some site-specific conditions.

UNEP Publications

3

OECD SIDSHYDROQUINONESIDS SUMMARY
Hydroquinone
CAS NO: 123-31-9

SPECIESPROTOCOL

RESULTSPHYSICAL-CHEMICAL
2.1

Melting Point

169 °C

2.2

Boiling Point

286 °C

2.3

Density

2.4

Vapour Pressure

2.5

Partition Coefficient (log Pow)

2.6A

Water Solubility

2.6B

pH
pKa

2.12

Oxidation:Reduction Potential

1.341 kg/m3
2.34 x 10-3 Pa at 25°C
Calculated

0.50-0.61
73000 mg/L at 25°C
4.0 - 4.7
pK1 = 9.9+286 mV at 25°C and pH 7

ENVIRONMENTAL
FATE/BIODEGRADATION
3.1.1

Photodegradation

Calculated

In air T½ = < 5 weeks

3.1.2

Stability in waterOECD 111

T½ = 111 hrs at pH 7

3.2

Monitoring dataNA

In air = ND*
In surface water = ND
In soil/sediment = ND
In biota = ND

3.3

Transport and Distribution

3.5

Biodegradation

Calculated(Fugacity level I)

Similar to OECD 301D

* ND = None detected.

4

UNEP Publications

In AirIn Water
In Sediment
In Soil
In Biota

0.21%
99.6%
0.06%
0.01%
< 0.001%

readily biodegradable

OECD SIDS
CAS NO: 123-31-9

HYDROQUINONESPECIESPROTOCOL

RESULTSECOTOXICOLOGY
4.1

Acute/Prolonged Toxicity to Fish

Pimephales promelas
Brachydanio rerio

Similar to OECD 203

LC50 (96 hr) = > 0.4 mg/L
LC50 (96 hr) = 0.17 mg/L

4.2

Acute/Prolonged Toxicity to
Aquatic Invertebrates Daphnia

Daphnia magna

Similar to OECD 202

LC50 (24 hr) = 0.09 mg/L
LC50 (24 hr) = 0.12 mg/L
LC50 (96 hr) = 0.05 mg/L

4.3

Toxicity to Aquatic Plants e.g.
Algae

Selenastrum
capricornutum

Similar to OECD 201

LC50 (7 d) = 1-4 mg/L
NOEC = 0.4 mg/L

4.5.2

Chronic Toxicity to Aquatic
Invertebrates (Daphnia)

-

-

-

4.6.1

Toxicity to Soil Dwelling
Organisms

-

-

-

4.6.2

Toxicity to Terrestrial Plants

Ryegrass
RadishLettuce

ASTM STP 1091

NOEC = 10 mg/L

Corn
Marigold
Lettuce
RadishSimilar to OECD 208

NOEC (corn) = 100 mg/L
NOEC = 10 mg/L

Pigeonother

LD50 = 500 mg/kg

4.6.3

Toxicity to Other NonMammalian Terrestrial Species(Including Birds)

UNEP Publications

5

OECD SIDS

CAS NO: 123-31-9

HYDROQUINONESPECIESPROTOCOL

RESULTSRat (?)Rat (OsborneMendel)
Rat (Wistar)
Rat (Sprague)
Mouse (?)
Mouse (Swiss)

Similar to OECD 401

LD50 = 390 mg/Kg
LD50 = 302 mg/Kg

TOXICOLOGY
5.1.1

Acute Oral Toxicity

LD50 = 298 mg/Kg
LD50 = 323 mg/Kg
LD50 = 680 mg/Kg
LD50 = 390 mg/Kg

5.1.2

Acute Inhalation Toxicity

-

-

-

5.1.3

Acute Dermal Toxicity

Guinea pig (?)

Similar toOECD 402

LD50 = > 1000 mg/Kg

5.4

Repeated Dose Toxicity

Rat (Sprague)

USEPA TSCA 40 CFR
798.6050
other
other
other
other
Similar toOECD 411

Rat (F-344)
Mouse (B6C3F1)
Rat (F-344)
Mouse (B6C3F1)
Rat (F-344)
5.5
A

Genetic Toxicity in Vitro
Bacterial Test
(Gene Mutation)

Salmonella
typhimurium

Similar to OECD 471

Similar to OECD 473

NOEL (dermal) =1920 mg/Kg (14 d)
NOEL (dermal) =4800 mg/Kg (14 d)
NOEL (oral) < 25 mg/Kg (13 w)
NOEL (oral) < 25 mg/Kg (13 w)
NOAEL (dermal) = 74 mg/Kg (13 w)

Negative (with metabolic activation)
Negative (without metabolic activation)
Positive(with metabolic activation)
Negative (without metabolic activation)B

Non-Bacterial in Vitro Test
(Chromosomal aberrations)

ChineseHamsterOvary

5.6

Genetic Toxicity in Vivo

Mouse (CD-1)

Similar to OECD 474

5.8

Toxicity to Reproduction

Rat (Sprague)

OECD 416

NOEL = 15 mg/Kg (General toxicity)
NOEL = 150 mg/Kg (Repro. Tox.
parental)
NOEL=150mg/Kg(Repro. Tox. F1)

5.9

Developmental Toxicity/
Teratogenicity

Rat (Sprague)

OECD 414

NOEL = 100 mg/Kg (General toxicity)
NOEL = 300 mg/Kg (Pregnancy/litter)
NOEL = 300 mg/Kg (Foetal data)

Rabbit (NZW)OECD 414

NOEL = 25 mg/Kg (General toxicity)
NOEL = 75 mg/Kg (Pregnancy/litter)
NOEL = 75 mg/Kg (Foetal data)

NA

NA

Less than 100 workers are potentially
exposed during manufacture. One report(1947) attributes eye injury to vapors ofquinone or hydroquinone. No otherreports have demonstratedhydroquinone-related effects. Nonindustrial exposure occurs in consumers
using nonprescription drugs containing
2% hydroquinone and photohobbyiststhat develop black-and-white film.

5.11

6

NOEL (oral) = 20 mg/Kg (13 w)

Experience with Human
Exposure

UNEP Publications

Positive (ip injection)
Weak (oral gavage)

OECD SIDSHYDROQUINONE

COVER PAGE
SIDS Initial Assessment Report (SIAR)

Chemical Name:

Hydroquinone

CAS No.:123-31-9

Sponsor Country:

United States of America

SIDS Contact Point
in Sponsor Country:

Mr. Charles Auer

HISTORY:
SIDS Dossier and Testing Plan were reviewed at the 3rd SIDS Review Meeting,
September 1993. Agreed that no tests were needed. At the SIAM 3, this chemical was
identified as having a potential concern due to widespread consumer exposure and reportsof skin whitening from mis-use. It was recommended to gather exposure information.
After the SIAM, some additional information on this chemical was gathered using the
proposed OECD format. The SIDS Initial Assessment Report, with any changes, as
appropriate, to the conclusion and recommendations, were reviewed and discussed at
SIAM 4.
Following SIAM 4 in Tokyo on 20-22 May 1996, additional environmental modelinginformation for hydroquinone use at specific sites was submitted by the French
representative. This information was incorporated into the final SIAR document.

COMMENTS:
The submitted information confirmed the SIAR presented at SIAM 3 and SIAM 4 and has
been revised to include additional information collected following the SIAM 4 meeting.
The recommendation continues to be low priority for further work.

UNEP Publications

7

OECD SIDSHYDROQUINONESIDS INITIAL ASSESSMENT REPORT
1.

IDENTITY
Chemical name:

1,4-Benzenediol

Synonyms:

Hydroquinone
para-Dihydroxybenzene
para-Benzenediol
Ι-Hydroquinone

CAS number:

123-31-9

Empirical formula:

C6H6O2

Structural formula:
HO

Molecular weight:

110.11Degree of purity:> 99%

Major impurities:< 1% water

Essential additives:

none

OH

2.

GENERAL INFORMATION ON EXPOSURE

2.1

Production Volume

Production is estimated at 35000 tonnes per year worldwide in 1992 (IPCS, 1994). Production in
the U.S.A. was 18700 - 20900 tonnes per year in 1992 (U.S.E.P.A., 1995). Hydroquinone ismanufactured in the U.S.A., Japan, France, Italy, China, and Canada. Eastman Chemical Company,
the major producer of hydroquinone in the U.S.A., is located in Kingsport, Tennessee.
Hydroquinone is produced at a single site in Canada at 0.1 - 1 tonne per year (Taylor, 1995).
2.2

Production Processes

There are three current manufacturing processes for hydroquinone: oxidative cleavage of
diisopropylbenzene, oxidation of aniline, and hydroxylation of phenol.
At Eastman Chemical Company, diisopropyl benzene is air oxidized to the intermediate
diisopropylbenzene bishydroperoxide. This hydroperoxide is purified by extraction and reacted
8

UNEP Publications

OECD SIDSHYDROQUINONE

further to form hydroquinone. Process solvents are recycled. Water-insoluble impurities areincinerated, and the two water-based impurity streams are biodegraded in the plant wastewater
treatment system. The purified product is isolated by filtration, and packaged. The process isalmost entirely closed, continuous, computer-controlled, and monitored.
Hydroquinone can also be prepared by oxidizing aniline to quinone in the presence of manganesedioxide and sulfuric acid. Quinone is then reduced to hydroquinone using iron oxide. The resultinghydroquinone is crystallized and dried. The process occurs in a closed system.
Hydroquinone is also manufactured by hydroxylation of phenol using hydrogen peroxide as ahydroxylation agent. The reaction is catalyzed by strong mineral acids, or ferrous or cobalt salts.
2.3

Uses and Functions

Virtually all the uses of hydroquinone are industrial. Approximately 25% of the hydroquinone
manufactured is used as an intermediate for synthesis of antioxidants and antiozonants for use inrubber. Another 25% is used as an intermediate for chemical conversion to inhibitors used tostabilize monomers. An additional 33% is used in the photographic industry including black-andwhite photographic film, lithography, and hospital x-ray film. Other uses (11-12%) include
chemical conversion to stabilizers for paints, varnishes, motor oils, and fuels, and for antioxidants
for industrial fats and oils. Hydroquinone has been used in water cooling towers as a rust inhibitor.
About 0.05% of the hydroquinone manufactured is used in skin lightening creams. Hydroquinone
is also used as a coupler in oxidative hair dyes. Small amounts of hydroquinone are used byphotohobbyists for the development of black-and-white films and paper.
2.4

Form of Marketed Products

Hydroquinone is sold by manufacturers as a dry, crystalline solid packaged in plastic film lined
sacks or drums. For photographic purposes, hydroquinone is sold in powder formulations or inaqueous solution (concentrated pre-mixes are 1-10% while working strength solutions are 0.5-3%).
Rust inhibitors may contain <1% hydroquinone in a powder mixture. Polymerization inhibitors
may contain <1% hydroquinone in solution or dry powder. Skin lightening formulations which aresold as non-prescription drugs contain 2% hydroquinone in a hydroalcoholic cream.
2.5

Sources of Release to the Environment

Hydroquinone is a naturally occurring substance found in several foods (e.g., wheat products, fruits)
and beverages (e.g., brewed coffee, some teas, beer, red wine) (Deisinger et al., 1996).
Hydroquinone is formed as a byproduct of metabolism in several bacteria and marine species. It isestimated that approximately 5 x 104 kg of hydroquinone is generated per year during cigarettesmoking.
During manufacture, hydroquinone is potentially released to the air, water, soil, or other sites (e.g.,
waste water treatment works). Data from the 1992 Toxic Release Inventory (TRI, 1992) reported to
the U.S.E.P.A. indicated that 4215 kg was released to the air (35% of total) or off-site (65% towaste water treatment facilities and an unidentified off-plant site). The TRI releases areapproximately 0.02% of the total amount of hydroquinone manufactured in the U.S.A.
Hydroquinone is processed or used by an estimated 16000 - 66000 facilities in the U.S.A. 1992
TRI releases from processing and use operations were 216000 kg/yr or 1.0-1.2% of the total amount
UNEP Publications

9

OECD SIDSHYDROQUINONE

produced. TRI releases by processor/users were 2% to air, 1% to water, 53% to land, and 44% offsite including waste water treatment works. Hydroquinone releases to the environment in Canada
during 1993 were reported by four facilities to be a total of 0.153 tonnes/yr into an unspecified
environmental compartment(s) (Taylor, 1995).
Releases in other countries are assumed to be at equivalent levels.
Releases of hydroquinone may occur during drumming/bagging operations which are typicallyconducted in protected but not totally closed systems. Releases may also occur during cleaning andmaintenance.
During processing and use, hydroquinone exposure may occur during the opening and dumping ofbags and drums into hoppers, reactors, or mixing vessels. Bags are typically opened and emptied
manually while drums are typically opened and their plastic liners slit manually, and then dumped
with mechanical lifting devices. Releases during processing typically occur over periods of 10-60
minutes, one-four times/day.
Hydroquinone should not volatilize from photoprocessing solutions because of its water solubility,
very low vapor pressure, and high vapor density. Thus potential exposure during photoprocessing
is limited to mixing operations where dry powder formulations containing hydroquinone are added
to water to make working-strength solutions. Hydroquinone present in developers for black-andwhite and x-ray films can appear in the diluted effluent from photoprocessing. The amount ofhydroquinone in the effluent depends on its concentration in the original developing solution, thephotodeveloper replenishment rate, and the volume of waste waters. The hydroquinone content offresh working solutions is ca. 0.5-2.5% (w/v).
2.6

Material Safety Data Sheet Information on Safe Handling

The following information is provided from an Eastman Chemical Company MSDS forhydroquinone.
HMIS Hazard Ratings: Health - 2, Flammability - 1, Chemical reactivity - 0.
NFPA Hazard Ratings: Health - 2, Flammability - 1, Chemical reactivity - 0.
NOTE: HMIS and NFPA ratings involve data and interpretations that may vary. They are intended
only for rapid, general identification of the magnitude of the specific hazard. To deal adequately
with the safe handling hydroquinone, all the information contained in the MSDS must be
considered.
First-Aid Measures
Inhalation: Move to fresh air. Treat symptomatically. Get medical attention if symptoms persist.
Eyes: Immediately flush with plenty of water for at least 15 minutes. If easy to do, remove contactlenses. Get medical attention.
Skin: Immediately remove contaminated clothing and shoes and wash skin with soap and plenty ofwater. If skin irritation or an allergic skin reaction develops, get medical attention. Wash
contaminated clothing before reuse. Destroy or thoroughly clean contaminated shoes.

10

UNEP Publications

OECD SIDSHYDROQUINONE

Ingestion: Call a physician or poison control center immediately. Induce vomiting as directed by
medical personnel. Never give anything by mouth to an unconscious person.
Fire Fighting Measures
Extinguish Media: Water spray, dry chemical.
Special fire-Fighting Procedures: Wear self-contained breathing apparatus and protective clothing.
Hazardous Combustion Procedures: Carbon dioxide, carbon monoxide.
Unusual Fire and Explosion Hazards: Powdered material may form explosive dust-air mixtures.
Accidental Release Measures
Sweep up and place in a container for chemical waste.
Handling and Storage
Personal Precautionary Measures: Avoid contact with eyes, skin, and clothing. Avoid breathing
dust. Do not taste or swallow. Use only with adequate ventilation. Wash thoroughly after handling.
Regular cleaning of working surfaces, gloves, etc., will help minimize the possibility of a skinreaction.
Prevention of Fire and Explosion: Keep from contact with oxidizing materials. Minimize dust
generation and accumulation. Refer to NFPA Pamphlet No. 654, "Prevention of Fire and Dust
Explosions in the Chemical, Dye, Pharmaceutical, and Plastics Industries."
Storage: Keep container closed.
Exposure Controls/Personal Protection
Exposure Limits:
ACGIH Threshold Limit Value (TLV): hydroquinone: 2 mg/m3 8-hr TWA.
OSHA (U.S.A.) Permissible Exposure Limit (PEL, 1989 Table Z-1-A values or section-specificstandards: hydroquinone: 2 mg/m3 TWA.
Ventilation: Good general ventilation (typically 10 air changes per hour) should be used.
Ventilation rates should be matched to conditions. Use process enclosures, local exhaust
ventilation, or other engineering controls to maintain airborne levels below recommended exposure
limits.
Respiratory Protection: If engineering controls do not maintain airborne concentrations below
recommended exposure limits, an approved respirator must be worn. Respirator type: dust. If
respirators are used, a program should be instituted to assure compliance with OSHA Standard 29
CFR 1910.134.
Eye Protection: Wear safety glasses with side shields (or goggles) and a face shield. Wear a fullface respirator, if needed.
UNEP Publications

11

OECD SIDSHYDROQUINONE

Skin Protection: Wear chemical-resistant gloves, boots, and protective clothing appropriate for therisk of exposure.
Recommended Decontamination Facilities: Eye bath, washing facilities, safety shower.
Physical and Chemical Properties (Properties not provided elsewhere in SIAR.)
Odor: odorless
Odor Threshold: not applicableFlash Point (closed cup): 165oC (329oF)
Lower Explosive Limit: not available
Upper Explosive Limit: not available
Autoignition Temperature (ASTM D 2155): 499oC (930oF)
Sensitivity to Mechanical Impact: insensitive at 550 inch-pounds
Sensitivity to Static Discharge: not available
Stability and Reactivity
Stability: Stable.
Incompatibility: Material can react with strong oxidizing agents.
Hazardous Polymerization: Will not occur.
Disposal Considerations
Discharge, treatment, or disposal may be subject to national, state, or local laws. Incinerate. Since
emptied containers retain product residue, follow label warnings even after container is emptied.
Transport Information
DOT (U.S.A.) Status: regulated
Class 6.1, packing group III
TDG (Canada) Status: regulated
Class 6.1, packing group III
Air - International Civil Aviation Organization (ICAO)ICAO Status: regulated
Class 6.1, packing group III
Sea - International Maritime Dangerous Goods (IMDG)
IMDG Status: regulated
Class 6.1, packing group III

12

UNEP Publications

OECD SIDS
3.

ENVIRONMENT

3.1

Environmental Exposure

HYDROQUINONE

3.1.1 General Discussion
Exposure relevant properties:
Water solubility:
Partition coefficient log Pow:
Vapor pressure:
BOD5
COD5
BOD5/COD5•
Degradation:

73 g/L at 25οC
0.50-0.61
2.34 x 10-3 Pa at 25οC
1.00 g O2/g
1.83 gO2/g
0.55

Hydroquinone degrades by both biotic and abiotic mechanisms. Biodegradation is affected by pH,
temperature, aerobic/anaerobic conditions, and acclimation of the microorganisms involved(Devillers et al., 1990).
Under aerobic conditions, Harbison and Belly (1982) reported that 74% of the radioactivity fromthe incubation of activated sludge and 14C-hydroquinone was recovered as carbon dioxide in 5-10
days. Small amounts of 1,4-benzoquinone, 2-hydroxy-1,4-benzoquinone, and β-ketoadipic acid areformed as metabolites of hydroquinone. A maximum concentration of 0.11% (1.05 mg/L) 1,4benzoquinone was detected at 2 hr during incubation of 950 mg/L hydroquinone by yeast cultures(Harbison and Belly, 1982) At later time points 1,4-benzoquinone levels were lower andbenzoquinone was not detected in the effluent from the activated sludge unit. Gerike and Fischer(1979) reported that 82% of hydroquinone was converted to CO2 in a 28-day Sturm test and that
97% of the dissolved organic carbon was removed in 28 days. Thus hydroquinone is primarily
converted to CO2 or mineralized during aerobic degradation.
Under anaerobic conditions, hydroquinone is metabolized through phenol, instead of 1,4benzoquinone, prior to mineralization (IPCS, 1994).
As the organisms which biodegrade hydroquinone are widely distributed in the environment insludges, soils, sediments, and composts (Devillers et al, 1990), hydroquinone is expected to readily
biodegrade in soils and water.
Due to its intrinsic properties, hydroquinone is relatively rapidly photodegraded;phototransformations may occur from direct excitation or from induced or photocatalytic reactions(IPCS, 1994).
•

Bioaccumulation:

With measured partition coefficients log Pow = 0.50-0.61, hydroquinone is not considered toundergo bioaccumulation (IPCS, 1994). Bioaccumulation factors of 40 have been determined foralgae and fish (Freitag et al., 1985).
•

Distribution between environmental compartments and occurrence in the environment:

UNEP Publications

13

OECD SIDSHYDROQUINONE

The environmental transport of hydroquinone can be partially predicted based on its physicalchemical properties. With a melting point of 169oC, a vapor pressure of 2.34 x 10-3 Pa at 25oC anda relative vapor density of 3.81 (air=1), it is not expected to transport into the atmosphere. A
calculation of fugacity using Mackay's model I indicates that hydroquinone will be distributed to
the water compartment (99.6%) when released into the environment.
(i)

Air

Hydroquinone is essentially non-volatile in its solid form. Its solubility in water (which increases
with temperature), low vapor pressure, and high relative vapor density, and low Henry's law
constant (3.84x10-11 atm-m-3/mole; Meylan and Howard, 1991) indicate that hydroquinone will notevaporate from water into the atmosphere. The half-life of hydroquinone in the air is 14 hr(U.S.E.P.A., 1990)
In its dry solid form, hydroquinone is stable and darkens only slowly if exposed to the air. In thepresence of moisture and ambient levels of oxygen, hydroquinone can undergo oxidation to 1,4benzoquinone which is more likely to volatilize because of its higher vapor pressure. As thispotential reaction is well recognized, manufacturing plants do not let hydroquinone powders standin open environments prior to bagging or drumming operations. For the same reason,hydroquinone-containing products such as photographic developers contain stabilizers such as
sodium sulfite to prevent or retard oxidation.
(ii)

Water

Due to its physical chemical properties, hydroquinone can be expected to partition to the watercompartment. As its melting point is 169oC, vapor pressure is low, Henry's law constant isrelatively low, and its solubility in water increases with temperature, hydroquinone is not likely to
be volatilized to the air compartment from water. In waste water, hydroquinone would be expected
to be readily biodegradable. If hydroquinone were present in an open body of water, it would be
expected to both biodegrade and photodegrade. Hydroquinone half-life in surface water is 20 hr(U.S.E.P.A., 1990). While 1,4-benzoquinone would be expected to be one of the degradation
products of hydroquinone, its ready degradation (Harbison and Belly, 1982) would not be expected
to impact the toxicity of a hydroquinone release. Releases of 1,4-benzoquinone itself to water are
small and decreasing. TRI data indicate the following total releases of 1,4-benzoquinone to thewater environment in the U.S.A.: 50 kg/yr (1987), 64 kg/yr (1988), 5.5 kg/yr (1989), 2.3 kg/yr(1990), 0 kg/yr (1991), and 1.8 kg/yr (1992). These data suggest that there is unlikely to be asignificant additivity of effect between water releases of hydroquinone and 1,4-benzoquinone.
(iii) Soil
Hydroquinone released to the soil would be expected to mineralize as organisms which can degradehydroquinone are commonly found in soils and compost. Half-life in soil is 2-14 days and depends
on photo-oxidation and bacterial degradation (U.S.E.P.A., 1990). Hydroquinone present in soil
could be expected to partition to water in the soil and be mobile. Half-life values in ground waterare 4-14 days (aerobic conditions) and up to a month (anaerobic conditions) (U.S.E.P.A., 1990).
However, hydroquinone and its immediate degradation product, 1,4-benzoquinone may also be
absorbed to the soil. Since hydroquinone and 1,4-benzoquinone are electron donor and electron
acceptor molecules respectively, they could form charge transfer complexes with soil particles.
Hydroquinone and its biodegradation products may contribute to the formation of humic acids
which are polymerization products of polyphenols commonly formed during the biodegradation of
14

UNEP Publications

OECD SIDSHYDROQUINONE

plants. Much of the naturally occurring hydroquinone in plants may be reincorporated into soils inthis manner.
3.1.2 Predicted Environmental Concentrations
Estimates of predicted environmental concentrations (PEC) from hydroquinone manufacturing,processing, and use are based on 1992 TRI data reported to the U.S.E.P.A. (1995). These "what-if
scenarios" estimate the hydroquinone concentration in air and water using simple, conservative
atmospheric dispersion models (EAB, 1994; Versar, 1992a). Surface water concentrations were
estimated using site-specific receiving stream flow data and a simple dilution model. These "whatif scenarios" have been developed to assess potential exposure under a set of hypotheticalconditions or under a set of conditions for which actual exposure parameter data are incomplete or
non-existent. The calculated PECs are not intended to provide information about how likely the
combination of exposure parameter values might be in the actual population or approximately how
many, if any, persons might actually be exposed to the calculated value. The PECs determinedfrom "what-if scenarios" may exceed PECs calculated based on realistic worst case scenarios.
Ambient Air Concentrations
Maximum annual average concentrations resulting from fugitive releases to air were predicted using
the PMN PLUME Model (Versar, 1992a). This model is a computerized version of Turner's sector
averaging form of the Gaussian algorithm (Turner, 1970). Concentrations were predicted for a
receptor located at the facility fence line (assumed to be 100 meters down wind). Neutral
atmospheric stability, an average wind speed of 5.5 m/sec, and wind direction toward the receptor
25% of the year were assumed. Because all of the release sources for a given facility were assumed
to be within 100 meters of each other, all emissions were assessed as coming from a single
representative stack assumed to be 3 meters in height.
The 1992 TRI data for all manufacturing sites indicates the following releases: 100 kg/yr (fugitive
air release), 1390 kg/yr (stack releases), and 2825 kg/yr (off-site to waste water treatment); water
releases, and on-site land releases were 0 kg/yr. TRI releases from processing and use operations in
1992 were 216000 kg/yr, with 2% released to air, 1% released to water, 53% released to land, and
44% released off-site (includes waste water treatment).
The PEClocal estimated from ambient air hydroquinone concentrations for the three manufacturing
sites were negligible or 0 to 4.9x10-4 mg/m3 for fugitive emissions and 7.8x10-8 to 3.0x10-6 mg/m3
for stack emissions. The overall average air concentration was 8.2x10-5 mg/m3.
The PEClocal estimated from ambient air hydroquinone concentrations for processor and user sites
were negligible or 0 to 8.5x10-3 mg/m3 for fugitive emissions and 0 to 8.1x10-6 mg/m3 for stackemissions. The highest average value for fugitive and stack emissions combined was
4.2x10-3 mg/m3.
Surface Water Concentrations
Surface water concentrations for the U.S.A. were calculated using site-specific receiving stream
flow data obtained from Versar (1992a). Complete dilution of the chemical releases to the entire
stream flow is assumed, but the effect of in stream degradation and removal processes was notaddressed. For facilities which discharge waste water to a treatment plant (i.e., indirect dischargers),
removal during waste water treatment was assumed to be 90% based primarily on expectedbiodegradation.
UNEP Publications

15

OECD SIDSHYDROQUINONE

The PEClocal estimated as the harmonic mean surface water concentration for two manufacturing
sites was negligible or zero and 8.2 µg/L for a third site. For processors and users who were directdischargers to fresh water, the harmonic mean surface water concentrations were estimated to be
8.2x10-5 to 6.8x10-2 µg/L except for one discharge site which had an estimate of 180 µg/L. Forprocessors who were indirect dischargers to fresh water, the harmonic mean surface water
concentrations were estimated to be 1.9x10-5 to 0.88 µg/L except for three discharge sites whichwere 1.3, 32, and 130 µg/L. For processors and users who were indirect discharges to salt water
bodies, the estimated harmonic mean surface water concentrations were 1.5 µg/L and 3.8 µg/L.
The sea water discharge estimates refer to concentrations at the end of the discharge pipe without
further dilutions, therefore, the values are overestimates of the actual environmental concentrations.
In 1977 and 1978 when discharges may have been greater than they currently are, U.S.E.P.A.
contractors (Ewing et al., 1977; Perry et al., 1978) looked for but did not detect hydroquinone insurface waters associated with effluents from hydroquinone manufacturing sites.
Hydroquinone present in x-ray film developers can appear in the effluent from photoprocessors.
Generic predicted environmental concentrations can be derived using the following scenarios (R.
Diderich, personal communication), based on the EU-Technical Guidance Documents;
Scenario 1: It is supposed that the overflow (replenishment rate) of the processing solution isdischarged into waste water by the photographic finishers (in this case mostly hospitals and medical
practices).
Content of hydroquinone in fresh working strength solution:
Surface processed per day:

5 - 25 g/L
20 m2/day (default)

The EU - Technical Guidance Document proposes to use a processed surface of 2000 m2/d. This
amount is valid for big photographic laboratories. For x-ray film, the highest consumption would
be expected at large hospitals. According to the research institute INFU in Dortmund, Germany, aconsumption of up to 6000 m2/yr in mean sized hospitals (100 beds) and up to 20000 m2/yr in large
hospitals is to be expected. Even for a mean-sized hospital of 100 beds, it would not be appropriate
to use the default waste water flow of 2000 m3/d for the corresponding town (ca. 10000
inhabitants). It would be more realistic to place this hospital into a larger town of ca. 20000
inhabitants with a corresponding waste water flow of 4000 m3/d. The processed surface would be6000 m2/yr (i.e., 20 m2/d) for a release period of 300 d/yr).
Consumed processing solution:
Percentage removed or converted during processing:

350 ml/m2 (default)
10%

Due to the high chemical reactivity of hydroquinone (autooxidation) a certain conversion can beassumed. No measured data are available though.
Waste water flow in the domestic waste water treatment plant:
4000 m3/d (default)
Elimination in the waste water treatment plant:
91%(SIMPLETREAT: log Pow - 0.5, log H < 0, ready biodegradation)
Dilution factor upon entering the surface water:
10 (default)
PEClocal = (0.005*350*20*0.9*0.09) / (4000*10) = 0.07 to 0.35 µg/l

16UNEP Publications

OECD SIDSHYDROQUINONE

Scenario 2: It is supposed that the overflow is recycled. A part of the overflow, which is not fit forrecycling is discharged. Additionally, part of the processing solution is discharged with the rinsing
water into waste water (carry-over).
Percentage of processing solution not fit for recycling:
Carry-over rate:

20% (default)
0.1 L/m2 (default)

PEClocal = (0.005*(350*0.2+0.1)*20*0.9*0.09)/(4000*10) = 0.014 to 0.07 µg/L
According to one formulator, the developing solution is not commonly recycled but rather the fixer
solution is recycled. The above scenario is therefore probably not representative.
Scenario 3: It is supposed that the overflow is collected and not discharged into waste water. Only
the carry-over is released into the waste water.
PEClocal = (0.005*0.1*20*0.09) / (4000*10) = 0.000023 to 0.00011 µg/L
Scenario 3 implies that the collected overflow is externally treated for silver recovery and that the
spent solution is released to waste water after treatment. No scenario is available so far for the
release during treatment of spent development solutions.
3.2 Effects on the Environment
3.2.1 Aquatic effects
The toxicity of hydroquinone to several species of fish, crustacea, and other organisms has beenreviewed by IPCS (1994). The most significant results are listed in the attached SIDS Profilesummary.
For the purposes of this assessment, a 96 hr LC50 of 0.044 mg/L for Pimephales promelas was
selected as the most sensitive fish toxicity value.
Kuhn et al. (1989) reported a calculated 48-hr LC50 value (immobilization) of 0.29 mg/L for
Daphnia magna in a test conducted according to DIN 38412, Part II. However for the purposes ofthis assessment, a 96 hr LC50 = 0.05 mg/L for Daphnia magna was selected for analysis(Bringmann and Kuhn, 1977). Although this study was conducted before the 48-hr testing scheme
became a standard length of exposure for this test, the LC50 values of 0.12 mg/L for 24 hr and 0.05
mg/L for 96 hr provide reasonable estimates of toxicity for this species. Based on simple linear
interpolation the 48 hr LC50 is calculated to be 0.096 mg/L.
For the salt water shrimp, Crangon septemspinosa, the 84 hr LC50 = 0.83 mg/L (McLeese et al.,1979) was selected as a sensitive species for analysis.
A three-day EC50 (growth) of 0.335 mg/L for S. capricormutum was selected as the most sensitive
algal test for analysis.
Based on these data and calculations, hydroquinone is considered to have high acute toxicity foraquatic organisms.

UNEP Publications

17

OECD SIDSHYDROQUINONEThe U.S.E.P.A. (1995a) has predicted ecotoxicity effect levels for a number of species. These
values are shown along with experimentally determined values below.
Predicted Toxic Value(mg/L)

Experimental Value(mg/L)

Fathead Minnow
LC50

0.060

0.044
(96 hr)Daphnia magna
LC50

< 1.0

0.050
(96 hr)C. septemspinosa
LC50

-

0.830
(84 hr)S. capricormutum
EC50

< 1.0

0.335
(72 hr)Ecotoxicity EffectS. quadricauda
EC50

4 (96 hr)0.93 (7 d)Fish Chronic Value< 0.100

Daphnid Chronic Value< 0.100

Algal Chronic Value< 0.100

0.600

Predicted values based on SARs for hydroquinones-quinones, MW = 110; LogPow = 0.81
(CLOGP); pH 7; hardness < 180.0 mg/L as CaCO3; TOC < 2.0 mg/L; solid; MP 169-171oC,
Water Sol 73000 mg/l @25oC; hydrolysis t½ to quinone = 20 hr (U.S.E.P.A., 1995a).

Estimation programs are based on mathematical relationships between Log Pow and effect for aseries of hydroquinones/quinones evaluated at the U.S. EPA. Acute toxicity coupled withpersistence can produce long-term adverse effects in the environment. Due to the rapid degradationof hydroquione by biotic and abiotic mechanisms, hydroquinone has not been labelled a long term
hazard in a provisional classification for Europe.
3.2.2 Terrestrial Effects
Growth test on terrestrial plants OECD 208
Corn, Marigold, Lettuce, Radish
LOEC (corn) = 1000 mg/L
NOEC (corn) = 100 mg/L
LOEC = 100 mg/L
NOEC = 10 mg/L
Seed germination test ASTM STP 1091
Ryegrass, Radish, Lettuce
LOEC = 100 mg/L
NOEC = 10 mg/L

18

UNEP Publications

OECD SIDSHYDROQUINONE

Significant exposure to the terrestrial environment is not expected. 1992 TRI data indicated no onsite land releases of hydroquinone from manufacturing sites. Of the 16000 to 66000 facilities
estimated to process or use hydroquinone, only 5 reported releases to land which were on plant site.
Since hydroquinone is a solid, which is unlikely to vaporize on spilling, spills to soil are expected tobe easily recovered. Spills of hydroquinone-containing solutions (e.g., photographic developers)
would also be insignificant sources of terrestrial contamination as the concentrates are supplied insmall packages and the working solutions are typically dilute (0.5-2.5%).
3.2.3 Other effects
As hydroquinone readily biodegrades and photodegrades, it is unlikely to bioaccumulate.
Hydroquinone largely partitions to the water compartments, therefore, effects in othercompartments are not expected.
3.3

Initial Assessment for the Environment

3.3.1 Aquatic Compartment
The aquatic toxicity of hydroquinone to fresh water fish, Daphnia, and algae was between 0.0500.335 mg/L; the predicted chronic values for these fresh water taxa were calculated to be < 0.100.
The 84 hr LC50 for the salt water shrimp, C. septemspinosa, was selected as the only salt water
species for analysis. Based on these data and on the predicted aquatic toxicity values, theU.S.E.P.A. (1995a) identified concern concentrations or predicted no effect concentrations (PNECs)
at 1.0 µg/L for fresh water species and 8.0 µg/L for salt water species.
Alternatively, a PNEC can be derived using the assessment factors recommended in the SIDS
manual. As only acute effect data for fish and daphnids are available, an assessment factor of 1001000 would be appropriate. Due to the large available database, a factor of 100 would be
acceptable. Applied to the lowest experimental value of 0.044 mg/L (Fathead minnow), a PNEC of
0.44 µg/L can be derived.
These PNECs are compared to the maximum annual estimated water concentrations based on the
1992 TRI release levels and the "what-if scenarios" for manufacturing, processing, and use sites
which were considered to be conservative estimates of the predicted environmental concentrations(PECs) (U.S.E.P.A., 1995).
For two of the manufacturing sites in the U.S.A., the surface water concentrations were predicted tobe negligible or zero. Since both of these plants discharge to fresh water bodies the PEC/PNEC
ratios are < 1. The third manufacturing plant discharges to a salt water body (Galveston Bay). In
calculating the predicted surface water concentration critical dilution factors for this plant were notavailable and, therefore, the concentration predicted (8.2 µg/L) is the predicted concentration at thedischarge point without mixing. When the PEC for salt water species (8.2 µg/L) is compared to the
PNEC (8 µg/L) and the dilution of the discharge with sea water is considered, the PEC/PNEC ratiois < 1.
The estimated environmental surface water concentrations for processors and users have been
separated into direct dischargers and indirect dischargers which discharge into publicly owned
waste water treatment works.

UNEP Publications

19

OECD SIDSHYDROQUINONE

All of the direct discharges are into bodies of fresh water. All but one of the direct discharge sites
have PECs less than 0.07 µg/L and, therefore, the PEC/PNEC ratios range from 8.2x10-5 to 6.8x10-2
using a PNEC of 1.0 µg/L. One direct discharger has a predicted surface water concentration of
180 µg/L which would indicate a PEC/PNEC ratio of greater than one. However, in investigatingsite specific information for this discharger, it became apparent that the plant PEC/PNEC ratio wassignificantly less than 1 as no hydroquinone was detected from its NPDES-regulated outfall prior todischarge (O'Donoghue and David, 1995).
Among the indirect dischargers to fresh water there were three processor/users with estimated PECs
above 1.0 µg/L. The PEC for these plants were reported to be 1.3, 32, and 130 µg/L. The PECs forall other plants in this category were less than 1.0 µg/L and had calculated PEC/PNEC ratios of
1.9x10-5 to 8.8x10-1 using a PNEC of 1 µg/L. The two processor/users with indirect discharges tothe ocean had PECs of 1.5 µg/L and 3.8 µg/L. In both of these cases the critical dilution factors forthese facilities were not available and, therefore, the predicted concentrations do not include a salt
water dilution factor. The PEC/PNEC ratios for these plants prior to dilution are 0.19 and 0.48
using a PNEC of 1 µg/L.
Use of the alternative PNEC of 0.44 µg/L causes an additional four indirect discharges to exceed a
PEC/PNEC ratio of one (PEC/PNEC ratios of 1.5-2.0), however, considering that there are
estimated to be 16000 to 66000 processor/users of hydroquinone in the U.S.A., the number ofpredicted PEC/PNEC ratios ≥ 1 are small. Since all of the direct and indirect discharges identified
in the exposure assessment have NPDES regulated discharges, it is very unlikely that they actually
have discharges with PEC/PNEC ratios ≥ 1. It is much more likely that the "what-if scenario" hasoverestimated the actual PEC.
Scenarios for the release of hydroquinone from photographic activities in Europe are estimated in
Section 3.1.2. The PEC/PNEC rations range from 5.2x10-5 - 7.9x10-1 using a PNEC of 0.44 µg/l.
The frequency of exceeding a PEC/NPEC of 1 can be calculated using the Probabilistic Dilution
Model (PDM 3) program and the following inputs derived from the European exposure scenarios(R. Diderich, personal communication).
Days used/year:
Concentration of HQ:Consumed processing solution:
Surface processed/day:
Percent removal during processing:
Elimination in waste water treatment plant:

300.
2.5% in highest working solutions = 0.025 g/ml.
350 ml/m2.
20 m2.
10%.
91%.

0.25 g/ml x 350 ml/m2 x 20 m2/d x 0.9 x 0.09 = 0.014 kg/d
Using this input to the PDM3 program, a concern concentration of 1 µg/L is predicted to be
exceeded 0.5 days/yr (0.14% of the year) and a concern level of 0.044 µg/L is predicted to be
exceeded 3 days/yr (0.81% of the year).
3.3.2 Terrestrial Compartment
Significant exposures to the terrestrial environment are not expected, therefore, an effects
assessment was not conducted.
20

UNEP Publications

OECD SIDSHYDROQUINONE

3.3.3 Other Compartments
Releases of hydroquinone to the air compartment are discussed in the human health section of thisassessment.
4.

HUMAN HEALTH

4.1

Human Exposure

4.1.1 Occupational Exposure•

Occupational exposure during hydroquinone manufacture.

Average concentrations in air during manufacturing and processing of hydroquinone have beenreported to be in the range of 0.13 to 0.79 mg/m3 (IPCS, 1994). The average airborne hydroquinone
concentration (~8000 breathing zone and area samples) in one hydroquinone manufacturing plant
has decreased from 6.0 mg/m3 in the 1950's to 0.1 mg/m3 in 1990 (Pifer et al., 1993).
Hydroquinone manufacture is a heavily automated procedure, thus only 81 employees in the U.S.A.
are potentially exposed during manufacture, materials handling, maintenance, quality control
sampling, and analysis. Employee protective clothing and engineering controls, such as local
exhaust ventilation systems, are used to further prevent exposure at points in the process where
exposure can occur.
"What-if scenarios" were used to estimate inhalation exposure levels in two U.S.A. manufacturing
plants and calculated dose rates are shown in Table 2 (U.S.E.P.A., 1995). These estimated exposurelevels assume that no personal protective devices are used. However, producers in the U.S.A. havereported the use of engineering controls (local exhaust and dust collectors) and personal protective
devices (e.g., gloves, uniforms, goggles, respirators, boots) to control exposure, therefore, thecalculated dose rates exceed actual expected dose rates.

UNEP Publications

21

OECD SIDSHYDROQUINONE
Table 2Estimated Occupational Inhalation Exposures Associatedwith the Manufacture of Hydroquinone in the U.S.A.

Type of Worker

Number ofWorkers/Hours per
Day/Days per Year

Airborne
Concentrations1(mg/m3)

Potential Inhalation
Dose Rate,2,3,4(mg/kg/day)Average

Maximum

Average

Maximum

Operator/Sampler

34/1->8/100-250

0.116

0.3

0.01660.0429Loader/Packager

34/1->8/100->250

0.254

1.87

0.03630.267

13/1-8/1-250

0.135

0.295

0.01930.0421

Maintenance
Personnel/Housekeeper
1234Air concentrations are based on 29 samples.
Assumes the medium work inhalation rate of 1.25 m3/hr (CEB, 1991).
Assumes the maximum number of hours in a range.
Assumes no use of PPE and that the chemical is 100% concentrated (CEB, 1991). Actual
exposures may be less than estimated if PPE is properly selected, used, and maintained.
Assumes 70 kg body weight.

Very rough bounding estimates of total dermal contact with hydroquinone (650-18200 mg/day) can
be calculated using models which assume that employees regularly immerse their hands inhydroquinone for the entire work day without protective equipment (U.S.E.P.A., 1995; Versar,
1992 and 1992b). All U.S.A. manufacturers of hydroquinone report that engineering controls andpersonal protective equipment are used to minimize exposure, therefore, the bounding estimatessignificantly overestimate the potential contact that employees can have with hydroquinone dust.
As hydroquinone is a dry solid with a relatively high melting point (169oC), and because it is apolar substance and water soluble, it is unlikely that solid hydroquinone would be absorbed throughthe skin of manufacturing personnel. Even when dissolved in an aqueous medium, the absorption
rate through human skin is expected to be slow and thus limit the amount absorbed (Barber et al.,1995).
•

Occupational exposure during processing and use

The number of employees working in U.S.A. industries which use hydroquinone has been estimatedat 350000 to 560000 at 16000 to 66000 facilities (NIOSH, 1982-1984). The amount of exposure tohydroquinone in these work sites is not available and, therefore, for this analysis, it has been
assumed that the exposures are equivalent to that of hydroquinone manufacturing employees (Table2). There are several reasons to believe that this assumption will overestimate occupational
exposures at processor/user sites. The first is that many operations which use or processhydroquinone are batch operations in which hydroquinone is added to hoppers, reactors, or mixing
vessels which are then closed. In these types of operations, bags or drums are opened and theircontents emptied out during periods of 10-60 min. Automation also reduces exposure tohydroquinone. For example, commercial photoprocessors are heavily automated and emissions
from machines are typically below detectable levels (CMA, 1995). A study by the National
22

UNEP Publications

OECD SIDSHYDROQUINONE

Institute of Occupational Safety and Health (NIOSH) did not detect hydroquinone in theatmosphere of rooms where film was being developed. Monitoring data are also available from the
OSHA Compliance Information System on airborne concentrations of hydroquinone inprocessor/user facilities. The data base includes 78 air samples from facilities in 16 different
standard industrial code categories. Seventy-seven of the samples were less than the analytical limit
of detection or less than half of the PEL of 2 mg/m3; the majority of samples were below detectablelevels.
Information from the United Kingdom indicates that there are 3000-5000 people estimated to be
exposed to hydroquinone at work. The main route for work-related potential exposure is byinhalation (UKHSE, 1993).
In the manufacturing of photographic developers, monitoring data are commonly collected as total
dust in the breathing zone or area samples. Estimates using this methodology overestimate actual
exposure. Exposure levels recorded by manufacturers indicate the 8-hr TWA values are below 1
mg/m3 with average exposures at ~0.15 mg/m3 (UKHSE, 1993).
Measurements for hydroquinone among users of photographic developers indicate hydroquinone
levels in the air below the analytical limit of detection (0.01 mg/m3 ; UKHSE, 1993).
Spills of photodevelopers in the workplace could result in exposure to hydroquinone. Actual
exposure to hydroquinone in such circumstances would be expected to be minimal as hydroquinone
has a low vapor pressure and a high vapor density which limit volatilization, and a slow penetration
rate through the skin which limits absorption.
Biological monitoring of darkroom workers did not indicate an increase in work-relatedhydroquinone exposure as urinary hydroquinone levels were less than control worker values(UKHSE, 1993).
Estimates of employee exposures in other industries are shown in Table 3.

UNEP Publications

23

OECD SIDSHYDROQUINONE
Table 3
Estimated Occupational Exposure Associated with the Processing ofHydroquinone in the United Kingdom
Average Airborne
Concentration1(mg/m3)

Potential Inhalation Dose Rate for
Typical Exposure Periods2(mg/kg)Average (Maximum)

10 min60 minFood

0.42

1.2x10-3

7.5x10-3

Rubber4.3 (10.2)

1.2x10-2 (2.9x10-2)

7.7x10-2 (1.8x10-1)

Agrochemical

0.03 (0.1)

8.6x10-5 (2.9x10-4)

5.4x10-4 (1.8x10-3)

Industry
Category

12

Sampling periods were 5-120 min. Data obtained from UK manufacturers (UKHSE, 1993).
Assumes 1.25 m3 of air inhaled in 1 hr, 0.2 m3 of air inhaled in 10 min, 70 kg body weight,
and that chemical hoppers or reaction vessels are filled once per 8-hr work shift. If vessels
are loaded more or less frequently, the daily dose would differ accordingly.

The potential dose rates shown in Table 3 assume a worst case that personal protective equipment is
not worn. Available information indicates that hydroquinone users in the UK rely on personal
protective equipment for control of exposure. Current control measures in the UK maintainexposure levels below the TLV of 2 mg/m3 and in many cases below 1 mg/m3(UKHSE, 1993). A
combination of local ventilation and appropriate handling procedures should be adequate to control
exposures below 0.5 mg/m3 8-hr TWA (UKHSE, 1993).
4.1.2 Consumer Exposure
Photohobbyist exposure
Photohobbyists may be exposed to hydroquinone through dermal contact with developing solution
or by inhalation of dry chemical used to prepare developing solutions.
Inhalation of hydroquinone dust by photohobbyists is expected to be negligible. Photohobbyists
typically prepare developer solutions by pouring powdered developer into an appropriate volume ofwater. This process takes very little time (1-5 mins) and is not repeated until the developer solution
is expended which might occur 1-4 times/month. Accidental spills of developer solution are likely
to result in negligible inhalation exposures as hydroquinone has a low vapor pressure.
Although protective gloves or tongs are recommended when handling hydroquinone-containing
black-and-white developers, dermal exposure may occur as a result of a spill or splash on
unprotected skin areas. Actual absorption of hydroquinone through the skin, however, can be
expected to be negligible to minimal for several reasons. First, black-and-white developers typicallycontain only 0.5-2.5% hydroquinone limiting the exposure concentration. In addition, hydroquinone
is only slowly absorbed through the skin. The flux (i.e., the amount of chemical absorbed across adefined surface area of the skin per unit time) for hydroquinone from an aqueous solution
formulated to represent a developing solution is approximately 0.5 mg/cm2/hr (Barber et al., 1995).
Barber et al. (1995) estimated the amount of hydroquinone absorbed through the skin if an
individual immersed one hand in a 5% hydroquinone developer for 1 hr to be 200 µg or 2.9x10-3
24

UNEP Publications

OECD SIDSHYDROQUINONE

mg/kg for a 70 kg person. Actual absorbed doses of hydroquinone can be expected to be much
lower. If recommended practices are not followed, the surface area of the skin exposed tohydroquinone by putting a hand into a developer tray is small as developer trays are typically 5-10
cm in depth and photographs would be grasped by their edge. Thus, a typical unprotected exposure
would involve the tips of three fingers of one hand. The exposure time to hydroquinone would also
be brief as a photohobbyist not using tongs or gloves would be expected to carry this habit forwardand dilute any hydroquinone on the hands with stop bath, wash water, and fixer. Alternatively, if
the photohobbyist intended to reduce contamination of post-developer solutions with developer, thephotohobbyist would have to wipe his/her hands between trays resulting in removal ofhydroquinone by toweling and dilution.
Biological monitoring of professional darkroom workers in the U.K. revealed no increase in urinary
excretion of hydroquinone (UKHSE, 1993), thus exposure of photohobbyists, who can be expectedto spend considerably less time exposed to hydroquinone, is expected to be negligible.
Cosmetic, non-prescription drug, and prescription drug exposure
Dermal exposure may also result from the use of cosmetic or medical products containinghydroquinone, such as skin lighteners. The E.U. countries have restricted its use in cosmetics to 2%
or less. In the U.S.A., the Food and Drug Administration restricts hydroquinone concentration to
1.5 - 2% in non-prescription skin lighteners. Concentrations up to 4% may be found in prescription
skin lighteners.
Cosmetic exposure to hydroquinone is limited to few products. In 1984, FDA product formulation
information indicated that hydroquinone was present at concentrations of ≤1% in 185 out of 1112
hair dye and coloring products (CIR, 1994). It was also present in 21 out of 2031 other skin care
preparations at 1-5% (CIR, 1994). In hair dyes, hydroquinone acts as a regulating agent and isconsumed during the dyeing procedure (CIR, 1994). Simulated dyeing procedures demonstrated
that within 4 mins, 50% of the hydroquinone is already consumed while after 30 min <3% of theinitial amount remained (CIR, 1994).
As the actual concentration of hydroquinone decreases sharply as the color-forming reaction occurs,
the amount of hydroquinone absorbed is limited both by decreasing concentration and the length oftime the hair dye is applied before being rinsed off (CIR, 1994). The CIR (1994) concluded thathydroquinone is safe at concentrations of ≤1.0% for aqueous cosmetic formulations designed for
discontinuous, brief use followed by rinsing from the skin and hair. The CIR also stated thathydroquinone should not be used in leave-on non-drug cosmetic products.
Hydroquinone is also used in products intended to lighten small areas of skin. 2% Hydroquinone
preparations are the only agents considered safe and effective for over-the-counter treatment of
cutaneous hyperpigmentation (Fed. Reg., 1978 and 1982). This type of use has sometimes been
incorrectly referred to as "skin bleaching," however, hydroquinone does not bleach the skin.
Instead, it is thought to act through competitive inhibition of tyrosinase resulting in a gradual fadingof hyperpigmented spots by a reduction in the formation of new pigment. Skin lighteners, which
are regulated in the E.U. and the U.S.A. (Food and Drug Administration), are undergoing reviews.
New labeling guidelines for skin lightening products were put into place in May 1992 by the NonPrescription Drug Manufacturers. Key aspects of the new guidelines include: apply a small amountof lightener as a thin layer to the affected areas of dark brownish skin discoloration; use with asunscreen to prevent or minimize reoccurrence of pigmentation; discontinue use after the
discoloration is gone; apply again only if the discoloration reappears, stop use if any skin irritation
becomes severe or any darkening persists; do not use with other topical products containing
UNEP Publications

25

OECD SIDSHYDROQUINONE

resorcinol, phenol, or salicylic acid; do not apply to inflamed or broken skin; and test overnight on asmall section of skin inside the elbow for sensitivity.
Misuse of products containing higher concentrations of hydroquinone and products containing
phenol, resorcinol, salicylic acid, and mercury in addition to hydroquinone led to restrictions onskin lighteners in South Africa to 2% hydroquinone.
4.1.3 Indirect Exposure Via the Environment
Estimates of predicted environmental concentrations (PEC) from hydroquinone manufacturing,processing, and use are based on 1992 TRI data reported to the U.S.E.P.A. (1995). These "what-if
scenarios" estimates of hydroquinone concentration in air and water were made using simple,
conservative atmospheric dispersion models (EAB, 1994; Versar, 1992a). The "what-if scenarios"
have been developed to assess potential exposure under a set of hypothetical conditions or under aset of conditions for which actual exposure parameter data are incomplete or non-existent. The
calculated PECs are not intended to provide information about how likely the combination of
exposure parameter values might be in the actual population or approximately how many, if any,
persons might actually be subjected to the calculated value. The PECs determined from "what-if
scenarios" may exceed PECs calculated based on realistic worst case scenarios.
Maximum annual average concentrations resulting from fugitive releases to air were predicted using
the PMN PLUME Model (Versar, 1992a). This model is a computerized version of Turner's sector
averaging form of the Gaussian algorithm (Turner, 1970). Concentrations were predicted for a
receptor located at the facility fence line (assumed to be 100 meters down wind). Neutral
atmospheric stability, an average wind speed of 5.5 m/sec, and wind direction toward the receptor
25% of the year were assumed. Because all of the release sources for a given facility were assumed
to be within 100 meters of each other, all emissions were assessed as coming from a single
representative stack assumed to be 3 meters in height.
The estimated ambient hydroquinone air concentrations from three manufacturing sites were 0 to
4.9x10-4 mg/m3 for fugitive emissions and 7.8x10-8 to 3.0x10-6 mg/m3 for stack emissions. The
estimated general population inhalation exposure from fugitive emissions were negligible for twosites and 4.3 or 1.7x10-4 mg/kg/day for the third site. The estimated exposures for stack emissions
were 7.8x10-4 to 1.1x10-2 mg/person/year or 3.1x10-8 to 4.3x10-7 mg/kg/day. Estimated exposuredue to drinking water and fish ingestion were negligible at all manufacturing sites.
The estimated ambient hydroquinone air concentrations for fugitive emissions from 29
processor/user sites were zero or negligible to 24 mg/person/day or 0 to 9.4x10-4 mg/kg/day(U.S.E.P.A., 1995). The estimated ambient hydroquinone air concentrations of stack emissions
were 0 or negligible to 8.1x10-2 mg/person/yr or 0 to 3.2x10-4 mg/kg/day. The average estimatedambient hydroquinone air concentration from 29 processor/user sites reported in the 1992 TRI database for fugitive emissions was 29.4 mg/person/year and for stack emissions was 6.7x10-3
mg/person/yr (U.S.E.P.A., 1995) or 1.1x10-3 to 0 2.6x10-7 mg/kg/day.
The estimated exposures resulting from direct surface water discharges of hydroquinone were
4.1x10-5 to 3.4x10-2 mg/person/yr or 1.6x10-9 to 1.3x10-6 mg/kg/day for four processor/user sites(U.S.E.P.A., 1995). A fifth site was not included in the estimates because the TRI data did notreflect actual discharge estimates (CMA, 1995). The average estimated exposure resulting fromdirect surface water discharges at four processor/user sites is 1.5x10-3 mg/person/yr or 5x10-7
mg/kg/day (U.S.E.P.A., 1995).
26

UNEP Publications

OECD SIDSHYDROQUINONE

The estimated exposures resulting for indirect surface water discharges of hydroquinone atprocessor/user sites were 9.3x10-6 to 67 mg/person/yr or 3.6x10-10 to 2.6x10-3 mg/kg/day(U.S.E.P.A., 1995). The average estimated exposure resulting from indirect surface water
discharges at 16 processor/user sites (U.S.E.P.A., 1995) was 5.4 mg/person/yr or 2.1x10-4
mg/kg/day.
Hydroquinone exposure through drinking water and fish consumption were considered negligible
for processor/user sites (U.S.E.P.A., 1995).
4.2

Health Effects Data

4.2.1 Mode of action, toxicokinetics, and metabolism
Hydroquinone is rapidly and extensively absorbed from the gut and lungs of animals. Absorption
via the skin is slow but may be accelerated with vehicles such as alcohols. Hydroquinone distributes
rapidly and widely among tissues. It is metabolized to 1,4-benzoquinone and other oxidized
products, and is detoxified by conjugation to monoglucuronide, monosulfate, and mercapturic
derivatives. The excretion of hydroquinone and its metabolites is rapid, and occurs primarily via
the urine.
Covalent binding and oxidative stress are mechanisms postulated to be associated withhydroquinone-induced toxicity (IPCS, 1994). Oxidized hydroquinone metabolites may covalently
bind cellular macromolecules or alkylate low molecular weight nucleophiles (e.g., glutathione(GSH)) resulting in enzyme inhibition, alterations in nucleic acids and oxidative stress; however,redox cycling is not likely to contribute significantly to oxidative stress (IPCS, 1994). The reactionof hydroquinone metabolites with GSH results in the formation of conjugates which can be further
processed to cysteine conjugates which are postulated to cause kidney toxicity (IPCS, 1994,
Whysner et al.; 1995; English et al., 1994). Cell proliferation associated nephrotoxicity in asensitive strain and species of animal (male F344 rat) has been postulated to be involved in the
production of renal tumors in rats (Whysner et al., 1995; English et al., 1994 and 1994a).
4.2.2 Interaction with Phenols:
Recently there have been a number of studies reporting interactive effects between hydroquinone
and other phenolic compounds (IPCS, 1994). Initially, Eastmond et al. (1987) showed that the coadministration of hydroquinone and phenol (75 mg/kg), when given by intraperitoneal injection
twice per day, produced a synergistic decrease in bone marrow cellularity in B6C3F1 mice that was
similar to that induced by benzene. This compound treatment was significantly more myelotoxic
than that observed when either hydroquinone or phenol was administered separately. Associated invitro studies suggested that this interactive effect was due to a phenol-induced stimulation of the
myeloperoxidase-mediated conversion of hydroquinone to 1,4-benzoquinone in the bone marrow.
Subsequent studies have indicated that interactions between hydroquinone and other phenolic
compounds can result in a variety of cytotoxic, immunotoxic and genotoxic effects. Studies
conducted using routes of exposure relevant to risk assessment in occupational or environmental
situations have not been conducted.
4.2.3 Non-Human Dataa)

Acute toxicity
Oral: OECD 401
UNEP Publications

27

OECD SIDSHYDROQUINONE
Rat (?)Rat (Osborne-Mendel)
Rat (Wistar)
Rat (Sprague)
Mouse (?)
Mouse (Swiss)

LD50 = 390 mg/kg
LD50 = 302 mg/kg
LD50 = 298 mg/kg
LD50 = 323 mg/kg
LD50 = 680 mg/kg
LD50 = 390 mg/kg

Dermal: OECD 402
LD50 = > 1000 mg/kg

Guinea pig (?)
Sensitization: OECD 406
Magnussen-Kligman:
Draize:sensitizer
weak sensitizer

Hydroquinone exhibits moderate acute oral toxicity for animals. The IPCS reported that limited datasuggest that powdered hydroquinone causes transient eye irritation and corneal opacity in dogs andguinea-pigs; in rabbits powdered hydroquinone induced slight irritation of the eye. Hydroquinone
may be a skin sensitizer in animals. The ability to induce sensitization has been found to vary from"weak'' to "strong'' depending on the test procedure and vehicle used.
b)

Repeated dose oral toxicity
Rat (Sprague-Dawley)
Rat (F-344)
Mouse (B6C3F1)
Rat (F-344)
Mouse (B6C3F1)
Rat (F-344)

NOEL (oral) = 20 mg/kg (13 w)
NOEL (dermal) = 1920 mg/kg (14 d)
NOEL (dermal) = 4800 mg/kg (14 d)
NOEL (oral) < 25 mg/kg (13 w)
NOEL (oral) < 25 mg/kg (13 w)
NOAEL (dermal) = 74 mg/kg (13 w)

Repeated oral dosing caused tremors and reduced activity (≥64 mg/kg), reduced body weight gain(≥200 mg/kg), convulsions (≥400 mg/kg), and nephropathy in F-344 rats (≥100 mg/kg). No
adverse effects on the kidneys were reported in Sprague-Dawley rats treated for the same length oftime with the same dose levels. Effects in mice include tremors and convulsions (400 mg/kg),
increased liver weight (≥25 mg/kg), and irritation of the forestomach (≥200 mg/kg). A functionalobservational battery and neuropathological examinations of rats failed to give any evidence of
persistent or structural neurotoxicity after repeated dosing for 90 days. A NOEL for all effects was
20 mg/kg per day.
c)

Repeated dose dermal toxicity

Fourteen days of repeated dermal dosing caused reduced body weights of male rats at the 3840
mg/kg dose level (6% relative to the controls), but the body weights of female rats at this dose leveland of mice at 4800 mg/kg were comparable to controls. There were no clinical signs of toxicity ineither species. Prolonged dermal dosing over 13 weeks with 2.0, 3.5, or 5.0% hydroquinone in an
oil-in-water emulsion cream resulted in minimal to minor dermal irritation, but no overt toxicity.
No adverse effects or compound-related effects occurred in organ weight, clinical pathology, or
histopathology. A NOEL was not determined because of the dermal irritation in all treated groups,
28

UNEP Publications

OECD SIDSHYDROQUINONE

but the NOAEL was the highest dose level of 5% hydroquinone (74 mg/kg in males and 110 mg/kg
in females) based on the lack of systemic effects.
d)Reproductive toxicity
Rat (Sprague-Dawley)

NOEL = 15 mg/kg (General toxicity)
NOEL = 150 mg/kg (Repro. Tox. parental)
NOEL = 150 mg/kg (Repro. Tox. F1)

A two-generation reproduction study was conducted in rats. The NOAEL for reproductive effects
through two generations was 150 mg/kg per day (the highest dose tested).
e)

Genetic toxicity
Bacterial (Ames) test:

not mutagenic with or without activation

In vitro chromosomal aberration test: positive with activation, negative without activation
In vivo micronucleus test:

positive by ip injection, weak by oral gavage

Dominant lethal assay:

negative

Mouse spot test:

negative

Numerous genotoxicity studies of hydroquinone have been conducted. Hydroquinone is not
mutagenic in the Salmonella/microsome test. Other data indicate that hydroquinone induces
structural chromosome aberrations and c-mitotic effects in vivo in mouse bone-marrow cells
following ip injection. In vitro studies with various cell lines showed that hydroquinone wascapable of inducing gene mutations, structural chromosome aberrations, sister-chromatid exchange,
and DNA damage. Hydroquinone produces adducts with DNA in vitro, but recent in vivo studies
were unable to produce DNA adducts. While several experiments with hydroquinone have shown
mutagenic effects; the relevance of these results to human risk is uncertain (IPCS, 1994). The
majority of positive mutagenicity studies use routes of exposure (parenteral or in vitro) which are
not relevant to human exposures. A dominant lethal assay in rats was negative.
f)

Other health related information
Carcinogenicity:
Rat (Sprague-Dawley)
Rat (F-344)
Mouse (B6C3F1)

negative at 1.0% in dietrenal tubular adenomas in male rats andmononuclear cell leukemia in female rats at 25
and 50 mg/kg
hepatocellular adenomas in female mice at 50
and 100 mg/kg; hepatocellular adenomas in malemice at 1046 mg/kg

A study by Carlson and Brewer (1953) using Sprague-Dawley rats treated for two-years withhydroquinone in the diet indicated "atrophy of the liver cord cells, lymphoid tissue of the spleen,
adipose tissue, and striated muscle together with superficial ulceration and hemorrhage of thestomach mucosa" but no carcinogenesis. Two-year studies performed by the NTP reported that
UNEP Publications

29

OECD SIDSHYDROQUINONE

hydroquinone exposure was associated with some evidence of carcinogenicity in F-344 rats and
B6C3F1 mice. In the NTP study, renal tubular cell adenomas occurred in male rats andmononuclear cell leukemia in female rats, and hepatocellular neoplasms, mainly adenomas, infemale mice. The NTP concluded that these data indicated "some evidence of carcinogenic
activity'' in male and female rats and in female mice. In a study by Shibata et al. (1991) using F344 rats and B6C3F1 mice, renal tubular cell adenomas were also noted in male rats; hepatocellularadenomas and renal cell hyperplasia were noted in male mice; and hyperplasia of the forestomach
was noted in both male and female mice fed 0.8% hydroquinone diets for two years. The evidence
provided by cancer bioassay studies is considered limited (IPCS, 1994). A U.S.E.P.A. (1990)
review of the NTP bioassay found the bioassay results provide limited evidence of carcinogenicity
in animals.
Studies by English et al. (1994) of cell proliferation in the kidneys of F-344 and Sprague-Dawley
rats indicate that a dose level of 50 mg/kg hydroquinone resulted in cell proliferation in the kidney
and excretion of urinary enzymes indicative of proximal tubule damage but only in male F-344 rats.
Female F-344 rats and male Sprague-Dawley rats were unaffected. Thus, renal carcinogenicity may
be limited to male F-344 rats via a mechanism including nephrotoxicity and increased cellproliferation.
g)

Developmental toxicity
Rat (Sprague-Dawley)

NOEL = 100 mg/kg (General toxicity)
NOEL = 300 mg/kg (Pregnancy/litter)
NOEL = 300 mg/kg (Fetal data)

Rabbit (NZW)NOEL = 25 mg/kg (General toxicity)
NOEL = 75 mg/kg (Pregnancy/litter)
NOEL = 75 mg/kg (Fetal data)
Oral dosing of pregnant rats on days 6-15 of gestation with 100 or 300 mg/kg caused maternal
toxicity at the higher dose level (a statistically significant reduction in body weight gain and feed
consumption). A reduction in mean fetal body weight was correlated with the reduced maternal
body weight. No compound-related teratogenic effects were produced at this dose level; thus, 100
mg/kg was considered the NOEL for maternal and developmental toxicity in rats. Findings ofincreased resorption rates in rats given hydroquinone orally at about 100 mg/kg per day were notconfirmed in this study, and, consequently, the NOAEL for maternal reproductive effects andteratogenicity was 300 mg/kg. In rabbits, 150 mg/kg caused reductions in body weight and feedintake and an increased (but not statistically significant) incidence of malformations in the fetuses.
The malformations may have been associated with maternal toxicity. The dose level of 200 mg/kg
produced an increased number of resorptions, indicating embryotoxicity. The NOEL for
developmental toxicity in rabbits was 75 mg/kg per day.
h)

Dermal Absorption

The rate of percutaneous absorption of a 5% aqueous hydroquinone solution through human stratum
corneum and whole rat skin was measured in vitro (Barber et al., 1995). The absorption rate thoughhuman skin is 0.522 µg/cm2/hr. The absorption rate through rat skin is 1.09 µg/cm2/hr. Thisabsorption rate is considered to be "slow" based on published definitions of absorption (Marzulli etal., 1969).
4.3
30

Initial Assessment for Human Health
UNEP Publications

OECD SIDSHYDROQUINONE

4.3.1 Occupational Exposure•

Health Assessment for Hydroquinone Manufacture

The primary route of exposure to hydroquinone during its manufacture is the inhalation route. The
highest average estimated inhalation dose of hydroquinone during manufacturing is 0.0363
mg/kg/day for loader packagers (Table 2). The highest estimated maximum inhalation dose ofhydroquinone is 0.267 mg/kg/day. Inhalation studies with experimental animals are not available
for comparison to these estimates, however, comparison to the most sensitive oral dose NOEL (15mg/kg/day) observed in the rat reproduction study provides a worst case Estimated Human
Exposure/Estimated Dose of Low Concern (EHE/EDLC) ratios of 2x10-3 (highest average exposuregroup) and 1.8x10-2 (highest maximum exposure group).
EHE/EDLC ratios for all other manufacturing employees would be expected to be smaller.
Dermal absorption of hydroquinone by manufacturing employees is estimated to be negligible forseveral reasons: manufacturing is conducted in closed systems, all manufacturers report use of
personal protective equipment, manufacture involves exposure to only dry crystalline solid material,
and the physical properties of hydroquinone (relatively high melting point, polar substance, watersolubility) limit the potential for absorption. No published reports of dermal toxicity or
sensitization have been reported to be associated with hydroquinone manufacturing.
Ocular lesions of varying degree have been described in employees of a U.S.A. plant manufacturinghydroquinone (Anderson, 1947 and 1958; Oglesby et al., 1947; Sterner et al., 1947). Concomitant
exposure to 1,4-benzoquinone was reported in the plant and the corneal damage observed may havebeen associated with oxidation products of hydroquinone rather than the parent material. The
airborne concentrations of hydroquinone and quinone present at the time ocular damage was seen
were much higher than the current TLV of 2 mg/m3. The corneal damage observed occurred
gradually over several years of exposure and no serious cases were seen until after 5 or more yearsof exposure (IPCS, 1994).
Following recognition in 1947 of the possibility that hydroquinone manufacturing practices could
be associated with serious ocular damage, control measures were put into place and regular air
monitoring and ocular examinations were conducted. Based on the experience gained during
monitoring activities an exposure value of 0.1 ppm quinone vapor and 2-3 mg/m3 hydroquinone
dust (time-weighted average) were recommended to control eye irritation which was considered aprelude to the onset of ocular pigmentation. The lower recommended value for hydroquinone (2mg/m3) was eventually adopted as the ACGIH 8-hr time-weighed TLV value. Experience with thisTLV in U.S.A. hydroquinone manufacturing plants has demonstrated its utility in controlling
occupational exposures for ocular damage. Since no animal model has been developed for theocular effects observed during hydroquinone manufacturing, it is difficult to know the size of the
EHE/EDLC ratio. However, it is possible to calculate a TLV/current exposure ratio which spans
the range of 5.8x10-2 to 1.27x10-1 for loader/packer and operator/sampler employee exposures.
Calculation of an EHE/EDLC or other quantitative endpoint for carcinogenicity is not consideredappropriate for this analysis because of the limited evidence of carcinogenicity provided by animalstudies. This view is supported by statements published by the U.S.E.P.A. in relationship tomethodologies for analysis of animal bioassay when the animal data cannot be interpreted toindicate clear evidence of carcinogenicity.

UNEP Publications

31

OECD SIDSHYDROQUINONE

Both IPCS (1994) and the U.S.E.P.A. (1990) have found the animal bioassay data for hydroquinone
to provide limited evidence of carcinogenicity in animals. Since these reviews have been
completed, additional mechanistic data have been collected which indicate that the primary tumorof concern, kidney adenomas in male rats, may be associated with cell proliferation brought about
by chronic renal toxicity and age-induced nephropathy in an unusually sensitive strain and sex ofanimal (male F344 rats).
In addition, a recently completed epidemiology study of hydroquinone manufacturing employees
reduces concern levels for carcinogenicity further (Pifer, 1995). Mortality in a 1942-1990 cohort of858 men and 21 women employed in the manufacture and use of hydroquinone was evaluatedthrough 1991. The population studied included all hydroquinone manufacturing and use personnel
for a 50 yr period for the largest U.S.A. producer of hydroquinone. Average exposure
concentrations, 1949-1990, ranged from 0.1 to 6.0 mg/m3 for hydroquinone dust and from less than
0.1 to 0.3 for quinone vapor (estimated 8-h time-weighted averages). Compared with general
population and occupational referents there were statistically significant deficits in total mortalityand deaths due to cancer. No significant excesses were observed for such hypothesized causes as
kidney cancer [2 observed vs. 1.3 expected (both control groups), p ~ 0.39], liver cancer (0 vs. 0.8,1.3), and leukemia (0 vs. 2.3, 2.7). Dose-response analyses of selected causes of death, including
renal carcinoma, demonstrated no statistically significant heterogeneities or linear trends according
to estimated career hydroquinone exposure (mg/m3-years) or time from first exposure.
In 1992, this same plant employed 76 of 81 or 93.8% of the U.S.A. manufacturing employee
population for hydroquinone. Based on 1992 production volumes, this plant is estimated to employ
half of all hydroquinone production employees in the world. Considering the limited nature of theanimal bioassay data and the absence of evidence of carcinogenicity in a large fraction of thehydroquinone manufacturing employees, the current control measures in place are consideredadequate for protecting human health.
•

Health Assessment for Hydroquinone Processing and Use

The inhalation route is considered to represent the main route of exposure for employee exposuresin industries processing or using hydroquinone. In industries which make photographic developers
containing hydroquinone and in those which use hydroquinone developers average exposure
concentrations (UKHSE, 1993) are ~0.15 mg/m3 (developer manufacturers) and <0.01 mg/m3(developer users). Estimated doses for these exposures are ~2.1x10-2 mg/kg/day (developer
manufacturers) and <1.4x10-3 mg/kg/day (developer users). When compared to the most sensitive
oral dose NOEL (15 mg/kg/day) observed in the rat reproduction study, EHE/EDLC ratios are
1.4x10-3 (developer manufacturers) and <6.7x10-4 (developer users).
For other processor/user employee groups (Table 3), the highest average inhalation dose rate isestimated to be 7.6x10-2 mg/kg/day. The EHE/EDLC ratio for this exposure is 5.1x10-3 assuming
the longest exposure is 1 hr/day. If instead it is assumed that the maximum reported averageairborne concentration were continued for 8-hr, the EHE/EDLC would still not be ≥1.
Dermally absorbed doses of hydroquinone dust are estimated to be negligible for the same reasonsconsidered relevant for manufacturing employees.
A small number of case reports involving dermal sensitization or depigmentation have beenreported among employees of processors or users of hydroquinone containing developers. These
include two case reports of vitiligio-like depigmentation. One case (Frenk and Loi-Zedda, 1980)
involved a black man who frequently immersed his right arm and forearm in 0.06% hydroquinone
32

UNEP Publications

OECD SIDSHYDROQUINONE

developer. Irregular depigmented spots developed on the arm and forearm after 8-9 months. The
second case report involved a black man who showed signs of focal depigmentation on the hands,
wrists, and mouth, however, exposure to hydroquinone was not confirmed. The man worked
servicing automatic self-photography machines which used a 7% hydroquine developer solution(Kersey and Stevenson, 1981).
Lidén (1984) during an investigation of occupational dermatoses in a movie film laboratory, patch
tested 23 employees and 200 controls with 1% hydroquinone in petrolatum. None of theindividuals had positive test results. Lidén (1989) re-examined this same facility after
improvements had been made to the facility and occupational dermatoses had been reduced. The
population patch-tested included individuals with chemical exposures or occupational dermatosis
from a plant population of 78 employees. Of seven individuals tested with aqueous or petrolatum
mixtures of up to 1% hydroquinone, four had positive reactions of unstated severity. Three of thefour individuals, however, did not demonstrate evidence of an occupational dermatosis. One woman
who tested positive did have hand eczema. This woman also had reactions to other chemicals in thework environment and had apparently tested negative to hydroquinone in the earlier study (Lidén,
1984) when she also had signs or symptoms of eczema as no new cases were reported in this facility
following modernization. Thus, although the report describes 4 of 7 people with positive skinreactions, 3 cases were asymptomatic and one may have been exacerbated but not induced byhydroquinone.
The ocular lesions observed for hydroquinone manufacturing employees either do not occur inprocessing/user employees or occur with a very low frequency as published reports forprocessor/user populations are not available. The most likely reasons for this difference is that
exposures to hydroquinone are lower, exposure durations are shorter, and exposure periods are lessfrequent.
Current experience with handling hydroquinone indicate that measures in place are adequate tocontrol occupational dermal reactions to hydroquinone.
As indicated in the section assessing carcinogenicity for hydroquinone manufacturing employees,
animal data on carcinogenicity are considered limited. As exposures in processor/user employee
populations are estimated to be lower than for manufacturing employees, the risks associated withprocessing and use activities should also be lower. Epidemiologic evidence supports the conclusionthat measures in place are adequate to control risks associated with hydroquinone.
4.3.2 Health Assessment for Consumer Exposure•

Health Assessment for Photohobbyist Exposure

Photohobbyist health risks associated with inhalation of hydroquinone are estimated to be negligible
as exposure potential is estimated to be well below that of occupational groups.
If it is assumed that a photohobbyist immerses his/her hand in a 5% hydroquinone photodeveloperfor 1 hr/day, the absorbed hydroquinone dose would be 2.9x10-3 mg/kg/day. When this value iscompared to the most sensitive oral dose NOEL (15 mg/kg/day) observed in the rat reproduction
study the EHE/EDLC ratio is 1.9x10-3.
Cases of ocular damage and depigmentation which have been reported in occupationally exposedgroups have not been reported for photohobbyists and thus if such endpoints do occur, they occur at
UNEP Publications

33

OECD SIDSHYDROQUINONE

very low incidences. Based on the low potential for exposure and the absence of reported adverse
effects, measures in place to control health risks are considered to be adequate.
•

Health Assessment for Cosmetic, Non-Prescription Drug, and Prescription Drug Exposures

The Cosmetic Ingredient Review (CIR) recently extensively reviewed the use of hydroquinone incosmetic formulations in the U.S.A. Based on its review, the CIR (1994) found that hydroquinone
as used in hair coloring preparations is a consumable and therefore exposure to hydroquinone islimited. The CIR concluded that hydroquinone is safe at concentrations of ≤1.0% for aqueous
cosmetic formulations designed for discontinuous, brief use following rinsing from the skin and hairand that it should not be used in leave-on non-drug cosmetic products. A review of hydroquinone
use in cosmetics is currently underway in the EU.
The use of 2% hydroquinone in skin lightening products to control hyperpigmentation has been
considered safe and effective by the U.S.F.D.A. (Fed. Reg. 1978 and 1982). At the present time, theuse of hydroquinone in skin lighteners is being reviewed both in the U.S.A. and the EU. A recent
survey of the literature for cases of adverse outcomes (exogenous ochronosis) from use of 2%hydroquinone creams found only 17 cases in the U.S.A. (Burke and Maibach, 1997). A survey
conducted by the Non-Prescription Drug Manufacturers covering responses from 2108 American
physicians with a collective patient population of 44 million yielded 46 cases of exogenous
ochronosis. The American experience with skin lighteners is different from that reported in South
Africa where until 1984 the amount of hydroquinone in skin lighteners was not controlled andadverse reactions were commonly reported. The South African experience differs from theAmerican experience in a number of ways since the South African skin lighteners also contained
phenol and resorcinol.
Hardwick et al. (1989) has reported a high incidence of ochronosis among black persons in the U.K.
associated with the use of 2% hydroquinone creams. The reasons for the difference between theAmerican and British experience with skin lighteners is not clear but it may depend on a differencein use patterns as the example of a use pattern shown in a brief note by Godlee (1992) differs fromthe recommended method of use in the U.S.A.
A small number of cases of other types of adverse effects (leukoderma and brown staining of thefinger nails) have been reported among users of hydroquinone (Mann and Harman, 1983; Pray,
1993; IPCS, 1994). Dermal sensitization associated with use of skin lighteners is considerednegligible (Pray, 1993).
As voluntary changes have been made to the labelling of product and the use of skin lightenercreams is under review in the U.S.A. and EU, current activities to control hazards associated withthe use of hydroquinone in skin lighteners are considered adequate.
Published or unpublished reports associated with adverse reactions to prescription use ofhydroquinone are rare. A single case of dermal cross-sensitization in a patient exposed to both 2%hydroquinone and 5% hydroquinone monobenzyl ether is described (IPCS, 1994).
•

Health Assessments for Other Exposures to Hydroquinone

Two reports have been published on possible skin sensitization reactions to hydroquinone from useof rubber footwear in Brazil and India (George et al., 1990; Moriearty et al., 1978). These reports
appear to be isolated events which cannot clearly be linked to hydroquinone exposure.
34

UNEP Publications

OECD SIDSHYDROQUINONE

A small number of poisoning or suicides have been attempted with hydroquinone or hydroquinonecontaining developers. Individuals have survived estimated doses of 1g and 12g hydroquinone.
The last hydroquinone poisoning was reported in 1927. A small number of deaths have beenreported following ingestion (accidental or suicidal) of hydroquinone containing developers.
Reports of these cases occurred in 1939, 1945, 1969, and 1974 (IPCS, 1994). The current
classification of "harmful if ingested" is considered adequate to control such unintended exposures.
•

Health Assessment for Indirect Exposure via the Environment

Using the most sensitive oral dose NOEL observed in the rat reproduction study (15 mg/kg/day),
EHE/EDLC ratios can be estimated for ambient air and water exposures at manufacturing andprocessor/user sites (U.S.E.P.A., 1995).
The EHE/EDLC ratios for fugitive air emissions at manufacturing sites were 0 for two sites and1.1x10-5 for the third site. The EHE/EDLC ratios for stack air emissions were 2.1x10-9 to 2.9x10-8.
The EHC/EDLC ratios for surface water, drinking water, and fish consumption were all considerednegligible.
The EHE/EDLC ratios for fugitive air emissions at processor/user sites were 0 to 6.3x10-5. The
EHE/EDLC ratios for stack emissions were 0 to 1.3x10-8. The EHC/EDLC ratios for direct surface
water discharges were 1.1x10-10 to 8.7x10-8. The EHC/EDLC ratios for indirect surface water
discharges were 2.4x10-11 to 1.7x10-4. The EHC/EDLC ratios for drinking water and fishconsumption were all considered negligible for processor/user sites.
As all ambient environmental exposures are estimated to be considerably less than occupational
exposures, carcinogenicity concerns are considered negligible. The U.S.E.P.A. (1990) assessed
potential for adverse health based on the 1987 TRI database for hydroquinone (201470 kg/yr total
TRI reported release as compared to the 1992 total TRI release of 4315 kg/yr). The 1990
U.S.E.P.A. analysis also concluded ambient air and water releases resulted in negligible healthrisks. Since the 1992 total TRI release was only 2% of the 1987 TRI release, any potential risk
should be equivalently lower.
The low EHE/EDLC ratios observed for ambient hydroquinone exposures and the decrease in TRI
releases indicate that current measurements to control exposure are effective.
5.

CONCLUSIONS AND RECOMMENDATIONS

5.1

Conclusions

The environmental and toxicity profiles for hydroquinone have been well studied. Environmental
effects are of low concern due to low exposure levels and the ready biodegradability andphotodegradability of the substance, but processing sites such as in industrial photography, may
present local environmental concern based on default modeling. While toxicity to mammalian
species is associated with high doses of hydroquinone, these effects are either species- and strainspecific or minimized in humans through reduced exposure. Dermal effects in humans who usehydroquinone-containing skin products appear to be limited to individuals who misuse the products
or to products which contain other active ingredients. Similar dermal effects have not been
demonstrated in animals treated with similar or higher concentrations of hydroquinone. Potential
hazards from dermal exposure to aqueous solutions of hydroquinone are also low based on dermal
UNEP Publications

35

OECD SIDSHYDROQUINONE

absorption rates. Because no human health concerns have been identified, this substance has a low
priority for further work.
5.2

Recommendations

An assessment of the environmental and human health effects associated with hydroquinone
indicate that measures currently in effect are adequate to control potential risks. As the data baseavailable on ecologic and human health effects is adequate for assessment of risk and no significant
exposure concerns were identified following submission of additional exposure information from
OECD member countries, hydroquinone has a low priority for further work. Depending on theextent of use, national action to avoid risk to the aquatic environment could be warranted on somesite-specific conditions.

36

UNEP Publications

OECD SIDS
6.

HYDROQUINONEREFERENCES
Anderson, B. (1947). Corneal and conjunctival pigmentation among workers engaged in
manufacture of hydroquinone. Archives of Ophthalmology 38:812-826.
Anderson, B. (1958). Corneal changes from quinone-hydroquinone exposure. Archives ofOphthalmology 59:495-501.
Barber, E.D., Hill, T., and Schum, D.B. (1995). The percutaneous absorption ofhydroquinone (HQ) through rat and human skin in vitro. Toxicology Letters, 80:167-172.
Bringmann, G., and Kühn, R. (1977). Findings concerning the harmful effect of waterpollutants on Daphnia magna. Z. Wasser. Abwasser Fosch 10:161-166.
Burke, P.A., and Maibach, H.I. (1997). Exogenous ochronosis: An overview. Journal of
Dermatological Treatment. In press.
Carlson, A.J., and Brewer, N.R. (1953). Toxicity studies on hydroquinone. Proc. Soc. Exper.
Biol. Med. 84: 684-688.
Chemical Engineering Branch (CEB). Manual for the Preparation of Engineering
Assessments, U.S. Environmental Protection Agency, February, 1991.
Chemcial Manufacturers Association (1995). Comments on the use and exposure profile forhydroquinone (Revised Draft).
Cosmetic Ingredient Review (CIR) (1994). Addendum to the final report on the safetyassessment of hydroquinone. Journal of the American College of Toxicology 13:167-230.
Deisinger, P.J., Hill, T.S., and English, J.C. (1996). Human exposure to naturally occurringhydroquinone. Journal of Toxicology and Environmental Health, 47:101-116.
Devillers, J., Boule, P., Vasseur, P., Prevot, P., Steiman, R., Seigle-Murandi, F., BenoitGuyod, J.L., Nendza, M., Grione, C., Dive, D., and Chambon, P. (1990). Environmental andhealth risks of hydroquinone. Ecotoxicology and Environmental Safety 19:327-354.
Eastmond, D.A., Smith, M.T., and Irons, R.D. (1987). An interaction of benzene metabolites
reproduces the myelotoxicity observed with benzene exposure. Toxicology and Applied
Pharmacology 91:85-95.
English, J.C., Perry, L.G., Vlaovic, M., Moyer, C., and O'Donoghue, J.L. (1994).
Measurement of cell proliferation in the kidneys of Fischer 344 and Sprague-Dawley rats after
gavage administration of hydroquinone. Fundamental and Applied Toxicology 23:397-406.
English, J.C., Hill, T., O'Donoghue, J.L., and Reddy, M.V. (1994a). Measurement of nuclear
DNA modification by 32P-postlabeling in the kidneys of male and female Fischer 344 rats
after multiple gavage doses of hydroquinone. Fundamental and Applied Toxicology 23:391396.

UNEP Publications

37

OECD SIDSHYDROQUINONE

Ewing, B.B., Chiang, E.S.K., Cook, J.C., Evans, C.A., Hopke, P.K., and Perkins, E.G. (1977).
Monitoring to detect previously unrecognized pollutants in surface waters, U.S.E.P.A. Officeof Toxic Substances. EPA 560 7-77-001, (for ordering use NTIS # PB 273-349/PB 273-350).
Exposure Assessment Branch (EAB). Guidelines for Completing the Initital Review
Exposure Report, U.S. Environmental Protection Agency, Final Draft, March 1, 1994.
FDA (1978). Skin bleaching drug products for over-the-counter human use; establishment ofa monograph. Federal Register 43:51547.
FDA (1982). Skin bleaching drug products for over-the-counter human use; tentative final
monograph. Federal Register 47:39108.
Freitag, D., Ballhorn, L., Geyer, H., and Korte, F. (1985). Environmental hazard profile oforganic chemicals. Chemosphere 14:1589-1616.
Frenk, E., and Loi-Zedda, P. (1980). Occupational depigmentation due to a hydroquinonecontaining photographic developer. Contact Dermatitis 6:238-239.
George, N.D., Srinivas, C.R., Balachandran, C., and Shenoi, S.D. (1990). Sensitivity tovarious ingredients of topical preparations following prolonged use. Contact Dermatitis
23:367-368.
Gerike, P., and Fischer, W.K. (1979). A correlation study of biodegradability determinations
with various chemicals in various tests. Ecotoxicol. Environ. Safety 3:159-173.
Godlee, F. (1992). Skin lighteners cause permanent damage. Br. Med. J. 305:332-333.
Harbison, K.G., and Belly, R.T. (1982). The biodegradation of hydroquinone. Environmental
Toxicology and Chemistry 1:9-15.
Hardwick, N., Van Gelder, J.W., Van der Merwe, C.A., and Van der Merwe, M.P. (1989).
Exogenous ochronosis: An epidemiological study. Brit. J. Dermatol. 120:229-238.
International Programme on Chemical Safety (IPCS), Environmental Health Criteria 157:
Hydroquinone. World Health Organization, 1994.
Kersey, P., and Stevenson, C.J. (1981). Vitiligo and occupational exposure to hydroquinone
from servicing self-photographing machines. Contact Dermatitis 7:285-287.
Kühn, R., Pattard, M., Pernak, K-D., and Winter, A. (1989). Results of the harmful effects of
selected water pollutants (anilines, pheonls, aliphatic compounds) to Daphnia magna. Wat.
Res. 23:495-499.
Lidén, C. (1984). Occupational dermatoses at a film laboratory. Contact Dermatitis 10:7787.
Lidén, C. (1989). Occupational dermatoses at a film laboratory. Follow-up after
modernization. Contact Dermatitis 20:191-200.

38

UNEP Publications

OECD SIDSHYDROQUINONE

Mann, J.R., and Harman, R.R.M. (1983). Nail staining due to hydroquinone skin-lightening
creams. Br. J. Dermatol. 108:363-365.
Marzulli, F.N., Brown, D.W.C., and Maibach, H.I. (1969). Techniques for studying skinpenetration. Toxicol. Appl. Pharmacol. Suppl 3: 76-83.
McLeese, D.W., Zitko, V., and Peterson, M.R. (1979). Structure-lethality relationships forphenols, anilines and other aromatic compounds in shrimp and clams. Chemophere 2:53-57.
Meylan, W.M., and Howard, P.H. (1991). Bond contribution method for estimating Henry's
law constants. Environmental Toxicology and Chemistry 10:1283-1293.
Moriearty, P.L., Pereira, C., and Guimaraes, N.A. (1978). Contact dermatitis in Salvador,
Brazil. Contact Dermatitis 4:185-189.
National Institute of Occupational Safety and Health (NIOSH). National Occupational
Exposure Survey (NOES), 1982-1984.
O'Donoghue, J.L., and David, R. Letter to Dr. Oscar Hernandez, U.S. Environmental
Protection Agency, 10 February 1995.
Oglesby, F. L., Sterner, J. H., and Anderson, B. (1947). Quinone vapors and their harmful
effects. Journal of Industrial Hygiene and Toxicology 29:74-84.
Perry, D.L., Chuang, C.C., Jungslaus, G.A., and Warner, J.S. (1979). Identification of organic
compounds in industrial effluent discharges, U.S.E.P.A. Office of Toxic Substances. EPA
600 4-79-0-16, (for ordering use NTIS # PB 294-794).
Pifer, J.W., Hearne, F.T., Swanson, F.A., and O'Donoghue, J.L. (1995). Mortality study of
employees engaged in the manufacture and use of hydroquinone. Int. Arch. Occup. Environ
Health 67:267-280.
Pray, W.S. (1993). Topical therapy of pigmented skin lesions. U.S. Pharmacist June, 42-48.
Shibata, M.A., Hirose, M., Tanaka, H., Asakawa, E., Shirai, T., and Ito, N. (1991). Inductionof renal cell tumors in rats and mice, and enhancement of hepatocellular tumor development
in mice after long-term hydroquinone treatment. Jpn. J. Cancer Res. 82: 1211-1219.
Sterner, J. H., Oglesby, F. L., and Anderson, B. (1947). Quinone vapors and their harmful
effects. The Journal of Industrial Hygiene and Toxicology 29:60-73.
Taylor, M. Letter to C. Auer, U.S.E.P.A. Canadian hydroquinone exposure data for OECD
HPV SIDS, 5 May 1995.
TRI (1992). Toxic Release Inventory. 1992 Data Release, U.S. Environmental Protection
Agency.
Turner, D.B. (1970). Workbook of Atmospheric Dispersion Estimates, U.S. Environmental
Protection Agency, Office of Air Programs, Research Triangle Park, NC.
United Kingdom Health and Safety Executive (UKHSE), (1993). Unpublished information.
UNEP Publications

39

OECD SIDSHYDROQUINONE

U.S. Environmental Protection Agency, (1990). RMI briefing paper on hydroquinone.
U.S. Environmental Protection Agency. Use and Exposure Profile for Hydroquinone, Revised
Draft. March 20, 1995.
U.S. Environmental Protection Agency, (1995a). Pre-SIAR meeting comments.
Versar, Inc. (1992). Exposure Assessment for Retention of Chemical Liquids on Hands. U.S.
Environmental Protection Agency, Office of Pollution Prevention and Toxics, Contract
Number 68-01-6271, Washington, D.C.
Versar, Inc. (1992a). PMN PLUM Exposure Model. U.S. Environmental Protection Agency,
Office of Pollution Prevention and Toxics, Contract Number 68-D9-0166, Washington, D.C.
Versar, Inc. (1992b). DERMAL Exposure Model. U.S. Environmental Protection Agency,
Office of Pollution Prevention and Toxics, Contract Number 68-D9-0166, Washington, D.C.
Whysner, J., Verna, L., English, J.C., and Williams, G.M. (1995). Analysis of studies related
to tumorigenicity induced by hydroquinone. Regulatory Toxicology and Pharmacology
21:158-176.

40

UNEP Publications

OECD SIDSHYDROQUINONESIDS PROFILE

1.1

CAS No.

123-31-9

1.2

CHEMICAL NAME

1,4-Benzenediol

1.5

STRUCTURALFORMULAHOOH

OTHER CHEMICALIDENTITYINFORMATION

Hydroquinone
para-Dihydroxybenzene
para-Benzenediol
alpha-Hydroquinone

3.

SOURCES AND LEVELS
OF EXPOSURE

Industrial workers are potentially exposed tohydroquinone during the manufacture, andsubsequent processing as rubber antioxidants,
monomer inhibitors, photographic developers,
and other products. Non-industrial exposure
occurs in consumers using nonprescription
drugs containing 2% hydroquinone. A relatively
small number of photohobbyists that develop
black and white film are also potentially
exposed.

3.1

PRODUCTION
RANGE

40,000-45,000 tonnes per year (worldwide)

3.3

CATEGORIES AND
TYPES OF USE

50% used to manufacture antioxidants,
antiozonants, and inhibitors for industry(industrial)
33% in photography (industrial)
0.05% in skin creams (consumer)
11-12% for other uses such as to manufacture
food antioxidants (industrial)

Issues fordiscussion

UNEP Publications

41

HYDROQUINONE

Other
Study

Estimation
Methods

Acceptable?

SIDS
Testing
Required ?

Y/N

Y/N

Y/N

Y/N

Y/N

Y/N

Y/N

2.1 Melting Point

Y

N

N

Y

N

Y

N

2.2 Boiling Point

Y

N

N

Y

N

Y

N

2.3 Vapour Pressure

Y

N

N

Y

N

Y

N

2.4 Partition Coefficient

Y

N

N

N

Y

Y

N

2.5 Water Solubility

Y

N

N

Y

N

Y

N

Y

N

N

Y

N

Y

N

4.1.3.1 Hydrolysis

Y

N

N

Y

N

Y

N

4.1.3.2 Photodegradability

Y

N

N

N

Y

Y

N

4.3

Env. Fate/Distribution

Y

N

N

Y

N

Y

N

Env. Concentration

Y

N

N

Y

N

Y

N

CAS NO: 123-31-9

STUDY

GLP

OECD
Study

Information
Available

OECD SIDS

PHYSICAL-CHEMICALOTHER STUDIES RECEIVEDY

ENVIRONMENTAL FATE/BIODEGRADATION
4.1.1 Aerobic Biodegradability
4.1.3 Abiotic Degrability

OTHER STUDIES RECEIVEDY

ECOTOXICOLOGY
5.1 Acute Toxicity Fish

Y

N

N

Y

N

Y

N

5.2 Acute Toxicity Daphnia

Y

N

N

Y

N

Y

N

5.3 Acute Toxicity Algae

Y

N

N

Y

N

Y

N

5.6.1 Acute Toxicity Terrest. Organisms

N

-

-

-

-

-

N

5.6.2 Acute Toxicity Terrest. Plants

Y

N

N

Y

N

Y

N

5.6.3 Acute Toxicity Avians

Y

N

N

Y

N

Y

N

5.6.4 Avian Reproduction

N

-

-

-

-

-

N

Y

Y

N

Y

N

Y

N

Acute Dermal

Y

N

N

Y

N

Y

N

Acute Inhalation

N

-

-

-

-

-

N

6.4 Repeated Dose

Y

Y

Y

N

N

Y

N

- Gene Mutation

Y

N

N

Y

N

Y

N

- Chromosome Aberration

Y

N

N

Y

N

Y

N

Y

Y

Y

N

N

Y

N

OTHER STUDIES RECEIVEDYTOXICOLOGY
6.1 Acute Oral

6.5 Genetic Toxicity

6.7 Reproductive Toxicity
OTHER STUDIES RECEIVED

42

Y

UNEP Publications

OECD SIDSHYDROQUINONE
Summary of Responses to the OECD Request for
Available Data on HPV Chemicals

0.

General Information
Name of Sponsor country

United States of America

Contact point

Mr. Charles Auer
Director - Chemical Control Division
Office of Toxic Substances (TS-788)
U S Environmental Protection Agency
401 M Street SW
Washington, DC 20460
Telephone (202) 260-3749
Fax (202) 260-8168

Name of Lead OrganizationU S EPA1.

Chemical Identity*1.1

CAS - number*1.2

Name (Name supplied by the OECD): 1,4-Benzenediol

1.3

Common Synonyms

Hydroquinone
para-Dihydroxybenzene
para-Benzenediol
Ι-Hydroquinone

1.4

Empirical formula

C6H6O2*1.5

Structural formula

123-31-9

HO

OH

1.6

Purity of industrial product1.6.1

Degree of Purity (percentage by weight/volume): 98.5%

1.6.2

Identity of major impurities (Typical analysis): 1% H2O

1.6.3

Essential additives (stabilizing agents,inhibitors, other additives), if applicable:
Not Applicable
UNEP Publications

43

OECD SIDSHYDROQUINONE

2.

Physical-Chemical Data

*2.1

Melting or Decomposition Point: 169οC (melting point)
Method (e.g., OECD, others):

*2.2

GLP:

YES [ ]NO [X]

Comments:

Information predates GLP regulations.

Reference:

Material Safety Data Sheet, Eastman Chemical Company.

Boiling Point (including temperature of decomposition, if relevant).
286°C
Method (e.g., OECD, others):

*2.3

GLP:

YES [ ]NO [X]

Comments:

Information predates GLP regulations.

Reference:

Material Safety Data Sheet, Eastman Chemical Company.

Vapor pressure
2.34 x 10-10 kPa at 25°C
Method (e.g., OECD, others):

*2.4

GLP:

YES [ ]NO [X]

Comments:

Information predates GLP regulations.

Reference:

Material Safety Data Sheet, Eastman Chemical Company.

Partition coefficient n-Octanol/waterlog Pow = 0.50-0.61 at 25°C

44

Method:calculated
measured

GLP:

YES [ ]NO [X][X][]

UNEP Publications

OECD SIDS

*2.5

HYDROQUINONE

Analytical Method:

Estmation by method of Hansch and Leo

Comments:

Information predates GLP regulations.

Reference:

Hansch, C., and Leo, A. (1979). Substituent Constants for
Correlation Analysis in Chemistry and Biology, John Wileyand Sons, New York.

Water solubility:
73,000 mg/L at 25°C
Method (e.g., OECD, others): None provided

2.6

GLP:

YES [ ]NO [X]

Analytical Method:

None provided.

Comments:

Information predates GLP regulations.

Reference:

Sterner, J.H., Oglesby, F.L., and Anderson, B. (1947).
Quinone Vapors and Their Harmful Effects. I. Corneal andConjunctival Injury, J. Ind. Hyg. Toxicol. 29, 60-73.

Flash point (liquids)

177°C

closed cup [ ]2.7

open cup [X]Method:Cleveland Open Cup

GLP:

YES [ ]NO [X]

Comments:

Information predates GLP regulations.

Reference:

Material Safety Data Sheet, Eastman Chemical Company.

Flammability
Method (e.g., OECD, others): ASTM D1255

2.8

GLP:

YES [ ]NO [X]

Test results:

Autoignition temperature = 499°C

Comments:

Information predates GLP regulations.

Reference:

Material Safety Data Sheet, Eastman Chemical Company.

pH in water
UNEP Publications

45

OECD SIDSHYDROQUINONE

pH of 4.00 to 4.70
pKa of 9.9 for the first hydrogen ion
Method (e.g., OECD, others): None provided

2.9

GLP:

YES [ ]NO [X]

Comments:

Information predates GLP regulations.

Reference:

Technical data bulletin, Eastman Chemical Products, Inc.,
1975.

Other data
Density:

1.341 g/cc

Comments:

Information predates GLP regulations.

Reference:

Material Safety Data Sheet, Eastman Chemical Company.

3.

Source of exposure*3.1

Production levels expressed as tonnes per annum:
40,000-45,000 tonnes per year worldwide and 10,000-12,000 tonnes in the U.S.

3.2

Processes:
There are three current manufacturing processes for hydroquinone: oxidative cleavage of
diisopropylbenzene, oxidation of aniline, and hydroxylation of phenol.
At Eastman Chemical Company, diisopropyl benzene is air oxidized to the intermediate
diisopropylbenzene bishydroperoxide. This hydroperoxide is purified by extraction andreacted further to form hydroquinone. Process solvents are recycled. Water-insoluble
impurities are incinerated, and the two water-based impurity streams are biodegraded in
the plant wastewater treatment system. The purified product is isolated by filtration, andpackaged. The process is almost entirely closed, continuous, computer-controlled andmonitored. Less than 100 workers are potentially exposed during manufacture, materials
handling, maintenance, and quality control sampling and analysis. Worker protective
clothing and engineering controls, such as local exhaust and ventilation systems, are used
to further prevent exposure at points in the process where exposure can occur.
Reference: Roderick D. Gerwe, Ph.D., Eastman Chemical Company
Hydroquinone can also be prepared in a closed system in which aniline is oxidized toquinone in the presence of manganese dioxide and sulfuric acid. Quinone is then reduced
to hydroquinone using iron oxide. The resulting hydroquinone is crystallized and dried.

46

UNEP Publications

OECD SIDSHYDROQUINONE

Reference: Oglesby, F.L., Sterner, J.H., and Anderson, B. (1947). Quinone Vapors andTheir Harmful Effects. II. Plant Exposures Associated with Eye Injuries, J. Ind. Hyg.
Toxicol. 29, 74-84.
Hydroquinone is also manufactured by hydroxylation of phenol using hydrogen peroxide
as a hydroxylation agent. The reaction is catalyzed by strong mineral acids, or ferrous orcobalt salts.
Reference: Varagnat, J. (1981). Hydroquinone, resorcinol, and cathecol. In: Encyclopediaof Chemical Technology, Grayson, M., ed. John Wiley & Sons, New York.
*3.3

Information concerning Uses (including categories and types of uses expressed inpercentage terms):
Virtually all the uses of hydroquinone are industrial. Approximately 25% of thehydroquinone manufactured is used as an intermediate for chemical conversion tohydroquinone-based rubber antioxidants and antiozonants. Another 25% is used as anintermediate for chemical conversion to inhibitors used to stabilize monomers. An
additional 33% is used in the photographic industry including black and whitephotographic film, lithogrpahy, and hospital x-ray film. Other uses (11-12%) include
chemical conversion to stabilizers for paints, varnishes, motor oils, and fuels, and forantioxidants for industrial use fats and oils and food.
A small amount of the hydroquinone is used by photohobbyists, and about 0.05% is usedin nonprescription drugs such as skin bleaching creams. Both are considered consumer
use.

3.4

Options for disposal: Incineration.

3.5

Other remarks

4.

Environmental Fate and Pathways*4.1

Degradability (biotic and abiotic)

4.1.1

Biodegradability
Test substance:

Hydroquinone

Test type,aerobic [X], anaerobic [ ]Test medium:

Activated sludge

In the case of poorly soluble chemicals, treatment given (nature, concentration, etc.):
Test method:

Similar to OECD Guideline 301D. Activated sludge wasincubated in a concentration of 10 mg/L hydroquinone for 5 or
20 days.
UNEP Publications

47

OECD SIDS

4.1.2

HYDROQUINONEGLP:YES [ ]NO [X]

Test results:

BOD5 = 1.00 g/g O2, COD = 1.83 g/g, THOD = 1.89 g/g
BOD20 = 1.15 g/g O2

Comments:

Information predates GLP regulations. Additional studies
listed in the attached bibliography.

Reference:

Young, R.H.F., Ryckman, D.W., and Buzzell, Jr., J.C. (1968).
An Improved Tool for Measuring Biodegradability, J. Water
Pollut. Control Fed. 40, 354-368.

Sewage Treatment
Test substance:

Hydroquinone

Test species:

Unacclimated, Activated sludge

Test method (e.g., OECD, others): Eastman Kodak Company, Health and Environment
Laboratories Protocol. A laboratory sewage treatment unit wasused to degrade concentrations of 55-400 mg/L hydroquinone.
After 8-18 hours, the total organic carbon (TOC) was
determined. Similar to OECD Guideline 303A.
••

Type of test: IC50; Secondary Waste Treatment [X]Other (e.g., field observation) [ ]GLP:

YES [ ]NO [X]

Test results:

[HQ]
mg/L
-----055100400Comments:

Study predates GLP regulations.

Reference:

Harbison, K.G., and Belly, R.T. (1982). The Biodegradationof Hydroquinone, Environ. Toxicol. Chem. 1, 9-15.

[HQ] removed%---------------->99.9
99.9
93.1

ADDITIONAL REFERENCES
Section 4.1 Degradability

48

UNEP Publications

TOC removed%----------69
70
87
89

OECD SIDSHYDROQUINONE

Dore, M., Brunet, N., and Legube, B. (1975). Participation de différents composésorganiques à la valeur des critères globaux de pollution. La Tribune du Cebadeau 374, 311.
Rott, B., Viswanathan, R., Freitag, D., and Korte, F. (1982). Vergleichende Untersuchungder Anwendbarkeit Verschiedener Tests zur Überprüfung der Abbaubarkeit von
Umweltchemikalien. Chemosphere 11, 531-538.
Tabak, H.H., Chambers, C.W., and Kabler, P.W. (1964). Microbial metabolism ofaromatic compounds.
I.
Decomposition of phenolic compounds and aromatichydrocarbons by phenol-adapted bacteria. J. Bact. 87, 910-919.
4.1.3

Stability in air (e.g., photodegradability)
Test substance:

Hydroquinone

Test method or estimation method (e.g., OECD, others): Estimation

4.1.3

GLP:

YES [ ]NO [X]

Test results:

t½ of photodegradation = < 5 weeks in June to > 240 weeks in
January

Comment:

The reaction of hydroquinone with oxygen in the presence ofhydroxide ions [OH⋅] in water vapor is very rapid but the rate
has not been determined (NIOSH, 1978).

Reference:

Devillers, J., Boule, P., Vasseur, P., Prevot, P., Steiman, R.,
Seigle-Murandi, F., Benoit-Guyod, J.L., Nendza, M., Grioni,C., Dive, D., and Chambon, P. (1990). Environmental and
Health Risks of Hydroquinone, Ecotoxicol. Environ. Safety
19, 327-354.

Stability in water (e.g., hydrolysis)
Test substance:

Hydroquinone

Test method:

Oxygen utilization was measured in a Warburg respirometer at
a buffered pH of 7.0, 8.0, and 9.0. Similar to OECD Guideline
111.

GLP:

YES [ ]NO [X]

Test results:
t½ for O2 utilization
111 hrs
41 hrs0.8 hrs
UNEP Publications

pH
7.0
8.0
9.0
49

OECD SIDS

4.1.4

HYDROQUINONE

Comment:

No analysis of test substance. No determinations at acidic pH.

Reference:

Moussavi, M. (1979). Effect of Polar Substitution on
Autoxidation of Phenols, Water Res. 13, 1125-1128.

Identification of main mode of degradability in actual use
In photofinishing, hydroquinone is chemically converted to sulfonic acid derivatives.
Wastewater sludge readily biodegrades the hydroquinone that is not already oxidized aswell as hydroquinone sulfonates.

4.2

Bioaccumulation
Test substance:

Hydroquinone

Test method (e.g., OECD, others): Organisms were exposed to a concentration of
0.05 mg/L 14C-Hydroquinone for 24, 72, or 120 hours. The
amount of radiolabel accumulated was then determined.
Similar to OECD Guideline 305E.
••

Type of test: static [ ], semi-static [ ], flow-through [X]Other (e.g., field test) [ ]GLP:

YES [ ]NO [X]

Bioaccumulation factor:

The BCF-24 h in Chorella fusca (green alga) and the BCF-72
h in Leuciscus idus melanotus (golden ide) is 40.

Calculated results:

BF = 40

Comments:
Reference:

Freitag, D., Ballhorn, L., Geyer, H., and Korte, F. (1985).
Environmental Hazard Profile of Organic Chemicals. An
Experimental Method for the Assessment of the Behaviour ofOrganic Chemicals in the Ecosphere by Means of Simple
Laboratory Test with 14C-Labelled Chemicals, Chemosphere14, 1580-1616.

ADDITIONAL REFERENCES
Section 4.2 Bioaccumulation
Freitag, D., Geyer, H., Kraus, A., Viswanathan, R., Kotzias, D., Attar, A., Klein, W., andKorte, F. (1982). Ecotoxicological profile analysis. VII. Screening chemicals or theirenvironmental behavior by comparative evaluation. Ecotoxicol. Environ. Safety 6, 60-81.
Geyer, H., Viswanathan, R., Freitag, D., and Korte, F. (1981). Relationship between watersolubility of organic chemicals and their bioaccumulation by the alga Chlorella.
Chemosphere 10, 1307-1313.
50

UNEP Publications

OECD SIDS
*4.3

HYDROQUINONE

Transport and distribution between environmental compartments including
estimated environmental concentrations and distribution pathways
Type of transport and distribution processes between compartments (e.g., air, water,soil): Based on the low vapor pressure (see Section 2.3), transport of hydroquinone vapor
to the air is expected to be minimal in the environment. Transport to soil is possible, wherehydroquinone is expected to be distributed to the water compartment due to the high watersolubility. Persistence is not expected because hydroquinone is readily biodegradable (seeSection 4.1).
Reference: Hydroquinone/Quinone Test Rules Support Document, Dynamac Corp., 1982.
Estimation of environmental concentrations: Estimated release of hydroquinone is 10.1
x 104 kg/yr from the manufacture of methyl methacrylate.
Reference: Eimutis, E.C., Quill, R.P., and Rinaldi, G.M. (1978). Source Assessment:
Noncriteria Pollutant Emissions, USEPA Industrial Environmental Research Lab.
Hydroquinone is also found in several berry plants and is formed as a byproduct fromseveral bacteria and marine species. Approximately 5 x 104 kg of hydroquinone is
generated per year in cigarette smoke.
Reference: Hydroquinone/Quinone Test Rules Support Document, Dynamac Corp., 1982.
Hydroquinone concentrations range from 0.14 to 15 µg/g in some foods such as coffee, tea,
whole wheat bread, and certain types of pears. Milk, melons, yogurt, and soft drinks havenondetectable levels of hydroqunone.
Reference: Deisinger, P.J., Hill, T.S., and English, J.C. (1994). Human Exposure to
Naturally Occurring Hydroquinone, The Toxicologist 14, 788.

4.4

Monitoring data (environment)
No concentrations have been detected in wastewater, surface water, or emissions fromareas in which hydroquinone is manufactured.
References: Ewing, B.B., Chian, E.S.K., Cook, J.C., Evans, C.A., Hopke, P.K., andPerkins, E.G. (1977). Monitoring to Detect Previously Unrecognized Pollutants in Surface
Waters, USEPA Office of Toxic Substances.
Eimutis, E.C., Quill, R.P., and Rinaldi, G.M. (1978). Source Assessment: Noncriteria
Pollutant Emissions, USEPA Industrial Environmental Research Laboratory.
Nunn, A.B., III (1978). Volatile Organic Compound Emission Inventory for Tennessee
Eastman Company, USEPA Air and Hazardous Material Division.
Perry, D.L., Chuang, C.C., Jungclaus, G.A., and Warner, J.S. (1978). Identification ofOrganic Compounds in Industrial Effluent Discharges, USEPA Office of Toxic
Substances.
UNEP Publications

51

OECD SIDSHYDROQUINONE

Indicate whether the data are measurements of background concentrations ormeasurements at contaminated sites:- air: None detected in film-developing room (Chrostek, NIOSH, 1975)
Air monitoring of the workplace environment indicated that concentrations ranged from
6.0 mg/m3 in the 1950s to 0.1 mg/m3 in the 1990s.
Pifer, J.W., Hearne, F.T., Swanson, F.A., O'Donoghue, J.L. (1995). Mortality Study of
Employees Engaged in the Manufacture and Use of Hydroquinone, Int. Arch. Occup.
Environ. Health accepted for publication.
5.

Ecotoxicological Data

5.1

Toxicity to fish

*5.1.1Results of acute tests
Test substance:

Hydroquinone

Test species:

Pimephales promelas (Fathead minnow)

Test method:

Similar to OECD Guideline 203. Fish exposed to various
concentrations for 96 hours.
•
•

5.1.1

GLP:

YES [ ]NO [X]

Test results:

LC50 = > 0.4 mg/L

Comments:

Study predates GLP regulations. No analysis for test
substance. Additional studies listed in the attachedbibliography.

Reference:

Terhaar, C.J., Ewell, W.S., Dziuba, S.P., and Fassett, D.W.
(1972). Toxicity of Photographic Processing Chemicals toFish, Phot. Sci. Eng. 16, 370-377.

Results of acute tests (Additional study)
Test substance:

Hydroquinone

Test species:

Pimephales promelas (Fathead minnow)

Test method:

Fish exposed to concentrations of 0.1-0.18 mg/L for 96 hours.
•

52Type of test static [X], semi-static [ ], flow-through [ ]Other (e.g., field observation) [ ]Type of test static [X], semi-static [ ], flow-through [ ]UNEP Publications

OECD SIDSHYDROQUINONE
•

5.1.1

GLP:

YES [ ]NO [X]

Test results:

LC50 = 0.1-0.18 mg/L

Comments:

Study predates GLP regulations. No analysis for test
substance. Additional studies listed in the attachedbibliography.

Reference:

Environmental Effects of Photoprocessing Chemicals,
National Association of Photographic Manufacturers, Inc.,
1974.

Results of acute tests (Additional study)
Test substance:

Hydroquinone

Test species:

Brachydanio rerio (Zebrafish)

Test method:

Fish exposed to various concentrations for 96 hours. Similar
to OECD Guideline 203.
•
•

5.1.2

Other (e.g., field observation) [ ]Type of test static [X], semi-static [ ], flow-through [ ]Other (e.g., field observation) [ ]GLP:

YES [ ]NO [X]

Test results:

LC50 = 0.17 mg/L

Comments:

Study predates GLP regulations. No analysis for test
substance. Additional studies listed in the attachedbibliography.

Reference:

Wellens, H. (1982). Comparison of the Sensitivity ofBrachydanio rerio and Leuciscus idus in the Study of the
Toxicity to Fish of Chemical Compounds and Wastewaters, Z.
Wasser Abwasser Forsch. 15, 49-52.

Results of long-term e.g., prolonged toxicity, early life stage
Test substance:
Test species:
Test method (e.g., OECD, others):•

Type of test static [], semi-static [], flow-through []UNEP Publications

53

OECD SIDSHYDROQUINONE•

Other (e.g., field observation) []GLP:

YES [ ]NO [ ]

Test results:

No Data Available

Comments:
Reference:
ADDITIONAL REFERENCES
Section 5.1 Toxicity to Fish
Bandt, H.J. (1955). Fischereischäden
Wassertechnik 5, 290-294.

durch

Phenolabwässer.

Wasserwirtschaft-

Hodson, P.V., Dixon, D.G., and Kaiser, K.L.E. (1984). Measurement of median lethal doseas a rapid indication of contaminant toxicity to fish. Environ. Toxicol. Chem. 3, 243-254.
Juhnke, I., and Lüdemann, D. (1978). Ergebnisse der Untersuchung von 200 chemischen
Verbindungen auf akute Fischtoxizität mit dem Goldorfentest. Z. Wasser Abwasser
Forsch. 11, 161-164.
Sollmann, T. (1949). Correlation of the aquarium goldfish toxicities of some phenols,
quinones and other benzene derivatives with their inhibition of autooxidative reactions. J.
Gen. Physiol. 32, 671-679.
Tissot, A., Boule, P., Lemaire, J., Lambert, S., and Palla, J.C. (1985). Photochimie etenvironnement. X. Evaluation de la toxicite des produits de phototransformation del'hydroquinone et des chlorophenols en milieu aqueux. Chemosphere 14, 1221-1230.
*5.2

Toxicity to daphnids

5.2.1

Results of acute tests
Test substance:

Hydroquinone

Test species:

Daphnia magna

Test method (e.g., OECD, others): Daphnids exposed for 96 hours under static conditions.
Similar to OECD Guideline 202.

54

GLP:

YES [ ]NO [X]

Test results:

LC50 = 0.05mg/L

Comments:

Additional studies listed in the attached bibliography.
UNEP Publications

OECD SIDS
Reference:

5.2.1

HYDROQUINONE
Environmental Effects of Photoprocessing Chemicals,
National Association of Photographic Manufacturers, Inc.,
1974.

Results of acute tests(Additional study)
Test substance:

Hydroquinone

Test species:

Daphnia magna

Test method (e.g., OECD, others): Daphnids exposedfor 24 hours under static
conditions. Similar to OECD Guideline 202.

5.2.1

GLP:

YES [ ]NO [X]

Test results:

LC50 = 0.09 mg/L

Comments:

Study predates GLP regulations. Additional studies listed in
the attached bibliography.

Reference:

Bringmann, G., and Kühn, R. (1977). Results of the Damaging
Effect of Water Pollutants on Daphnia magna, Z. Wasser
Abwasser Forsch. 10, 161-166.

Results of acute tests (Additional study)
Test substance:

Hydroquinone

Test species:

Daphnia magna

Test method (e.g., OECD, others): Daphnids exposed for 24 hours under static conditions.
Similar to OECD Guideline 202.

5.2.2

GLP:

YES [ ]NO [X]

Test results:

EC50 = 0.12 mg/L

Comments:

Study predates GLP regulations. Additional studies listed in
the attached bibliography.

Reference:

Bringmann, G., and Kühn, R. (1982). Results of Toxic Actionof Water Pollutants on Daphnia magna (Straus) Tested by an
Improved Standardized Procedure, Z. Wasser Abwasser
Forsch. 15, 1-6.

Results of long-term tests e.g., reproduction
Test substance:
UNEP Publications

55

OECD SIDSHYDROQUINONE

Test species:
Test method (e.g., OECD, others):
GLP:

YES [ ]NO [ ]

Test results:

No Data Available

Comments:
Reference:
ADDITIONAL REFERENCES
Section 5.2 Toxicity to Daphnids
Kühn, R., Pattard, M., Pernak, K-D., and Winter, A. (1989). Results of the harmful effects
of selected water pollutants (anilines, phenols, aliphatic compounds) to Daphnia magna.
Water Res. 23, 495-499.
*5.3

Toxicity to algae
Test substance:

Hydroquinone

Test species:

Selenastrum capricornutum

Test method (e.g., OECD, others): Organisms exposed to concentrations of 0.1-40 mg/L
for 7 days. Similar to OECD Guideline 201.
GLP:

YES [ ]NO [X]

Test results:

Growth was initially inhibited at 1.0 mg/L but recovered after
an initial lag period. A concentration of 4.0 mg/L wascompletely inhibitory.
EC50 (duration, e.g. 24, 48, 72 hours) = 1-4 mg/L
Maximum concentration at which no effect was observed
within the period of the test: 0.4 mg/L
Minimum concentration at which effect was observed within
the period of the test: 1.0 mg/L

56

Comments:

Study predates GLP regulations. No analyses of test substancein water.

Reference:

Environmental Effects of Photoprocessing Chemicals,
National Association of Photographic Manufacturers, Inc.,
1974.
UNEP Publications

OECD SIDSHYDROQUINONE

ADDITIONAL REFERENCES
Section 5.3 Toxicity to Algae
Bringmann, G., and Kühn, R. (1959). Vergleichende wasser-toxikologische
Untersuchungen an Bakterien, Algen und Kleinkrebsen. Gesundheits-Ingenieur 4, 115120.
Fitzgerald, G.P., Gerloff, G.C., and Skoog, F. (1952). Studies on chemicals with selective
toxicity to blue-green algae. Sewage Ind. Wastes 24, 888-896.
Wängberg, S.A., and Blanck, H. (1988). Multivariate patterns of algal sensitivity tochemicals in relation to phylogeny. Ecotoxicol. Environ. Safety 16, 72-82.
5.4

Toxicity to other aquatic organisms
Test substance:

Hydroquinone

Test species:

Dugesia tigrina (current taxonomy: Dugesia dorotocephalo;
flatworm)

Test method:

Eastman Kodak Company, Health and Environment
Laboratories Protocol according to Ewell, W.S., Gorsuch,
J.W., Kringle, R.O., Robillard, K.A., and Spiegel, R.C.
(Simultaneous Evaluation of the Acute Effects of Chemicals
on Seven Species, Environ. Toxicol. Chem. 5, 831-840, 1986).
Similar to OECD Guideline 202. Organisms exposed toconcentrations of 0.1 to 10 mg/L at pH 8.0.
•
•

5.4

Type of test static [X], semi-static [ ], flow-through [ ]Other (e.g., field observation) [ ]GLP:

YES [ ]NO [X]

Test results:

LC50 = 2 mg/L at 96 hours

Comments:

Study predates GLP regulations. Additional studies listed in
the attached bibliography.

Reference:

Dagon, T.J. (1975). Aquatic Toxicity Report (Unpublishedreport), Health and Safety Laboratory, Eastman Kodak
Company.

Toxicity to other aquatic organisms (Additional study)
Test substance:

Hydroquinone

Test species:

Physa and Planorbis species (snails)
UNEP Publications

57

OECD SIDSHYDROQUINONE

Test method (e.g., OECD, others): Health and Safety Laboratory protocol, Eastman
Kodak Company. Six organisms were exposed toconcentrations of 1, 10, or 100 mg/L hydroquinone for 96
hours. Similar to OECD Guideline 202.
GLP:

YES [ ]NO [X]

Test results:

LC50 at 96 hours = 3.2 mg/L

Comments:

Details of methodology not provided.

Reference:

Dagon, T.J. (1975). Aquatic Toxicity Report (Unpublishedreport), Health and Safety Laboratory, Eastman Kodak
Company.

ADDITIONAL REFERENCES
Section 5.4 Toxicity to Other Aquatic Organisms
Bringmann, G., and Kühn, R. (1959b). Wasser-toxikologische Untersuchungen mit
Protozoe als Testorganismen. Gesundheits-Ingenieur 8, 239-240.
DeGraeve, G.M., Geiger, D.L., Meyer, J.S., and Bergman, H.L. (1980). Acute and embryolarval toxicity of phenolic compounds to aquatic biota. Arch. Environ. Contam. Toxicol. 9,557-568.
McLeese, D.W., Zitko, V., and Peterson, M.R. (1979). Structure-lethality relationships forphenols, anilines and other aromatic compounds in shrimp and clams. Chemosphere 2, 5357.
Stom, D.J. (1977). Influence of polyphenols and quinones on aquatic plants and theirblocking of SH-groups. Acta hydrochim. hydrobiol. 5, 291-298.
5.5

Toxicity to Bacteria
Test substance:

Hydroquinone

Test species:

Photobacterium phosphorium NZ11D

Test method (e.g., OECD, others): Five concentrations of test substance were incubatedwith the bacterium for 1 or 24 hours and the luminescence
determined in a Photobioluminometer.
••

58

Type of test: IC50; Secondary Waste Treatment [ ]Other (e.g., field observation) [ ]GLP:

YES [ ]NO [X]

Test results:

EC50 for 1 hour incubation = 23.75 mg/L
UNEP Publications

OECD SIDSHYDROQUINONE
EC50 for 24 hour incubation = 29.25 mg/L

Comments:
Reference:

McFeters, G.A., Bond, P.J., Olson, S.B., and Tchan, Y.T.
(1983). A Comparison of Microbial Bioassays for the
Detection of Aquatic Toxicants, Water Res. 17, 1757-1762.

ADDITIONAL REFERENCES
Section 5.5 Toxicity to Bacteria
Bringmann, G., and Kühn, R. (1977). Grenzwerte der Schadwirkung wassergefährdender
Stoffe gegen Bakterien (Pseudomonas putida) und Grünalgen (Scenedesmus quadricauda)
im Zellvermehrungshemmtest. Z. Wasser Abwasser Forsch. 10, 87-98.
Bringmann, G., and Kühn, R. (1978). Grenzwerte der Schadwirkung wassergefährdender
Stoffe gegen Blaualgen (Microcystis aeruginosa) und Grünalgen (Scenedesmus
quadricauda) im Zellvermehrungshemmtest. Vom Wasser 50, 45-60.
Bringmann, G., and Kühn, R. (1980). Bestimmung der biologischen Schadwirkung
wassergefährdender Stoffe gegen Protozoen. II. Bakterienfressende Ciliaten. Z. Wasser
Abwasser Forsch. 1, 26-31.
Lebsack, M.E., Anderson, A.D., DeGraeve, G.M., and Bergman, H.L. (1981). Comparisonof bacterial luminescence and fish bioassay results for fossil-fuel process waters andphenolic constituents. In Aquatic Toxicology and Hazard Assessment,
FourthConference, ASTM STP 737, DR Branson and KL Dickson, Eds, American Society for
Testing and Materials, pp. 348-356.
Ribo, J.M., and Kaiser, K.L.E. (1983). Effects of selected chemicals to photoluminescentbacteria and their correlations with acute and sublethal effects on other organisms.
Chemosphere 12, 1421-1442.
Stom, D.J., Geel, T.A., and Balayan, A.E. (1986). Effect of individual phenolic compounds
and of their mixtures on luminous bacteria. Part I: Use of bacterial luminescence
extinguishing for biotesting of phenols. Acta hydrochim. hydrobiol. 14, 283-292.
Trevors, J.T., and Basaraba, J. (1980). Toxicity of benzoquinone and hydroquinone inshort-term bacterial bioassays. Bull. Environ. Contam. Toxicol. 25, 672-675.
*5.6

Toxicity to terrestrial organisms

5.6.1

Toxicity to soil dwelling organisms
Test substance:
Test species:
Test method (e.g., OECD, others):
UNEP Publications

59

OECD SIDSHYDROQUINONEGLP:YES [ ]NO [ ]

Test result:

No Data Available

Comments:
Reference:
5.6.2

Toxicity to plants
Test substance:

Hydroquinone

Test species:

Ryegrass
RadishLettuce

Test method:

Eastman Kodak Company, Health and Environment
Laboratories Protocol according to Gorsuch, J.W., Kringle,
R.O., and Robillard, K.A. (Chemical Effects on theGermination and Early Growth of Terrestrial Plants, Plants for
Toxicity Assessment, ASTM STP 1091, 1990). Eighty seedsof each species were exposed to a concentration of 10, 100, or
1000 mg/L for 7 days and germination compared to control
shoots.

GLP:

YES [ ]NO [X]

Test results:

Hydroquinone had little effect at 10 mg/L, but at 100 mg/L,
the hypocotyls of radish and lettuce were inhibited. At 100
mg/L, the roots of all three plant species were also inhibitedand to a greater extent. The 1000 mg/L concentration greatly
reduced or prevented root growth and suppressed growth of
the hypocotyls.
Maximum concentration at which no effect was observed
within the period of the test: 10 mg/L
Minimum concentration at which effect was observed within
the period of the test: 100 mg/L

5.6.2

Comments:

Study predates GLP regulations. No analysis of test substance.

Reference:

Dagon, T.J. (1975). Vascular Phytotoxicity Report(Unpublished report), Health and Safety Laboratory, Eastman
Kodak Company.

Toxicity to plants (Additional study)
Test substance:

60

Hydroquinone
UNEP Publications

OECD SIDSHYDROQUINONE

Test species:

Corn
Marigold
Lettuce
RadishTest method:

Eastman Kodak Company, Health and Environment
Laboratories Protocol. Ten to twenty seedlings of eachspecies were exposed to a concentration of 10, 100, or 1000
mg/L for 7 days and growth of shoots and roots comparedwith seedlings grown without hydroquinone. Similar toOECD Guideline 208.

GLP:

YES [ ]NO [X]

Test results:

The growth of corn was reduced at 1000 mg/L, but not at
100 mg/L. The leaves were brown and shriveled and root hairs
missing. The growth of marigolds and lettuce were slightly
reduced at 100 mg/L, and severely reduced at 1000 mg/L.
Root growth of radishes was slightly inhibited at 10 mg/L, andthe growth of the entire plant was slightly inhibited at
100 mg/L. Radish growth was severely inhibited at 1000
mg/L.
Maximum concentration at which no effect was observed
within the period of the test: 10 mg/L for Marigold, Lettuce,
and Radish. 100 mg/L for Corn.
Minimum concentration at which effect was observed within
the period of the test: 100 mg/L for Marigold, Lettuce, andRadish. 1000 mg/L for Corn.

5.6.3

Comments:

Study predates GLP regulations. No analysis of test substance.

Reference:

Dagon, T.J. (1975). Vascular Phytotoxicity Report(Unpublished report), Health and Safety Laboratory, Eastman
Kodak Company.

Toxicity to birds
Test substance:

Hydroquinone in water

Test species:

PigeonTest method (e.g., OECD, others): Birds were treated with a single dose of 100, 200, 300,
600, 1000, or 2000 mg/kg by oral gavage and observed for
mortality and clinical signs of toxicity.
GLP:

YES [ ]NO [X]UNEP Publications

61

OECD SIDS
Test results:

HYDROQUINONE
Mortality occurred at 600 mg/kg, but not at 300 mg/kg andbelow. A dose of 300 mg/kg produced emesis. Other
symptoms were "similar to those exhibited in rats".
LD50 = 500 mg/kg
Maximum concentration at which no effect was observed
within the period of the test (semi-chronic or chronic): 200
mg/kg
Minimum concentration at which effect was observed within
the period of the test (semi-chronic or chronic): 300 mg/kg

5.7Comments:

Study predates GLP regulations. No analysis of test solutions.
No description of individual animal clinical signs of toxicity.
No measurement of body weight.

Reference:

Woodard, G.D.L. (1951). The Toxicity, Mechanism of Action,and Metabolism of Hydroquinone. Doctoral dissertation,
George Washington University.

Biological Effects Monitoring (including biomagnification)
Test substance:
Organism or ecosystem studied:
Effects monitored:
Test results:

No Data Available

Chemical analysis:
Comments:

Because hydroquinone is readily biodegraded, it is notexpected to biomagnify.

Reference:
5.8

Biotransformation and kinetics in environmental species
No Data Available

6.

Toxicological Data (oral, dermal and inhalation, as appropriate)*6.1

Acute Toxicity

6.1.1

Acute oral toxicity
Test substance:

62

Hydroquinone in water
UNEP Publications

OECD SIDSHYDROQUINONE

Test species/strain:

Rat/strain not specified
Mouse/strain not specified

Test method :Similar to OECD Guideline 401. Fasted rats and mice (sex not
specified) were treated with a single dose of hydroquinone bygavage, and animals observed for mortality and clinical signsof toxicity over the course of 14 days.

GLP:

YES [ ]NO [X]

Test results:

Convulsions occurred immediately after treatment, but did not
persist.
Discriminating dose (for fixed dose only):
LD50 (rats) = 390 mg/kg
LD50 (mice) = 680 mg/kg

6.1.1

Comments:

Study predates GLP regulations. No analysis of dosing
solutions. No description of clinical signs of toxicity for
individual animals. No body weight measurements.

Reference:

Hodge, H.C., Maynard, E.A., Wilt, Jr., W.G., and Kesel, R.
(1949). Studies of the Acute Toxicity of Hydroquinone(Unpublished report), Division of Pharmacology and
Toxicology, University of Rochester School of Medicine andDentistry.

Acute oral toxicity (Additional study)
Test substance:

Hydroquinone in water, propylene glycol, or glycerin

Test species/strain:

Rat/Priestly
Rat/Sprague-Dawley
Rat/Wistar

Test method :Similar to OECD Guideline 401. Fasted and unfasted rats (sexnot specified) were treated with a single dose of hydroquinone
by gavage, and animals observed for mortality and clinicalsigns of toxicity over the course of 14 days.

GLP:

YES [ ]NO [X]UNEP Publications

63

OECD SIDS

6.1.1

HYDROQUINONE

Test results:

StrainPriestly
Sprague
Sprague
Sprague
Sprague
Wistar
WistarCarrier
Glycerin
Prop Glycol
Water
Glycerin
Prop Glycol
Prop Glycol
Prop Glycol

Condition
Unfasted
Unfasted
Unfasted
Unfasted
FastedUnfasted
FastedLD50
1295 mg/kg
1090 mg/kg
1182 mg/kg
1081 mg/kg
323 mg/kg
731 mg/kg
298 mg/kg

Comments:

Study predates GLP regulations. No analysis of dosing
solutions. No description of clinical signs of toxicity. No bodyweight measurements.

Reference:

Carlson, A.J., and Brewer, N.R. (1953). Toxicity Studies on
Hydroquinone, Proc. Soc. Exper. Biol. Med. 84, 684-688.

Acute oral toxicity (Additional study)
Test substance:

Hydroquinone in water

Test species/strain:

Rat/Osborne-Mendel
Mice/Swiss

Test method :Similar to OECD Guideline 401. Male and female fasted rats
or unfasted mice were treated with a single dose ofhydroquinone by gavage, and animals observed for mortality
and clinical signs of toxicity over the course of 14 days.

GLP:

YES [ ]NO [X]

Test results:

There was a rapid onset of twitching of the eyelids and of themuscles around the head and neck. This progressed to tremorsof "virtually all muscles" and occasionally convulsions.
Respiration was impeded and death occurred within a few
hours. Animals receiving lower doses recovered from tremors
and exhibited no other symptoms.
LD50 = 302 mg/kg (rats); 390 mg/kg (mice)

6.1.2

Comments:

Study predates GLP regulations. No analysis of dosing
solutions. No body weight measurements.

Reference:

Woodard, G.D.L. (1951). The Toxicity, Mechanism of Action,and Metabolism of Hydroquinone. Doctoral dissertation,
George Washington University.

Acute inhalation toxicity
Test substance:

64

UNEP Publications

OECD SIDSHYDROQUINONE

Test species/strain:
Test method:
GLP:

YES [ ]NO [ ]

Test results:

No Data Available
LC50:

Comments:
Reference:
6.1.3

Acute dermal toxicity
Test substance:

Hydroquinone

Test species/strain:

Guinea pig/strain not designatedTest method:

Laboratory of Industrial Medicine Protocol, Eastman Kodak
Company. Similar to OECD Guideline 402. Quantities (0.25,
0.5, or 1.0 g/kg) of hydroquinone were applied topically tothree guinea pigs, one dose level per animal, and theapplication sites wrapped for 24 hours under occlusive patch.
Animals were observed for mortality, weight gain, andirritation for 14 days.

GLP:

YES [ ]NO [X]

Test results:

No mortality occurred and all animals gained weight. Slight tomoderate edema and moderate erythema was observed 24
hours after dosing, but not thereafter.
LD50: > 1 g/kg

Comments:

Results from repeated dose dermal toxicity studies in mice andrats (see Section 6.4) indicated no toxicity or mortality atdoses of 3840 mg/kg in rats and 4800 mg/kg in mice.

Reference:

Toxicity Report (Unpublished report), Laboratory of Industrial
Medicine, Eastman Kodak Company, 1971.

6.2

Corrosiveness/Irritation

6.2.1

Skin Irritation
Test substance:
UNEP Publications

65

OECD SIDSHYDROQUINONE

Test species/strain:
Test method:
GLP:

YES [ ]NO [ ]

Test results:

No Data Available

Comments:

See Section 6.1.3. Slight erythema was observed in guinea
pigs that were exposed for 24 hours. No irritation wasobserved 7 days after treatment.

Reference:
6.2.2

Eye Irritation
Test substance:

Hydroquinone

Test species/strain:

Rabbit/strain not designatedTest method (e.g., OECD, others): Several crystals of hydroquinone powder (no amountprovided) were placed into the right eye of two rabbits. The
treated eye of one animal was washed, while the treated eye ofthe other animal remained unwashed. Irritation was scored at
1, 24, 48 hours, and 14 days after treatment.

6.3

66

GLP:

YES [ ]NO [X]

Test results:

Slight erythema of the palpebra developed after 1 hour in both
washed and unwashed eyes. Erythema of the nictitating
membrane was also evident in the unwashed eye at 1 hour.
By 24 hours, the washed eye appeared normal, but theunwashed eye continued to demonstrate slight erythema of thepalpebra, orbital, and nictitating membranes. Erythema of thenictitating membrane persisted to 48 hours after instillation
but was not observed 14 days after treatment.

Comments:

Study predates GLP regulations.

Reference:

Toxicity Report (Unpublished report), Laboratory of Industrial
Medicine, Eastman Kodak Company, 1971.

Skin sensitisation
Test substance:

Hydroquinone (2% in 0.9% saline for injection and 10% in
distilled water for dermal induction; 5% in distilled water forchallenge)

Test species/strain:

Guinea Pig/strain not specified
UNEP Publications

OECD SIDSHYDROQUINONE

Test method:

Maximization test in compliance with OECD Guideline 406.

GLP:

YES [ ]NO [X]

Test results:

Number of animals with skin reaction at challenge: 7/10
Number of animals with skin reaction in control group atchallenge: Not indicated.

6.3

Comments:

Study not intended to comply with GLP regulations. Reaction
in control animals assumed to be negative.

Reference:

Goodwin, B.F.J., Crevel, R.W.R., and Johnson, A.W. (1981).
A Comparison of Three Guinea-Pig Sensitization Proceduresfor the Detection of 19 Reported Human Contact Sensitizers,
Contact Derm. 7, 248-258.

Skin sensitisation (Additional study)
Test substance:

Hydroquinone (2.5% in 0.9% saline for injection; challengewith 1.0% in saline by intradermal injection and 30% in
distilled water for topical challenge)

Test species/strain:

Guinea Pig/strain not specified

Test method:

Draize pocedure in compliance with OECD Guideline 406.

GLP:

YES [ ]NO [X]

Test results:

Number of animals with skin reaction at challenge: 3/10
Number of animals with skin reaction in control group atchallenge: Not indicated.

*6.4

Comments:

Study not intended to comply with GLP regulations. Reaction
in control animals assumed to be negative.

Reference:

Goodwin, B.F.J., Crevel, R.W.R., and Johnson, A.W. (1981).
A Comparison of Three Guinea-Pig Sensitization Proceduresfor the Detection of 19 Reported Human Contact Sensitizers,
Contact Derm. 7, 248-258.

Repeated dose toxicity
Test substance:

Hydroquinone (>99%)

Test species/strain:

Sprague-Dawley rats
UNEP Publications

67

OECD SIDSHYDROQUINONE

Test method:

According to USEPA TSCA Guideline 40 CFR 798.6050.
Neurohistopathology was conducted on the forebrain,
cerebrum, midbrain, cerebellum, pons, medulla oblongata,cervical spinal cord swelling, lumbar spinal cord swelling,cervical and lumbar dorsal root, dorsal-ventral spinal roots,
sciatic nerve and tibial nerve. The kidneys of the high-doseand control male rats were also processed for histopathology.
Animals received 0, 20, 64, or 200 mg/kg in distilled water by
gavage for 13 weeks (5 days per week).

GLP:

YES [X]NO [ ]

Test results:

No mortality occurred. Tremors and reduced home-cage
activity were observed in mid- and high-dose groups
immediately after dosing with the incidence increased in adose-dependent manner. All treated groups were noted withbrown discolored urine. No differences in body weight or feed
consumption were noted. No differences in brain or kidneyweight were observed. No morphologic lesions associatedwith treatment were observed.

Comments:
Reference:

6.4

68

Bernard, L.G. (1988). Subchronic Oral Toxicity Study ofHydroquinone in Rats Utilizing a Functional-Observational
Battery and Neuropathology to Detect Neurotoxicity(Unpublished report TX-88-78), Eastman Kodak Company.

Repeated dose toxicity (Additional study)
Test substance:

Hydroquinone (>99%) in ethanol

Test species/strain:

Fischer 344 rats
B6C3F1 mice

Test method:

Groups of five rats per sex were treated with 0, 240, 480, 960,
1920, or 3840 mg/kg by dermal application, while mice weretreated with 0, 300, 600, 1200, 2400, or 4800 mg/kg bydermal application. Animals were given 12 doses over 14
days. Animals were observed daily for clinical signs of
toxicity. Body weights were measured on Days 0, 7, and 14.
All procedures were in accordance with the NTP Statement of
Work.

GLP:

YES [ ]NO [X]

Test results:

All animals survived treatment. The body weights of male rats
at the highest dose level were reduced by 6% relative to thecontrols. The body weights of female rats and all mice were
UNEP Publications

OECD SIDSHYDROQUINONE
comparable to controls. There were no clinical signs of
toxicity in either species.

6.4

Comments:

Feed consumption or water consumption were not measured.
Tissues were not evaluated histologically. Study conducted in
1981. Animals were group housed.

Reference:

Toxicology and Carcinogenesis Studies of Hydroquinone in
F344/N Rats and B6C3F1 Mice (Technical report No. 366),
National Toxicology Program, 1989.

Repeated dose toxicity (Additional study)
Test substance:

Hydroquinone (>99%) in corn oil

Test species/strain:

Fischer 344 rats

Test method:

Groups of 10 animals per sex were treated with 0, 25, 50, 100,
200, or 400 mg/kg by gavage for 13 weeks (5 days per week).
Animals were observed twice daily for clinical signs of
toxicity. Body weights were measured weekly. Histologicalexamination performed on tissues from all animals in the 0,200, and 400 mg/kg dose groups. Target tissues (liver,kidneys, and stomach in male rats; and kidneys in female rats)
were examined in the 100 mg/kg dose group. All procedures
were in accordance with the NTP Statement of Work. Similar
to OECD Guideline 408.

GLP:

YES [ ]NO [X]

Test results:

All rats in the 400 mg/kg group and 3/10 female rats in the
200 mg/kg group died on test. Animals at 200 mg/kg were
lethargic after 10 weeks of dosing, and female rats exhibited
tremors and occasional convulsions. No treatment-related
clinical signs of toxicity were observed in other dose groups.
Body weights of male rats given 200 mg/kg were 9% less thanin the control group. All other groups, including the
200 mg/kg female rats, had body weights that werecomparable to the control group. Absolute and relative (tobody weight) liver weights in all treated male groups werelower than in the control group. In female rats, absolute andrelative liver weights were significantly higher in the 50, 100,
and 200 mg/kg group compared with the control group.
Hemorrhage, intra-abdominal bleeding, and gastrointestinal
inflammation were evident at necropsy of animals in the 400
and 200 mg/kg groups.
Inflammation and epithelial
hyperplasia occurred in 4/10 males and 1/10 females at
200 mg/kg, but not in other groups. Toxic nephropathy wasobserved in 7/10 male and 6/10 female rats at 200 mg/kg and1/10 females at 100 mg/kg. The severity ranged from
UNEP Publications

69

OECD SIDSHYDROQUINONE
moderate to marked in males and was less severe in females.
Tubular cell degeneration and regeneration in the cortex was
evident.

6.4

70

Comments:

Feed consumption or water consumption were not measured.
Study conducted in 1981. Animals were group-housed.
Sprague-Dawley rats treated with 200 mg/kg hydroquinone bygavage for 13 weeks did not demonstrate renal toxicity or
unusual lesions in the kidney (see Section 6.8).

Reference:

Toxicology and Carcinogenesis Studies of Hydroquinone in
F344/N Rats and B6C3F1 Mice (Technical report No. 366),
National Toxicology Program, 1989.

Repeated dose toxicity (Additional study)
Test substance:

Hydroquinone (>99%) in corn oil

Test species/strain:

B6C3F1 mice

Test method:

Groups of 10 animals per sex were treated with 0, 25, 50, 100,
200, or 400 mg/kg by gavage for 13 weeks (5 days per week).
Animals were observed twice daily for clinical signs of
toxicity. Body weights were measured weekly. Histologicalexamination performed on tissues from all animals in the 0,200, and 400 mg/kg dose groups. All procedures were inaccordance with the NTP Statement of Work. Similar toOECD Guideline 408.

GLP:

YES [ ]NO [X]

Test results:

Eight male and eight female mice in the 400 mg/kg group, and2/10 male mice in the 200 mg/kg group, died on test. One
death at 200 mg/kg was attributed to gavage error. All treatedmale mice, and all females in the top three dose groups, were
lethargic after dosing. All mice in the 400 mg/kg groupexhibited tremors followed by convulsions. Body weights oftreated mice were comparable to the control group. Absoluteand relative (to body weight) liver weight in all treated malegroups were higher than in the control group. In female mice,
absolute liver weight in the 100 and 400 mg/kg groups, andrelative liver weight in the 200 and 400 mg/kg groups, weresignificantly higher compared with the control group.
Ulceration, inflammation, or epithelial hyperplasia of theforestomach occurred in 3/10 males and 2/10 females at 400
mg/kg, and 1/10 females at 200 mg/kg. No other lesions werenoted.

Comments:

Feed consumption or water consumption were not measured.
Study conducted in 1981. Animals were group-housed.
UNEP Publications

OECD SIDS
Reference:

6.4

HYDROQUINONE
Toxicology and Carcinogenesis Studies of Hydroquinone in
F344/N Rats and B6C3F1 Mice (Technical report No. 366),
National Toxicology Program, 1989.

Repeated dose toxicity (Additional study)
Test substance:

Hydroquinone (>99%) in an oil-in-water emulsion cream

Test species/strain:

Fischer 344 rats

Test method:

Groups of 20 male and female Fischer-344 rats were topicallytreated with 0, 2.0, 3.5, or 5.0% (w/w) of hydroquinone in an
oil-in-water emulsion cream. The formulation of the cream
chosen was representative of commercially available
preparations sold in the United States of America and theEuropean Union. The high concentration of 5.0% was selected
as the highest concentration which could be administeredunder occlusion without exceeding the maximum tolerated
dose or altering the barrier properties of the skin. Preparations
were applied to the shaved skin of the back under semioccluded patch for 6 hr/day, 5 days/week for 13 weeks.
Animals were observed daily for clinical signs of toxicity.
Signs of dermal irritation were scored daily during Weeks 1,
2, 6, 7, 12, and 13 or once per week at other times. Body
weights and feed consumption were measured at least once
weekly. Water consumption was measured three times a weekduring Weeks 1, 2, 6, 7, 12, and 13. After 13 weeks oftreatment, animals were euthanatized and blood collected forclinical pathology. The liver, kidneys, testes/ovaries, brain,lungs, adrenal glands, and thymus were weighed. All tissues
were preserved in fixative. The bone marrow (sternum),kidneys, liver, lymph nodes, spleen, thymus, thyroid gland,skin (application site and control site), Zymbal's gland, andgross lesions from the 5.0% and control groups, and grosslesions from all groups were examined microscopically.
Similar to OECD Guideline 411.

GLP:

YES [X]NO [ ]

Test results:

One animal died on the first day of dosing apparently because
the wrappings were too tight. All other animals survived totheir scheduled times of necropsy. Hydroquinone exposure
was associated with increased incidence of scaly skin, ageneral brown discoloration of the skin (primarily in malerats), and brown spots at the application site. These conditions
were observed in control and hydroquinone-treated groups
suggesting that they were related to the treatment procedures
such as repeated shaving or the use of a semi-occlusive patch.
Erythema at the application site was also observed primarily
UNEP Publications

71

OECD SIDSHYDROQUINONE
in the hydroquinone-treated groups, but irritation was notobserved after 2 days of recovery. No significant differences
in body weight were noted among groups. Feed consumption
by the 3.5 and 5.0% male rats on Day 4 were significantly(p ≤ 0.05) lower than by the control group, but no differenceswere noted among female groups. Water consumption bytreated rats was generally within 10% of consumption bycontrol rats. No ophthalmic lesions were noted at the end of
the study. After 13 weeks of treatment, animals wereeuthanatized and blood collected for clinical pathology. No
biologically significant changes occurred in hematology or red
blood cell morphology. Changes in serum chemistries among
male groups were not considered to be biologicallymeaningful, and no changes in serum chemistries were notedamong female groups. No differences in absolute or relative
organ weight were noted. No hydroquinone-related gross or
microscopic lesions were noted. Based on these results,dermal application of 5.0% hydroquinone in a oil-in-water
emulsion cream (73.9 mg/kg/day in males and 109.6
mg/kg/day in females) under occlusion produced onlytransient minor irritation of the skin. Based on erythema in allhydroquinone-treated groups, a no-observable-effect level(NOEL) could not be determined. Based on the lack ofadverse systemic effects or histopathology, the no-observableadverse-effect level (NOAEL) was 5.0% hydroquinone.

*6.5
72

Comments:

At the beginning of Weeks 3, 6, and 13, an additional fiveanimals per sex per group were used for cell proliferation in
the kidneys. Osmotic pumps filled with bromodeoxyuridine(BrdU) were implanted 3 days prior to necropsy. On the third
day post-implantation, animals were placed into metabolism
cages to collect urine for analysis. No biologically significant
changes were observed in the urine of treated rats. On the
fourth day post-implantation, the animals were euthanatizedand the kidneys and a section of small intestine were removed
for histology and staining with BrdU antibody. One kidneyfrom each animal was evaluated for cell proliferation.
Evaluation of cell proliferation indicated only a modest,
transient increase in replication of P1 cells of 5.0% male rats
at 3 Weeks, but not thereafter, and an increase in distal tubule
cell (other cells) replication in female 3.5 and 5.0% rats at 13
Weeks.
These increases were not considered to bebiologically significant.

Reference:David, R. (1994). NDMA High HQ Formulation Cream: A
Thirteen-Week Dermal Toxicity and Cell Proliferation Studyin the Rat (unpublised report), Nonpresciption Drug
Manufacturers Association.

Genetic Toxicity
UNEP Publications

OECD SIDS
6.5.1

HYDROQUINONE

Bacterial test
Test substance:

Hydroquinone in DMSO

Test species/strain:

Salmonella typhimurium/TA-98, TA-100, TA-1535, and TA1537

Test method:

Bacteria/test substance mixtures were incubated with a 30%
concentration of S-9 from rats or hamsters treated with
Aroclor 1254. Similar to OECD Guideline 471.

GLP:

YES [ ]NO [X]

Test results:
Minimum concentration of test substance at which toxicity tobacteria was observed:
with metabolic activation:>666 Τg/plate
without metabolic activation: 333 Τg/plate
Concentration of the test compound resulting in precipitation:
NA
Genotoxic effects:+ ? with metabolic activation:[ ] [ ] [X]without metabolic activation: [ ] [ ] [X]Comments:

Conducted under Government contract. Not under GLP
regulations. Additional studies listed in the attachedbibliography.

Reference:

Haworth, S., Lawlor, T., Mortelmans, K., Speck, W., andZeiger, E. (1983). Salmonella Mutagenicity Test Results For
250 Chemicals, Environ. Mut. Suppl. 1, 3-142.

ADDITIONAL REFERENCES
Section 6.5.1 Bacterial Tests
Cotruvo, J., Simmon, V., and Spanggord, R. (1977). Investigation of mutagenic effects ofproducts of ozonation research in water. Ann. N. Y. Acad. Sci. 298, 124-140.
Epler, J. L., Larimer, F. W., Rao, T. K., Nix, C. E., and Ho, T. (1978). Energy-related
pollutants in the environment: Use of short-term tests for mutagenicity in the isolation andidentification of biohazards. Environ. Health Perspect. 27, 11-20.
Florin, I., Rutberg, L., Curvall, M., and Enzell, C. R. (1980). Screening of tobacco smoke
constituents for mutagenicity using the Ames' test. Toxicology 18, 219-232.
UNEP Publications

73

OECD SIDSHYDROQUINONE

Gocke, E., King, M-T., Eckardt, K., and Wild, D. (1981). Mutagenicity of cosmetics
ingredients licensed by the European community. Mutat. Res. 90, 91-109.
Koike, N., Haga, S., Ubukata, N., Sakurai, M., Shimizu, H., and Sato, A. (1988).
Mutagenicity of benzene metabolites by fluctuation test. Jpn. J. Ind. Health 30, 475-480.
Rapson, W. H., Nazar, M. A., and Butsky, V. V. (1980). Mutagenicity produced byaqueous chlorination of organic compounds. Bull. Environ. Contam. Toxicol. 24, 590-596.
Sakai, M., Yoshida, D., and Mizusaki, S. (1985). Mutagenicity of polycyclic aromatichydrocarbons and quinones on salmonella typhimurium TA97. Mutat. Res. 156, 61-67.
6.5.2

Non-bacterial in vitro test
Test substance:

Hydroquinone in DMSOType of cell used:

Chinese Hamster Ovary

Test method (e.g., OECD, others): Populations of 50-100 cells were incubated inconcentrations of 0, 5, 7.5, 10, or 20 Τg/ml for 10.5 hours in
the absence of S9 and the cells arrested in metaphase withcolcemid. Cells (100) were also incubated in concentrationsof 0, 150, 450, or 600 Τg/ml for 10.5 hours in the presence of
S9 and the cells arrested in metaphase with colcemid. The
cells were stained and the number of chromosomal aberrations
counted. Similar to OECD Guideline 403.
GLP:

YES [ ]NO [X]

Test results:
Lowest Concentration producing cell toxicity: Not determinedwith metabolic activation:
without metabolic activation:

µg/mL
µg/mL

Genotoxic effects:
with metabolic activation:
without metabolic activation:74+ ? [X] [ ] [ ][ ] [ ] [X]Comments:

Conducted under Government contract. Not under GLP
regulations. Additional studies listed in the attachedbibliography.

Reference:

Galloway, S.M., Armstrong, M.J., Reuben, C., Colman, S.,
Brown, B., Cannon, C., Bloom, A.D., Nakamura, F., Ahmed,
M., Duk, S., Rimpo, J., Margolin, B.H., Resnick, M.A.,
Anderson, B., Zeiger, E. (1987). Chromosome Aberrations
and Sister Chromatid Exchanges in Chinese Hamster Ovary
UNEP Publications

OECD SIDSHYDROQUINONE
Cells: Evaluations of 108 Chemicals, Environ. Mol. Mutagen.
10(Suppl), 1-175.

ADDITIONAL REFERENCES
Section 6.5.2 Non-bacterial in vitro Tests
Ciranni, R., and Adler, I. (1991). Clastogenic effects of hydroquinone:
chromosomal aberrations in mouse germ cells. Mutat. Res. 263, 223-229.

induction of

Erexson, G. L., Wilmer, J. L., and Kligerman, A. D. (1985). Sister chromatid exchange
induction in human lymphocytes exposed to benzene and its metabolites in vitro. Cancer
Res. 45, 2471-2477.
Gocke, E., Wild, D., Eckhardt, K., and King, M.-D. (1983). Mutagenicity studies with themouse spot test. Mutat. Res. 117, 201-212.
Knadle, S. (1985). Synergistic interaction between hydroquinone and acetaldehyde in the
induction of sister chromatid exchange in human lymphocytes in vitro. Cancer Res. 45,
4853-4857.
McGregor, D. B., Brown, A., Cattanach, P., Edwards, I., McBride, D., and Caspary, W. J.
(1988). Responses of the L5178Y tk+/tk- mouse lymphoma cell forward mutation assay.
II: 18 coded chemicals. Environ. Mol. Mutagen. 11, 91-118.
McGregor, D. B., Riach, C. G., Brown, A., Edwards, I., Reynolds, D., West, K., andWillington, S. (1988). Reactivity of catecholamines and related substances in the mouse
lymphoma L5178Y cell assay for mutagens. Environ. Mol. Mutagen. 11, 523-544.
Miller, B. M., and Adler, I.-D. (1992). Aneuploidy induction in mouse spermatocytes.
Mutagenesis 7, 69-76.
Morimoto, K., and Koizumi, A. (1978). Inhibition of rejoining of radiation-induced
chromosome lesions and induction of sister chromatid exchanges - effects of benzene or its
metabolites in cultured human leukocytes. Jpn. J. Human Gen. 23, 279-281.
Morimoto, K., and Wolff, S. (1980). Increase of sister chromatid exchanges andperturbations of cell division kinetics in human lymphocytes by benzene metabolites.
Cancer Res. 40, 1189-1193.
Morimoto, K., Wolff, S., and Koizumi, A. (1983). Induction of sister-chromatid exchanges
in human lymphocytes by microsomal activation of benzene metabolites. Mutat. Res. 119,355-360.
Painter, R. B., and Howard, R. (1982). The HeLa DNA-synthesis inhibition test as a rapid
screen for mutagenic carcinogens. Mutat. Res. 92, 427-437.
Parmentier, R. (1953). Production of 'three-group metaphases' in the bone-marrow of thegolden hamster. Nature 171, 1029-1030.

UNEP Publications

75

OECD SIDSHYDROQUINONE

Parmentier, R., and Dustin, P. (1948). Early effects of hydroquinone on mitosis. Nature
171, 527-528.
Parry, J.M., Parry, E.M., Warr, T., Lynch, A., and James, S. (1990). The detection of
aneugens using yeast and cultured mammalian cells. Mutation and the Environment, Part
B, Wiley-Liss, New York, 247-266.
Pellack-Walker, P., and Blumer, J. L. (1986). DNA damage in L5178YS cells following
exposure to benzene metabolites. Mol. Pharmacol. 30, 42-47.
Pellack-Walker, P., Walker, J. K., Evans, H. H., and Blumer, J. L. (1985). Relationshipbetween oxidation potential of benzene metabolites and their inhibitory effect on DNA
synthesis in L5178YS cells. Mol. Pharmacol. 28, 560-566.
6.5.3

Non-bacterial test in vivo
Test substance:

Hydroquinone in water

Test species/strain:

CD-1 mice

Test method (e.g., OECD, others): Animals (3 per group) were given a single dose of 0,40, 60, or 80 mg/kg by intraperitoneal injection andeuthanatized 18 hours after injection. Bone marrow wascollected and 3000 polychromatic cells scored from eachanimal. Similar to OECD Guideline 474.
GLP:

YES [ ]NO [X]

Test results:
Lowest dose producing toxicity: Not determined
Effect on Mitotic Index or P/N Ratio:
Dose
0
40
60
80

P/N Ratio
0.938
0.903
0.983
0.961

Genotoxic effects+ ? [X] [ ] [ ]76Comments:

Study not intended to comply with GLP regulations.
Additional studies listed in the attached bibliography.

Reference:

Barale, R., Marrazzini, A., Betti, C., Vangelisti, V., Loprieno,
N., and Barrai, I. (1990). Genotoxicity of Two Metabolites of
UNEP Publications

OECD SIDSHYDROQUINONE
Benzene: Phenol and Hydroquinone Show Strong Synergistic
Effects In Vivo, Mutat. Res. 244, 15-20.

6.5.3

Non-bacterial test in vivo (Additional study)
Test substance:

Hydroquinone in water

Test species/strain:

CD-1 mice

Test method (e.g., OECD, others): Animals (4 per group) were given a single dose of 80
mg/kg by oral gavage and euthanatized 0-48 hours after
treatment.
Bone marrow was collected and 3000
polychromatic cells scored from each animal. Similar toOECD Guideline 474.
GLP:

YES [ ]NO [X]

Test results:
Lowest dose producing toxicity: toxicity was observed at thisdose.
Effect on Mitotic Index or P/N Ratio:
HarvestTime (hrs)
0
18
24
42
48

Micronuclei
< 2%
~ 4%
~ 2%
~ 4%
~ 4%

P/N Ratio
> 1.2
> 1.2
>1.2
0.6
> 1.2

Genotoxic effects+ ? [ ] [X] [ ]Comments:

Study not intended to comply with GLP regulations.
Additional studies listed in the attached bibliography.

Reference:

Ciranni, R., Barale, R., Ghelardini, G., and Loprieno, N.
(1988). Benzene and the genotoxicity of its metabolites. II.
The effect of the route of administration on the micronuclei
and bone marrow depression in mouse bone marrow cells.
Mutat. Res. 209, 23-28.

ADDITIONAL REFERENCES
Section 6.5.3 Non-bacterial Tests in vivo

UNEP Publications

77

OECD SIDSHYDROQUINONE

Adler, I.-D. and Kliesch, U. (1990). Comparison of single and multiple treatment regimens
in the mouse bone marrow micronucleus assay for hydroquinone (HQ) andcyclophosphamide (CP). Mutat. Res. 234, 115-123.
Barale, R., Ciranni, R., Casini, D., and Loprieno, N. (1987). Clastogenic activity ofbenzene and its metabolites in mice. Mutat. Res. 181, 322.
Barale, R., Marrazzini, A., Betti, C., Vangelisti, V., Loprieno, N., and Barrai, I. (1990).
Genotoxicity of two metabolites of benzene: phenol and hydroquinone show strong
synergistic effects in vivo. Mutat. Res. 244, 15-20.
Chatterjee, P., and Sharma, A. (1972). Effect of phenols on nuclear division in Chara
zeylanica. The Nucleus 15, 214-218.
Ciranni, R., Barale, R., Marrazzini, A., and Loprieno, N. (1988). Benzene and the
genotoxicity of its metabolites. I. Transplacental activity in mouse fetuses and in theirdams. Mutat. Res. 208, 61-67.
Gad-El-Karim, M. M., Ramanujam, V. S., and Legator, M. (1986). Correlation between
the induction of micronuclei in bone marrow by benzene exposure and the excretion of
metabolites in urine of CD-1 mice. Toxicol. Appl. Pharmacol. 85, 464-477.
Gad-El-Karim, M. M., Ramanujam, V. S., Ahmed, A. E., and Legator, M. S. (1985).
Benzene myeloclastogenicity: a function of its metabolism. Am. J. Ind. Med. 7, 475-484.
Gad-El-Karim, M. M., Ramanujam, V. S., and Legator, M. S. (1986). Correlation between
the induction of micronuclei in bone marrow by benzene exposure and the excretion of
metabolites in urine of CD-1 mice. Toxicol. Appl. Pharmacol. 85, 464-477.
Marrazzini, A., Betti, C., Barale, R., Bernacchi, F., and Loprieno, N. (1991). Cytogenetic
effects of possible aneuploidizing agents. Mutat. Res. 252, 195-196.
Shimada, H., Sato, T., and Takayama, S. (1988). Induction of micronuclei by benzene andits metabolites. Tokyo: Research Institute of Daiichi Seiyaku Co., Ltd.
Tunek, A., Hogstedt, B., and Olofsson, T. (1982). Mechanism of benzene toxicity, effectsof benzene and benzene metabolites on bone marrow cellularity, number of granulopoietic
stem cells and frequency of micronuclei in mice. Chemical-Biological Interactions 39,
129-138.
Tunek, A., Olofsson, T., and Berlin, M. (1981). Toxic effects of benzene and benzene
metabolites on granulopoietic stem cells and bone marrow cellularity in mice. Toxicol.
Appl. Pharmacol. 59, 149-156.
Xu, W., and Adler, I. (1990). Clastogenic effects of known and suspected spindle poisonsstudied by chromosome analysis in mouse bone marrow cells. Mutagenesis 5, 371-374.
Xu, W., Miller, B., Kliesch, U., and Adler, I. (1989). Spindle inhibition and chromosomal
breakage in mouse bone marrow by econazole (EZ) and hydroquinone (HQ). Mutat. Res.
216, 305.
78

UNEP Publications

OECD SIDS
6.6

HYDROQUINONE

Carcinogenicity
Test substance:

Hydroquinone

Test species/strain:

Sprague-Dawley Rats

Test method (e.g., OECD, others): Groups of 20 rats per group were treated with 0, 0.1,
0.5, and 1.0% hydroquinone in a synthetic diet of skim milk,lard, whole wheat, and salt for 103 weeks. Diets wereprepared weekly. Body weights were measured periodically.
Hematology was conducted at termination.
Histologic
examinations of the liver, omentum, kidney, spleen, heart,
lung, bone marrow, stomach wall, pancreas, adrenal,
subperitoneal and intramuscular abdominal fat were
performed after 103 weeks.

6.6

GLP:

YES [ ]NO [X]

Test results:

No treatment-related changes in hematology were observed.
Survival was not impacted by treatment. No differences interminal body weight were observed. However, body weightsof mid- and high-dose rats were lower than body weights ofthe controls during the first 4 weeks on test. Histopathology
indicated "atrophy of the liver cord cells, lymphoid tissue ofthe spleen, adipose tissue, and striated muscle together withsuperficial ulceration and hemmorrhage of the stomachmucosa".

Comments:

Feed consumption or water consumption were not measured.
Animals were not observed for clinical observations. No
analysis of the test substance in the diet. Non-standard dietused.

Reference:

Carlson, A.J., and Brewer, N.R. (1953). Toxicity Studies on
Hydroquinone, Proc. Soc. Exper. Biol. Med. 84, 684-688.

Carcinogenicity (Additional study)
Test substance:

Hydroquinone in deionized water

Test species/strain:

Fischer 344 Rats
B6C3F1 Mice

Test method (e.g., OECD, others): Groups of 65 rats per sex were treated with 0, 25, 50
mg/kg for 103 weeks (5 days per week). Groups of 64-65
mice per sex were treated with 0, 50, 100 mg/kg for 103
weeks (5 days per week). Animals were observed twice daily
for clinical signs of toxicity. Body weights were measured
weekly for the first 13 weeks, and monthly thereafter.
Hematology and clinical chemistry was conducted after 15months on test. Histologic examinations of all tissues of rats,and high-dose and control mice, were performed after 104
UNEP Publications

79

OECD SIDSHYDROQUINONE
weeks. All procedures in accordance with the NTP Statementof Work. Similar to OECD Guideline 451.

GLP:

YES [X]NO [ ]

Test results:

No compound-related clinical signs of toxicity and notreatment-related changes in clinical pathology were observed.
Survival was not impacted by treatment.
The body weights of treated male rats were significantly (912%) lower than body weights of the controls. Body weights
of female rats were comparable. Relative (to body weight)
brain, kidney, and liver weights in the 50 mg/kg male groupwere significantly higher than in the control group. Relative
brain weight in the 25 mg/kg male group was alsosignificantly higher. No differences were evident among thefemale groups. Treatment-related lesions occurred in thekidneys with a significant increase in the severity of
spontaneous nephropathy in high-dose male rats. In addition,
a dose-related increase in animals with single renal tubular
adenomas occurred in the low- and high-dose male groups.
Other lesions in male rats were not considered toxicologicallysignificant or treatment-related. In females, a dose-related
increase in the incidence of mononuclear leukemia was noted.
This lesion was considered to be the proximate cause of deathin many treated female rats.
The body weights of treated male mice were 4-6% lower thanbody weights of the controls, and body weights of treatedfemale mice were 3-13% lower than controls. No significant
differences in body weight were noted. Relative liver weights
of high-dose male and female mice, and low-dose male mice,
were significantly higher than in the control group.
Treatment-related increases in non-neoplastic lesions(anisokaryosis, syncytial alteration, and basophilic focus) of
the liver occurred in male mice. In female mice, there was atreatment-related increase in the incidence of hepatocellularadenomas. Both male and female treated mice had anincreased incidence of follicular cell hyperplasia of the thyroid
gland, although the effect was not dose-related. All otherlesions were not considered to be treatment-related.

6.6

Comments:

Feed consumption or water consumption were not measured.
Animals were group-housed.

Reference:

Toxicology and Carcinogenesis Studies of Hydroquinone in
F344/N Rats and B6C3F1 Mice (Technical report No. 366),
National Toxicology Program, 1989.

Carcinogenicity (Additional study)
Test substance:

80

Hydroquinone (0.8% in the diet)
UNEP Publications

OECD SIDS
Test species/strain:

HYDROQUINONE
Fischer 344 Rats
B6C3F1 Mice

Test method (e.g., OECD, others): Groups of 30 rats per sex were treated with 0.8%hydroquinone in the diet for 103 weeks. Groups of 30 mice
per sex were treated with the same diet 96 weeks. Animals
were observed twice daily for clinical signs of toxicity. Body
weights were measured weekly for the first 13 weeks, andmonthly thereafter. Feed and water consumption were
measured for two days prior to each weighing. The liver andkidneys were weighed at necropsy. Histologic examinationsof all tissues were performed after 104 weeks. Similar toOECD Guideline 451.
GLP:

YES [ ]NO [X]

Test results:

No compound-related clinical signs of toxicity. Survival was
not impacted by treatment.
Body weight gains of treated rats and male mice weresignificantly lower than of the controls. However, only
terminal body weights of female mice and female rats weresignificantly lower than of the control groups. Feed and water
consumption of treated groups were comparable to the control
groups. Absolute and relative (to body weight) liver andkidney weights in treated male rats were significantly higher
than in the control group. Relative liver and kidney weights offemale treated mice, and relative kidney weights of female
rats, were also significantly higher than in the control groups.
Chronic nephropathy occurred in treated rats with a significant
increase in the severity compared with control rats. In
addition, treated male rats had significantly increased
incidences of tubular adenomas, tubular hyperplasia, andepithelial hyperplasia of the renal papilla. The hyperplasia of
the renal papilla was considered to be reflective of the chronic
nephropathy. Other lesions in male rats were not considered
toxicologically significant or treatment-related. No changes in
the forestomach were noted.
In mice, a treatment-related increase in renal tubular
hyperplasia was noted in treated males compared with
controls. Centrilobular hypertrophy of the hepatocytes wasobserved in treated male mice, and there was an increased
incidence of hepatocellular adenomas and foci of cellularalteration, but not hepatocellular carcinoma. An increase in
the incidence of hyperplasia of the forestomach was observedin both male and female treated mice compared with control
mice.

Comments:

Animals were group-housed.
UNEP Publications

81

OECD SIDS
Reference:

HYDROQUINONE
Shibata, M.A., Hirose, M., Tanaka, H., Asakawa, E., Shirai,
T., and Ito, N. (1991). Induction of Renal Cell Tumors in Rats
and Mice, and Enhancement of Hepatocellular Tumor
Development in Mice after Long-term Hydroquinone
Treatment, Jpn. J. Cancer Res. 82, 1211-1219.

ADDITIONAL REFERENCES INTO MECHANISMS OF CELLULAR EVENTS
Reddy, M. V., Bleicher, W. T., Blackburn, G. R., and Mackerer, C. R. (1990). DNA
adduction by phenol, hydroquinone, or benzoquinone in vitro but not in vivo: nuclease P1enhanced 32P-postlabeling of adducts as labeled nucleoside biphosphates, dinucleotides andnucleoside monophosphate. Carcinogenesis 11, 1349-1357.
Boatman, R.J., English, J.C., Perry, L.G., and Bialecki, V.E. (1992). Indicators ofnephrotoxicity for hydroquinone and for 2-(glutathion-S-yl)hydroquinone in Fischer-344
and Sprague-Dawley rats and in B6C3F1 mice (Unpublished report), Health andEnvironment Laboratories, Eastman Kodak Company.
English, J.C., Hill T., O'Donoghue, J.L., and Reddy, M.V. (1994). Measurement of
nuclear DNA modification by 32P-postlabeling in the kidneys of male and female Fischer
344 rats after multiple gavage doses of hydroquinone, Fundam. Appl. Toxicol. 23, 391396.
English, J.C., Perry, L.G., Vlaovic, M., Moyer, C., and O'Donoghue, J.L. (1994).
Measurement of cell proliferation in the kidneys of Fischer 344 and Sprague-Dawley rats
after gavage adminstration of hydroquinone, Fundam. Appl. Toxicol. 23, 397-406.
*6.7

Reproductive and Developmental toxicity

6.7.1

Reproductive toxicity
Test substance:

Hydroquinone (99%) in distilled water

Test species/strain:

Sprague-Dawley Rats

Test method (e.g., OECD, others): OECD Guideline 416. Animals treated with 0, 15, 50,
or 150 mg/kg/day by gavage.
GLP:

YES [X]NO [ ]

Test results:

NOEL for P generation = 15 mg/kg/day
NOEL for F1 generation = 150 mg/kg/day
NOEL for F2 generation = 150 mg/kg/day
Maternal and Paternal general toxicity: At the 15 and 50
mg/kg/day dose levels, no adverse effects of treatment were
evident from mortality, body weight, or feed consumption
data. Tremors were observed in one male at 50 mg/kg/day,and in several males and females in the 150 mg/kg dosegroups.

82

UNEP Publications

OECD SIDSHYDROQUINONE
Reproductive toxicity observed in parental animals (fertility,
gestation, reproductive organ toxicity, etc.): No adverse
effects were seen in body weight, sex distribution, survival, or
gross pathology of pups delivered.
Reproductive toxicity observed in offspring (weights of litter,postnatal growth, viability, etc.): No adverse effects wereseen in body weight, sex distribution, survival, or grosspathology of pups delivered.

Comments:
Reference:

6.7.2

Schroeder, R.E. (1989). A Two-Generation Reproduction
Study in Rats with Hydroquinone (Unpublished report),
Eastman Kodak Internal Report TX-90-13, Bio-dynamics Inc.,
East Millstone, NJ.

Teratogenicity/Developmental toxicity
Test substance:

Hydroquinone (99%) in distilled water

Test species/strain:

Sprague-Dawley Rats

Test method (e.g., OECD, others): OECD Guideline 414. Animals treated with 0, 30, 100,or 300 mg/kg/day by gavage.
GLP:

YES [X]NO [ ]

Test results:

Body weights and feed consumption were significantly
reduced in dams receiving 300 mg/kg. No other toxicity wasobserved. Reproductive indices were comparable in allgroups. A few spontaneous soft-tissue and skeletal
malformations were observed in all dose groups and were notconsidered to be treatment-related. Fetal body weights in the
300 mg/kg dose group were slightly reduced compared withthe control group, but this was correlated to the reduced
maternal weight gain.
NOEL for maternal animals = 100 mg/kg
NOEL for offspring = 300 mg/kg

Comments:
Reference:

6.7.2

Krasavage, W.J., Blacker, A.M., English, J.C., and Murphy,
S.J. (1992). Hydroquinone: A Developmental Toxicity Studyin Rats, Fundam. Appl. Toxicol. 18, 370-375.

Teratogenicity/Developmental toxicity (Additional study)
Test substance:

Hydroquinone (99%) in distilled water
UNEP Publications

83

OECD SIDS
Test species/strain:

HYDROQUINONE
New Zealand White Rabbits

Test method (e.g., OECD, others): OECD Guideline 414. Animals treated with 0, 25, 75,
or 150 mg/kg/day by gavage.
GLP:

YES [X]NO [ ]

Test results:

No mortality occurred. Pregnancy rates were 15/18 in thecontrol group, 18/18 in the low-dose group, 18/18 in the middose group, and 17/18 in the high-dose group. No spontaneousabortions were observed, and the incidence of early delivery(Day 26 and Day 30) was comparable in all groups. No
maternal
toxicity,
embryotoxicity,
fetotoxicity,orteratogenicity was observed at 25 or 75 mg/kg. At 150 mg/kg,
maternal toxicity was evident as lower body weight and feed
consumption. No clinical signs of toxicity were noted. A few
soft-tissue and skeletal abnormalities were noted in the highdose group, but these were not significantly different from thecontrol group and were considered to reflect maternal toxicity.
NOEL for maternal animals = 25 mg/kg
NOEL for offspring = 75 mg/kg

Comments:
Reference:

6.8

84

Murphy, S.J., Schroeder, R.E., Blacker, A.M., Krasavage,
W.J., and English, J.C. (1992). A Study of Developmental
Toxicity of Hydroquinone in Rabbits, Fundam. Appl. Toxicol.
19, 214-221.

Specific toxicities (Neurotoxicity)
Test substance:

Hydroquinone (>99%)

Test species/strain:

Sprague-Dawley rats

Test method:

According to USEPA TSCA Guideline 40 CFR 798.6050.
Neurohistopathology was conducted on the forebrain,
cerebrum, midbrain, cerebellum, pons, medulla oblongata,cervical spinal cord swelling, lumbar spinal cord swelling,cervical and lumbar dorsal root, dorsal-ventral spinal roots,
sciatic nerve and tibial nreve. Animals received 0, 20, 64, or
200 mg/kg in distilled water by gavage for 13 weeks (5 days
per week).

GLP:

YES [X]NO [ ]UNEP Publications

OECD SIDS
Test results:

HYDROQUINONE
No mortality occurred. Tremors and reduced home-cage
activity were observed in mid- and high-dose groups
immediately after dosing with the incidence increased in adose-dependent manner. All treated groups were noted withbrown discolored urine. No differences in body weight or feed
consumption were noted. No differences in brain or kidneyweight were observed. No morphologic lesions associatedwith treatment were observed.

Comments:
Reference:

6.9

Bernard, L.G. (1988). Subchronic Oral Toxicity Study ofHydroquinone in Rats Utilizing a Functional-Observational
Battery and Neuropathology to Detect Neurotoxicity(Unpublished report TX-88-78), Eastman Kodak Company.

Toxicodynamics, toxico-kinetics
Test substance:

Hydroquinone (97% radiochemical purity)

Test species/strain:

Sprague-Dawley Rats

Test method:

Male rats were divided into groups of 4 animals per group andreceived: 14C-Hydroquinone in a single oral dose of 5, 30, or
200 mg/kg; and 200 mg/kg unlabeled hydroquinone for 4 days
by gavage followed by a single dose of 200 mg/kg dose 14CHydroquinone. In order to identify metabolites, animals were
given hydroquinone in the the feed (5.6%) for 2 days, whileother animals were given 311 mg/kg 14C-Hydroquinone bygavage. The urine from these animals was collected, pooled
and analyzed for metabolites.

GLP:

YES [ ]NO [X]

Test results:

With 97-102% of the total radioactivity accounted for, theprimary route of elimination is the urine (92-99%) with 87%
of the total radioactivity recovered being excreted in the first
24 hours. The feces contained 2-4% of the total radioactivity
recovered. Less than 1% of the dose was expired as CO2 andless than 2% remained in the carcass after 96 hours. The dose
administered did not influence the excretion pattern ofradioactivity.
Tissues
concentrationsofremainingradioactivity in the carcass were highest the liver and kidneys,
with all other organs having comparable levels. The
distribution did not change with repeated dosing.
Analysis of urine for metabolites indicated that 1% of theradioactivity was excreted as unchanged hydroquinone. The
majority of the radioactivity was identified as a glucuronide
conjugate with a smaller portion as a sulfate conjugate.
UNEP Publications

85

OECD SIDSHYDROQUINONE
However, the relative amounts of each conjugate weredifferent after single and repeated dosing. After repeateddosing, 72% of the radioactivity was glucuronide and 23%
sulfate conjugate, while after a single dose 56% was
glucuronide and 43% sulfate conjugate. No differences in themetabolite pattern was observed in animals treated by gavage
or as dietary admix.

6.9

Comments:

Study predates GLP regulations. Additional studies listed in
the attached bibliography.

Reference:

DiVincenzo, G., Hamilton, M., Reynolds, R., and Ziegler, D.
(1984). Metabolic Fate and Disposition of [14C]Hydroquinone
Given Orally to Sprague-Dawley Rats, Toxicology 33, 9-18.

Toxicodynamics, toxico-kinetics (Additional study)
Test substance:

Hydroquinone (99.6%)

Test species/strain:

Male Fischer 344 Rats

Test method:

Groups of 4 rats per group were treated with 50 mg/kg ofhydroquinone by gavage (i.g.), intravenous injection (i.v.), or
intratracheal (i.t.) instillation and blood collected for up to 8
hours through an indwelling catheter. Other animals weretreated and euthanatized at 10 min, 20 min, 40 min, 1 hr, 2 hr,
and 4 hr after treatment and the levels of radioactivity in thetissues determined.

GLP:

YES [X]NO [ ]

Test results:

Absorption was rapid after i.g. administration with a t½ valueof approximately 1 min. Distribution of radioactivity was
similar for all three routes of administration. The ϑt½ was 22,
19, and 15 min for i.t., i.v., and i.g. treatment, respectively.
Elimination was also rapid with Κt½ values of 626, 326, and425 min for i.t., i.v., and i..g., respectively. Radioactivity inthe blood was associated initially with the plasma, but theselevels decline rapidly in the first 60 min. By 4 hours, 64% of
the radioactivity is associated with the red blood cells.
Analysis of plasma indicates rapid metabolism ofhydroquinone. Only 1% of the total radioactivity in the plasma
ultrafiltrate was unaltered hydroquinone. Glucuronide andglutathione conjugates of hydroquinone were detected 40 min
after i.g. administration. A fourth material was also detected
but not identified.

Comments:
86

Additional studies listed in the attached bibliography.
UNEP Publications

OECD SIDS
Reference:

6.9

HYDROQUINONE
Fox, J.A., English, J.C., and Lockhart, Jr., H.B. (1986). Blood
Elimination Kinetics of [U-14C]Hydroquinone Administeredby Intragastric Intubation, Intratracheal Instillation or
Intravenous Injection to Male Fischer 344 Rats (Unpublishedreport TX-86-1), Eastman Kodak Company.

Toxicodynamics, toxico-kinetics (Additional study)
Test substance:

Hydroquinone (99.6%)

Test species/strain:

Fischer 344 Rats

Test method:

OECD Guideline 417. Groups of animals received 14CHydroquinone in a single oral dose of 350 or 25 mg/kg; after
14 repeated doses of unlabelled 25 mg/kg/day; and as a single
dermal application (24 hour occlusive exposure) of 150 or 25
mg/kg. Urine and feces were collected for 7 days and plasma
concentrations determined for 96 hours. Tissue levels were
determined 48 and 72 hours after the single oral dose, 48
hours the repeated doses, and 168 hours after the dermal dose.

GLP:

YES [X]NO [ ]

Test results:

After oral administration, the blood concentrations indicatedrapid absorption (14-19 min after single 25 mg/kg dose; 10-14
after repeated 25 mg/kg doses; 34-48 min after single 350
mg/kg dose) followed by a biphasic elimination phase. The
Ιt½ ranged from 0.2 - 1.7 hours. The ϑt½ for the low dose
ranged from 2.8 - 10.5 hours and could not be estimated forthe high dose. Blood concentrations after dermal application
were generally below the limit of detection.
Elimination of radioactivity occurred within the first 8 hours
after oral administration primarily in the urine (92-97% after adose of 25 mg/kg, and 87% after 350 mg/kg dose).
Approximately 1.3-2.0% was excreted in the feces. No
differences between the excretion from males or females wereobserved. Less than 1% remained in the tissues. The liverand kidneys contained the highest concentrations with females
generally having higher concentrations than males.
Approximately 61-71% of the dermal dose was recoveredfrom the application site immediately after dosing. After 168
hours, the skin at the application site contained 0.14-2.2% of
the total radioactivity. Only 15-18% of the total radioactivity
was recovered in the urine with 1.7-3.7% in the feces.
Approximately 2.6 - 12.9% of the total radioactivity was
associated with the tissues and carcass.

UNEP Publications

87

OECD SIDSHYDROQUINONE
Urinary metabolites were separated by HPLC and identified.
Approximately 45-53% of the excreta from an oral dose was
the glucuronide conjugate of hydroquinone, and 19-33% was
the sulfate conjugate. A mercapturic acid conjugate was also
identified but accounted for only 4.7% of the dose in females
and 2.3% of the dose in males at 350 mg/kg. Mercapturate
was occasionally detected in the urine from the 25 mg/kg
group. The parent compound was less than 3% of the dose.
After dermal exposure, 27-45% of the radioactivity recoveredin the urine was the glucuronide conjugate with only a small
fraction identified as the sulfate conjugate. The parent
compound accounted for 3-8% of the recovered radioactivity.
Mercapturic acid conjugates were occasionally detected indermally-dosed animals.

6.9

Comments:

Additional studies listed in the attached bibliography. Test
material leaked from the application site, and oral exposure
could not be ruled out.

Reference:

English, J.C., Deisinger, P.J., Perry, L.G., Schum, D.B., andGuest, D. (1988). Toxicokinetics Studies with Hydroquinone
in Male and Female Fischer 344 Rats (Unpublished report
TX-88-84), Eastman Kodak Company.

Toxicodynamics, toxico-kinetics (Additional study)
Test substance:

Hydroquinone (99%) in water

Test species/strain:

male Beagle dogs

Test method:

Skin on the thorax of six male dogs was shaved and 25 mL ofa [14C]-hydroquinone in water solution (4.5 g/L) was added toa 15 x 4 cm absorption cell. The solution was held in contact
with the skin for 60 minutes. Blood was collected 4, 8, 24,
and 48 hours after application of the test substance. Urine wascollected 4, 8, 24, 48, 72, 96, and 120 hours after applicationof the test substance. The level of radioactivity determined inblood and urine samples.

GLP:

YES [X]NO [ ]

Test results:

No measurable radioactivity was found in blood. Urinary
excretion of radioactivity was low with the peak between 24
and 48 hours. The dermal absorption rate was calculated to be
1.1/µg/cm2hr.

Comments:
Reference:
88

Hamilton, M.L., Guest, D., and DiVincenzo, G.D. (1985).
The Percutaneous Absoprtion of [U-14C]Hydroquinone in
UNEP Publications

OECD SIDSHYDROQUINONE
Beagle Dogs (Unpublished report TX-85-87), Eastman Kodak
Company.

6.9

Toxicodynamics, toxico-kinetics (Additional study)
Test substance:

5% (w/v) Hydroquinone (>99%) in water

Test species/strain:

Fischer 344 Rats and Human abdominal skin

Test method:

Whole skin sections from the abdominal area of rats or
stratum corneum of human abdominal skin were placed onto
Franz-type diffusion cells. Tritiated water or [14C]hydroquinone in water were added to donor chambers
containing buffered, nutrient saline with antibiotic. Samples
were withdrawn from the receptor chamber each hour for a
total of eight hours and the level of radioactivity determined.

GLP:

YES [X]NO [ ]

Test results:

The permeation constant for the hydroquinone through whole
rat skin was 2.26 x 10-5 cm/hr compared with a constant of
2.34 x 10-3 cm/hr for 3H2O. Using human stratum corneum,
the permeation constants were 9.33 x 10-6 cm/hr forhydroquinone and 0.97 x 10-3 cm/hr for 3H2O. These values
indicate that dermal absorption of hydroquinone is "slow"
using the criteria of Marzulli et al. (1969).

Comments:
Reference:

Barber, E.D., Hill, T., and Schum, D.B. (1993). The
Absorption of Hydroquinone (HQ) through Rat and Human
Skin in vitro. Toxicology Letters 80:167-172.

ADDITIONAL REFERENCES
Bolcsak, L. E., and Nerland, D. E. (1983). Inhibition of Erythropoiesis by Benzene andBenzene Metabolites. Toxicol. Appl. Pharmacol. 69, 363-368.
Lockhart, H. B., Fox, J. A., and DiVincenzo, G. (1984). The Metabolic Fate of [U14C]Hydroquinone Administered by Gavage to Male Fischer 344 Rats (Unpublished report
BC-84-14), Health and Environment Laboratories, Eastman Kodak Company.
Lockhart, H. B., and Fox, J. A. (1985). Metabolic Fate of [U-14C]Hydroquinone
Administered by Gavage to Female Fischer 344 Rats (Unpublished report TX-85-55),
Health and Environment Laboratories, Eastman Kodak Company.
Lockhart, H. B., and Fox, J. A. (1985). The Metabolic Fate of [U-14C]Hydroquinone
Administered by Intratracheal Instillation to Male Fischer 344 Rats (Unpublished report
TX-85-76), Health and Environment Laboratories, Eastman Kodak Company.
UNEP Publications

89

OECD SIDS
7.

HYDROQUINONE

Experience with Human Exposure (give full description of study design, effects ofAccidental or Occupational Exposure, epidemiology)
A study of the levels of hydroquinone ingested from natural sources was conducted inhuman volunteers. A group of two nonsmoking males and two nonsmoking females were
given diets that consisted of low and high levels of hydroquinone. A group of smokers(two males and two females) received only the low-hydroquinone diet followed bysmoking four cigarettes in 20 minutes. Blood samples were collected and analyzed at 30,
60, and 120 minutes after eating or immediately, 30, and 90 minutes after smoking.
Plasma levels of hydroquinone following the high-HQ diet increased five fold above
background, while plasma levels decreased after a low-HQ diet. Plasma levels ofhydroquinone increased by 50% immediately after smoke and declined to near backgroundlevels by 90 minutes. Urine was collected for up to 8 hours. Rates of urinary excretion ofhydroquinone reflect plasma levels.
Reference: Deisinger, P.J., Hill, T.S., and English, J.C. (1994). Human Exposure to
Naturally Occurring Hydroquinone, The Toxicologist 14, 788.
Two male volunteers ingested 500 mg of hydroquinone daily for 5 months. Doses weredivided into thirds and given with meals. Blood samples were analyzed for hemoglobin
concentration, hematocrit, red blood cell count, differential white blood cell count,sedimentation rate, platelet count, coagulation time, and icteric index. Urine was analyzed
for albumin, reducing sugars, blood cells, casts, and urobilinogen. No abnormal findings
were reported in blood or urine.
Reference: Carlson, A.J., and Brewer, N.R. (1953). Toxicity Studies on Hydroquinone,
Proc. Soc. Exper. Biol. Med. 84, 684-688.
Seventeen male and female volunteers ingested 300 mg of hydroquinone daily for 3-5
months. Doses were divided into thirds and given with meals. Blood samples wereanalyzed for hemoglobin concentration, hematocrit, red blood cell count, differemtial
white blood cell count, sedimentation rate, platelet count, coagulation time, and ictericindex. Urine was analyzed for albumin, reducing sugars, blood cells, casta, andurobilinogen. No abnormal findings were reported in blood or urine.
Reference: Carlson, A.J., and Brewer, N.R. (1953). Toxicity Studies on Hydroquinone,
Proc. Soc. Exper. Biol. Med. 84, 684-688.

7.1

Biological Monitoring (including clinical studies, case reports, etc.)
A retrospective study was conducted in which 50 cases of eye injury in workers involvedin the manufacture of hydroquinone were evaluated. Workmen exposed to vapors ofquinone and dust of hydroquinone developed reversible discoloration of the cornea andinterpalpebral fissure, or frank corneal opacity. These lesions developed slowly and were
not evident in workers that were exposed for less than five years. Hematology from theseworkers, and from all workers exposed to hydroquinone, were evaluated over a two year
period with no systemic effects indicated.
Reference: Sterner, J.H., Oglesby, F.L., and Anderson, B. (1947). Quinone Vapors andTheir Harmful Effects, J. Ind. Hyg. Toxicol. 29, 60-73.

90

UNEP Publications

OECD SIDSHYDROQUINONE

Another study in which 31 employees involved in the packaging of photochemicals(including hydroquinone) were evaluated for eye injury. The group consisted of 15 maleswith 6 months to 24 years of exposure, and 12 females with 8 to 18 years of exposure.
Four additional males who had exposure for 2-6 years were also included. No ocularlesions attributable to hydroquinone were noted.
Reference: Sutton, W.L. (1961). Internal memo, Laboratory of Industrial Medicine,
Eastman Kodak Company.
An increase in the prevalence of coughing in response to a "smoky environment",
increased immunoglobulin G, and lower respiratory function values (FEV) were noted in
33 workers exposed to a combination of hydroquinone, trimethylhydroquinone, andretinene-hydroquinone compared to a control group from the same plant. Duration of
employment, age, and the percentage of smokers were matched.
No airborne
concentrations of hydroquinone are provided and there was no indication of the duration of
exposure to hydroquinone versus other chemicals.
Reference: Choudat, D., Neukirch, F., Brochard, P., Barrat, G., Marsac, J., Conso, F., andPhilbert, M. (1988). Allergy and Occupational Exposure to Hydroquinone and toMethionine, Br. J. Ind. Med. 45, 376-380.
A single case of vitiligo and lichenoid eruption was reported in a individual who serviced
automatic self-photography machines which contained a developer that used 7%hydroquinone. The individual did demonstrate sensitization to a color developer.
Reference: Kersey, P., and Stevenson, C.J. (1981). Vitiligo and Occupational Exposure
to Hydroquinone from Servicing Self-Photography Machines, Contact Derm. 7, 285-287.
A single case of vitiligo was reported in a dark-skinned West African man who had
immersed his hand into a commercial black-and-white developer containing 0.06%
hydroquinone.
Reference: Frenk, E., and Loi-Zedda, P. (1981). Occupational Depigmentation Due to a
Hydroquinone-containing Photographic Developer, Contact Derm. 6, 238-239.
A cohort study of 478 photographic processors in nine Eastman Kodak Color Print andProcessing laboratories reported no significant excess mortality, sickness-absence, orcancer incidence. The mortality experience compared favorably with two control
industrial populations.
Reference: Friedlander, B.R., Hearne, F.T., and Newman, B.J. (1982). Mortality, Cancer
Incidence, and Sickness-Absence in Photographic Processors: An Epidemiological Study,
J. Occup. Med. 24, 605-613.
A cohort study of 9,040 men employed at Eastman Chemical Co. in Tennessee reported
significantly decreased mortality and diseases of the circulatory system compared with thegeneral population in Tennessee. Among the chemicals that some of these individuals
were exposed to is hydroquinone, although it was not the only source of exposure.

UNEP Publications

91

OECD SIDSHYDROQUINONE

Reference: Pifer, J.W., Hearne, F.T., Friedlander, B.R., and McDonough, J.R. (1986).
Mortality Study of Men Employed at a Large Chemical Plant, 1972 Through 1982, J.
Occup. Med. 28, 438-444.
A study of 78 photographic processors in the Sweden Television Film Laboratory was
conducted in which individuals who were patch tested for sensitization to chemicals usedin the workplace were monitored for occupation-related illness. The Laboratory had
undergone modernization which reduced the potential exposure of these workers and theinvestigators monitored the workers to determine if the modernization was effective in
reducing occupation-related problems. The study showed that occupation-related illness
and leave was reduced to an incidence of zero. No contact dermatitis or other skin disorder
was noted after modernization compared with 37 cases prior to modernization.
Reference: Lidén, C. (1989). Occupational Dermatoses at a Film Laboratory, Contact
Dermat 20, 191-200.
A cohort study of 858 men and 21 women involved in the manufacture and use ofhydroquinone was conducted to evaluate total mortality and cancer-related deaths.
Individuals worked for a mean of 13.7 years in jobs that involved the manufacture or useof hydroquinone. No increase in the incidence of renal cancer was detected in the study
population, and no deaths from liver cancer or leukemia occurred. The incidences of otherpathological conditions such as respiratory malignancies, cardiovascular disease, anddigestive disease were below expected levels.
Reference: Pifer, J.W., Hearne, F.T., Swanson, F.A., O'Donoghue, J.L. (1995). Mortality
Study of Employees Engaged in the Manufacture and Use of Hydroquinone, Int. Arch.
Occup. Environ. Health 67:267-280.
8.

Recommended Precautions, Classification (use and/or transportation) and Safety
Data Sheets.

9.

Availability and reference(s) for existing review(s)International Programme on Chemical Safety (IPCS), Environmental Health Criteria 157:
Hydroquinone. World Health Organization, 1994.

10.

Name of responder
Raymond M. David, Ph.D., DABTCorporate Health and Environment Laboratories
Eastman Kodak Company
Rochester, NY 14652-6272
Telephone: (716) 588-4763
Fax: (716) 722-7561

92

UNEP Publications

OECD SIDSHYDROQUINONE

APPENDIX OF REPORTS REFERENCED IN THE DOSSIER BUT NOT CITED IN THE
LITERATURE
The following lists the reports in this Appendix.
1. Dagon, T.J. (1975). Aquatic Toxicity Report (Unpublished report), Health and Safety
Laboratory, Eastman Kodak Company.
2. Dagon, T.J. (1975). Vascular Phytotoxicity Report (Unpublished report), Health and Safety
Laboratory, Eastman Kodak Company.
3. Hodge, H.C., Maynard, E.A., Wilt, Jr., W.G., and Kesel, R. (1949). Studies of the Acute
Toxicity of Hydroquinone (Unpublished report), Division of Pharmacology and Toxicology,
University of Rochester School of Medicine and Dentistry.
4. Toxicity Report (Unpublished report), Laboratory of Industrial Medicine, Eastman Kodak
Company, 1971.
5. Bernard, L.G. (1988). Subchronic Oral Toxicity Study of Hydroquinone in Rats Utilizing a
Functional-Observational Battery and Neuropathology to Detect Neurotoxicity (Unpublished report
TX-88-78), Eastman Kodak Company.
6. David, R. (1994). NDMA High HQ Formulation Cream: A Thirteen-Week Dermal Toxicity andCell Proliferation Study in the Rat (unpublised report), Nonpresciption Drug Manufacturers
Association.
7. Hamilton, M.L., Guest, D., and DiVincenzo, G.D. (1985). The Percutaneous Absoprtion of [U C]Hydroquinone in Beagle Dogs (Unpublished report TX-85-87), Eastman Kodak Company.

14

8. Schroeder, R.E. (1989). A Two-Generation Reproduction Study in Rats with Hydroquinone(Unpublished report), Eastman Kodak Internal Report TX-90-13, Bio-dynamics Inc., East
Millstone, NJ.
9. Fox, J.A., English, J.C., and Lockhart, Jr., H.B. (1986). Blood Elimination Kinetics of [UC]Hydroquinone Administered by Intragastric Intubation, Intratracheal Instillation or Intravenous
Injection to Male Fischer 344 Rats (Unpublished report TX-86-1), Eastman Kodak Company.

14

10. English, J.C., Deisinger, P.J., Perry, L.G., Schum, D.B., and Guest, D. (1988). Toxicokinetics
Studies with Hydroquinone in Male and Female Fischer 344 Rats (Unpublished report TX-88-84),
Eastman Kodak Company.

UNEP Publications

93

OECD SIDSHYDROQUINONEEXTRACT FROM IRPTC LEGAL FILES

94

UNEP Publications

OECD SIDSHYDROQUINONE

file: 17.01 LEGAL
rn : 100268
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
area
: ARG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
OCC
|
MPC
|
-------------------------------8H-TWA : 2 MG/M3
entry date: OCT 1991

rtecs notype

:MX3500000: REG

effective date: 29MAY1991

title: LIMIT VALUES FOR CHEMICAL SUBSTANCES IN THE WORKINGENVIRONMENT-RESOLUTION NO. 444/1991 OF THE MINISTRY OF WORK AND SOCIALSECURITY (AMENDING REGULATION DECREE NO. 351/1979 UNDER LAW NO.
19587/1972: HYGIENE AND SAFETY AT WORK)
original : ARGOB*, BOLETIN OFICIAL DE LA REPUBLICA ARGENTINA(ARGENTIANOFFICIAL BULLETIN), 24170 , I , 1 , 1979
amendment: ARGOB*, BOLETIN OFICIAL DE LA REPUBLICA ARGENTINA(ARGENTIANOFFICIAL BULLETIN), 27145 , I , 4 , 1991*******
file: 17.01 LEGAL
rn : 300104
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: CAN
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
OCC
|
TLV
|
-------------------------------TWA: 2 mg/m3. Prescribed by the Canada Occupational Safety and HealthRegulations, under the Canada Labour Code (administered by the
Department of Employment and Immigration). The regulations state that no
employee shall be exposed to a concentration of an airborne chemical
agent in excess of the value for that chemical agent adopted by ACGIH(American Conference of Governmental Industrial Hygienists) in its
publication entitled: "Threshold Limit Value and Biological Exposure
Indices for 1985-86". The regulations also state that the employer
shall, where a person is about to enter a confined space, appoint a
qualified person to verify by means of tests that the concentration of
any chemical agent or combination of chemical agents will not result in
the exposure of the person to a concentration in excess of the value
indicated above. These regulations prescribe standards whose enforcement
will provide a safe and healthy workplace.
entry date: OCT 1994
effective date: 24MCH1994
amendment: CAGAAK, CANADA GAZETTE PART II, 128 , 7 , 1513 , 1994*******
file: 17.01 LEGAL
rn : 301985
systematic name:1,4-Benzenediol
UNEP Publications

95

OECD SIDSHYDROQUINONE

common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: CAN
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| TRNSP ||CLASS ||||RQR|
| LABEL |||| PACK |||-------------------------------Schedule II, List II - Dangerous Goods other than Explosives: PIN(Product Identification No.): UN2662. Class (6.1): Poisonous. Packing
group III, (I=Great danger, III=Minor danger). Passenger Vehicles: 100
kg. Prescribed by the Transportation of Dangerous Goods Regulations,
under the Transportation of Dangerous Goods Act (administered by the
Department of Transport). The act and regulations are intended topromote safety in the transportation of dangerous goods in Canada, as
well as provide comprehensive regulations applicable to all modes oftransport accross Canada. These are based on United Nations
recommendations. The act and regulations should be consulted for
details. Information is entered under the proper shipping name found in
the regulations; this may include general groups of chemical substances.
entry date: OCT 1994
effective date: 02DEC1993
amendment: CAGAAK, CANADA GAZETTE PART II, 127 , 25 , 4056 , 1993*******
file: 17.01 LEGAL
rn : 303138
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: CAN
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| USE
|
OCC
|
RQR
|
| STORE |||| LABEL |||-------------------------------Ingredient Disclosure List - Concentration: 1% weight/weight. The
Workplace Hazardous Materials Information System (WHMIS) is a national
system providing information on hazardous materials used in theworkplace. WHMIS is implemented by the Hazardous Products Act and theControlled Products Regulations (administered by the Department ofConsumer and Corporate Affairs). The regulations impose standards on
employers for the use, storage and handling of controlled products. The
regulations also address labelling and identification, employee
instruction and training, as well as the upkeep of a Materials Safety
Data Sheet (MSDS). The presence in a controlled product of an ingredientin a concentration equal to or greater than specified in the Ingredient
Disclosure List must be disclosed in the Safety Data Sheet.
entry date: APR 1991
effective date: 31DEC1987
amendment: CAGAAK, CANADA GAZETTE PART II, 122 , 2 , 551 , 1988

96

UNEP Publications

OECD SIDSHYDROQUINONE*******

file: 17.01 LEGAL
rn : 401860
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
area
: CSK
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| GOODS ||PRO|-------------------------------PROHIBITED IN COSMETICS
entry date: DEC 1991

rtecs notype

:MX3500000: REG

effective date:

1JAN1971

title: DIRECTIVE NO. 34 ON HYGIENIC REQUIREMENTS ON COSMETICS,
DETERGENTS, AND GOODS OF PERSONAL USE
original : HPMZC*, HYGIENICKE PREDPISY MINISTERSTVA ZDRAVOTNICTVICSR(HYGIENIC REGULATIONS OF MINISTRY OF HEALTH OF CSR), 32 ,, , 1970*******
file: 17.01 LEGAL
rn : 523103!!! WARNING - not original IRPTC record - WARNING !!!
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: DEU
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| AQ||
CLASS |
| USE
|
INDST
|
RQR
|
-------------------------------This substance is classified as hazardous to water (Water Hazard Class:
WHC 2). (There are 3 water hazard classes: WHC 3 = severely hazardous;
WHC 2 = hazardous; WHC 1 = moderately hazardous; and the classificationas "not hazardous to water"). The purpose of the classification is to
identify the technical requirements of industrial plants which handle
substances hazardous to water.
entry date: SEP 2001
effective date: 01JUN1999
title: Administrative Order relating to Substances Hazardous to Water(Verwaltungsvorschrift wassergefaehrdende Stoffe)
original : BUANZ*, Bundesanzeiger, 51 , 98a , 1 , 1999*******
file: 17.01 LEGAL
rn : 540458!!! WARNING - not original IRPTC record - WARNING !!!
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
UNEP Publications

97

OECD SIDSHYDROQUINONE

area
: DEU
type
: REC
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
OCC
|
MAK
|
-------------------------------No MAK value established. - Carcinogen category 2: Substance that is
considered to be carcinogenic for man because sufficient data fromlong-term animal studies or limited evidence from animal studies
substantiated by evidence from epidemiological studies indicate that it
can make a significant contribution to cancer risk. Limited data fromanimal studies can be supported by evidence that the substance causes
cancer by a mode of action that is relevant to man and by results of invitro tests and short-term animal studies. - Germ cell mutagen category
3 (old classification): Substance which has been demonstrated to cause
genetic damage in mammalian (including human) germ cells without proofof transmission. Classification in one of the new categories is inprogress.
entry date: MAY 2001
title: List of MAK and BAT Values 2000. Maximum Concentrations andBiological Tolerance Values at the Workplace. (MAK- und BAT-Werte-Liste
2000. Maximale Arbeitsplatzkonzentrationen und Biologische
Arbeitsstofftoleranzwerte.)original : MPGFDF, Mitteilung der Senatskommission zur Pruefung
gesundheitsschaedlicher Arbeitsstoffe, 36 , , , 2000*******
file: 17.01 LEGAL
rn : 600172
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Quinol
cas no:123-31-9
rtecs no:MX3500000
area
: GBR
type
: REC
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AQ
|
METHD
|
RQR
|
|
|
DRINK
|
|
-------------------------------Determines this substance in rivers, waters, sewage effluents andindustrial effluents using the trimethyl-silylethers and gas
chromatrography.
entry date: MCH 1995
effective date:1981

title: Phenols in Waters and Effuents by Gas Liquid Chromatography or
3-Methyl-2-benzothiazoline Hydrazone.
original : SCAA**, , , , , 1983*******
file: 17.01 LEGAL
rn : 700694
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
area
: IND
98

rtecs notype

UNEP Publications:MX3500000: REG

OECD SIDSHYDROQUINONE-------------------------------|subject|specification|descriptor||-------+-------------+----------|| MANUF ||RQR|| SAFTY ||RQR|| STORE ||RQR|| IMPRT ||RQR|-------------------------------These rules define the responsabilities of occupiers of any industrial
activity in which this toxic and hazardous substance may be involved.
These responsabilities encompass: (a) assessment of major hazards(causes, occurrence, frequency); (b) measures to prevent accidents andlimit eventual impairment to human health and pollution of theenvironment; (c) provision of relevant factual knowledge and skills toworkers in order to ensure health and environmental safety when handlingequipments and the foregoing chemical; (d) notification of the competentauthorities in case of major accidents; (e) notification of sites to thecompetent authorities 3 months before commencing; (f)preparation of an
on-site emergency plan as to how major accidents should be coped with;(g) provision of competent authorities with information and means to
respond quickly and efficiently to any off-site emergency; (h) provisionof information to persons outside the site, liable to be affected by amajor accident; (i) labelling of containers as to clearly identify
contents, manufacturers, physical, chemical and toxicological data; (j)preparation of a safety data sheet including any significant information
regarding hazard of this substance and submission of safety reports tothe competent authorities; (k) for the import of a hazardous chemical to
India, importers must supply the competent authorities with specified
information regarding the shipment.
entry date: SEP 1992
effective date: 27NOV1989
title: THE MANUFACTURE, STORAGE AND IMPORT OF HAZARDOUS CHEMICALS RULES.
1989
original : GAZIN*, THE GAZETTE OF INDIA, 787 , , , 1989*******
file: 17.01 LEGAL
rn : 1010157
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :DIHYDROXYBENZENE
cas no:123-31-9
rtecs no:MX3500000
area
: MEX
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
OCC
|
MXL
|
-------------------------------AT ANY WORKPLACE WHERE THIS SUBSTANCE IS PRODUCED, STORED OR HANDLED A
MAXIMUM PERMISSIBLE LEVEL OF 2MG/M3 MUST BE OBSERVED FOR A PERIOD OF 8
HOURS.
entry date: DEC 1991
effective date: 28MAY1984
title: INSTRUCTION NO.10 RELATED TO SECURITY AND HYGIENIC CONDITIONS AT
WORKPLACES. (INSTRUCTIVO NO. 10, RELATIVO A LAS CONDICIONES DE SEGURIDADE HIGIENE DE LOS CENTROS DE TRABAJO).
original : DOMEX*, DIARIO OFICIAL, , , , 1984*******UNEP Publications

99

OECD SIDSHYDROQUINONE

file: 17.01 LEGAL
rn : 1105209
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
area
: RUS
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AQ
|
SURF
|
MAC
|
|
|
|
CLASS |-------------------------------0.2 MG/L HAZARD CLASS: IV
entry date: JUL 1990

rtecs notype

:MX3500000: REG

effective date:

1JAN1989

amendment: SPNPV*, SANITARNYE PRAVILA I NORMY OKHRANY POVERKHNOSTNYKHVOD OT ZAGRIAZNENIA (HEALTH REGULATION AND STANDARDS OF
SURFACE WATER PROTECTION FROM CONTAMINATION), 4630-88 , , ,1988*******
file: 17.01 LEGAL
rn : 1111547
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no
area
: RUS
type
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
OCC
|
MAC
|
|
|
|
CLASS |-------------------------------CLV: 1.0MG/M3 (AEROSOL) HAZ. CLASS: II
entry date: MAY 1990

:MX3500000: REG

effective date:

NOV1989

amendment: PDKAD*, PREDELNO DOPUSTIMYE KONTSENTRATSII VREDNYKHVESHCHESTV V VOZDUKHERABOCHEI ZONY (MAXIMUM ALLOWABLE
CONCENTRATIONS OF HARMFUL SUBSTANCES IN OCCUPATIONAL AIR),5147-89 , , , 1989*******
file: 17.01 LEGAL
rn : 1121881
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
area
: RUS
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
AMBI
|
PSL
|
-------------------------------0.02MG/M3 1X/D
100

rtecs notype

UNEP Publications:MX3500000: REG

OECD SIDSHYDROQUINONE

entry date: SEP 1985

effective date:

DEC1983

amendment: OBUAV*, ORIENTIROVOCHNYE BEZOPASNYE UROVNI VOZDEISTVIA (OBUV)ZAGRAZNIAIUSHCHIKH VESHCHESTU V ATMOSFERNOM VOZDUKHENASEKENNYKH MEST (TENTATIVE SAFE EXPOSURE LIMITS (TSEL) OF
CONTAMINANTS IN AMBIENTAIR OF RESIDENTIAL AREAS), 2947-83 , ,, 1983*******
file: 17.01 LEGAL
rn : 1200045
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: SWE
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
OCC
|
HLV
|
-------------------------------1D-TWA: 0.5MG/M3; 15MIN-STEL: 1.5MG/M3. SENSITIZING.
entry date:1992
effective date: 01JUL1991
title: HYGIENIC LIMIT VALUES.
original : AFS***, ARBETARSKYDDSSTYRELSENS FOERFATTNINGSSAMLING, 1990:13, , 5-64 , 1990*******
file: 17.01 LEGAL
rn : 1301168
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: USA
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| MANUF |
REQ
|
PRMT
|
| USE
|
OCC
|
PRMT
|
| SAFTY |
OCC
|
MXL
|
-------------------------------; Summary - THE FOLLOWING CHEMICAL IS INCLUDED ON A LIST OF CHEMICALSAND MIXTURES FOR WHICH REPORTING IS CURRENTLY REQUIRED UNDER THE TOXICSUBSTANCES CONTROL ACT SECTION 2607A. THIS TOXIC SUBSTANCE IS SUBJECT TO
PRELIMINARY ASSESSMENT INFORMATION RULES ON PRODUCT ION QUANTITIES,USES, EXPOSURES, AND ADVERSE EFFECTS. MANUFACTURERS INCLUDING IMPORTERS
MUST SUBMIT A REPORT FOR THIS LISTED CHEMICAL MANUFACTURED AT EACH SITE.
entry date: OCT 1991
effective date:1982
title: PRELIMINARY ASSESSMENT INFORMATION RULES
original : FEREAC, FEDERAL REGISTER, 47 , , 26998 , 1982
amendment: CFRUS*, CODE OF FEDERAL REGULATIONS, 40 , 712 , 30 , 1990*******UNEP Publications

101

OECD SIDSHYDROQUINONE

file: 17.01 LEGAL
rn : 1307147
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: USA
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
EMI
|
RQR
|
-------------------------------; Summary - FROM A LIST OF POLLUTANTS JUDGED TO BE HAZARDOUS FOR WHICH
EMISSION STANDARDS WILL BE DEVELOPED
entry date: SEP 1991
effective date:1985
title: CLEAN AIR ACT, 112--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIRPOLLUTANTS
original : FEREAC, FEDERAL REGISTER, 50 , , 46290 , 1985
amendment: CFRUS*, CODE OF FEDERAL REGULATIONS, 40 , 61 , 1 , 1990*******
file: 17.01 LEGAL
rn : 1325189
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
area
: USA
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| SAFTY |
OCC
|
MXL
|
| USE
|
OCC
|
MXL
|
-------------------------------200 MG/M3
entry date: OCT 1991

rtecs notype

:MX3500000: REC

effective date:

JUN1990

title: POCKET GUIDE TO CHEMICAL HAZARDS
original : XPHPAW, US PUBLIC HEALTH SERVICE PUBLICATION, 90 , 117 , 128, 1990amendment: XPHPAW, US PUBLIC HEALTH SERVICE PUBLICATION, 90 , 117 , 128, 1990*******
file: 17.01 LEGAL
rn : 1335161
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: USA
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| SAFTY |
INDST
|
RQR
|
| STORE |
INDST
|
RQR
|
-------------------------------TPQ=500/10,000 RQ=1; Summary - THE PRESENCE OF EXTREMELY HAZARDOUS
102

UNEP Publications

OECD SIDSHYDROQUINONE

SUBSTANCES IN EXCESS OF THE THRESHOLD PLANNING QUANTITY (TPQ), IN
POUNDS, REQUIRES CERTAIN EMERGENCY PLANNING ACTIVITIES TO BE CONDUCTED.
FOR CHEMICALS THAT ARE SOLIDS, THERE MAY BE TWO TPQ'S GIVEN. IN THESE
CASES, T HE LOWER QUANTITY APPLIES FOR SOLIDS IN POWDER FORM WITH
PARTICLE SIZE LESS THAN 100 MICRONS, OR IF THE SUBSTANCE IS IN SOLUTION
OR IN MOLTEN FORM. OTHERWISE, THE HIGHER QUANTITY APPLIES. THESE
CHEMICALS ARE ALSO SUBJECT TO REGULATION UNDER SARA 304. RELEASES OFSUBSTANCES, IN QUANTITIES EQUAL TO OR GREATER THAN THEIR REPORTABLEQUANTITY (RQ), IN POUNDS, ARE SUBJECT TO REPORTING TO THE NATIONALRESPONSE CENTER UNDER THE COMPREHENSIVE ENVIRONMENTAL RESPONSE,
COMPENSATION, AND LIABILITY ACT OF 1980.
entry date: OCT 1991
effective date:1987
title: SARA, SECTION 302(A) EMERGENCY PLANNING AND COMMUNITY RIGHT TOKNOW ACT; LIST OF EXTREMELY HAZARDOUS SUBSTANCES AND THEIR THRESHOLD
PLANNING QUANTITIES
original : FEREAC, FEDERAL REGISTER, 52 , , 13395 , 1987
amendment: CFRUS*, CODE OF FEDERAL REGULATIONS, 40 , 355 , , 1990*******
file: 17.01 LEGAL
rn : 1336202
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: USA
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
EMI
|
RQR
|
| SOIL |
EMI
|
RQR
|
| AQ
|
EMI
|
RQR
|
| MANUF |
EMI
|
RQR
|
-------------------------------; Summary - FACILITIES THAT EXCEEDED A MANUFACTURING, IMPORTATION, OR
PROCESSING THRESHOLD OF 25,000 LBS OR THE USE OF 10,000 LBS FOR THISCHEMICAL MUST REPORT TO EPA ANY RELEASES OF THE CHEMICAL (OR CATEGORYCHEMICAL) TO AIR, LAND, WATER, POTW, UNDERGROUND INJECTIO N, OR OFF SITE
TRANSFER. THIS REGULATION COVERS STANDARD INDUSTRIAL CLASSIFICATION(SIC) CODES 20-39 ONLY).
entry date: OCT 1991
effective date:1987
title: SUPERFUND AMENDMENTS AND REAUTHORIZATION ACT, TITLE III. EPCRASECTION 313 LIST OF TOXIC SUBSTANCES
original : CFRUS*, CODE OF FEDERAL REGULATIONS, 40 , 372 , 65 , 1988
amendment: CFRUS*, CODE OF FEDERAL REGULATIONS, 40 , 372 , 65 , 1988*******
file: 17.01 LEGAL
rn : 1340208
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
area
: USA

rtecs notype

UNEP Publications:MX3500000
: REC

103

OECD SIDSHYDROQUINONE-------------------------------|subject|specification|descriptor||-------+-------------+----------|
| AIR
|
OCC
|
TLV
|
-------------------------------Time Weighted Avg (TWA) 2 MG/M3; Summary - THIS THRESHOLD LIMIT VALUE IS
INTENDED FOR USE IN THE PRACTICE OF INDUSTRIAL HYGIENE AS A GUIDELINE OR
RECOMMENDATION IN THE CONTROL OF POTENTIAL HEALTH HAZARDS.
entry date: DEC 1991
effective date:1989
title: THRESHOLD LIMIT VALUES
original : ACGIH*, AMERICAN CONFERENCE OF GOVERNMENT INDUSTRIAL
HYGIENISTS, , , 11 , 1989
amendment: ACGIH*, AMERICAN CONFERENCE OF GOVERNMENT INDUSTRIAL
HYGIENISTS, , , 11 , 1991*******
file: 17.01 LEGAL
rn : 1345144
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: USA
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| MONIT ||RQR|-------------------------------; Summary - THIS IS A CHEMICAL OR MIXTURE FOR WHICH REPORTING IS
CURRENTLY REQUIRED UNDER THE TOXIC SUBSTANCE CONTROL ACT HEALTH AND
SAFETY STUDIES SECTION 2607D. PERSONS WHO CURRENTLY MANUFACTURE OR
PROCESS CHEMICAL SUBSTANCES OR MIXTURES FOR COMMERCIAL PURPOSES, THOSE
WHO PROPOSE TO DO SO, AND THOSE WHO ARE NOT CURRENTLY INVOLVED WITH A
LISTED CHEMICAL BUT WHO MANUFACTURED OR PROCESSED IT OR PROPOSED TO DO
SO ANY TIME DURING THE TEN YEAR PERIOD PRIOR TO THE TIME IT BECAME
LISTED MUST SUBMIT TO THE ADMINISTRATOR OF THE U.S. EPA STUDIES OR LISTSOF HEALTH AND SAFETY STUDIES CONDUCTED ON THIS SUBSTANCE FOR EVALUATION.
entry date: OCT 1991
effective date:1986
title: HEALTH AND SAFETY DATA REPORTING RULES SECTION 8(D)original : FEREAC, FEDERAL REGISTER, 51 , , 32726 , 1986
amendment: CFRUS*, CODE OF FEDERAL REGULATIONS, 40 , 716 , 120 , 1990*******
file: 17.01 LEGAL
rn : 1407770
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
area
: EEC
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| GOODS |
CSMET
|
RSTR
|
| GOODS |
CSMET
|
MXL
|
| GOODS |
CSMET
|
RQR
|
-------------------------------104

rtecs notype

UNEP Publications:MX3500000: REG

OECD SIDSHYDROQUINONETHE SUBSTANCE WHICH COSMETIC PRODUCTS MUST NOT CONTAIN EXCEPT SUBJECT TO
THE FOLLOWING RESTRICTIONS AND CONDITIONS: FIELD OF APPLICATION: A)
OXIDIZING COLOURING AGENT FOR HAIR-DYEING: MXL = 2%; B) AGENTS FOR
LOCALIZED SKIN LIGHTENER: MXL = 2%. THE SUBSTANCE MAY BE USED SINGLY OR
IN COMBINATION PROVIDED THAT THE SUM OF THE RATIOS OF THE LEVELS OF EACH
OF THEM IN THE COSMETIC PRODUCT EXPRESSED WITH REFERENCE TO THE MXL
AUTHORIZED FOR EACH OF THEM DOES NOT EXCEED 2. WARNING WHICH MUST BE
PRINTED ON THE LABEL IS GIVEN. MEMBER STATES SHALL TAKE ALL MEASURES
NECESSARY TO ENSURE THAT THE COSMETIC PRODUCTS MAY BE MARKETED ONLY IF
THEIR PACKAGING, CONTAINERS OR LABELS BEAR THE INFORMATION LAID DOWN.
entry date: SEP 1995
effective date: 27MCH1978
title: COUNCIL DIRECTIVE OF 27 JULY 1976 ON THE APPROXIMATION OF THE
LAWS OF THE MEMBER STATES RELATING TO COSMETIC PRODUCTS (76/768/EEC)
original : OJEC**, OFFICIAL JOURNAL OF THE EUROPEAN COMMUNITIES, L262 ,, 169 , 1976
amendment: OJEC**, OFFICIAL JOURNAL OF THE EUROPEAN COMMUNITIES, L181 ,, 31 , 1994*******
file: 17.01 LEGAL
rn : 1408194
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :1,4-BENZENEDIOL
cas no:123-31-9
rtecs no:MX3500000
area
: EEC
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| GOODS |
CSMET
|
RQR
|
| GOODS |
METHD
|
RQR
|
-------------------------------THE OFFICIAL METHOD FOR IDENTIFICATION AND SEMI-QUANTITATIVE
DETERMINATION OF THE SUBSTANCE IN HAIR DYES IS LAID DOWN. THE SUBSTANCE
IS EXTRACTED AT PH 10 WITH 96% ETHANOL FROM DYES AND IDENTIFIED BY
THIN-LAYER CHROMATOGRAPHY, EITHER ONE- OR TWO-DIMENSIONAL. FOR
SEMI-QUANTITATIVE DETERMINATION OF THE SUBSTANCE , THE CHROMATOGRAM OF
THE SAMPLE IS COMPARED BY MEANS OF FOUR DEVELOPING SYSTEMS WITH THOSEFOR REFERENCE SUBSTANCES PRODUCED AT THE SAME TIME AND UNDER AS SIMILAR
CONDITIONS AS POSSIBLE.
entry date: SEP 1995
effective date: 31DEC1983
title: SECOND COMMISSION DIRECTIVE OF 14 MAY 1982 ON THE APPROXIMATION
OF THE LAWS OF THE MEMBER STATES RELATING TO METHODS OF ANALYSIS
NECESSSARY FOR CHECKING THE COMPOSITION OF COSMETIC PRODUCTS(82/434/EEC)
original : OJEC**, OFFICIAL JOURNAL OF THE EUROPEAN COMMUNITIES, L185 ,, 1 , 1982*******
file: 17.01 LEGAL
rn : 1408371
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :1,4-Dihydroxybenzene
cas no:123-31-9
rtecs no
area
: EEC
type
UNEP Publications:MX3500000
: REG
105

OECD SIDSHYDROQUINONE-------------------------------|subject|specification|descriptor||-------+-------------+----------|| FOOD ||RQR|| GOODS ||MXL|| GOODS ||PRMT|-------------------------------THE SUBSTANCE IS INCLUDED IN THE LIST OF AUTHORIZED MONOMERS AND OTHER
STARTING SUBSTANCES, WHICH SHALL BE USED FOR THE MANUFACTURE OF PLASTICS
AND ARTICLES INTENDED TO COME INTO CONTACT WITH FOODSTUFFS. THE USE OF
THE SUBSTANCE IS SUBJECT TO THE RESTRICTIONS SPECIFIED THEREIN. SPECIFICMIGRATION LIMIT: 0.6 MG/KG. VERIFICATION OF COMPLIANCE WITH THE
MIGRATION LIMITS SHALL BE CARRIED OUT IN ACCORDANCE WITH DIRECTIVES
82/711/EEC AND 85/572/EEC.
entry date: SEP 1995
effective date: 01JAN1991
title: COMMISSION DIRECTIVE OF 23 FEBRUARY 1990 RELATING TO PLASTICS
MATERIALS AND ARTICLES INTENDED TO COME INTO CONTACT WITH FOODSTUFFS(90/128/EEC)
original : OJEC**, OFFICIAL JOURNAL OF THE EUROPEAN COMMUNITIES, L75 , ,19 , 1990
amendment: OJEC**, OFFICIAL JOURNAL OF THE EUROPEAN COMMUNITIES, L90 , ,26 , 1993*******
file: 17.01 LEGAL
rn : 1470517!!! WARNING - not original IRPTC record - WARNING !!!
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: EEC
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| MANUF |INDST|CLASS || IMPRT |INDST|
CLASS |-------------------------------The substance is included in a list of existing substances produced orimported within the Community in quantities exceeding 1000 tonnes per
year. - A system of data reporting by any manufacturer who has produced
or any importer who has imported the substance, as such or in a
preparation, in quanities exceeding 10 tonnes per year is established.
entry date: AUG 1999
effective date: 04JUN1993
title: Council Regulation (EEC) No 793/93 of 23 March 1993 on theevaluation and control of the risks of existing substancesoriginal : OJECFC, Official Journal of the European Communities, L84 , ,1 , 1993*******
file: 17.01 LEGAL
rn : 1478780!!! WARNING - not original IRPTC record - WARNING !!!
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :1,4-Dihydroxybenzene
106

UNEP Publications

OECD SIDSHYDROQUINONE

cas no:123-31-9
rtecs no:MX3500000
area
: EEC
type
: REG
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| CLASS ||CLASS || LABEL ||RQR|| PACK ||RQR|-------------------------------Classification: Carcinogen Category 3; R40. Mutagen category 3; R40. Xn;
R22. Xi: Irritant; R41. R43. N; R50. - Labelling: Xn: Harmful; N:
Dangerous for the environment. Risk phrases (R): 22-40-41-43-50. Harmful
if swallowed (R22). - Limited evidence of a carcinogenic effect (R40). Risk of serious damage to eyes (R41). - May cause sensitization by skincontact (R43). - Very toxic to aquatic organisms (R50). Safety advice
phrases (S): (2-)26-36/37/39-61. (Keep out of the reach of children(S2).) - In case of contact with eyes, rinse immediately with plenty ofwater and seek medical advice (S26). - Wear suitable protective
clothing, gloves and eye/face protection (S36/37/39). - Avoid release to
the environment. Refer to special instructions/safety data sheets (S61).
entry date: FEB 2002
effective date: 24AUG2001
title: Council Directive of 27 June 1967 on the approximation of thelaws, regulations and administrative provisions relating to theclassification, packaging and labelling of dangerous substances(67/548/EEC)
original : OJECFC, Official Journal of the European Communities, 196 , ,1 , 1967
amendment: OJECFC, Official Journal of the European Communities, L225 ,, 1 , 2001*******
file: 17.01 LEGAL
rn : 1662296!!! WARNING - not original IRPTC record - WARNING !!!
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: IMO
type
: REC
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| TRNSP |MARIN|
CLASS || LABEL ||RQR|| PACK ||RQR|-------------------------------UN No. 2662. Class: 6.1 = Toxic substance. Packing group: III = Low
danger. Applies to Hydroquinone solution and to solid Hydroquinone.
entry date: NOV 2000
effective date: 01JAN2001
title: IMDG Code - Dangerous Goods List
original : IMDGC*, International Maritime Dangerous Goods Code,
Amendment 30-00, Volume 2 , , , 2000*******
file: 17.01 LEGAL

rn : 1761296
UNEP Publications

107

OECD SIDSHYDROQUINONE!!! WARNING - not original IRPTC record - WARNING !!!
systematic name:1,4-Benzenediol
common name:p-Hydroquinone
reported name :Hydroquinone
cas no:123-31-9
rtecs no:MX3500000
area
: UN
type
: REC
-------------------------------|subject|specification|descriptor||-------+-------------+----------|| TRNSP ||CLASS || LABEL ||RQR|| PACK ||RQR|-------------------------------UN No. 2662. Class: 6.1 = Toxic substance. Packing group: III = Low
danger.
entry date: NOV 2000
title: UN Orange Book - Dangerous Goods List
original : !RTDGFK, Recommendations on the Transport of Dangerous Goods
prepared by the United Nations Committee of Experts on theTransport of Dangerous Goods, 11th revised ed., , , 1999

108

UNEP Publications

OECD SIDSHYDROQUINONE

UNEP Publications

109