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SECTION 1. CHEMICAL IDENTIFICATION

CHEMINFO Record Number: 725
CCOHS Chemical Name: Adipic acid

Synonyms:
Adipinic acid
1,4-Butanedicarboxylic acid
Hexanedioic acid
1,6-Hexanedioic acid
Acide adipique

Chemical Name French: Acide adipique
Chemical Name Spanish: Acido adípico
Acido hexanodioico
CAS Registry Number: 124-04-9
RTECS Number(s): AU8400000
EU EINECS/ELINCS Number: 204-673-3
Chemical Family: Saturated aliphatic carboxylic acid / aliphatic dicarboxylic acid / alkanedioic acid
Molecular Formula: C6-H10-O4
Structural Formula: HO-(O=)C-CH2-CH2-CH2-CH2-C(=O)-OH

SECTION 2. DESCRIPTION

Appearance and Odour:
Colourless or white crystalline solid. Odourless.(14,20)

Odour Threshold:
Not applicable; essentially odourless.(20)

Warning Properties:
Insufficient information available for evaluation, however, since the material is odourless and irritant properties are unreliable, assume warning properties are poor.

Composition/Purity:
Commercial adipic acid is one of the purest chemicals produced on a large scale (99.8%) because of the extreme sensitivity of polyamide synthesis to impurities. Typical impurities include other acids (monobasic acids and lower dibasic acids) (60 ppm), nitrogenous materials, trace metals such as iron (2 ppm), heavy metals (10 ppm), arsenic (3 ppm) and hydrocarbon oil (10 ppm).(2,14)

Uses and Occurrences:
Most adipic acid is used for the manufacture of nylon 66 fibres and resins. Other uses include the manufacture of ester-type plasticizers and polyurethane resins which are used in specialty foams, lacquers, adhesives, surface coatings, spandex fibres and synthetic lubricants. Used to produce adiponitrile; as a food acidulant; to modify properties of unsaturated polyesters for use in reinforced plastics and alkyd coatings; wet-strength resins; as a buffer in flue gas desulfurization treatment in power plants.(14,15)


SECTION 3. HAZARDS IDENTIFICATION

EMERGENCY OVERVIEW:
White, crystalline, odourless solid. POTENTIAL COMBUSTIBLE DUST HAZARD. Powdered material may form explosive dust-air mixtures. Practically non-toxic. Causes eye irritation.



POTENTIAL HEALTH EFFECTS

Effects of Short-Term (Acute) Exposure

Inhalation:
Adipic acid does not easily form a vapour and animal evidence suggests that it is not very toxic by inhalation. Vapour from heated solutions, mists or dusts may cause mild irritation of the nose, throat and upper respiratory passages. A single-exposure study with human volunteers, showed that adipic acid dust caused mucous membrane irritation above 20 mg/m3.(1)

Skin Contact:
There is no human or animal information available. Adipic acid dust is not expected to cause skin irritation. Solutions may cause mild to moderate skin irritation.

Eye Contact:
There is no human information available. The dust can probably cause eye irritation as a "foreign body". Some tearing, blinking and mild temporary pain may occur as the solid material is rinsed from the eye by tears. Limited animal information suggests that adipic acid is a moderate eye irritant.

Ingestion:
Animal information suggests that adipic acid is low in toxicity. Small amounts may be present in food as an additive and are generally recognized as safe. Ingestion of large amounts may cause irritation to the mouth, throat and gastrointestinal tract. Adverse effects were not observed in volunteers who ingested 100 mg/kg/day for periods up to 8 days.(2) Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

SKIN CONTACT: Prolonged or repeated contact may cause dermatitis (dry, cracked, red skin).

INHALATION: Effects on the respiratory, gastrointestinal, central nervous and immune systems were reported in Russian adipic acid production workers chronically exposed to up to 26 mg/m3 adipic acid dust.(1) These effects cannot be directly attributed to adipic acid due to concurrent exposure to other chemicals and the lack of statistical analysis.

SENSITIZATION: Despite widespread use, both in industry and as a food additive, there are very few reports of allergic sensitivity developing following exposure to adipic acid. A skin allergy to adipic acid was reported in one research worker.(3) There are also reports of two workers who developed asthma following exposure to adipic acid salts. Subsequent testing showed positive reactions to adipic acid.(4) However, insufficient details are available to evaluate these reports and they do not prove that adipic acid is a skin or respiratory sensitizer.

Carcinogenicity:

There is no human information available. Two animal studies suggest that it is not carcinogenic.(6)

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has not assigned a carcinogenicity designation to this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
There is no human information available. No adverse effects were observed in one animal study conducted on 3 species.(9)

Reproductive Toxicity:
There is no human or animal information available.

Mutagenicity:
Adipic acid produced negative results in mutagenicity assays conducted with human embryonic lung cultures.(5) Negative results have also been obtained in mammalian in vivo tests and in short-term in vitro tests on mammalian cells and bacteria.

Toxicologically Synergistic Materials:
There is no information available.

Potential for Accumulation:
Does not accumulate. Small amounts are readily broken down and used by the body to produce energy. Larger amounts (for example, 100 mg/kg/day for up to 8 days) may not be readily broken down and are largely excreted (54% to 75%) unchanged.(2)


SECTION 4. FIRST AID MEASURES

Inhalation:
If symptoms develop, remove source of contamination or move victim to fresh air. Obtain medical advice.

Skin Contact:
As quickly as possible, flush with lukewarm, gently flowing water for at least 5 minutes or until the chemical is removed. If irritation persists, repeat flushing. Obtain medical advice.

Eye Contact:
Do not allow victim to rub eye(s). Let the eye(s) water naturally for a few minutes. Have victim look right and left, and then up and down. If particle/dust does not dislodge, flush with lukewarm, gently flowing water for 5 minutes or until particle/dust is removed, while holding the eyelid(s) open. If irritation persists, obtain medical attention. DO NOT attempt to manually remove anything stuck to eye(s).

Ingestion:
If irritation or discomfort occur, obtain medical advice.

First Aid Comments:
Consult a doctor and/or the nearest Poison Control Centre for all serious exposures. All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.



SECTION 5. FIRE FIGHTING MEASURES

Flash Point:
196 deg C (385 deg F) (closed cup) (14)

Lower Flammable (Explosive) Limit (LFL/LEL):
Not available

Upper Flammable (Explosive) Limit (UFL/UEL):
Not available

Autoignition (Ignition) Temperature:
420 deg C (788 deg F) (14)

Sensitivity to Mechanical Impact:
Probably not sensitive. Stable material.

Combustion and Thermal Decomposition Products:
Cyclopentane.(20) Incomplete combustion may also produce irritating fumes and acrid smoke.

Flammable Properties:

Extinguishing Media:
Water spray or fog, carbon dioxide, dry chemical powder, alcohol foam or polymer foam (21)

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location. Approach fire from upwind to avoid toxic decomposition products.
Avoid generating dust to minimize risk of explosion. Water or foam may cause frothing. The frothing may be violent and could endanger personnel close to the fire. However, a water spray or fog that is carefully applied to the surface of the liquid, preferably with a fine spray or fog nozzle, will cause frothing that will blanket and extinguish the fire. In addition, water can be used in the form of spray or fog to prevent dust formation, absorb heat, keep containers cool and protect fire-exposed material. Solid streams of water may be ineffective and spread material.
As in any fire, wear self-contained breathing apparatus (SCBA), pressure-demand, (MSHA/NIOSH approved or equivalent) and full protective equipment (Bunker Gear).



NATIONAL FIRE PROTECTION ASSOCIATION (NFPA) HAZARD IDENTIFICATION

NFPA - Health: 1 - Exposure would cause significant irritation, but only minor residual injury.
NFPA - Flammability: 1 - Must be preheated before ignition can occur.
NFPA - Instability: 0 - Normally stable, even under fire conditions, and not reactive with water.

SECTION 9. PHYSICAL AND CHEMICAL PROPERTIES

Molecular Weight: 146.14

Conversion Factor:
1 ppm = 5.96 mg/m3; 1 mg/m3 = 0.168 ppm at 25 deg C (calculated)

Physical State: Solid
Melting Point: 152.1 deg C (305.8 deg F) (14,15)
Boiling Point: 265 deg C (509 deg F) at 13.3 kPa; 337.5 deg C (639.5 deg F) at 101.3 kPa (decomposes).(15). Also reported to decompose at about 330 deg C (626 deg F).(2,20)
Relative Density (Specific Gravity): 1.344 at 18 deg C (solid); 1.07 at 170 deg C (liquid) (water=1) (14,15,20)
Solubility in Water: Moderately soluble (1.42 g/100 g at 15 deg C) (14,15)
Solubility in Other Liquids: Very soluble in methanol and ethanol; soluble in acetone and ethyl acetate; very slightly soluble in cyclohexane and benzene.(14,15)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = -0.13; 0.08 (22)
pH Value: Weak acid. 2.7 (saturated solution at 25 deg C); 3.2 (0.1% solution) (15)
Vapour Density: 5.04 (air = 1) (14,16)
Vapour Pressure: Very low; 0.0097 kPa (0.073 mm Hg) at 18.5 deg C (14,20)
Saturation Vapour Concentration: 96 ppm at 18.5 deg C (calculated)
Evaporation Rate: Practically zero
Critical Temperature: Not applicable

Other Physical Properties:
VISCOSITY-DYNAMIC: 4.54 mPa.s (4.54 centipoises) at 160 deg C (molten) (14,15)
ACIDITY: pKa1 = 4.43 (K1 = 3.7 X 10(-5)); pKa2 = 5.41 (K2 = 3.86 X 10(-6)) at 25 deg C (14)


SECTION 10. STABILITY AND REACTIVITY

Stability:
Normally stable. Decomposes at or above the boiling point (about 330 deg C) to produce volatile acidic vapours of valeric acid and other substances.(20)

Hazardous Polymerization:
Does not occur

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.


STRONG OXIDIZERS - mixture reacts vigorously or violently. Risk of fire and explosion.(14,20,21)
STRONG BASES or REDUCING AGENTS - may react vigorously, generating heat and pressure.(20,21)
ALCOHOLS, GYCOLS, ALDEHYDES, EPOXIDES or POLYMERIZABLE COMPOUNDS - contact may result in violent polymerization.(20)

Hazardous Decomposition Products:
None reported

Conditions to Avoid:
Generation of dust, static charge, sparks, heat and other ignition sources.

Corrosivity to Metals:
Aqueous solutions are very mildly corrosive to most metals.(23) Generally, austenitic stainless steels containing nickel and molybdenum and over 18% chromium are resistant.(14)


SECTION 11. TOXICOLOGICAL INFORMATION

LD50 (oral, male rat): Greater than 5000 mg/kg; no deaths occurred.(5)
LD50 (oral, male mouse): 1900 mg/kg (6)
An oral LD50 of 940 mg/kg has been reported for male rats. However, when the study was repeated with similar weight male rats, no deaths were reported at 5000 mg/kg.(5) Based on this inconsistency, as well as data from repeated oral dose studies which indicate that rats tolerate repeated doses well in excess of 1000 mg/kg adipic acid, an LD50 of 940 mg/kg seems unlikely.

Eye Irritation:

Application of 20 mg produced moderate irritation in rabbits in a 24-hour standard Draize test.(7)

Effects of Short-Term (Acute) Exposure:

Skin Contact:
High oral doses produced inactivity, irritation, swelling and bleeding of the gastrointestinal tract, diarrhea, liver and kidney injury and deaths in mice and rabbits.(2,6) A dose of 5000 mg/kg produced no deaths, no signs of toxicity or abnormal behaviour, and no pathological changes in male rats.(5) Symptoms of central nervous system depression (e.g. depression, dyspnea, ataxia, and convulsions) were observed in male rats administered up to 5600 mg/kg/day for 5 days. Deaths occurred at 3600 mg/kg (3/6), 4000 mg/kg (5/6) and complete lethality was observed at the higher doses.(5)

Effects of Long-Term (Chronic) Exposure:

Inhalation:
Harmful effects were not observed in rats exposed by inhalation to 126 mg/m3 adipic acid dust for 15 days.(8) In a poorly reported study, effects were reported in animals exposed to 13 or 129 mg/m3 adipic acid dust for 4 months.(1) Insufficient details are available provided to interpret this data.

Ingestion:
Long-term oral exposure to adipic acid has not produced significant toxic effects. In one study, male rats were administered up to 5.0% adipic acid in the diet for 2 years. At 3.0 and 5.0%, body weight gain was significantly decreased during periods of rapid growth. No other treatment-related effects were observed.(6) In another study, rats were administered 200, 400 or 800 mg/day for up to 33 weeks. In the mid- and high-dose groups, slight cellular changes in the liver and kidneys, and inflammation of the intestinal mucosa were observed.(2) Other studies have not shown significant effects in rats administered adipic acid orally for 3 weeks to 2 years.(1,2,6)

Carcinogenicity:
An increased incidence of tumours was not observed in male rats administered up to 5.0% adipic acid in the diet for 2 years; nor in female rats administered 1.0% adipic acid in the diet for 2 years.(6)

Teratogenicity, Embryotoxicity and/or Fetotoxicity:
No effects were observed in offspring of pregnant mice, rats and hamsters administered adipic acid by gavage, daily, for several days during pregnancy.(9)

Mutagenicity:
Adipic acid was not mutagenic in rat bone marrow cells in vivo when administered orally.(5)
Negative results were also reported in short-term in vitro tests using mammalian cells and bacteria.(10,11,12,13)


SECTION 16. OTHER INFORMATION

Selected Bibliography:
(1) Krapotkina, M.A., et al. Clinico-experimental characteristics of the toxic effects of adipic acid and justification of its MAC in the air of the work zone. Gigiena truda i professional'nye zabolevaniya. No. 5 (1981). p. 46-47 (English translation)
(2) Syracuse Research Corporation. Information profiles on potential occupational hazards: adipic acid. Second draft. National Institute for Occupational Safety and Health, March, 1981.
(3) Malten, K.E., et al. Unsaturated polyesters. In: Industrial toxicology and dermatology in the production and processing of plastics. Elsevier Publishing Company, 1964. p. 71-84
(4) Moscato, G., et al. Bronchial asthma due to spiramycin and adipic acid. Clinical Allergy. Vol. 14, no. 4 (1984). p. 355-361
(5) Litton Bionetics, Inc. Mutagenic evaluation of compound FDA-71-50, Adipic acid. Report number FDABF-GRAS-310. NTIS PB-245 466. Food and Drug Administration, December 9, 1974.
(6) Horn, H.J., et al. Safety of adipic acid as compared with citric and tartaric acid. Journal of Agricultural and Food Chemistry. Vol. 5, no. 10 (October, 1957). p. 759-762
(7) RTECS record for adipic acid. Date of last update: 9510
(8) Gage, J.C. The subacute inhalation toxicity of 109 industrial chemicals. British Journal of Industrial Medicine. Vol. 27 (1970). p. 1-18
(9) Food and Drug Research Laboratories, Inc. Teratologic evaluation of FDA 71-50 (adipic acid). Report number FDABF-GRAS-069. NTIS PB-221 802. Food and Drug Administration, February, 1972.
(10) Katz, G.V., et al. Aliphatic carboxylic acids. In: Patty's Industrial Hygiene and Toxicology. Edited by G.D. Clayton et al. 4th edition. Volume II. Toxicology. Part E. John Wiley and Sons, 1994. p. 3523-3526, 3585-3587
(11) Shimizu, H., et al. The results of microbial mutation test for forty- three industrial chemicals. Japanese Journal of Industrial Health. Vol. 27 (1985). p. 400-419
(12) Brusick, D.J., et al. An evaluation of the Escherichia coli WP2 and WP2 uvrA reverse mutation assay. Mutation Research. Vol. 76 (1980). p. 169-190
(13) Heidelberger, C., et al. Cell transformation by chemical agents: a review and analysis of the literature. Mutation Research. Vol. 114 (1983) p. 283-385
(14) Davis, D.D., et al. Adipic acid. In: Kirk-Othmer encyclopedia of chemical technology. 4th edition. Volume 1. John Wiley and Sons, 1991. p. 466-493
(15) Davis, D.D. Adipic acid. In: Ullmann's encyclopedia of industrial chemistry. 5th revised edition. Volume A 1. VCH Verlagsgesellschaft, 1985. p. 269-278
(16) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 325
(17) Field, P. Explosibility assessment of industrial powders and dusts. Building Research Establishment, 1983
(18) Grossel, S.S. Safety considerations in conveying of bulk solids and powders. Journal of Loss Prevention in the Process Industries. Vol. 1 (April, 1988). p. 62-74
(19) Schwab, R.F. Dusts. In: Fire protection handbook. Edited by A.E. Cote. 18th edition. National Fire Protection Association, 1991. p. 4-174 to 4-181
(20) Emergency action guide for adipic acid. Association of American Railroads. March, 1995
(21) The Sigma-Aldrich library of chemical safety data. Edition II. Volume 1. Sigma-Aldrich Corporation, 1988. p. 68D
(22) Leo, A., et al. Partition coefficients and their uses. Chemical Reviews. Vol. 71, no. 6 (December. 1971). p. 573
(23) Corrosion data survey. Metals section. 6th edition. National Association of Corrosion Engineers, 1985. p. 4-5
(24) European Economic Community. Commission Directive 93/72/EEC. September 1, 1993
(25) Workplace environmental exposure level guide. AIHA Journal. Vol. 56, no. 2, 1995. p. 202
(26) National Institute for Occupational Safety and Health (NIOSH). Particulates Not Otherwise Regulated, Total. In: NIOSH Manual of Analytical Methods (NMAM(R)). 4th ed. Edited by M.E. Cassinelli, et al. DHHS (NIOSH) Publication 94-113. Aug. 1994. Available at: <www.cdc.gov/niosh/nmam/nmammenu.html>
(27) National Institute for Occupational Safety and Health (NIOSH). Particulates Not Otherwise Regulated, Respirable. In: NIOSH Manual of Analytical Methods (NMAM(R)). 4th ed. Edited by M.E. Cassinelli, et al. DHHS (NIOSH) Publication 94-113. Aug. 1994. Available at: <www.cdc.gov/niosh/nmam/nmammenu.html>

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.


Review/Preparation Date: 1996-03-25

Revision Indicators:
EU number 1996-06-01
EU class 1996-06-01
EU risk 1996-06-01
EU safety 1996-06-01
TDG 2002-06-11
NFPA (health) 2003-04-16
Bibliography 2005-03-03
Sampling/analysis 2005-03-03
LFL/LEL 2006-10-05
UFL/UEL 2006-10-05



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