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CHEMINFO Record Number: 286
CCOHS Chemical Name: Cyanuric acid

Pseudocyanuric acid
Tricyanic acid
Isocyanuric acid
s-Cyanuric acid

Chemical Name French: Acide cyanurique
CAS Registry Number: 108-80-5
RTECS Number(s): XZ1800000
EU EINECS/ELINCS Number: 203-618-0
Chemical Family: Nitrogen heterocyclic compound / cyclic triimide / symmetrical triazine / trihydroxy triazine / symmetrical triazinetriol / symmetrical triazinetrione
Molecular Formula: C3-H3-N3-O3
Structural Formula: [-C(OH)=N-C(OH)=N-C(OH)=N-] = [-C(=O)=N-C(=O)=N-C(=O)=N-] (6-member triazine ring)


Appearance and Odour:
White, odourless, crystalline solid, granules or powder.(1) Hygroscopic (absorbs moisture from the air).(7)

Odour Threshold:
Cyanuric acid is odourless.

Warning Properties:
Insufficient information available for evaluation.

Cyanuric acid exists as an equilibrium mixture of two chemical forms (tautomers), the keto or oxo form and the enol or trihydroxy form. The keto or oxo form is called isocyanuric acid, while the enol or trihydroxy form is called cyanuric acid. In solution and in the solid state, the keto form is the main form. In alkaline solution, the enol form predominates.(1,4) Cyanuric acid (or isocyanuric acid) is available as the anhydrous material and as a dihydrate. The anhydrous form is the main commercial compound. Cyanuric acid is sold mainly in coarse granular form. It is also available as a powder. Typical commercial products contain 98.5% and greater cyanuric acid. Impurities present include ammelide and ammeline.(1) Crude cyanuric acid contains up to 30% impurities consisting of melamine and its precursors, biuret, triuret, ammelide and ammeline.(6)

Uses and Occurrences:
Cyanuric acid is widely used to produce chlorinated isocyanurates, which are used as swimming pool, and spa and hot tub disinfectants, scouring powders, household bleaches, institutional and industrial cleansers, automatic dishwasher compounds and general sanitizers; as a stabilizer to inhibit ultraviolet destruction of chlorine and hypochlorous acid in swimming pools. It is also used as a laboratory source of isocyanic acid gas; and in the preparation of melamine, sponge rubber, selective herbicides, dyes, resins and antimicrobial agents.(1,4,6) Cyanuric acid is used on a small scale for reducing nitrogen oxides in stationary diesel engine exhaust gases and coal, oil or gas fired boilers.(1)


White, odourless, crystalline solid, granules or powder. Hygroscopic. May burn if strongly heated. Decomposes above 320-330 deg C to form explosive, corrosive and highly toxic isocyanic acid gas. Essentially non-toxic following short-term exposure.


Effects of Short-Term (Acute) Exposure

Cyanuric acid is a solid, which absorbs moisture from the air, and does not form a vapour at normal temperatures. It is not irritating and is not expected to pose an inhalation hazard. In general, high airborne concentrations of dusts or mists formed from solutions can cause irritation of the nose and throat and coughing. However, there is no human or animal information available for cyanuric acid.

Skin Contact:
Cyanuric acid is not expected to be irritating to the skin, based on animal information. In a review of pesticide injuries in California from 1949-1988, there is a single report of skin injury from exposure to cyanuric acid as a pesticide.(13) No other details are available for evaluation.
Cyanuric acid is not expected to be absorbed through the skin in harmful amounts, based on limited animal toxicity information.

Eye Contact:
Cyanuric acid is expected to cause no to very mild eye irritation, based on animal information. The dust may cause mechanical or abrasive injury to the eye and tearing as it is rinsed from the eye. In a review of pesticide injuries in California from 1949-1988, there is a report of 4 cases of eye injury from exposure to cyanuric acid as a pesticide.(13) No other details are available for evaluation.

Cyanuric acid is not expected to be toxic, based on limited animal information. There is no human information available. Ingestion is not a typical route for occupational exposure.

Effects of Long-Term (Chronic) Exposure

There is no human information available.

Kidneys/Urinary System:
Based on animal studies, long-term ingestion of relatively high doses can result in the formation of crystals in the kidneys resulting in kidney injury. Ingestion is not a typical route of occupational exposure.


There is no human information available. The limited information available from animal studies does not indicate that cyanuric acid is a carcinogen.

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 no listing for 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. The limited information available from an unconfirmed animal study does not indicate that cyanuric acid is a developmental toxin.

Reproductive Toxicity:
There is no human information available. The limited information available from an unconfirmed animal study does not indicate that cyanuric acid causes reproductive toxicity.

The available evidence does not indicate that cyanuric acid is mutagenic. Negative results were obtained in 2 tests in live rats with the closely related chemical sodium cyanurate and in tests using mammalian cells and bacteria. A positive result was reported in an unconfirmed test using mammalian cells.

Toxicologically Synergistic Materials:
There is no information available.

Potential for Accumulation:
Does not accumulate. Two volunteers who ingested unreported quantities eliminated half of it within 3 hours and greater than 98% of it in the urine within 24 hours. Swimmers in chlorinated pools were found to absorb cyanuric acid and then eliminate it quickly in the urine.(14) Rats dosed orally with cyanuric acid rapidly absorbed and eliminated it with no accumulation in any tissues.(15)


If symptoms are experienced, remove source of contamination or move victim to fresh air. Obtain medical advice.

Skin Contact:
Remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Wash gently and thoroughly with lukewarm, gently flowing water and non-abrasive soap for 5 minutes. If irritation persists, 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, immediately obtain medical attention. DO NOT attempt to manually remove anything stuck to the eye(s).

If irritation or discomfort occur, obtain medical advice.

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


Flash Point:
Not combustible (does not burn).

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

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

Autoignition (Ignition) Temperature:
Not applicable

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

Electrical Conductivity:
Not available

Minimum Ignition Energy:
Not applicable

Potential for Dust Explosions:
No information is available on whether cyanuric acid powder or dust can accumulate static charge and cause a dust explosion. Cyanuric acid is not included in lists of compounds that cause dust explosions.

Combustion and Thermal Decomposition Products:
Cyanuric acid decomposes when heated above 320-330 deg C to produce explosive, corrosive and highly toxic isocyanic acid, which can decompose to ammonia and carbon dioxide.(1,6) Nitrogen oxides, oxides of carbon and other irritating and/or toxic fumes and gases may be formed in a fire.

Fire Hazard Summary:
Cyanuric acid does not burn. It decomposes in a fire to form explosive, corrosive and highly toxic isocyanic acid gas and toxic and irritating nitrogen oxides. The heat from a fire can cause a rapid build-up of pressure inside closed containers, which may cause explosive rupture.

Extinguishing Media:
Cyanuric acid does not burn. Use extinguishing media suitable for surrounding fire.

Fire Fighting Instructions:
Evacuate area and fight fire from a protected, explosion-resistant location or maximum possible distance. Approach fire from upwind to avoid explosive and very toxic decomposition products, such as isocyanic acid. Wear full protective suit if exposure is possible. See Protection of Firefighters.
If possible, isolate containers exposed to heat, but not directly involved in the fire. Move containers from the fire area if this can be done without risk. Protect personnel. Otherwise, use water in flooding quantities as a spray or fog streams to keep fire-exposed cylinders and tanks cool and to absorb heat to help prevent rupture. Cooling should begin as soon as possible (within several minutes) and should concentrate on any unwetted portions of the container. Apply water from the side and a safe distance. Cooling should continue until well after the fire is out. Water spray may also be used to knock down irritating/toxic combustion products which may be produced in a fire. Dike fire control water for appropriate disposal. Stay away from ends of tanks, but be aware that flying material (shrapnel) from ruptured tanks may travel in any direction. Withdraw immediately in case of rising sound from venting safety device or any discolouration of tank. In an advanced or massive fire, the area should be evacuated.
Containers should not be approached after they have been involved in a fire until they have completely cooled down. After the fire has been extinguished, explosive and toxic atmospheres may linger. Before entering such an area, especially confined areas, check the atmosphere with an appropriate monitoring device while wearing a full protective gear.

Protection of Fire Fighters:
Cyanuric acid decomposes to very toxic isocyanic acid and toxic and irritating nitrogen oxides when heated in a fire. Firefighters may enter the area if positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) and full Bunker Gear is worn. Do not enter without wearing specialized equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. Chemical protective clothing (e.g. chemical splash suit) and positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) may be necessary.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 129.08

Conversion Factor:
Not applicable

Physical State: Solid
Melting Point: Does not melt. Sublimes and decomposes at 320-330 deg C (608-626 deg F) (1,6); also reported to decompose at greater than 360 deg C (680 deg F) (16)
Boiling Point: Not applicable. Decomposes.
Relative Density (Specific Gravity): 1.75 at 25 deg C (anhydrous); 1.66 at 25 deg C (dihydrate) (water = 1) (1,4)
Solubility in Water: Slightly soluble (200 mg/100 mL water at 25 deg C) (1,4,17)
Solubility in Other Liquids: Soluble in hot alcohols, pyridine, concentrated hydrochloric acid, concentrated sulfuric acid, aqueous alkali (e.g. sodium hydroxide and potassium hydroxide), N,N-dimethylformamide and dimethyl sulfoxide; slightly soluble in common organic solvents, such as acetone, benzene, diethyl ether and hexane.(1,4)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = 0.61 (estimated) (18)
pH Value: Approximately 4.8 (saturated water solution at room temperature).(1)
Acidity: Weak tribasic acid (6)
Dissociation Constant: pKa1 = 6.88; pKa2 = 11.40; pKa3 = 13.5 (1,4)
Viscosity-Dynamic: Not applicable
Surface Tension: Not applicable
Vapour Density: Not applicable
Vapour Pressure: Extremely low at room temperature.(8,17)
Saturation Vapour Concentration: Not applicable
Evaporation Rate: Negligible.
Henry's Law Constant: 1.38 x 10(-13) Pa.m3/mol (cited as 1.36 x 10(-18) atm.m3/mol) at 25 deg C (17); log H = -16.22 (dimensionless constant; calculated)

Other Physical Properties:
The dihydrate loses water in dry air and converts to the anhydrous compound at about 57 deg C.(1)


Normally stable.(1)

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.

CHLORINE - during chlorination of cyanuric acid, the presence of certain impurities or an unusually low pH value may lead to formation of explosive nitrogen trichloride.(19)
TRICHLOROISOCYANURIC ACID and SODIUM HYDROXIDE - explosive nitrogen trichloride is evolved in the reaction.(19)
STRONG OXIDIZING AGENTS (e.g. sodium chlorite, potassium permanganate) - reaction may be vigorous or violent.(7)

Hazardous Decomposition Products:
None reported.

Conditions to Avoid:
Temperatures above 300 deg C.

Corrosivity to Metals:
No information is available.

Corrosivity to Non-Metals:
No information is available.


Note: Cyanuric acid or isocyanuric acid is the same chemical compound, which exists in two different tautomeric forms. These chemical names are used interchangeably in the literature, and for all intents and purposes refer to the same chemical compound.

LC50 (rat): greater than 612 mg/m3 (reported as minimum toxic concentration; aerosol) (8, unconfirmed)

LD50 (oral, mouse): 3400 mg/kg (8, unconfirmed)
LD50 (oral, rat): greater than 5000 mg/kg (crude cyanuric acid; composition not specified) (2)
LD50 (oral, rat): 7700 mg/kg (8, unconfirmed)

LD50 (dermal, rabbit): greater than 5000 mg/kg (crude cyanuric acid; composition not specified) (2)
LD50 (dermal, rabbit): greater than 7940 mg/kg (8, unconfirmed)

Eye Irritation:

Crude cyanuric acid caused no to mild irritation in a confirmed study. Moderate irritation was reported in unconfirmed studies.

Application of 82 mg of powdered crude cyanuric acid (composition not specified) caused no to very mild irritation in rabbits (average score 0.3/110 for 24, 48 and 72 hours).(2) Two unconfirmed studies (one unpublished and the other not available in English), report that application of 20 or 500 mg for 24 hours caused moderate irritation in rabbits.(8, unconfirmed) No other details are available for evaluation.

Skin Irritation:

Cyanuric acid is not expected to be irritating to the skin, based on information for crude cyanuric acid.

Application of 500 mg of powdered crude cyanuric acid (composition not specified), moistened with physiological saline, to intact and damaged skin, for 24 hours caused no irritation in rabbits (primary irritation score 0/8).(2)

Effects of Long-Term (Chronic) Exposure:

The details of most of the reported studies cannot be unconfirmed, and many studies were conducted with the closely related chemical sodium cyanurate. Several studies show damage to the kidneys from long-term ingestion of high doses. This effect is thought to be caused by the formation of crystals in the kidneys. Cyanuric acid is well absorbed orally and rapidly eliminated in the urine. However, at higher doses it can precipitate to form crystals.(8) A limited study with rats exposed to sodium cyanurate for 20 weeks showed mortality and kidney damage in both sexes at 560 mg/kg/day. No effects were seen at 56 mg/kg/day. For more details on this study, refer to the CHEMINFO review of sodium cyanurate.

Rats were given 0, 10, 40, 150, or 600 mg/kg/day of cyanuric acid in sesame oil for 45 days for males or from 14 days before mating until day 3 of lactation for females. Harmful effects were only noted in both sexes at 600 mg/kg/day. In males, decreased body weight gain, and excretion of reddish urine caused by precipitated crystals of cyanuric acid was observed. Blood analysis indicated significant decreases in numbers and volumes of red blood cells and in hemoglobin. There were also some changes in blood chemistry. Excretion of reddish urine was also observed in females. In both sexes, kidney weights and relative adrenal weights were increased (significance not reported). Detailed examination of tissues showed degenerative changes in the kidneys. In females, there was also atrophy of the thymus.(8,9-unconfirmed) In studies, which are not available in English, ingestion of 30 mg/kg/day of cyanuric acid by guinea pigs and rats for 6 months caused kidney damage, while doses of 3 mg/kg/day did not.(5, unconfirmed) There are no further details available for evaluation.

The limited evidence available for cyanuric acid and sodium cyanurate, a closely related chemical, indicates that cyanuric acid is not a carcinogen.
In a study, which is not available in English and apparently did not use a control group, oral and dermal administration of cyanuric acid caused a low rate of tumour production in rats and mice after 18 months.(3,5-unconfirmed) There are few details available for evaluation and no conclusions can be drawn from this study.

Teratogenicity, Embryotoxicity and/or Fetotoxicity:
The limited evidence available does not indicate that cyanuric acid is a developmental toxin. No significant effects on fetal development were reported in an unconfirmed study with rats.
Male rats were given 0, 10, 40, 150, or 600 mg/kg/day of cyanuric acid in sesame oil for 44 days, while female rats were similarly dosed from 14 days before mating to day 3 of lactation. No increases in external or internal abnormalities were caused by the treatment.(8,9-unconfirmed)

Reproductive Toxicity:
The limited evidence available does not indicate that cyanuric acid causes reproductive toxicity.
Male rats were given 0, 10, 40, 150, or 600 mg/kg/day of cyanuric acid in sesame oil for 44 days, while female rats were similarly dosed from 14 days before mating to day 3 of lactation. No changes were noted in any reproductive parameters including copulation index, fertility index, gestation length, numbers of implantations or corpora lutea, implantation index, gestation index, delivery index or behaviour at delivery or lactation.(8,9-unconfirmed)

The available evidence does not indicate that cyanuric acid is mutagenic. Negative results were obtained with the closely related sodium cyanurate in two tests using live rats. Negative results were obtained for cyanuric acid in tests in mammalian cells and bacteria. A positive result was obtained in an unconfirmed test in mammalian cells.
A negative result (chromosome aberrations) was obtained in mammalian cells, with and without metabolic activation.(9) In unconfirmed tests using mammalian cells, negative results (sister chromatid exchange, gene mutation) were obtained.(8,10-unconfirmed) A positive result (chromosome aberrations) was observed in an unconfirmed test using mammalian cells.(10, unconfirmed) Negative results (gene mutation) were obtained in two studies using bacteria, with and without metabolic activation.(11,12)


Selected Bibliography:
(1) Wojtowicz, J.A. Cyanuric and isocyanuric acids. In: Kirk-Othmer encyclopedia of chemical technology. 4th ed. Vol. 7. John Wiley and Sons, 1993. p. 834-851
(2) Initial submission: letter from Monsanto Co. to US EPA regarding isocyanuric acid crude with attachments and cover letter dated 07/23/92. Monsanto, Co. Date produced: July 1992. EPA/OTS 88-920007730. NTIS/OTS0538650.
(3) Cyanuric acid and chlorinated derivatives CAS No. 108-80-5: chemical hazard information profile (draft report). US Environmental Protection Agency, March 13, 1981
(4) Cyanuric acid. The Merck index: an encyclopedia of chemicals, drugs and biologicals. Edited by M.J. O'Neil, et al. 13th ed. Merck and Company, 2001. p. 469
(5) Canelli, E. Chemical, bacteriological, and toxicological properties of cyanuric acid and chlorinated isocyanurates as applied to swimming pool disinfection: a review. American Journal of Public Health. Vol. 64, no. 2 (1974). p. 155-162
(6) Kriebitzsch, N., et al. Cyanuric acid and cyanuric chloride. In: Ullmann's encyclopedia of industrial chemistry. 5th completely revised ed. Vol. A 8. VCH Publishers, 1987. p. 191-200
(7) Cyanuric acid. In: The Sigma-Aldrich library of chemical safety data. Ed. II. Vol. 1. Sigma-Aldrich Corporation, 1985. p. 946C
(8) Isocyanuric acid. CAS no 108-80-5. Chemicals screening information data set (SIDS) for high production volume chemicals. Vol. 6, part 1. Organization for Economic Cooperation and Development (OECD). International Programme on Chemical Safety, June 2000. Available at: <>
(9) Isocyanuric acid. JETOC Information sheet. No. 38. Japan Chemical Industry-Toxicology and Information Center, 1999. p. 55-57
(10) Sobti, R.C., et al. Cytogenetic monitoring of environmental pollutants in South Florida. [Abstract]. Proceedings of the American Association of Cancer Research. Vol. 22 (1981). p. 110
(11) Lusby, A.F., et al. Variation in mutagenicity of S-triazine compounds tested on four Salmonella strains. Environmental Mutagenesis. Vol. 1 (1979). p. 287-290
(12) Haworth, S., et al. Salmonella mutagenicity test result for 250 chemicals. Environmental Mutagenesis. Vol. 5, suppl. 1 (1983). p. 1-142
(13) Maddy, K.T., et al. Illness injuries and death from pesticide exposures in California, USA 1949-1988. Reviews of Environmental Contamination and Toxicology. Vol. 114: 57-124
(14) Allen, L.M., et al. Absorption and excretion of cyanuric acid in long distance swimmers. Drug Metabolism Reviews. Vol. 13, no. 13 (1982). p. 499-516
(15) MacKellar, D.G., et al. Cyanuric acid: absorption, distribution, and excretion studies with 14C-labelled cyanuric acid (S-triazine trione) in rats. Toxicology and Applied Pharmacology. Vol. 45 (1978). p. 239
(16) Dean, J.A. Lange's handbook of chemistry. 15th ed. McGraw-Hill, Inc., 1999. p. 1.156
(17) Syracuse Research Corporation. The Physical Properties Database (PHYSPROP). Interactive PhysProp Database Demo. Date unknown. Available at: <>
(18) Syracuse Research Corporation. Interactive LogKow (KowWin) Database Demo. Date unknown. Available at: <>
(19) Urben, P.G., ed. Bretherick's reactive chemical hazards database. [CD-ROM]. 6th ed. Version 3.0. Butterworth-Heinemann Ltd., 1999
(20) National Institute for Occupational Safety and Health (NIOSH). Cyanuric Acid. 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: <>

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: 2005-10-03

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