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 CCOHS Chemical Name: Sodium hydroxide solid

Record Contents

 CHEMINFO Record Number: 737
 CCOHS Chemical Name: Sodium hydroxide solid

Caustic flake
Caustic soda
Soda lye
Sodium hydrate
White caustic
Hydroxyde de sodium (solide)
Sodium hydroxide

 Chemical Name French: Hydroxyde de sodium
 Chemical Name Spanish: Hidróxido de sodio
Hidróxido sódico
Sosa caústica
 CAS Registry Number: 1310-73-2
 UN/NA Number(s): 1823
 RTECS Number(s): WB4900000
 EU EINECS/ELINCS Number: 215-185-5
 Chemical Family: Sodium and compounds / inorganic sodium compound / alkali metal hydroxide
 Molecular Formula: H-Na-O
 Structural Formula: NaOH

Status of Record:
The CHEMINFO record for this chemical is complete. The full format provides a detailed evaluation of health, fire and reactivity hazards, as well as recommendations on topics such as handling and storage, personal protective equipment, accidental release and first aid.


 Appearance and Odour:
White, odourless, non-volatile pellets, flakes, beads, chips, sticks, lumps or solid cake. Deliquescent (absorbs moisture from the air and forms wet solutions).(3,21,25)

 Odour Threshold:
Odourless (3)

 Warning Properties:
POOR - sodium hydroxide has no odour.

Sodium hydroxide is produced mainly in three forms: 50% and 73% aqueous solutions, and anhydrous sodium hydroxide in the form of solid cakes, flakes or beads. The major impurities include sodium chloride, sodium carbonate, sodium sulfate, sodium chlorate, potassium and heavy metals such as iron and nickel.(25,35) This record reviews the information relevant to the solid form. CHEMINFO record 5 reviews information relevant to solutions.

 Uses and Occurrences:
The main uses of sodium hydroxide are in chemical manufacturing (pH control, acid neutralization, off-gas scrubbing and catalyst); pulp and paper manufacturing; in petroleum and natural gas industry (removing acidic contaminants in oil and gas processing); manufacture of soap and detergents and other cleaning products; and cellulosics, such as rayon, cellophane and cellulose ethers; cotton mercerizing and scouring. Other uses include water treatment, food processing, flue-gas scrubbing, mining, glass making, textile processing, refining vegetable oils, rubber reclamation, metal processing, aluminum processing, metal degreasing, adhesive preparations, paint remover, disinfectant, rubber latex stabilizer and stabilization of sodium hypochlorite.(25,35)


White, odourless, non-volatile solid. Commonly used as clear solution. Deliquescent. Will not burn. Highly reactive. Can react violently with water and numerous commonly encountered materials, generating enough heat to ignite nearby combustible materials. Contact with many organic and inorganic chemicals may cause fire or explosion. Reaction with metals releases flammable hydrogen gas. EXTREMELY CORROSIVE. Can cause blindness, permanent scarring and death. Aerosols can cause lung injury--effects may be delayed.


Effects of Short-Term (Acute) Exposure

Sodium hydroxide does not readily form a vapour and inhalation exposure is only likely to occur to aerosols since the solid is deliquescent and not likely to form a dust. Three case reports suggest that sodium hydroxide aerosols may cause severe irritation of the respiratory tract. In one case, permanent lung injury resulted. Due to its corrosive nature, sodium hydroxide aerosols could cause pulmonary edema (severe, life-threatening lung injury).
A worker, exposed to hot mists of sodium hydroxide in a confined space, experienced tightness of chest, dyspnea (difficult breathing) and cough during each exposure. The symptoms resolved when exposure stopped.(32) Irreversible obstructive lung disease resulted when an individual applied about 5 L of a 5% sodium hydroxide solution with a brush in a small room with very limited ventilation.(33) Severe lung injury occurred in a man who inhaled an aerosol given off when water was poured on sodium hydroxide pellets.(18)

 Skin Contact:
Sodium hydroxide is extremely corrosive and is capable of causing severe burns with deep ulceration and permanent scarring. It can penetrate to deeper layers of skin and corrosion will continue until removed. The severity of injury depends on the concentration (solutions) and the duration of exposure. The solid absorbs moisture from the skin, air and water used for removal and can also cause severe burns. Burns may not be immediately painful; onset of pain may be delayed minutes to hours.
Several human studies and case reports describe the corrosive effects of sodium hydroxide. A 4% solution of sodium hydroxide, applied to a volunteer's arm for 15 to 180 minutes, caused damage which progressed from destruction of cells of the hard outer layer of the skin within 15 minutes to total destruction of all layers of the skin in 60 minutes.(6) Solutions as weak as 0.12% have damaged healthy skin within 1 hour.(5) Sodium hydroxide dissolved the hair and caused reversible baldness and scalp burns when a concentrated solution (pH = 13.5) dripped onto a worker's head and treatment was delayed for several hours.(7)

 Eye Contact:
Sodium hydroxide is extremely corrosive. The severity of injury increases with the concentration (for solutions), the duration of exposure, and the speed of penetration into the eye. The solid will absorb moisture from the eye, or water being used for removal, forming a highly concentrated solution. Damage can range from severe irritation and mild scarring to blistering, disintegration, ulceration, severe scarring and clouding. Conditions which affect vision such as glaucoma and cataracts are possible late developments. In severe cases, there is progressive ulceration and clouding of eye tissue which may lead to permanent blindness.(8,9,10,11)

There are no reported cases of industrial workers ingesting sodium hydroxide. Non-occupational ingestion has produced severe corrosive burns to the esophageal tissue, which has in some cases progressed to stricture formation. Should ingestion occur, severe pain; burning of the mouth, throat and esophagus; vomiting; diarrhea; collapse and possible death may result.

Effects of Long-Term (Chronic) Exposure

SKIN: Owing to its corrosive nature, repeated or prolonged skin contact would be expected to cause drying, cracking, and inflammation of the skin (dermatitis).
INHALATION: A worker, exposed for 2 hours daily over 20 years to mists from boiling a solution of sodium hydroxide in 2 large containers in a small room with inadequate ventilation, developed severe obstructive airway disease. It was concluded that the massive and prolonged exposure induced irritation and burns to the respiratory system eventually leading to the disease. The authors noted that chronic exposure had not previously been reported, probably since the strong and immediate irritation would normally deter workers from further exposure.(32) Actual exposures to sodium hydroxide aerosols were not measured and the authors could not definitely exclude late onset asthma as a cause of the man's condition.
A report of workers exposed to sodium hydroxide aerosol for at least 16 months, was confounded by the presence of high concentrations of Stoddard solvent and other solvent vapours, as well as other chemicals.(2,4)
There was no trend of increased mortality in relation to duration (up to 30 years) or intensity of exposure (0.5 mg/m3 to 1.5 mg/m3) among 291 workers exposed to sodium hydroxide dust during the production of flakes or beads of concentrated sodium hydroxide from chlorine cell effluent.(12) This study is limited by the small population size.


Sodium hydroxide has been implicated as a cause of cancer of the esophagus in individuals who have ingested it. The cancer may develop 12 to 42 years after the ingestion incident. Similar cancers have been observed at the sites of severe thermal burns. These cancers may be due to tissue destruction and scar formation rather than the sodium hydroxide itself.(15,16,17)
A case-control study reported an association between renal cancer and history of employment in the cell maintenance area of chlorine production. The major exposures in this work were presumed to be to asbestos and sodium hydroxide. An association was made between renal cancer and sodium hydroxide exposure.(34) This study is limited by factors such as small numbers of exposed workers, multiple exposures, reliance on work histories and is not considered sufficiently reliable.

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 or animal information available.

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

There are no reports of human or animal in vivo studies available. Short-term testing (in vitro and bacterial) suggests that sodium hydroxide is not mutagenic.

 Toxicologically Synergistic Materials:
No information available.

 Potential for Accumulation:
Does not accumulate.


Remove source of contamination or move victim to fresh air. If breathing is difficult, oxygen may be beneficial if administered by trained personnel, preferably on a doctor's advice. DO NOT allow victim to move about unnecessarily. Symptoms of pulmonary edema can be delayed up to 48 hours after exposure. Immediately transport victim to an emergency care facility.

 Skin Contact:
Avoid direct contact with this chemical. Wear chemical protective clothing, if necessary. Quickly and gently blot or brush away excess chemical. As quickly as possible, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Flush contaminated area with lukewarm, gently flowing water for at least 60 minutes, by the clock. DO NOT INTERRUPT FLUSHING. If necessary, keep emergency vehicle waiting. Transport victim to an emergency care facility immediately. Discard contaminated clothing, shoes and leather goods.

 Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. Quickly and gently blot or brush away excess chemical. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for at least 60 minutes, by the clock, while holding the eyelid(s) open. Neutral saline solution may be used as soon as it is available. DO NOT INTERRUPT FLUSHING. If necessary, keep emergency vehicle waiting. Take care not to rinse contaminated water into the unaffected eye or onto the face. Quickly transport victim to an emergency care facility.

NEVER give anything by mouth if victim is rapidly losing consciousness, is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water to dilute material in stomach. If milk is available, it may be administered AFTER the water has been given. If vomiting occurs naturally, repeat administration of water. Quickly transport victim to an emergency care facility.

 First Aid Comments:
Provide general supportive measures (comfort, warmth, rest). Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation contact.
Some recommendations in the above sections may be considered medical acts in some jurisdictions. These recommendations should be reviewed with a doctor and appropriate delegation of authority obtained, as required.
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:
Not sensitive; stable material.

 Sensitivity to Static Charge:
Not applicable. Not combustible.

 Combustion and Thermal Decomposition Products:
Sodium oxide fumes can be generated by thermal decomposition at elevated temperatures.(25)

 Fire Hazard Summary:
Sodium hydroxide will not burn or support combustion. However, reaction of sodium hydroxide with water and a number of commonly encountered materials (see Chemical Reactivity) can generate sufficient heat to ignite nearby combustible materials. Sodium hydroxide can react with metals, such as aluminum, tin and zinc, to form flammable hydrogen gas.

 Extinguishing Media:
Use extinguishing media suitable for the surrounding fire. If water is used, care should be taken, since it can generate heat and cause spattering if applied directly to sodium hydroxide.

 Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location. Approach fire from upwind. If possible, isolate materials not involved in the fire and protect personnel. Move containers from fire area if it can be done without risk.
Water can be used with extreme caution to extinguish a fire in an area where sodium hydroxide is stored. The water must not come into contact with the sodium hydroxide. Water can be used in flooding quantities as a spray or fog to keep fire-exposed containers cool and absorb heat.
At high temperatures, fuming may occur, giving off a strong, corrosive gas. Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. Chemical resistant clothing (e.g. chemical splash suit) and positive pressure self-contained breathing apparatus (MSHA/NIOSH approved or equivalent) may be necessary.


 NFPA - Health: 3 - Short exposure could cause serious temporary or residual injury.
 NFPA - Flammability: 0 - Will not burn under typical fire conditions.
 NFPA - Instability: 1 - Normally stable, but can become unstable at elevated temperatures and pressures, or may react vigorously, but non-violently with water.


 Spill Precautions:
Restrict access to area. Provide adequate protective equipment and ventilation.
Remove chemicals which can react with the spilled material.
Notify occupational health and safety and environmental authorities.

Contain spill or leak. Do not allow entry into sewers or waterways. Shovel or sweep up dry sodium hydroxide for recycling or disposal. Neutralize the final traces and flush area with water.
Solutions should be contained by diking with inert material, such as sand or earth. Solutions can be recovered or carefully diluted with water and cautiously neutralized with acids such as acetic acid or hydrochloric acid.
Large spills: contact fire and emergency services and supplier for advice.


This material is EXTREMELY CORROSIVE. Before handling, it is very important that engineering controls are operating and that protective equipment requirements and personal hygiene measures are being followed. People working with this chemical should be properly trained regarding its hazards and its safe use.
Use the smallest possible amounts in an area separate from the storage area. Immediately report leaks, spills or failures of the engineering controls. Inspect containers for damage or leaks before handling. Use the type of containers recommended by the manufacturer.
Unprotected persons should avoid all contact with this chemical including contaminated equipment. Do not use with incompatible materials such as strong acids, nitroaromatic, nitroparaffinic or organohalogen compounds. See Incompatibilities - Materials to Avoid section for more information.
Avoid generating dusts. Prevent the release of dusts into the workplace air. Transfer solids using tools or equipment which are corrosion-resistant. Cautiously, transfer into sturdy containers made of compatible materials. Never return contaminated material to its original container.
Never add water to a corrosive. Always add corrosives to water. When mixing with water, stir small amounts in slowly. Use cold water to prevent excessive heat generation. In general, keep solid sodium hydroxide away from water. Post "DO NOT USE WATER" signs in area of use to prevent accidental contact.
Label containers. Avoid damaging containers. Keep containers tightly closed when not in use. Follow handling precautions on Material Safety Data Sheet. Have suitable emergency equipment for fires, spills and leaks readily available. Practice good housekeeping. Maintain handling equipment. Comply with applicable regulations.

Store in a cool, dry, well-ventilated area. Keep quantity stored as small as possible.
Store away from incompatible materials such as strong acids, nitroaromatic, nitroparaffinic or organohalogen compounds. Take measures to ensure storage area cannot be contaminated with water. See Incompatibilities - Materials to Avoid section for more information.
Inspect all incoming containers to make sure they are properly labelled and not damaged. Always store in original labelled container, or in the type of container recommended by the manufacturer/supplier. Protect the label and keep it visible. Keep containers tightly closed when not in use and when empty. Protect from damage.
Storage area should be clearly identified, clear of obstruction and accessible only to trained and authorized personnel. Keep storage area separate from work areas. Post warning signs. Inspect periodically for damage or leaks. Floors should be watertight and without cracks.
Have appropriate fire extinguishers and spill clean-up equipment in storage area. Follow any special instructions for storage on Material Safety Data Sheet (e.g. maximum storage quantities).
Keep empty containers in separate storage area. Empty containers may contain hazardous residues. Keep closed.
Avoid any dust build-up by frequent cleaning and suitable construction of storage area. Provide raised sills or ramps at doorways or create a trench which will contain any carried or dissolved solids and also prevent accidental water contamination.
Use corrosion-resistant structural materials and lighting and ventilation systems in the storage area.
Containers made of nickel alloys are preferred. Steel containers are acceptable if temperatures are not elevated.
Storage tanks for solutions should be above ground and surrounded with dikes capable of holding entire contents.


NOTE: Exposure to this material can be controlled in many ways. The measures appropriate for a particular worksite depend on how this material is used and on the extent of exposure. This general information can be used to help develop specific control measures. Ensure that control systems are properly designed and maintained. Comply with occupational, environmental, fire, and other applicable regulations.

Sampling and Analysis:
Use appropriate instrumentation and sampling strategy (location, timing, duration, frequency, and number of samples). Interpretation of the sampling results is related to these variables and the analytical method. Sampling should be carried out by trained personnel.

 OSHA Analytical Methods:
*NOTE: The method described below has been reported for metal and metalloid particulates and may also be suitable for sodium hydroxide solid. OSHA Method ID-121 - OSHA Analytical Methods Manual, 2nd ed. (39). Metal and Metalloid Particulates in Workplace Atmospheres (Atomic Absorption). Validated method. Collection on mixed cellulose ester membrane filter. Extraction with de-ionized water. Analysis by atomic absorption spectrophotometry or by atomic emission spectrophotometry. Detection limit: 0.009 ug/mL (analytical) and 0.0002 ug/mL (qualitative).

 NIOSH Analytical Methods:
*NOTE: The method described below has been reported for alkaline dusts including sodium hydroxide solid. NIOSH METHOD 7401, Issue 2 - NIOSH Manual of Analytical Methods. 4th ed. (40). Alkaline Dusts. Fully evaluated method. Collection on PTFE membrane filter. Extraction with 0.01N hydrochloric acid. Analysis by acid-base titration with 0.01N sodium hydroxide under nitrogen with endpoint by pH electrode. Estimated LOD: 0.03 mg per sample (as sodium hydroxide).

 Colorimetric Detector Tubes:
Not commercially available.

 Engineering Controls:
Engineering methods to control hazardous conditions are preferred. General methods include mechanical ventilation (dilution and local exhaust), process or personnel enclosure, control of process conditions and process modification (e.g., substitution of a less hazardous material). Administrative controls and personal protective equipment may also be required.

Use a corrosion-resistant ventilation system separate from other exhaust ventilation systems. Exhaust directly to the outside. Use local exhaust ventilation, and process enclosure if necessary, to control airborne dust and mist. Supply sufficient replacement air to make up for air removed by exhaust systems.

 Personal Protective Equipment:
If engineering controls and work practices are not effective in controlling exposure to this material, then wear suitable personal protective equipment including approved respiratory protection. Have appropriate equipment available for use in emergencies such as spills or fire.

If respiratory protection is required, institute a complete respiratory protection program including selection, fit testing, training, maintenance and inspection. Refer to the CSA Standard Z94.4-93, "Selection, Use, and Care, of Respirators," available from the Canadian Standards Association, Rexdale, Ontario, M9W 1R3.

 Respiratory Protection Guidelines:

UP TO 10 mg/m3: SAR operated in a continuous-flow mode; or full-facepiece respirator with high-efficiency particulate filter(s); or powered air- purifying respirator with dust and mist filter(s); or full-facepiece SCBA; or full-facepiece SAR.

EMERGENCY OR PLANNED ENTRY INTO UNKNOWN CONCENTRATIONS OR IDLH CONDITIONS: Positive pressure, full-facepiece SAR; or positive pressure, full-facepiece SAR with an auxiliary positive pressure SAR.

ESCAPE: Full-facepiece respirator with high-efficiency particulate filter(s); or escape-type SCBA.

NOTE: The IDLH concentration for sodium hydroxide is 10 mg/m3.

NOTE: The purpose of establishing an IDLH value is to ensure that the worker can escape from a given contaminated environment in the event of failure of the most protective respiratory protection equipment. In the event of failure of respiratory protective equipment every effort should be made to exit immediately.

NOTE: Substance causes eye irritation or damage; eye protection needed.

Air-purifying respirators do not protect against oxygen-deficient atmospheres.

ABBREVIATIONS: SAR = supplied-air respirator; SCBA = self-contained breathing apparatus. IDLH = Immediately Dangerous to Life or Health.

The respirator use limitations specified by the approving agency and the manufacturer must be observed.
Recommendations apply only to NIOSH approved respirators.

 Eye/Face Protection:
Chemical safety goggles. A face shield may also be necessary.

 Skin Protection:
Chemical protective gloves, coveralls, boots and/or other resistant protective clothing.

Have a safety shower/eye-wash fountain readily available in the immediate work area.

 Resistance of Materials for Protective Clothing:
Guidelines for sodium hydroxide, 30-70% (38):
RECOMMENDED (resistance to breakthrough longer than 8 hours): Butyl rubber, Natural rubber, Neoprene rubber,
Nitrile rubber, Polyethylene, Polyvinyl chloride, Viton(TM), Viton(TM)/Butyl rubber, Barrier (PE/PA/PE)
Silver Shield/4H(TM) (polyethylene/ethylene vinyl alcohol), Responder(TM), Trellchem(TM) HPS, Tychem(TM) BR/LV,
Tychem(TM) SL, Tychem(TM) TK.
NOT RECOMMENDED for use (resistance to breakthrough less than 1 hour): Polyvinyl alcohol.

Guidelines for sodium hydroxide, greater than 70% (38):
RECOMMENDED (resistance to breakthrough longer than 8 hours): Neoprene rubber, Polyvinyl chloride,
Trellchem(TM) HPS, Tychem(TM) BR/LV.

There is evidence that this material can cause serious skin injury (e.g. corrosion or absorption hazard).
Recommendations are NOT valid for very thin Natural rubber, Neoprene, Nitrile and PVC gloves (0.3 mm or less).
Resistance of specific materials can vary from product to product. Breakthrough times are obtained under conditions of continuous contact, generally at room temperature. Evaluate resistance under conditions of use and maintain clothing carefully.

 Personal Hygiene:
Remove contaminated clothing promptly. Keep contaminated clothing in closed containers. Discard or launder before rewearing. Inform laundry personnel of contaminant's hazards. Do not eat, drink or smoke in work areas. Wash hands thoroughly after handling this material. Maintain good housekeeping.



 Ceiling Exposure Limit (TLV-C): 2 mg/m3
 TLV Basis - Critical Effect(s): Irritation

 TLV Comments:
NOTE: In many jurisdictions, exposure limits are similar to the ACGIH TLVs. Since the manner in which exposure limits are established, interpreted and implemented can vary, obtain detailed information from the appropriate government agency in each jurisdiction.


 Ceiling Exposure Limit (PEL-C): 2 mg/m3

NOTE: The OSHA PEL Final Rule Limits are currently non-enforceable due to a court decision. The OSHA PEL Transitional Limits are now in force.


 Time-Weighted Average (PEL-TWA): 2 mg/m3

 Transitional Limit PEL Comments:
These Permissible Exposure Limits are taken from 29 CFR 1910.1000 Table Z - 1.


 ERPG-1: 0.5 mg/m3
 ERPG-2: 5 mg/m3
 ERPG-3: 50 mg/m3

The ERPG-1 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hr without experiencing other than mild transient adverse health effects or perceiving a clearly defined, objectionable odor.

The ERPG-2 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hr without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action.

The ERPG-3 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hr without experiencing or developing life-threatening health effects.

NOTE: Users of the ERPG values are strongly encouraged to consult the documentation before use.


 Molecular Weight: 40.00

 Conversion Factor:
Not applicable

 Melting Point: 318.4 deg C (605.1 deg F) (20,25)
 Boiling Point: 1390 deg C (2534 deg F) at 760 mm Hg (3,20)
 Relative Density (Specific Gravity): 2.13 at 20 deg C (water=1) (20,35)
 Solubility in Water: Very soluble (111 g/100 mL at 20 deg C (3))
 Solubility in Other Liquids: Soluble in absolute alcohol, methanol and glycerol; insoluble in acetone and diethyl ether.(25)
 Coefficient of Oil/Water Distribution (Partition Coefficient): Essentially zero (25)
 pH Value: 12 (0.05% solution) (25); 13 (0.5% solution) (25); 14 (5% solution) (25).
 Vapour Density: Not applicable
 Vapour Pressure: Essentially zero at room temperature (3)
 Saturation Vapour Concentration: Not applicable
 Evaporation Rate: Not applicable
 Critical Temperature: Not applicable


Normally stable. Sodium hydroxide rapidly absorbs carbon dioxide from the air (forming sodium carbonate).(25)

 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.

Sodium hydroxide reacts vigorously, violently or explosively with many organic and inorganic chemicals, such as strong acids, nitroaromatic, nitroparaffin and organohalogen compounds, glycols and organic peroxides.
Reacts violently with water generating significant heat and dangerously spattering corrosive sodium hydroxide.
Violently polymerizes acetaldehyde, acrolein or acrylonitrile.
Produces flammable and explosive hydrogen gas if reacts with sodium tetrahydroborate or metals, such as aluminum, tin, or zinc.
Can form spontaneously flammable chemicals upon contact with 1,2- dichloroethylene, trichloroethylene or tetrachloroethane.
Can produce carbon monoxide upon contact with solutions of sugars, such as fructose, lactose and maltose.
References 21 and 36 provide more complete lists of chemicals that may react hazardously with sodium hydroxide.

 Hazardous Decomposition Products:
None reported

 Conditions to Avoid:
Water, moisture, air

 Corrosivity to Metals:
Corrosive to aluminum, tin, zinc, copper, brass and bronze. Corrosive to steel at elevated temperatures (above 40 deg C). Not corrosive to nickel.(35,37)


Standard animal toxicity values are not available.
Toxicological information for solutions has been included, since sodium hydroxide purchased in solid form is commonly used in solution.

Eye Irritation:

Sodium hydroxide has been extensively studied in animals because of its ability to cause severe injury to the eyes. Factors which determine the extent and reversibility of the injury include physical state (solid or solution), concentration of solution, the amount of sodium hydroxide which comes into contact with the tissue and the duration of contact. Effects can range from mild irritation to severe corrosion with tissue destruction, and may include blindness, permanent scarring and death.(2,8,20) The following studies are typical of the research available for sodium hydroxide.

Application of a 1% solution of sodium hydroxide produced necrosis covering about 3/4 of the cornea, or a more severe necrosis covering a smaller area (a score of greater than 5.0 out of 10) in a standard Draize test with rabbits.(24)

Skin Irritation:

Sodium hydroxide has been extensively studied in animals because of its ability to cause severe injury to the skin. Factors which determine the extent and reversibility of the injury include physical state (solid or solution), concentration of solution, the amount of sodium hydroxide which comes into contact with the tissue and the duration of contact. Effects can range from mild irritation to severe corrosion with tissue destruction, and may include blindness, permanent scarring and death.(2,8,20) The following studies are typical of the research available for sodium hydroxide.

Application of 0.5 mL of 5, 10, 15 and 30% solutions of sodium hydroxide tested, produced severe necrosis in 6/6 rabbits in 4 hours. The 15 and 30% solutions produced severe ulcerative necrosis.(26) Application of 500 mg in a standard Draize test with rabbits produced severe damage to the skin in 24 hours.(19)

Effects of Short-Term (Acute) Exposure:

In one experiment, male rats were exposed to aerosols composed of sodium hydroxide, sodium carbonate and their hydrated forms. Because sodium hydroxide reacts rapidly with carbon dioxide in air to form sodium carbonate which is less alkaline, the researchers maintained a high concentration of sodium hydroxide by humidifying the air at 85%; later they removed all carbon dioxide from the dilution air.(1) This experiment is not considered relevant because of the combined exposure and the extraordinary measures the researchers took to maintain the sodium hydroxide aerosol. The researchers stated that the chemical reaction between sodium hydroxide and carbon dioxide to form sodium carbonate is so predominant, especially in the respiratory tract, the toxicity of sodium carbonate may be the only factor worth considering". Other historical studies on sodium hydroxide aerosol exposures have also been criticized from this viewpoint.(4)

Short-term oral exposure in animals has produced severe corrosive damage to the esophagus extending into surrounding tissues. In some cases, death has resulted. In some cases, esophageal strictures have subsequently developed in surviving animals.(27,28)

Effects of Long-Term (Chronic) Exposure:

Rats were exposed to a finely dispersed aerosol of a 40% sodium hydroxide solution twice weekly for 30 minutes for 2.5 months.(14) In a similar study, 20 rats were exposed to an aerosol generated from a 5, 10, 20 or 40% sodium hydroxide solution, twice a week for 30 minutes for a month before and a month after exposure to quartz dust for 3 days.(13) The concentrations of sodium hydroxide aerosol achieved were not specified for either study. In addition, neither study took into account the reaction of sodium hydroxide with carbon dioxide in air and, in one study the results are also confounded by the quartz exposure. Therefore, no conclusions can be drawn.


NOTE : Inclusion of Ecological Information on an MSDS is optional under the US Hazard Communication Standard and the Canadian Controlled Products Regulations (WHMIS). In other jurisdictions, inclusion of Ecological Information may be a requirement. For specific requirements, contact the relevant regulatory authorities in the jurisdiction where the MSDS is intended to be used.

The American National Standard for Hazardous Industrial Chemicals - Material Safety Data Sheets - Preparation (ANSI Z400.1-2004) provides advice on data that could be included in this section.

Databases in CCOHS's CD-ROM and Web collection which contain useful Ecological Information include CESARS, HSDB® (Hazardous Substances Data Bank) and CHRIS (Chemical Hazards Response Information System).


Federal, provincial and local regulations should be reviewed prior to disposal. May be possible to neutralize, dilute and flush the material into a sewer. May be possible to atomize dilute solutions in an approved combustion chamber.
Harmful to aquatic life in high concentrations.



Shipping Name and Description: SODIUM HYDROXIDE, SOLID
UN Number: UN1823
Class: 8
Packing Group/Risk Group: II
Special Provisions: ---
Passenger Carrying Road/Rail Limit: 15 kg or L
Marine Pollutant: ---

NOTE: This information incorporates the Transportation of Dangerous Goods Regulations SOR/2001-286, effective January 2, 2006.


Shipping Name and Description: SODIUM HYDROXIDE, SOLID
Hazard Class or Division: 8
Identification Number: UN1823
Packing Group: II

NOTE: This information was taken from the US Code of Federal Regulations Title 49 - Transportation and is effective July 1, 2004.



 CCOHS WHMIS Classification:
E - Corrosive material


 WHMIS Health Effects Criteria Met by this Chemical:
E - Corrosive to skin
E - TDG class 8 - corrosive substance

 WHMIS Ingredient Disclosure List:
Included for disclosure at 1% or greater.

Detailed WHMIS Classification According to Criteria:

Class A - Compressed Gas:
Does not meet criteria.

Class B - Flammable and Combustible Material:
Does not meet criteria.
Non- combustible (does not burn).

Class C - Oxidizing Material:
Does not meet criteria.

Class D - Poisonous and Infectious Material. Division 1 - Immediate and Serious Toxic Effects:
Insufficient information for classification.

Acute Lethality:
Insufficient information.

Class D - Poisonous and Infectious Material. Division 2 - Other Toxic Effects:
Does not meet criteria.
See detailed evaluation below.

Chronic Health Effects:
Insufficient information.

Does not meet criteria. Not included in standard reference lists.

Teratogenicity and Embryotoxicity:
Insufficient information.

Reproductive Toxicity:
Insufficient information.

Insufficient information.
No in vivo studies reported.

Respiratory Tract Sensitization:
Does not meet criteria.
Not reported as human respiratory sensitizer.

Skin Irritation:
Corrosive materials are not also classified as irritants.

Eye Irritation:
Corrosive materials are not also classified as irritants.

Skin Sensitization:
Insufficient information.

Class E - Corrosive Material:
Meets criteria.
Corrosive to animal skin and aluminum; TDG Class 8

Class F - Dangerously Reactive Material:
Does not meet criteria.


 OSHA Hazard Communication Evaluation:
Meets criteria for hazardous material, as defined by 29 CFR 1910.1200.


 EU Classification:
Corrosive. Causes severe burns. [C] (23)

 EU Risk Phrases:
Causes severe burns [R35]

 EU Safety Phrases:
Keep locked up and out of reach of children.* In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. Wear suitable gloves. Wear eye/face protection. In case of accident or if you feel unwell, seek medical advice immediately (show label where possible). [S:(1/2-)*26-37/39-45].
*This safety phrase can be omitted from the label when the substance or preparation is sold for industrial use only.

 EU Comments:
CONCENTRATION GREATER THAN OR EQUAL TO 5%: Corrosive. Causes severe burns. [C.; R35].
CONCENTRATION LESS THAN 2% AND GREATER THAN OR EQUAL TO 0.5%: Irritant. Irritant to eyes and skin. [Xi; R36/38].

Safety phrases relate to the highest concentration division indicated, but may also be applicable to lower concentrations.


 Selected Bibliography:
(1) Zwicker, G.M., et al. Toxicity of aerosols of sodium reaction products. Journal of Environmental Pathology and Toxicology. Vol. 2 (1979). p. 1139-50
(2) National Institute for Occupational Safety and Health. Criteria for a recommended standard: occupational exposure to sodium hydroxide. Department of Health, Education and Welfare, 1975
(3) NIOSH pocket guide to chemical hazards. National Institute for Occupational Safety and Health, June 1994. p. 284-285
(4) Cooper, D.W., et al. A critique of the US standard for industrial exposure to sodium hydroxide aerosols. American Industrial Hygiene Association Journal. Vol. 40, no. 5 (1979). p. 365-371
(5) Malten, K.E., et al. Injury to the skin by alkali and its regeneration. Dermatologica. Vol. 132 (1966). p. 124-130
(6) Nagao, S., et al. The effect of sodium hydroxide and hydrochloric acid on human epidermis: an electronmicroscopic study. Acta Dermatovener (Stockholm). Vol. 52 (1972). p. 11-23
(7) Morris, G.E. Chemical alopecia: a unique case. Archives of Industrial Hygiene and Occupational Medicine. Vol. 6 (1952). p. 530-531
(8) Grant, W.M. Toxicology of the eye. 4th edition. Charles C. Thomas, 1993. p. 82-86, 1302-1310
(9) Hughes, W.F. Jr. Alkali burns of the eye. I. Review of the literature and summary of present knowledge. Archives of Ophthalmology. Vol. 92 (1946). p. 423-449
(10) Dennis, R.H. A simple procedure for treatment of alkali burns of the eye. The Journal of the Maine Medical Association. Vol. 45 (1954). p. 332-34
(11) Girard, L.J., et al. Severe alkali burns. Transactions of the American Academy of Ophthalmology & Otolaryngology. Vol. 74 (July-August, 1970). p. 788-803
(12) Ott, M.G., et al. Mortality among employees chronically exposed to caustic dust. Journal of Occupational Medicine. Vol. 19, no. 12 (December, 1977). p. 813-861
(13) Vyskocil, J., et al. The effect of aerosol inhalations of sodium hydroxide on the elimination of quartz dust from lungs of rats: experimental studies of dust elimination from the lungs: IVth communication. Scripta Medica. Vol. 39, no. 1 (1966). p. 25-29
(14) Dluhos, M., et al. Experimental study of the effect of aerosol inhalations of sodium hydroxide on the respiratory tract of rats. Vnitrni Lekarstvi. Vol. 15, no. 1 (1969). p. 38-42 (English translation: NIOSHTIC Control Number: 00048773).
(15) Benedict, E.B. Carcinoma of the esophagus developing in benign stricture. New England Journal of Medicine. Vol. 224, no. 10 (March 6, 1941). p. 408-412
(16) Bigelow, N.H. Carcinoma of the esophagus developing at the site of lye stricture. Cancer. Vol. 6 (November, 1953). p. 1159-1164
(17) Kiviranta, U.K. Corrosion carcinoma of the esophagus: 381 cases of corrosion and nine cases of corrosion carcinoma. Acta Otolaryngologica. Vol. 42 (1952). p. 89-95
(18) Nash, P.E., et al. Pneumothorax following inhalation of caustic soda fumes. Archives of Emergency Medicine. Vol. 5, no. 1 (1988). p. 45-47
(19) RTECS record for sodium hydroxide. Date of last update: 9504
(20) Pierce, J.O. Alkaline Materials. In: Patty s Industrial Hygiene and Toxicology. 4th edition. Volume II. Toxicology. Part A. John Wiley & Sons, Inc., 1993. p. 771-773, 779-781
(21) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 49; NFPA 491
(23) European Economic Community. Commission Directive 93/72/EEC. September 1, 1993
(24) Carpenter, C.P., et al. Chemical burns of the rabbit cornea. American Journal of Ophthalmology. Vol. 29 (1946). p. 1363-1372
(25) HSDB record for sodium hydroxide. Last revision date: 95-01-24.
(26) Harton, E., et al. Toxicological and skin corrosion testing of selected hazardous materials. Final Report 1973-1974. Report No. DOT/MTB/OHMO-76/2. Office of Hazardous Materials Operations, U.S. Department of Transportation, April, 1976. (National Technical Information Service Report No. PB-264 975).
(27) Bosher, L.H., et al. The pathology of experimentally produced lye burns and strictures of the esophagus. The Journal of Thoracic and Cardiovascular Surgery. Vol. 21 (1951). p. 483-489
(28) Krey, H. On the treatment of corrosive lesions in the oesophagus: an experimental study. Acta Oto-Laryngologica. Supplementum 102 (1952).
(29) Morita, T., et al. Effects of pH in the in vitro chromosomal aberration test. Mutation Research. Vol. 225 (1989). p. 55-60
(30) Demerec, M., et al. A survey of chemicals for mutagenic action on E. Coli. The American Naturalist. Vol. 85, no. 821 (March-April, 1951). p. 119-136
(31) Martin, F.M. Summary review of the health effects associated with sodium hydroxide: health issue assessment. Report No. EPA/600/8-88/081. Office of Health and Environmental Assessment, U.S. Environmental Protection Agency, June, 1988. (National Technical Information Service Report No. PB88-231949).
(32) Rubin, A.E., et al. Obstructive airway disease associated with occupational sodium hydroxide inhalation. British Journal of Industrial Medicine. Vol. 49 (1992). p. 213-214
(33) Hansen, K.S., et al. Obstructive lung injury after treating wood with sodium hydroxide. Journal of the Society of Occupational Medicine. Vol. 41, no. 1 (1991). p. 45-46
(34) Bond, G.G., et al. A case-control study of renal cancer mortality at a Texas chemical plant. American Journal of Industrial Medicine. Vol. 7 (1985). p. 123-139
(35) Curlin L.C., et al. Alkali and chlorine products. In: Kirk-Othmer encyclopedia of chemical technology. 4th Edition. Volume 1. John Wiley and Sons, 1991. p. 1004-1025
(36) Bretherick, L. Bretherick's handbook of reactive chemical hazards. 4th edition. Butterworths, 1990. p. 11-12, 31, 121, 133, 223, 247-248, 418- 419, 603-604, 1182-1184, 1472, 1474, 1489, 1695-1696
(37) Corrosion data survey: metals section. 6th edition. National Association of Corrosion Engineers, 1985. p. 118-119
(38) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(39) Occupational Safety and Health Administration (OSHA). Metal and Metalloid Particulates in Workplace Atmospheres (Atomic Absorption). In: OSHA Analytical Methods Manual. Revision Date: Oct. 31, 2001. Available at: <>
(40) National Institute for Occupational Safety and Health (NIOSH). Alkaline Dusts. 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: 1995-11-29

 Revision Indicators:
Sampling 1996-06-01
Respiratory guidelines 1996-06-01
Resistance of materials 1996-06-01
US transport 1998-03-01
Resistance of materials 1998-06-01
Bibliography 1998-06-01
ERPG 2001-03-01
TDG 2002-05-29
Bibliography 2003-04-15
PEL transitional comments 2003-11-18
Resistance of materials for PPE 2004-03-31
Bibliography 2005-03-20
Sampling/analysis 2005-03-20

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