Product Name: Hydroxyquinone
Chemical Formula: C6H4(OH)2
SYNONYMS: Hydroquinone, 1,4-dihydroxybenzene, quinol
Use: Used in photographic developing, as an antioxidant in rubber, in hair dyes and skin-lightening creams, in polymerization inhibitor for monomers, and for laboratory research.
CAS Number: 123-31-9
Manufacturer Contact: Emergency and information lines should be available on the product label and Safety Sheet.
Recommended Restrictions: Professional or industrial application under controlled conditions.
Classification: Acute Toxicity (oral, dermal), Skin Sensitization, Eye Irritation, Carcinogenicity, Aquatic Hazard
Hazard Statements: Harmful if swallowed, in contact with skin, or inhaled. Causes skin and serious eye irritation. May cause allergic skin reaction. Suspected of causing cancer. Very toxic to aquatic life.
Signal Word: Danger
Pictograms: Health hazard, exclamation mark, environment
Precautionary Statements: Avoid breathing dust or vapors, wash hands after handling, keep away from food and drinks, wear protective clothing including gloves and eye protection, avoid release to environment.
Routes of Exposure: Inhalation, ingestion, skin, and eye contact.
Chemical Identity: Hydroquinone
Concentration: 98–100% w/w (typical for laboratory grade)
Impurities: Trace amounts of phenol, benzoquinone
Other Constituents: No significant non-hazardous components.
Inhalation: Move person to fresh air, keep at rest in a comfortable position. Seek medical advice if respiratory symptoms develop.
Skin Contact: Take off contaminated clothing, rinse skin thoroughly with water and soap. Seek medical help if irritation or redness appears.
Eye Contact: Rinse cautiously with water for several minutes, remove contact lenses if present, continue rinsing and seek medical attention.
Ingestion: Rinse mouth with water if conscious. Do not induce vomiting. Seek immediate medical attention.
Most Important Symptoms: Redness, irritation, dermatitis, respiratory distress, potential for methemoglobinemia (rare but serious reaction affecting blood oxygen).
Extinguishing Media: Water spray, dry chemical, CO2, foam.
Unusual Fire Hazards: Substance may form hazardous decomposition products such as carbon monoxide and carbon dioxide during combustion. Dust can form explosive mixtures with air.
Protective Equipment: Wear self-contained breathing apparatus and fully protective clothing. Adequate ventilation required in all fire situations.
Special Procedures: Cool exposed containers with water. Prevent runoff from entering sewers.
Personal Precautions: Evacuate unnecessary personnel, ventilate area, avoid breathing dust and vapors. Wear appropriate PPE including gloves, eye protection, and respiratory protection if warranted.
Environmental Measures: Avoid discharge into drains, surface waters, or soil. Spilled hydroxyquinone can severely impact aquatic environments due to toxicity.
Containment: Sweep up carefully to avoid dust formation. Place in properly labeled containers for disposal.
Cleanup: Use non-sparking tools and pick up solid without generating dust. Wash spill area thoroughly after removal.
Safe Handling: Use only in well-ventilated areas, avoid generation of dusts, prevent contact with eyes, skin, and clothing. Do not eat, drink, or smoke nearby. Wash hands and skin after handling. Implement controls for potential dust ignition.
Storage Conditions: Store in tightly closed containers, in a cool, dry, well-ventilated spot, away from incompatible materials like oxidizers. Keep out of direct sunlight. Separate from food and feed.
Incompatibles: Strong acids, bases, oxidizing agents, iron, and iron salts.
Packaging Materials: Use glass or plastic; metal could catalyze oxidation.
Occupational Exposure Limits: ACGIH TLV: 2 mg/m3 (TWA, skin notation). OSHA PEL: 2 mg/m3 (TWA).
Engineering Controls: Ventilation, fume hoods, or local exhaust systems to control airborne concentrations.
Personal Protective Equipment: Suitable chemical-resistant gloves (nitrile or neoprene), protective clothing, tightly fitting safety goggles. Respirator if dust or vapors exceed permissible exposure limits. Emergency eyewash station and safety shower recommended in work area.
Hygiene Measures: Wash thoroughly with soap and water after handling, remove contaminated clothing.
Appearance: White to off-white crystalline solid
Odor: Faint phenolic
Odor Threshold: Not established
pH: 4.5–6 (1% solution)
Melting Point: 172–174°C (341–345°F)
Boiling Point: 285°C (545°F), decomposes
Flash Point: 165°C (329°F) (closed cup)
Evaporation Rate: Not applicable (solid at ambient)
Flammability: Combustible
Vapor Pressure: 1 mmHg @ 108°C
Vapor Density: Not applicable (as solid)
Solubility: Soluble in water (7g/100 mL at 20°C), alcohol, ether
Partition Coefficient (log Kow): 0.59
Autoignition Temperature: 545°C
Decomposition Temperature: >330°C
Viscosity: Not applicable
Chemical Stability: Stable under recommended storage and handling practices, but may darken and degrade with air exposure.
Hazardous Reactions: May polymerize or oxidize in presence of light and air. Reacts with strong oxidizing agents, acids, or bases leading to hazardous products.
Decomposition Products: Produces carbon monoxide, carbon dioxide, phenol, and benzoquinone under fire or decomposition conditions.
Conditions to Avoid: Heat, flame, incompatibles, sunlight, humidity.
Incompatible Materials: Metals, oxidizers, iron, iron salts, alkalies.
Acute Toxicity: Oral (rat) LD50: 320 mg/kg; Dermal (rabbit): >2000 mg/kg
Skin Contact: May cause irritation, sensitization, possible allergic reaction over repeated exposure
Eye Contact: Serious irritation, lasting damage if not flushed immediately
Inhalation: Irritation of respiratory tract, symptoms may include coughing, headache, dizziness
Ingestion: Nausea, vomiting, methemoglobinemia at sufficient dose
Chronic Effects: Prolonged exposure linked to skin depigmentation, bone marrow suppression, possible cataract formation. IARC categorizes as Group 3 (not classifiable as to human carcinogenicity) based on animal studies.
Sensitization: Hydroxyquinone may lead to contact allergy in some persons.
Aquatic Toxicity: Highly toxic to aquatic life. LC50 (fish, 96h): approx. 0.044 mg/L (rainbow trout). EC50 (Daphnia, 48h): 0.17 mg/L
Persistence and Degradability: Incomplete evidence for rapid environmental degradation; may persist if released in large quantities.
Bioaccumulation Potential: Low bioaccumulation expected based on log Kow.
Mobility in Soil: Moves readily through soil to groundwater; soluble in water.
Adverse Effects: Use containment to prevent environmental contamination. Harmful effects extend to aquatic invertebrates and algae.
Waste Disposal Methods: Small amounts can be dissolved in water and neutralized with sodium bisulfite or sodium dithionite, then allow to oxidize in a controlled area before disposal following local, regional, and national regulations. Large spills require hazardous waste management contractor.
Contaminated Packaging: Rinse container with suitable solvent and dispose as hazardous waste. Reuse prohibited unless professionally cleaned and certified.
Precautions: Avoid release to environment; handle waste according to hazardous waste regulations.
UN Number: 3077
Proper Shipping Name: Environmentally hazardous substance, solid, n.o.s. (contains hydroquinone)
Transport Hazard Class: 9 (Miscellaneous dangerous substances and articles)
Packing Group: III
Labels Required: Miscellaneous hazard, Marine pollutant if shipped by sea
Special Precautions: Avoid mechanical shock or excessive vibration, secure containers to prevent leaks.
OSHA Status: Hazardous chemical under OSHA Hazard Communication Standard
TSCA: Listed
SARA 313: Subject to reporting
California Proposition 65: Not listed as a carcinogen or reproductive toxin
REACH Registration: Required for uses within Europe
Other Regulations: Subject to restrictions in cosmetics/skincare products outside professional supervision; strict workplace exposure standards apply internationally.
Label Elements: Warning labels must display GHS hazard and precautionary information in accordance with local regulations.
