HYDROQUINONE (DIHYDROXYBENZENE) | Occupational Safety and Health Administration

HYDROQUINONE (DIHYDROXYBENZENE)†

Chemical Identification
CAS #	123-31-9
Formula	C₆H₆O₂
Synonyms	p-benzenediol; 1,4-benzenediol; dihydroxybenzene; 1,4-dihydroxybenzene; quinol

Physical Properties
Physical description	Light-tan, light-gray, or colorless crystals.
Boiling point	545°F	Molecular weight	110.11
Freezing point/melting point	338°F	Vapor pressure	4 mmHg at 302°F
Flash point	329°F	Vapor density	3.81
Specific gravity	1.332 at 59°F	Ionization potential	7.95 eV
Lower explosive limit (LEL)		Upper explosive limit (UEL)
NFPA health rating	2	NFPA fire rating	1
NFPA reactivity rating	0	NFPA special instruction
Vapor hazard ratio (VHR)
Historical exceedance percentage
Target organs

Monitoring Methods Used by OSHA
Analyte code (IMIS no.)	1490
Sampling group
Sampler/Sampling media	XAD-7 (80/40 mg sections, 20/60 mesh) coated with 10% phosphoric acid [SKC 226-98]
Sampling time^*	100 min
Sampling volume (TWA)^*	20 L
Sampling flow rate (TWA)^*	0.2 L/min
Sampling volume (STEL/Peak/C)^*
Sampling flow rate (STEL/Peak/C)^*
Analytical method instruments	HPLC
Method reference	OSHA PV2094 (partially validated)
Notes
Special requirements

^* All sampling instructions above are recommended guidelines for OSHA Compliance Safety and Health Officers (CSHOs), please see the corresponding OSHA method reference for complete details.

Bulk/Wipe Method
Wipe Sampler/Sampling media
Bulk Method

On-Site Screening Techniques
Device
Model/Type
Sampling information (see manufacturer instructions)

**Exposure Limits**
OSHA PEL 8-hour TWA (ST) STEL (C) Ceiling Peak		NIOSH REL Up to 10-hour TWA (ST) STEL (C) Ceiling		ACGIH TLV© 8-hour TWA (ST) STEL (C) Ceiling		CAL/OSHA PEL 8-hour TWA (ST) STEL (C) Ceiling Peak
PEL-TWA	2 mg/m³	REL-TWA		TLV-TWA	1 mg/m³ [2007]	PEL-TWA	2 mg/m³
PEL-STEL		REL-STEL		TLV-STEL		PEL-STEL
PEL-C		REL-C	2 mg/m³ [15 minutes]	TLV-C		PEL-C
Skin notation	N	Skin notation	N	Skin notation	N	Skin notation	N
Notes: See 29 CFR 1910.1000 Table Z-1.		Notes:		Notes: dermal sensitizer (DSEN)		Notes:
Health factors: See NIH-NLM PubChem.		IDLH	50 mg/m³
Carcinogenic classifications: IARC-3, TLV-A3		Notes:
AIHA emergency response planning guidelines - ERPG-1/ERPG-2/ERPG-3:

Additional Resources and Literature References

NOAA: CAMEO Chemicals - Hydroquinone

NIOSH: Pocket Guide to Chemical Hazards - Hydroquinone

Literature References

ACGIH: Documentation of the Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Hydroquinone. See annual publication for most recent information.
International Chemical Safety Cards (WHO/IPCS/ILO): Hydroquinone.
DeCaprio, A.P.: The toxicology of hydroquinone - relevance to occupational and environmental exposure. Crit. Rev. Toxicol. 29(3): 283-330, 1999.
English, J.C. and Deisinger, P.J.: Metabolism and disposition of hydroquinone in Fischer 344 rats after oral or dermal administration. Food Chem. Toxicol. 43(3): 483-493, 2005.
Halder, R.M. and Richards, G.M.: Topical agents used in the management of hyperpigmentation. Skin Therapy Lett. 9(6): 1-3, 2004.
Pohanish, R.P. (editor): Hydroquinone. Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 1. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 1293-1295.

Last Updated Date : 12/31/2020

HYDROQUINONE (DIHYDROXYBENZENE)†

Chemical Identification

Physical Properties

Monitoring Methods Used by OSHA

Bulk/Wipe Method

On-Site Screening Techniques

Exposure Limits

Additional Resources and Literature References