PAC Database - Detailed Chemical Data
Chemical Identity
| Chemical | CAS# | UN# | Health Code Numbers | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Hydroquinone | 123-31-9 | 2662 |
13.00
15.01
4.01
11.01
14.02
4.08
4.05
7.01
8.00
7.00
|
|||||||||
| Formula | Synonyms | |||||||||||
| C6H6O2 | HYDROQUINONE, P-PHENYLENEDIOL, P-QUINOL, PARA-DIHYDROXYBENZENE, PARA-DIOXYBENZENE, PARA-HYDROQUINONE, PHIAQUIN, PYROGENTISIC ACID, QUINNONE, QUINOL, TECQUINOL, TENOX HQ, TEQUINOL, UN 2662, USAF EK-356, 1,4-BENZENEDIOL, 1,4-BENZOQUINOL, 1,4-DIHYDROXYBENZENE, 4-HYDROXYPHENOL, AIDA, ALPHA-HYDROQUINONE, ARCTUVIN, BENZENE, P-DIHYDROXY-, BENZOHYDROQUINONE, BENZOQUINOL, BETA-QUINOL, BLACK AND WHITE BLEACHING CREAM, BQ(H), DIAK 5, DIHYDROQUINONE, DIHYDROXYBENZENE, ELDOPAQUE, ELDOQUIN, HE 5, HIDROQUINONA (DOT SPANISH), HYDROQUINOL, HYDROQUINOLE, HYDROQUINONE (DOT FRENCH), NCI-C55834, P-BENZENEDIOL, P-DIHYDROQUINONE, P-DIHYDROXYBENZENE, P-DIOXOBENZENE, P-DIOXYBENZENE, P-HYDROQUINONE, P-HYDROXYPHENOL | |||||||||||
Physical Properties
| Mol Wt | State | MP (°C) | BP (°C) | VP (Hg) | VP (°C) | SG | LEL (ppm) |
|---|---|---|---|---|---|---|---|
| 110.12 | S | 172 | 285 | 25 | 1.358 @ 20°C |
PAC Values
| PAC-1 | PAC-2 | PAC-3 |
|---|---|---|
| 2.0 | 20 | 50 |
| PAC-1 | PAC-2 | PAC-3 |
|---|---|---|
| 0.44 | 4.4 | 11 |
Technical Basis
A review of available sources identified exposure limits (IDLH, STEL, ceiling limits, TWAs) and acute toxicity data (LD50, LDLo, TDLo). Data sources were selected according to the hierarchy listed in Table 3.1. Toxicity data were selected according to type of exposure, species, and route according to the hierarchies stated in Sections 3.3.1, 3.3.2, and evaluated using factors in Tables 3.2, 3.3, and 3.4. The 1990 and 1994 IDLH were evaluated; the 1990 IDLH was based on the PEL-TWA, while the 1994 IDLH included consideration of acute toxicity data in humans and animals. Considering this, analysts selected the 1994 IDLH as the TEEL-3. The LOC was selected as the TEEL-2. The lowest OEL-STEL (Sweden, 15-minute) was selected as the TEEL-1.
• PAC-1 = TEEL-1 = OEL-STEL (Finland, 2 mg/m3)
• PAC-2 = TEEL-2 = LOC (0.020 g/m3)
• PAC-3 = TEEL-3 = IDLH (1994, 50 mg/m3)
This review generated PAC-3 and PAC-1 values inconsistent with Rev. 29A and a PAC-2 value consistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a dog oral LD50¬, while the current TEEL-3 is a more preferred source, an IDLH (1994, Table 3.1). The Rev. 29A TEEL-1 basis was a TLV-TWA, while the current TEEL-1 is an OEL-STEL (see Note, Table 3.5). The Rev. 29A and current TEEL-2 values, source, and methodology are consistent.
• PAC-1 = TEEL-1 = OEL-STEL (Finland, 2 mg/m3)
• PAC-2 = TEEL-2 = LOC (0.020 g/m3)
• PAC-3 = TEEL-3 = IDLH (1994, 50 mg/m3)
This review generated PAC-3 and PAC-1 values inconsistent with Rev. 29A and a PAC-2 value consistent with Rev. 29A. The Rev. 29A TEEL-3 basis was a dog oral LD50¬, while the current TEEL-3 is a more preferred source, an IDLH (1994, Table 3.1). The Rev. 29A TEEL-1 basis was a TLV-TWA, while the current TEEL-1 is an OEL-STEL (see Note, Table 3.5). The Rev. 29A and current TEEL-2 values, source, and methodology are consistent.
References
Chemical information: https://pubchem.ncbi.nlm.nih.gov/compound/Hydroquinone
OELs: https://ilv.ifa.dguv.de/limitvalues/33801
LOC. Appendix C, pg. C-5. https://www.epa.gov/sites/default/files/2015-09/documents/technical_guidance_for_hazard_analysis.pdf
IDLH: https://www.cdc.gov/niosh/idlh/123319.html