Quinone is a federal hazardous air pollutant and was identified as a
toxic air contaminant in April 1993 under AB 2728.

CAS Registry Number: 106-51-4

Molecular Formula: C6H4O2

Quinone is formed as yellow crystals and has a characteristic irritating odor like that of chlorine (Merck, 1989). It is slightly soluble in water, alcohol, ether, hot petroleum ether, and alkalis. Quinone is an oxidizing agent and is reduced to hydroquinone (HSDB, 1991).

Physical Properties of Quinone

Synonyms: p-benzoquinone; cyclohexadienedione; 1,4-benzoquinone

Molecular Weight: 108.10
Melting Point: 115.7 oC
Vapor Pressure: 0.1 mm Hg at 25 oC
Vapor Density: 3.7 (air = 1)
Density/Specific Gravity: 1.318 at 20/4 oC (water = 1)
Log/Octanol Water Partition Coefficient: 0.20
Conversion Factor: 1 ppm = 4.42 mg/m3

(HSDB, 1991; Merck, 1989; U.S. EPA, 1994a)


A. Sources

Quinone is used in the manufacture of hydroquinone, in fungicides, as an analytical reagent, in photography, as a chemical intermediate, and as an oxidizing agent. It has also been detected in tobacco smoke (HSDB, 1991).

B. Emissions

No emissions of quinone from stationary sources in California were reported, based on data obtained from the Air Toxics "Hot Spots" Program (AB 2588) (ARB, 1997b).

C. Natural Occurrence

Quinone occurs naturally in a variety of arthropods and many insects synthesize simple benzoquinones (HSDB, 1991).


No Air Resources Board data exist for ambient measurements of quinone.


No information on indoor sources and concentrations of quinone was found in the readily-available literature.


Quinone will exist in the atmosphere in the gas phase. The dominant atmospheric loss process for quinone is expected to be by reaction with the hydroxyl (OH) radical [reaction with ozone is expected to be slow because of the >C(O) substituent groups (Atkinson and Carter, 1984)]. The estimated half-life and lifetime of quinone in the atmosphere due to reaction with the OH radical are about 3 hours and 4 hours, respectively (Kwok and Atkinson, 1995).


Quinone emissions are not reported from stationary sources in California under the AB 2588 program. It is also not listed in the California Air Pollution Control Officers Association Air Toxics "Hot Spots" Program Revised 1992 Risk Assessment Guidelines as having health values (cancer or non-cancer) for use in risk assessments (CAPCOA, 1993).


Probable routes of human exposure to quinone are inhalation and dermal contact (HSDB, 1991).

Non-Cancer: Quinone is a severe irritant of the eyes and respiratory tract. Exposure induces methemoglobinemia. Skin contact can cause skin ulceration and pigmentation changes (U.S. EPA, 1994a). Acute overexposure may also cause persons with a history of congenital or acquired eye defects to be at increased risk from exposure. Persons with poor visual acuity from high degrees of astigmatism, keratoconus, or existing corneal injury should be protected from repeated, uncontrolled exposure to quinone vapor (HSDB, 1991). Acute dermal exposure may result in dermatitis.

The United States Environmental Protection Agency (U.S. EPA) has determined that there are inadequate data to establish a Reference Concentration (RfC) for quinone, and has not set an oral Reference Dose (RfD) (U.S. EPA, 1994a).

No information is available on adverse reproductive or developmental effects of quinone in humans or animals (U.S. EPA, 1994a).

Cancer: No information is available regarding the carcinogenicity of quinone in humans. The U.S. EPA has not classified quinone for carcinogenicity (U.S. EPA, 1994a). The International Agency for Research on Cancer has classified quinone (para-quinone) in Group 3: Not classifiable as a carcinogen (IARC, 1987a).