Phthalic anhydride is a federal hazardous air pollutant and was identified as a toxic air contaminant in April 1993 under AB 2728.
CAS Registry Number: 85-44-9
Molecular Formula: C8H4O3
Phthalic anhydride occurs as white, lustrous crystalline needles, and has a characteristic pungent choking odor. It is soluble in hot water, benzene, carbon disulfide, and alcohol and is slightly soluble in water and ether (Merck, 1989; HSDB, 1991).
|Boiling Point||295 oC|
|Melting Point||130.8 oC|
|Vapor Pressure||2 x 10-4 mm Hg at 20 oC|
|Vapor Density||6.6 (air = 1)|
|Water Solubility||6200 ppm at 25 oC|
|Henry's Law Constant||6.2 x 10-9 atm-m3/mol|
|Density/Specific Gravity||1.20 at 135 oC|
|Log Octanol/Water Partition Coefficient||Hydrolyzes rapidly in water|
|Conversion Factor||1 ppm = 6.06 mg/m3|
(Howard, 1990; Merck, 1989; U.S. EPA, 1994a)
Phthalic anhydride is used in the manufacture of plasticizers, polyester and alkyd resins. It is also used in the manufacture of phthaleins, phthalates, benzoic acid, synthetic indigo, artificial resins, synthetic fibers, dyes, pigments, pharmaceuticals, and chlorinated products (Howard, 1990).
The primary stationary sources that have reported emissions of phthalic anhydride in California are manufacturers or users of plastic materials and synthetics, manufacturers of motor vehicles and equipment, and the wholesale petroleum and petroleum products industry (ARB, 1997b).
The total emissions of phthalic anhydride from stationary sources in California are estimated to be at least 11,000 pounds per year, based on data reported under the Air Toxics "Hot Spots" Program (AB 2588) (ARB, 1997b).
No information about the natural occurrence of phthalic anhydride was found in the readily-available literature.
No Air Resources Board data exist for ambient measurements of phthalic anhydride.
No information on indoor sources or concentrations of phthalic anhydride was found in the readily-available literature.
Based on the vapor pressure, phthalic anhydride is expected to exist in the atmosphere in the gas phase. The dominant tropospheric loss process for gaseous phthalic anhydride will be by reaction with the hydroxyl radical. No information is, however, available concerning the rate constant or tropospheric half-life for this reaction (Atkinson, 1995).
The Office of Environmental Health Hazard Assessment reviews risk assessments submitted under the Air Toxics "Hot Spots" Program (AB 2588). Of the approximately 89 risk assessments reviewed as of December 1996, for non-cancer health effects, phthalic anhydride contributed to a total chronic hazard index greater than 1 in 1 of these risk assessments (OEHHA, 1996b).
Probable routes of human exposure to phthalic anhydride are inhalation and dermal contact (Howard, 1990).
Non-Cancer: Exposure to phthalic anhydride may cause irritation of the eyes, respiratory tract, and skin. Phthalic anhydride is a potent skin and respiratory tract sensitizer. Results from animal studies indicate that phthalic anhydride vapor causes congestion, irritation, and injury to lung cells (U.S. EPA, 1994a).
A chronic non-cancer Reference Exposure Level (REL) of 7000 micrograms per cubic meter (µg/m3) is listed for phthalic anhydride in the California Air Pollution Control Officers Association Air Toxics "Hot Spots" Program, Revised 1992 Risk Assessment Guidelines. The toxicological endpoints considered for chronic toxicity are the kidney, gastrointestinal system, and liver (CAPCOA, 1993).
The United States Environmental Protection Agency (U.S. EPA) has not established a Reference Concentration (RfC) for phthalic anhydride. However, they have calculated a provisional RfC of 120 µg/m3. The U.S. EPA estimates that inhalation of this concentration, over a lifetime, would not likely result in the occurrence of chronic non-cancer effects. The U.S. EPA has established an oral Reference Dose (RfD) of 2.0 milligrams per kilogram per day for phthalic anhydride based on lung and kidney histopathology in mice. The U.S. EPA estimates that consumption of this dose or less, over a lifetime, would not likely result in the occurrence of chronic, non-cancer effects (U.S. EPA, 1994a).
Pertinent studies on adverse reproductive or developmental effects in humans or animals were not available (U.S. EPA, 1994a).
Cancer: No studies regarding the carcinogenicity of phthalic anhydride in humans are available, and information is inconclusive in animals. The U.S. EPA is currently reviewing the carcinogenicity of phthalic anhydride (U.S. EPA, 1994a). The International Agency for Research on Cancer has not classified phthalic anhydride as to its carcinogenicity (IARC, 1987a).