Risk Evaluation for Phthalic Anhydride

In April 2026, EPA released the draft risk evaluation and associated technical support documents for phthalic anhydride under the Toxic Substances Control Act (TSCA) for public comment. EPA designated phthalic anhydride as a High-Priority Substance in December 2019 and the chemical is currently undergoing risk evaluation.

Find other information about other chemicals undergoing risk evaluations under TSCA. 

On this page:

• Draft Risk Evaluation for Phthalic Anhydride
• What is phthalic anhydride?
• Conditions of use of phthalic anhydride
• Recent activities and opportunities for public comment
• Draft Risk Evaluation and Supporting Documents 

Draft Risk Evaluation for Phthalic Anhydride

EPA is preliminarily determining that phthalic anhydride presents an unreasonable risk of injury to human health driven by 38 of 44 evaluated conditions of use (COUs). Thirty six of those COUs are driven by risk to workers, and of those, four also indicate risk to ONUs. Two COUs are driven by risk to consumers. The two consumer uses with preliminary risk findings are adhesives and sealants (dermal) and paints and coatings (dermal and inhalation). EPA did not preliminarily identify any significant contribution to unreasonable risk for the general population or to the environment from the evaluated TSCA uses. EPA also did not identify significant contributions to unreasonable risk for five COUs: Processing–recycling, Distribution in commerce, Certain plastic/rubber articles with routine direct contact during normal use, Arts/crafts clear casting resins, and Disposal. For COUs with unreasonable risk to workers, these preliminary risk determinations do not reflect the use of personal protective equipment (PPE); however, as the draft risk evaluation shows, appropriate engineering controls and PPE can reduce exposures and mitigate risk.     

The draft risk evaluation differentiates exposures by form and context. Workers and consumers are expected to be exposed primarily to phthalic anhydride during manufacture, processing, and product use, where the most sensitive hazards are dermal and respiratory sensitization following acute dermal and inhalation exposure. After environmental release, phthalic anhydride rapidly hydrolyzes to o‑phthalic acid (i.e., half‑life is 30–90 seconds in surface water), so EPA evaluated the general population and environmental receptors for o‑phthalic acid. Based on available information, o‑phthalic acid is not a dermal or respiratory sensitizer. EPA’s confidence in the worker risk estimates is moderate to robust; confidence for ONU and environmental exposure estimates is slight to moderate due to greater uncertainties. EPA is seeking public comment and additional data, particularly real‑world exposure and control‑efficacy information for workers and ONUs and consumer use patterns for solvent‑based paints/coatings and adhesives/sealants, to inform the final risk evaluation. These preliminary conclusions apply only to TSCA COUs evaluated in this draft; uses excluded under TSCA section 3(2)(B) were not assessed.

What is Phthalic Anhydride?

Phthalic anhydride (CASRN 85-44-9) is a white solid. The primary use for phthalic anhydride is as a reactant used for processing. Information from the 2016 Chemical Data Reporting (CDR) for phthalic anhydride indicates reported production volume is between 500 million and 750 million pounds (manufacture and import).

Uses of Phthalic Anhydride

In the final scope, EPA identified conditions of use associated with the importing; processing; distribution in commerce; industrial, commercial and consumer uses; and disposal of phthalic anhydride, for example:

• Plastic material and resin manufacturing;
• Paint and coating manufacturing;
• Petroleum lubricating oil and grease manufacturing;
• Synthetic dye, pigment and printing ink manufacturing;
• Other basic organic and inorganic chemical manufacturing;
• Adhesives and sealant chemicals;
• Laboratory chemicals;
• In industrial and commercial products, including automobile interiors, aerospace products, electronic products, lubricants, plastic and rubber products, processing aids in hydraulic fracturing, water filtration applications, oil treatment of wood, and wire coating and insulation; and 
• In commercial and consumer products, including paints and coatings and adhesives.

The above listed conditions of use are ways that a person or the environment could be potentially exposed to this chemical. However, when conducting a risk evaluation, EPA also considers the hazards (i.e. health effects or environmental impacts) that could occur from coming in contact with a chemical.

Recent Activities and Opportunities for Public Comment

In April 2026, EPA released the draft risk evaluation for public comment and peer review by the agency’s Science Advisory Committee on Chemicals (SACC). Upon publication of a Federal Register notice, EPA will accept public comments on the draft risk evaluation for 60 days via the TSCA docket EPA-HQ-OPPT-2018-0459 at www.regulations.gov. 

In August 2020, EPA published a final scope document outlining the hazards, exposures, conditions of use, and the potentially exposed or susceptible subpopulations the agency expects to consider in its risk evaluation. The agency released the draft scope in April 2020 and took public comments on the draft document.

• Read the final scope of the risk evaluation for this chemical and EPA’s response to comments on the draft scope.
• View the docket for this chemical, EPA-HQ-OPPT-2018-0459 on www.regulations.gov.

As EPA continues to move through the risk evaluation process there will be additional opportunities for public comment, including a public comment period on the draft risk evaluation. In addition to public comment periods, EPA will continue to engage with stakeholders as it refines the risk evaluation and stakeholders should reach out to EPA via the staff contact to engage with the agency.

Draft Risk Evaluation and Supporting Documents

Read the Federal Register Notice and view the supporting documents in EPA-HQ-OPPT-2018-0459. 

• Draft Risk Evaluation for Phthalic Anhydride (pdf) (4.29 MB)
• Draft Systematic Review Protocol for Phthalic Anhydride (pdf) (993.44 KB)
• Draft Data Quality Evaluation and Data Extraction Information for Physical and Chemical Properties for Phthalic Anhydride (pdf) (1.27 MB)
• Draft Data Quality Evaluation and Data Extraction Information for Environmental Fate and Transport for Phthalic Anhydride (pdf) (808.7 KB)
• Draft Data Quality Evaluation and Data Extraction Information for Environmental Release and Occupational Exposure for Phthalic Anhydride (pdf) (1.65 MB)
• Draft Data Quality Evaluation Information for General Population, Consumer, and Environmental Exposure for Phthalic Anhydride (pdf) (355 KB)
• Draft Data Quality Evaluation Information for Human Health Hazard Epidemiology for Phthalic Anhydride (pdf) (625.53 KB)
• Draft Data Quality Evaluation Information for Human Health Hazard Animal Toxicology for Phthalic Anhydride (pdf) (874.6 KB)
• Draft Data Quality Evaluation Information for Environmental Hazard for Phthalic Anhydride (pdf) (373.79 KB)
• Draft Data Extraction Information for Environmental Hazard and Human Health Hazard Animal Toxicology and Epidemiology for Phthalic Anhydride (pdf) (632.39 KB)
• Draft Fate and Physical Chemistry Assessment for Phthalic Anhydride (pdf) (1011.36 KB)
• Draft Environmental Release and Occupational Exposure Assessment for Phthalic Anhydride (pdf) (2.65 MB)
• Draft Consumer and Indoor Exposure Assessment for Phthalic Anhydride (pdf) (939.11 KB)
• Draft Environmental Media, General Population, and Environmental Exposure for Phthalic Anhydride (pdf) (994.01 KB)
• Draft Environmental Hazard Assessment for Phthalic Anhydride (pdf) (1002.41 KB)
• Draft Human Health Hazard Assessment for Phthalic Anhydride (pdf) (4.09 MB)
• Draft Data Evaluation Record Information for in chemico, in vitro, and in vivo Assays for Human Health Hazard for Phthalic Anhydride (pdf) (1.65 MB)

Additional technical support files for the draft risk evaluation of phthalic anhydride (zip) (zip)