Cumulative Risk Evaluation of Phthalates Under TSCA

Area of Science:

• Environmental Science
• Toxicology
• Risk Assessment

Background:

• Seven phthalates undergo U.S. EPA Toxic Substances Control Act (TSCA) risk evaluations.
• Phthalates are common plastic additives with widespread human exposure via mixtures.
• Evidence indicates biological additivity of phthalate mixtures, potentially underestimating risks.

Approach:

• Proposes a cumulative risk assessment (CRA) approach for phthalate evaluations.
• Integrates physiology and algorithms to group chemical and nonchemical stressors.
• Reviews existing guidance, TSCA scoping documents, and peer-reviewed literature.

Key Points:

• Individual phthalate risk assessments may not be protective due to mixture effects.
• A cumulative risk approach is necessary for accurate public health protection.
• EPA is reconsidering the inclusion of CRA in phthalate risk evaluations.

Conclusions:

• Recommends a practical CRA strategy for EPA's phthalate risk evaluations.
• Suggests adjustments for interpreting hazard indices and margins of exposure.
• Aims to ensure "unreasonable risk" determinations are health-protective under TSCA.