EPA’s Assessment of DINP Under TSCA

On January 14, 2025, the U.S. Environmental Protection Agency (EPA) finalized its risk evaluation for diisononyl phthalate (DINP) under the Toxic Substances Control Act (TSCA). The evaluation concludes that DINP presents an unreasonable risk to human health, particularly for workers exposed to high concentrations of the substance in mist form when spraying certain products like adhesives, sealants, paints, and coatings.

Health Risks Linked to DINP Exposure

EPA's evaluation highlights the severe health risks associated with DINP, including developmental toxicity, liver damage, and cancer at high exposure levels. The substance is also linked to phthalate syndrome, a condition that negatively impacts the male reproductive system. This includes issues such as decreased fetal testosterone, malformations of the male reproductive tract, and reduced fertility in males.

Due to these risks, EPA has included DINP in its cumulative risk analysis for phthalates that exhibit these harmful effects.

Usage and Exposure Risks

DINP is primarily used as a plasticizer in the production of flexible polyvinyl chloride (PVC), and in various other industries, including construction, automotive, and consumer products. Workers handling DINP in manufacturing processes or product application are at the highest risk, particularly when working with spray-applied adhesives, sealants, and paints, which can release high concentrations of DINP into the air in the form of mist.

While consumer exposure to DINP was not identified as a significant risk in this evaluation, the EPA noted that workers using DINP in certain conditions were at risk due to the high concentrations of mist they could inhale in the absence of proper protection.

Risk Evaluation and EPA's Next Steps

The risk evaluation was requested by a manufacturer in 2019, who sought EPA’s assessment of DINP’s safety. Following this evaluation, EPA has determined that four specific conditions of use—representing about 3% of the U.S. DINP production volume—pose a significant risk to workers. These exposures typically occur in manufacturing settings where DINP is part of spray products.

EPA has excluded certain uses of DINP from this evaluation, such as food additives and cosmetics, as they are not regulated under TSCA.

Future Actions and Risk Management Process

Following the final risk evaluation, EPA will initiate the risk management process to address the identified risks. The agency plans to release a proposed rule under TSCA Section 6 to safeguard workers from the risks associated with DINP exposure.

Ongoing Efforts for Chemical Safety

This final risk evaluation marks a crucial step in the ongoing efforts to protect workers' health and ensure safe chemical practices. Companies and manufacturers handling DINP will need to follow EPA's forthcoming risk management rules to mitigate these identified risks.