The U.S. Environmental Protection Agency (EPA) released its draft risk evaluation for Diisodecyl phthalate (DIDP) and the physical, chemical, fate, and hazard assessments for Diisononyl phthalate (DINP) prepared under the Toxic Substances Control Act (TSCA). These documents are now available for public comment and peer review.
Preliminary Findings
Diisodecyl Phthalate (DIDP)
The EPA's preliminary findings indicate that most uses of DIDP do not contribute to unreasonable risks to human health under TSCA. However, one specific use scenario involving high-pressure spray application of adhesives and sealants could pose a risk to workers. DIDP is commonly used as a plasticizer in polyvinyl chloride (PVC) in various consumer, commercial, and industrial applications. While DIDP can cause developmental toxicity and liver damage, the EPA, along with other international bodies, did not find enough evidence to preliminarily determine that DIDP causes cancer.
Diisononyl Phthalate (DINP)
DINP, also used as a plasticizer in PVC, presents more significant health concerns compared to DIDP. The EPA's assessments suggest that DINP can cause liver damage at lower concentrations and potentially cause cancer at higher exposure levels. These findings warrant further peer review before releasing the full draft risk evaluation later this year.
Uses and Exposure
The primary uses of DIDP and DINP under TSCA are in PVC applications. However, some uses, such as in personal care products, cosmetics, and food contact materials, are excluded from TSCA and were not evaluated in this risk assessment. Past assessments have shown that DIDP exposure primarily occurs through diet, particularly affecting women, infants, toddlers, and children.
Manufacturer-Requested Evaluations
The risk evaluations for DIDP and DINP are the first conducted by the EPA at the request of manufacturers. These requests were made in 2019, highlighting a growing trend of manufacturers seeking official risk assessments for their chemicals.
Health and Environmental Impact
DIDP
DIDP is used in various products, including building materials, automotive care products, and electronics. When released into the environment, it can attach to dust particles and sediment in water bodies. Indoors, it may adhere to dust particles, posing inhalation or ingestion risks. The EPA found that DIDP has the potential to harm the liver and cause developmental toxicity but did not find sufficient evidence to conclude that it causes cancer.
DINP
DINP shares similar applications with DIDP but poses a higher health risk. It can cause liver damage and developmental toxicity at lower exposure levels and potentially lead to cancer at higher levels. These hazard differences necessitate a thorough peer review of the DINP human hazard assessments before final conclusions are made.
Cumulative Risk Assessment
The EPA is including DINP in its cumulative risk assessment for phthalates, along with five other phthalate chemicals, due to its potential to cause phthalate syndrome, a condition affecting male reproductive development. DIDP is excluded from this cumulative assessment as it does not exhibit these effects.
Next Steps
The EPA will accept public comments on the draft documents for 60 days via docket EPA-HQ-OPPT-2024-0073 at www.regulations.gov. The documents will also undergo peer review by the Agency’s Science Advisory Committee on Chemicals (SACC).
