PFDA IRIS Assessment Finalized Amid Ongoing PFAS Reviews
This July, EPA released the final Integrated Risk Information System (IRIS) assessment for PFDA. PFDA’s toxicological review is the third completed IRIS assessment for a PFAS. Two additional assessments, for PFHxS and PFNA, are still in progress.
Consistent with the draft, the final PFDA assessment concluded that evidence indicates “PFDA exposure is likely to cause liver, immune, developmental, and male and female reproductive effects in humans, given sufficient exposure conditions.” However, it had a higher maximum acceptable daily dose, known as an oral reference dose (RfD), than the draft assessment.
The draft’s lifetime and subchronic RfD was 4 x 10-10 mg/kg/day. But the final RfD was 2 x 10-9, partially due to the use of different points of departure (or the dose at which an effect is first observed) for immune and developmental effects.
July also saw the release of the external peer review report for the PFHxS draft IRIS assessment, and external peer review meetings for the draft PFNA assessment took place from July 30 to August 1. The most recent update to the IRIS Program Outlook, released in June, did not include expected release dates for the final PFHxS or PFNA assessments.
Following external peer review, EPA revises the assessment, conducts a final agency review, and holds a interagency science discussion before releasing the final version. It took nine months for EPA to finalize the assessment for PFDA after releasing the external peer review report.
EPA finalized drinking water standards for PFAS including PFHxS and PFNA in May; more on that can be found here. Additional information on the draft IRIS assessment for PFHxS is available in a previous blog post.
