2021.11.03_CCO.p18-19_COPY_DEQ Letter Re New GenX RfD

November 3, 2021

CERTIFIED MAIL / RETURN RECEIPT REQUESTED
Ms. Dawn Hughes
Plant Manager
Chemours Fayetteville Works
22828 NC Highway 87 W
Fayetteville NC 28306

RE: GenX Reference Dose: Potential Revision of Drinking Water Compliance Plan and
Feasibility Study
Dear Ms. Hughes:
In light of EPA’s finalized human health toxicity assessment (Toxicity Assessment) for
GenX chemicals1 and its plans to develop a drinking water health advisory for GenX chemicals,
the North Carolina Department of Environmental Quality is notifying Chemours of the potential
need to revise its April 26, 2019 Drinking Water Compliance Plan (as updated and amended)
under paragraph 24 of the Consent Order and its March 11, 2019 Feasibility Study Report for
Public Water Services under paragraph 19 of the Consent Order.
On October 25, 2021, EPA published the final version of its Toxicity Assessment for
GenX chemicals. This Toxicity Assessment set the chronic reference dose for GenX chemicals
at 3 x 10-6 mg/kg-day. This final reference dose is significantly lower than the reference dose
proposed in EPA’s 2018 Draft Toxicity Assessment for GenX chemicals. EPA projects that it
will develop a drinking water health advisory for GenX chemicals based on the final reference
dose in Spring 2022.

As you are aware, Paragraph 19 of the Consent Order provides that Chemours shall
Establish permanent replacement drinking water supplies in the form of
public water or a whole building filtration system for any party (i.e.,
household, business, school, or public building) with a private drinking
water well that has been found through testing validated by DEQ to be
contaminated by concentrations of GenX compounds in exceedance of
140 ng/L, or any applicable health advisory, whichever is lower.

1 Available at https://www.epa.gov/chemical-research/human-health-toxicity-assessments-genx-chemicals. As used in the toxicity
assessment, “GenX chemicals” includes Hexafluoropropylene Oxide Dimer Acid and its Ammonium Salt.

If EPA’s nationally applicable health advisory is lower than 140 ng/L, Chemours will be
required to revise its Drinking Water Compliance Plan and Feasibility Study Report and provide
public water or whole building filtration systems to affected parties under paragraph 19 of the
Consent Order. Revisions to these documents must address, among other things:
• Review of existing well sampling data to identify additional affected parties entitled to
public water or whole building filtration under paragraph 19;
• Revised and supplemental assessment of public water feasibility for all affected parties
under paragraph 19; and
• A plan for transitioning affected parties who have previously received reverse osmosis
systems to public water or whole house filtrations systems as appropriate.
DEQ is also reviewing N.C.G.S. 143-215.2A in light of the new information contained in
the EPA GenX Toxicity Assessment, the anticipated EPA action related to the GenX health
advisory, and the language in the Consent Order.
DEQ recommends that Chemours and DEQ confer regarding these obligations prior to
the release of EPA’s health advisory to ensure that the parties have the opportunity to address
any questions in a timely manner.
If you have any questions or would like to discuss these issues further, please call me at
[phone].
Sincerely,

Sushma Masemore, P.E.
Assistant Secretary for the Environment, NCDEQ