DEQ-CFW_00075306

Grzyb, Julie
From: Brower, Connie
Sent: Thursday, August 10, 2017 10:06 AM
To: Grzyb, Julie
Cc: Ventaloro, Christopher; Manning, Jeff
Subject: Health Goals vs WQS
Good morning, Julie,
believes that the Risk Evaluation (or
Thanks for the call. You are correct in stating that the public now Health
nlh a challenge for us WEL, or Health
all.
Screening Goal) performed by DHHS constitutes a water quality standard". It is Y
ty
of the
C.
such
Development and adoption of a state water quality standard (in surface water) is odifications toer the horithe egulat oM wouAs ld be, the
derivation would need to meet the regulations in 15A NCAC 02B, or as directed,
needed.
Id need to be addressed — I apologize in advance that this gets technical very quickly:
We note the following issues that wou
Per 15A NCAC 02B .0208:
WQS = {(RfD x WT) / [WI + (FC x BAF)]} x RSC
RfD reference dose ???? mg/kg/day70 kg
WT = Weight 70 kg
WI = average human water
intake 2 L/day **0,0175 kg/person-day
FC = Fish consumption rate ???? L/kg
BAF = bioaccumulation rate ??7
RSC= relative source contribution
RfD: DHHS derived a Reference Dose (RfD) using materials provided byours. theThe
reference
EPA. Thedose
used a d ffestarting
point of the derivation. This RfD has not (to my knowledge) been "approved"Y
RfD in their assessment of the TSCA risk evaluation, and also used different Uncertainty Factors to derive the RfD. We
would need some agreement on the RfD to begin.
At issue: is the DHHS RfD defensible ? Does it contain supportable Uncertainty Factors ?
WT: DHHS used an infant — our 02B rules are based upon an adult body weight — with allowance to calculate using a 10
kg child.
At issue: Discussions with the EMC and public would need to alter current rule to incorporate an infant's BW
WI: same as above — current regs use an adult intake rate
. _ FC: ** DHHS does not include the idea of consumption incorporationlshoudld fish.
be used fordaneadult - but, not an infant or them to do so we
as they were looking at finished drinking water. The
would need to assess how this would change the resulting number.
BAF: pertains to the amount of accumulation that may occur in fish — Again, DHHS does not account for this (and they
should not)
nly one paper to goon — it is not well written.
At issue: what BAF is correct? We have o
RSC: A relative source contribution (RSC) of 20%was used by DHHSconcentration on account water due to the potential for other
other routes like air and food. The RSC lowers the acceptable con
exposure routes. This is a challenge in that it is assumed that an infant would not get GenX from food — as they are
only consuming water.
1
DEQ-CFW 00075306

From DHHS correspondence:
NC DHHS calculated a drinking water equivalent level (DWEL) for GenX as follows:
• Dose (RfD) = 0.0001 mg/kg bw/day
• Body Weight = 7.8 kg (bottle-fed infant)
• Intake = 1.1 L/day (bottle-fed infant)
• Relative Source Contribution = 0.2
• Unit Conversion =106 ng/mg
Formula: dose (mg/kg bw/day) X body weight (kg)/intake (L/day) X RSC X Unit Conversion = DWEL
(0.0001 mg/kg/day) X 7.8kg/(1.1L/day) X 0.2 X 106 ng/mg = 140 ng/L
The values used for body weight and drinking water intake were based on bottle-fed infants in order to be maximally
protective, since infants consume the highest amount of water in relation to their body weight. DWEL is the same as a health
screening goal.