or received a “no determination” status
at the end of the determination process.
Table 1 in the full paper (see link in the box
below) provides information regarding
the values used for RHI calculations.
THIS ARTICLE is adapted from
a recent publication by the same
authors in AWWA Water Science
journal. The open-access publi-cation
can be accessed through
the following link: https://doi.
org/10.1002/aws2.1240.
Placing PFAS regulation
into context using RHI
Using the RHI metric, we calculated
a potential RHI-reduction obtained by
regulating a contaminant at a certain
concentration. We use arsenic and
uranium to set our boundaries for a
meaningful opportunity for health risk
reduction using two different approaches
(Figure 2) given the detailed monitoring
24 SOURCE winter 2022
data available prior to their respective
USEPA MCL revisions.
Our first approach used the two
quantifiable values (toxicity as a factor in
calculating RHI and occurrence in terms
of percent of the national population
exposed to certain concentration) to
create a regulatory region of meaningful
health risk reduction for recently
considered contaminants. On the left side
of the Approach #1 graph, the calculated
RHI values for PFOS and PFOA are
presented for the CA notification level
(6.5 and 5.1 ng/L respectively), ATSDR
(52 and 78 ng/L respectively) and USEPA
threshold values (70 ng/L each) with
black markers. Using the occurrence
data included in the recent Preliminary
Regulatory Determination, we had the
occurrence and RHI values for the USEPA
calculations on the right side of the plot.
The darker shaded box represents the
area on the plot where health impact
and occurrence are satisfied to create a
meaningful opportunity for health risk
reduction based on previous regulatory
actions for uranium and arsenic.
According to this assessment, if PFOS
occurrence exceeded 3.8%, it would enter
the meaningful health risk reduction
zone as the calculated total (cancer +
non-cancer) RHI PFOS value exceeds the
RHI threshold of 2.86E-06 as established
by uranium. This calculated RHI value
is a normalized scale and does not
predict cancer or health risk outcomes.
PFOA would not cross into the zone
of meaningful using this assessment
regardless of population exposure since
the calculated health risk reduction is
not greater than the threshold set by
uranium.
It is important to note that this is
solely based on previous determinations
and not a mandate as to what quantifies
meaningful exposure. According to
Approach #1, if PFOA is regulated using
the available risk and occurrence data,
the new box for meaningful opportunity
for health risk reduction would equal
the area shaded in light grey. This
positive regulatory determination could
PFAS: HEALTH RISK REDUCTION?
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