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Bogdan et al. J Environ Expo Assess 2024;3:14 https://dx.doi.org/10.20517/jeea.2024.08 Page 7 of 13

Volume of Central tendency = 0.56 (calculated from human CR of 0.39 mL/kg/day [26] ) and the half-life
distribution CR ÷ [ln(2)/half-life] = V
d
(L/kg) 0.39 mL/kg/day ÷ [ln(2)/996 days] = 560 mL/kg, rounded to 0.56 L/kg
PFOS: Perfluorooctanesulfonic acid; NHANES: National Health and Nutrition Examination Survey; t : half-life; TK: toxicokinetic; CR: clearance rate;
½
V : volume of distribution.
d
Table 3. PFOS detection in one dairy-based infant formula powder
PFOS in 20% w/v PFOS in formula Formula per PFOS per Water per PFOS in reconstituted
solution (SD) (ng/L) powder (SD) (ng/g) scoop (g) scoop (ng) scoop (L) formula (ng/L)
12 (0.6) 0.054 (0.003) 9.8 0.53 0.059 8.9
n = 3. PFOS: perfluorooctanesulfonic acid; SD: standard deviation.

Figure 1. Serum PFOS concentration of an infant exposed to PFOS from drinking contaminated infant formula (8.9 ng/L). PFOS:
Perfluorooctanesulfonic acid; MDH: Minnesota Department of Health; MI: mean fluid intake rate; 95th%: 95th percentile fluid intake
rate.

In 2024, MDH released an updated PFOS reference serum concentration (RfSC) of 2.6 ng/mL based on
epidemiological data . An RfSC is the concentration of a chemical (in this case, PFOS) in the serum
[19]
without an appreciable risk of noncancer health effects. With no other sources of PFOS exposure, an infant
with a mean fluid intake rate consuming formula contaminated with 8.9 ng/L PFOS would have a peak
serum concentration equal to 13% of the PFOS RfSC, while an infant with a 95th percentile fluid intake rate
would have a peak serum concentration equivalent to 24% of the PFOS RfSC [Table 4].

Exposure to PFOS from contaminated formula plus contaminated water
Powdered infant formula must be reconstituted with water before use, which allows for another possible
[30]
exposure route . Many states have created health-based and/or regulatory limits on PFOS and other PFAS
in drinking water [31,32] , and in 2024, the US EPA released Maximum Contaminant Levels (MCLs) for six
PFAS, including PFOS, under the Safe Drinking Water Act . MCLs are not strictly health-based and
[33]
account for factors such as technical feasibility and cost of treatment. The MCL for PFOS is 4 ng/L, the
practical quantitation level for PFOS defined by EPA. Public water systems with PFOS levels above 4 ng/L
will be required to take action to reduce PFOS below 4 ng/L.