Authors discovered a mass interference in calibration standards analyzed by liquid chromatography–high-resolution mass spectrometry that resulted in underestimation of serum concentrations for perfluoro-3,5,7,9,11-pentaoxadodecanoic acid [PFO5DoA; DTXSID50723994] in the published manuscript.
Since the original analyses, authors acquired an authentic analytical standard for PFO5DoA and reanalyzed a subset of the serum samples. Authors used the PFO5DoA results from the reanalysis to develop a model to predict corrected PFO5DoA results for the remaining samples that were not reanalyzed. Details of the reanalysis and modeling and the corrected PFO5DoA results have been reported in a separate research letter.1 Erroneous PFO5DoA results have been moved from the main manuscript to the Supporting Information for reference. However, the methodological details for PFO5DoA have been kept in the manuscript because this was one of the originally targeted analytes. None of the other analytes in the manuscript were impacted by the mass interference.
In addition, there were two other errors in the manuscript: a) The 95th percentile was incorrectly used for the upper limit of the PFO4DA serum concentration interquartile range (IQR) in the text rather than the 75th percentile. b) For the fluoroethers, the mean percentage change was incorrectly used to calculate the confidence intervals around the median.
Finally, references to “total PFAS” were changed to “summed PFAS,” which is a more accurate representation of the methods used.
To correct these errors, the following changes were made to the manuscript:
Abstract
The second sentence of the “Results” was corrected from “Six fluoroethers were detected in serum; Nafion by-product 2, PFO4DA, and PFO5DoA were detected in of participants.” to “Six fluoroethers were detected in serum; Nafion by-product 2 and PFO4DA were detected in 99% of participants.”
The fifth sentence of the “Results” was corrected from “In participants with repeated samples, the median decrease in fluoroether levels ranged from 28% for PFO5DoA to 65% for PFO4DA in 6 months due to wastewater discharge control.” to “In participants with repeated samples, the median decrease in fluoroether levels ranged from 34% for Nafion by-product 2 to 65% for PFO4DA in 6 months due to wastewater discharge control.”
The last sentence of the “Results” was corrected from “The sum concentration of fluoroethers contributed 24% to participants’ total serum PFAS (median: ).” to “The sum concentration of fluoroethers contributed 23% to participants’ summed serum PFAS (median: ).”
Results
The fourth and fifth sentences of the “PFAS Analysis in Blood” subsection of the “Results” section were corrected from “Nafion by-product 2 and PFO4DA were detected in serum from almost all participants (99%) and PFO5DoA was detected in most (88%). Concentrations of Nafion by-product 2 [, , ] and PFO4DA (, , ) were generally higher than PFO5DoA (, , ).” to “Nafion by-product 2 and PFO4DA were detected in serum from almost all participants (99%). Concentrations of Nafion by-product 2 [, , ] were similar to concentrations of PFO4DA (, , ).”
The following sentence was added to the end of the first paragraph of the “PFAS Analysis in Blood” subsection of the “Results” section: “Due to a mass interference in calibration standards analyzed by LC-HRMS that impacted PFO5DoA quantitation, we are not reporting PFO5DoA results in the main manuscript. The erroneous results originally published have been moved to Table S9 for reference.”
The fourth through sixth sentences of the second paragraph of the “PFAS Analysis in Blood” subsection of the “Results” section were corrected from “Total PFAS concentrations ranged from 1.5 to , with a median PFAS level of in adults and in children (Table 4). The median summed mass concentration of five fluoroethers was (, ). These fluoroethers accounted for 24% of the total mass concentration of PFAS detected in serum; the percentage was slightly higher for children (26%) than for adults (23%).” to “Summed PFAS concentrations ranged from 1.5 to , with a median PFAS level of in adults and in children (Table 4). The median summed mass concentration of four fluoroethers (NVHOS, PFO3OA, PFO4DA, and Nafion by-product 2) was (, ). These fluoroethers accounted for 23% of the summed mass concentration of PFAS detected in serum; the percentage was slightly higher for children (25.9%) than for adults (21.6%).”
Table 4.
Summed mass concentrations of fluoroethers (Nafion by-product 2, PFO4DA, PFO5DoA, NVHOS, and PFO3OA) and legacy PFAS (PFOS, PFOA, PFHxS, PFNA, and PFHpA) in serum from 344 Wilmington, North Carolina, residents (289 adults and 55 children).
| Category | Concentration [ (percentage of total PFAS)]a | ||||
|---|---|---|---|---|---|
| 10th percentile | 25th percentile | Median | 75th percentile | 95th percentile | |
| Adults | 1.5 (13.9) | 3.4 (20.4) | 6.3 (23) | 11.6 (28.2) | 20.6 (33.6) |
| Children | 1.7 (18.9) | 2.9 (22.8) | 4.5 (26.2) | 7.7 (34.1) | 14 (39.3) |
| Overall | 1.5 (14.6) | 3.2 (20.8) | 6 (23.7) | 10.7 (27.2) | 19.9 (32.5) |
| Adults | 8.0 (74.1) | 12.2 (73.1) | 20.8 (75.9) | 29.8 (72.3) | 47.8 (78) |
| Children | 6.8 (75.6) | 8.1 (63.8) | 11.3 (65.7) | 16.4 (72.6) | 24.0 (67.4) |
| Overall | 7.6 (73.8) | 11.1 (72.1) | 18.8 (74.3) | 28.7 (72.8) | 47.1 (77) |
| Adults | 10.8 | 16.7 | 27.4 | 41.2 | 61.3 |
| Children | 9 | 12.7 | 17.2 | 22.6 | 35.6 |
| Overall | 10.3 | 15.4 | 25.3 | 39.4 | 61.2 |
Note: Nafion by-product 2, perfluoro-2-{[perfluoro-3-(perfluoroethoxy)-2-propanyl]oxy}ethanesulfonic acid; NVHOS, 1,1,2,2-tetrafluoro-2-(1,2,2,2-tetrafluoroethoxy)ethanesulfonic acid; PFAS, per- and polyfluoroalkyl substances; PFHpA, perfluoroheptanoic acid; PFHxS, perfluorohexane sulfonic acid; PFNA, perfluorononanoic acid; PFOA, perfluoroctanoic acid; PFOS, perfluorooctane sulfonic acid; PFO3OA, perfluoro-3,5,7,9-butaoxadecanoic acid; PFO4DA, perfluoro-3,5,7,9-butaoxadecanoic acid; PFO5DoA, perfluoro3,5,7,9,11-pentaoxadecanoic acid.
Percentage of total PFAS concentration (the sum of fluoroethers and legacy PFAS analyzed for in this study) is shown in parentheses.
Table 4.
Summed mass concentrations of fluoroethers (NVHOS, PFO3OA, PFO4DA, Nafion by-product 2) and legacy PFAS (PFOS, PFOA, PFHxS, PFNA, and PFHpA) in serum from 344 Wilmington, North Carolina, residents (289 adults and 55 children).
| Category | Concentration [ (percentage of total PFAS)]a | ||||
|---|---|---|---|---|---|
| 10th percentile | 25th percentile | Median | 75th percentile | 95th percentile | |
| Adults | 1.5 (14.0) | 3.2 (19.5) | 5.9 (21.6) | 10.9 (26.7) | 19.7 (32.6) |
| Children | 1.7 (18.9) | 2.8 (22.2) | 4.4 (25.9) | 7.4 (33.0) | 13.5 (38.5) |
| Overall | 1.5 (14.6) | 3.0 (19.6) | 5.7 (22.8) | 10.2 (26.4) | 19.0 (31.6) |
| Adults | 8.0 (74.8) | 12.2 (74.4) | 20.8 (76.2) | 29.8 (72.9) | 47.8 (79.1) |
| Children | 6.8 (75.6) | 8.1 (64.3) | 11.3 (66.5) | 16.4 (73.2) | 24.0 (68.4) |
| Overall | 7.6 (73.8) | 11.1 (72.5) | 18.8 (75.2) | 28.7 (74.2) | 47.1 (78.2) |
| Adults | 10.7 | 16.4 | 27.3 | 40.9 | 60.4 |
| Children | 9.0 | 12.6 | 17.0 | 22.4 | 35.1 |
| Overall | 10.3 | 15.3 | 25.0 | 38.7 | 60.2 |
Note: Nafion by-product 2, perfluoro-2-{[perfluoro-3-(perfluoroethoxy)-2-propanyl]oxy}ethanesulfonic acid; NVHOS, 1,1,2,2-tetrafluoro-2-(1,2,2,2-tetrafluoroethoxy)ethanesulfonic acid; PFAS, per- and polyfluoroalkyl substances; PFHpA, perfluoroheptanoic acid; PFHxS, perfluorohexane sulfonic acid; PFNA, perfluorononanoic acid; PFOA, perfluorooctanoic acid; PFOS, perfluorooctane sulfonic acid; PFO3OA, perfluoro-3,5,7-trioxaoctanoic acid; PFO4DA, perfluoro-3,5,7,9-butaoxadecanoic acid.
Percentage of total PFAS concentration (the sum of fluoroethers and legacy PFAS analyzed for in this study) is shown in parentheses.
The second sentence of the third paragraph of the “PFAS Analysis in Blood” subsection of the “Results” section was corrected from “Nafion by-product 2 was highly correlated with both the fluoroether PFO5DoA () and the legacy PFOA ().” to “Nafion by-product 2 was highly correlated with the legacy PFOA ().”
The second and third sentences of the fourth paragraph of the “PFAS Analysis in Blood” subsection of the “Results” section were corrected from “Levels of the three fluoroethers (Nafion by-product 2, PFO4DA, and PFO5DoA) decreased significantly in the 6 months between sampling (Figure 3; see also Table S7). For the fluoroethers, the median percentage decrease across the 44 participants was 34% [95% confidence interval (CI): 29, 37%] for Nafion by-product 2, 65% (95% CI: 45, 68%) for PFO4DA, and 28% (95% CI: 24, 37%) for PFO5DoA.” to “Levels of the two fluoroethers (Nafion by-product 2 and PFO4DA) decreased significantly in the 6 months between sampling (Figure 3; see also Table S7). The median percentage decrease across the 44 participants was 34% [95% confidence interval (CI): 30, 38%] for Nafion by-product 2 and 65% (95% CI: 53, 76%) for PFO4DA.”
Discussion
The third sentence of the fifth paragraph of the “Discussion” section was corrected from “In serum, the highest detection frequencies among the 10 fluoroethers we targeted were for Nafion by-product 2, PFO4DA, and PFO5DoA; each of these chemicals is 9–12 atoms long when counting the carbon atoms, ether oxygen atoms, and sulfur atom (if a sulfonate group was present).” to “In serum, the highest detection frequencies among the 10 fluoroethers we targeted were for Nafion by-product 2 and PFO4DA; these chemicals are 9–12 atoms long when counting the carbon atoms, ether oxygen atoms, and sulfur atom (if a sulfonate group was present).”
The last sentence of the sixth paragraph of the “Discussion” section was corrected from “Second, serum PFOA in our cohort was highly correlated with serum levels of Nafion by-product 2 and PFO5DoA, to which our cohort was primarily exposed through consumption of drinking water.” to “Second, serum PFOA in our cohort was highly correlated with serum levels of Nafion by-product 2, to which our cohort was primarily exposed through consumption of drinking water.”
Conclusions
The third sentence of the “Conclusions” section was corrected from “The median summed mass concentration of five fluoroethers in serum was (, ), and these fluoroethers accounted for 24% of the total mass concentration of PFAS in the sera.” to “The median summed mass concentration of four fluoroethers (NVHOS, PFO3OA, PFO4DA, and Nafion by-product 2) in serum was (, ), and these fluoroethers accounted for 23% of the overall summed mass concentration of PFAS in the sera.”
Corrected Tables with captions
Table 1: Correction was made to PFO4DA U.S. EPA registry name. “PFO4DA, Perfluoro-3,5,7,9-tetraoxadecanoic acid” to “PFO4DA, Perfluoro-3,5,7,9-butaoxadecanoic acid” to be consistent with how PFO4DA is reported in table captions.
Table 3: PFO5DoA results were removed.
Table 4: Corrections were made to the entire table and the caption as follows:
Original
Corrected:
Table 5: All PFO5DoA correlations were removed and the PFO5DoA chemical name was removed from the caption.
Table 6: PFO5DoA results were removed and the PFO5DoA chemical name was removed from the caption.
Corrected Figures
Figure 3: The PFO5DoA panel was removed and the PFO5DoA chemical name was removed from the caption.
Supplemental Material
The supplemental material was corrected to remove PFO5DoDA results from Tables S6 and Table S7.
In addition, we replaced “PFO5DoDA” with “PFO5DoA” in Table S2 and Table S5 to adopt the more common chemical short name.
Finally, Table S9 was added to report the summary statistics of the erroneous PFO5DoA data for reference.
The authors regret these errors.
Supplementary Material
Environ Health Perspect 128(7):077005 (2020), https://doi.org/10.1289/EHP6837
References
- 1.Kotlarz N, McCord J, Wiecha N, Weed RA, Cuffney A, Enders JR, et al. 2024. Reanalysis of PFO5DoA levels in blood from Wilmington, North Carolina, residents, 2017–2018. Environ Health Perspect 132(2):027701, 10.1289/EHP13339. [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.