Reference values of per- and poly- fluoroalkyl substances concentration in serum and related factors in Korean adults: Korean National Environmental Health Survey

Yong Min Cho; Dahee Han; Jio Jeong; Mi Jeong Kim; Kyung-Hwa Choi; Woo Jin Kim; Young-Seoub Hong

doi:10.5620/eaht.2025021

Environ Anal Health Toxicol > Volume 40:2025 > Article

Cho, Han, Jeong, Kim, Choi, Kim, and Hong: Reference values of per- and poly- fluoroalkyl substances concentration in serum and related factors in Korean adults: Korean National Environmental Health Survey

Original Article

Environ Anal Health Toxicol 2025; 40: e2025021.

Published online: September 17, 2025

DOI: https://doi.org/10.5620/eaht.2025021

Reference values of per- and poly- fluoroalkyl substances concentration in serum and related factors in Korean adults: Korean National Environmental Health Survey

Yong Min Cho^1,^*

, Dahee Han¹

, Jio Jeong¹

, Mi Jeong Kim¹

, Kyung-Hwa Choi²

, Woo Jin Kim³

, Young-Seoub Hong⁴

¹Institute of Environmental Health and Department of Environmental & Chemical Engineering, Seokyeong University, Seoul, Republic of Korea

²Department of Preventive Medicine, Dankook University College of Medicine, Cheonan, Republic of Korea

³Department of Internal Medicine, Kangwon National University College of Medicine, Chuncheon, Republic of Korea

⁴Department of Preventive Medicine, Dong-A University College of Medicine, Busan, Republic of Korea

^*Correspondence: neworder@skuniv.ac.kr

Received December 6, 2024 Accepted July 23, 2025

This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This study determined reference values of per- and polyfluoroalkyl substance (PFAS) exposure in the general Korean population. Serum samples from 2,993 adults in the fourth Korean National Environmental Health Survey (KoNEHS) (2018 –2020) were analyzed for five PFAS: perfluorooctanoic acids (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), perfluorodecanoic acid (PFDA), and perfluorononanoic acid (PFNA). The geometric means (GMs) and 95th percentile concentrations of serum PFOA were 6.43 and 16.55 μg/L, respectively; those of PFOS were 15.07 and 43.96 μg/L; 4.17 and 14.91 μg/L for PFHxS; 2.06 and 5.98 μg/L for PFNA; and 0.91 and 2.40 μg/L for PFDA. Higher serum PFAS concentrations were observed in older adults, men, former smokers, and frequent seafood consumers. Exposure levels also varied based on socioeconomic factors such as income and education. Additionally, participants residing in coastal areas exhibited higher serum PFAS concentrations, whereas higher PFHxS levels were observed in those living near industrial complexes. Higher concentrations of PFDA and PFNA were detected in participants consuming local drinking water (GMs, 3.29, 2.86 and 2.82 μg/L for local-based water, tap water and purifier or mineral water for PFNA; 1.43, 1.22 and 1.20 μg/L for PFDA; p-values were <0.05). These findings suggest that the Korean PFAS exposure level is relatively high, and may be related with residential and lifestyle characteristics.

Keywords: per- and polyfluoroalkyl substances, Korean National Environmental Health Survey, Human biomonitoring, Exposure

Introduction

Today, individuals are exposed to a wide range of chemicals from various sources, including food, water, consumer products, clothing, cosmetics, medicines, and environmental media. Such exposures can have a significant impact on health, hence making the monitoring of chemical exposure vital for the development of effective environmental and health policies. Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are environmental pollutants of particular concern due to their high persistence, bioaccumulation, and toxicity, and managing them is crucial for public health [1-3]. In the general population, exposure to PFAS can occur through food and packaging materials [4-9], consumer or industrial products such as cosmetics, cookware, furniture, cleaning goods, firefighting forms, and carpets [8-12], and environmental media, including indoor and drinking water [4-6, 11, 13]. Recent epidemiological and experimental studies have strengthened the evidence linking various health effects, including cancer to PFAS exposure [14-15]. Therefore, monitoring PFAS levels in the general population is essential, and several countries have incorporated PFAS into their biomonitoring programs [16-18].

Reference value (RV) is defined a value derived from a series of corresponding measured values of a random sample from a defined population group according to a specified statistical procedure [19]. RV provides a representative value of exposure to environmental pollutants in a defined population and upper RV(RV95) indicates an assessment level that is rarely exceed in the reference population [19]. RVs derived from a biomonitoring program offer information of internal exposures of environmental pollutants and scientific evidences for environmental policies [20]. Several national biomonitoring programs, such as US National Health and Nutrition Examination Survey (NHANES), Canadian Health Measures Survey (CHMS), German Environmental Survey (GerES), and Human Biomonitoring for Europe (HBM4EU), have been in operation for a long time, and RVs representing the people of each country are derived from these programs.

The Korean National Environmental Health Survey (KoNEHS) is a national biomonitoring program conducted by the National Institute of Environmental Research (NIER) under the Environmental Health Act [21]. Initiated in 2009, KoNEHS operates on a 3-year cycle. In the fourth cycle (KoNEHS cycle 4), conducted from 2018 to 2020, serum PFAS concentrations were included as analytes [22]. KoNEHS cycle 4 provided RVs for serum PFAS concentrations in the general Korean population. A previous study reported Korean RVs for serum PFAS using data from 2009–2010 [23]. However, given the strengthened regulations following Korea’s adoption of the UN’s Stockholm Convention on persistent organic pollutants, it is essential to update the information on PFAS exposure in the general population. In this study, we present the RVs of serum PFAS concentrations and identify factors related to PFAS exposure in the general Korean population.

Materials and Methods

Study participants

KoNEHS cycle 4 encompassed all age groups, including children aged three and older, adolescents, and adults. However, blood sampling was applied to adolescents and adults, but excluded for children. This study includes serum PFAS concentrations of only adults.

Data collection

This study performed a secondary analysis using raw data from KoNEHS cycle 4, provided by the NIER. The data analysis was conducted according to NIER guidelines. The KoNEHS cycle 4 dataset included a comprehensive questionnaire covering personal information, environmental exposures, clinical tests, and biomonitoring data [22]. For this study, the questionnaire data and biomonitoring data for serum PFAS were used. The KoNEHS cycle 4 questionnaire includes residential characteristics, indoor environment, use of chemical products, dietary habits, socioeconomic statuses, living habits, medicine use, personal components such as smoking, job history, etc., and more. We used the information about residential characteristics, dietary habits, and social economic statuses to find related factors for PFAS exposure, and personal components as confounders to analyze in the statistical models. In this study, variables of income and education represent the social economic status. The income variable refers to monthly income, when <3 million Korean Won (₩) (approximately 2,070 US dollar) it was defined “Low”, “Middle” for 3 – 5 million ₩, and “High” for ≥5 million ₩. The variable of education means the highest schooling. In KoNEHS cycle 4 stratified the whole country to extract representative samples from across the country, defined city, rural, and coastal areas, and allocated and distributed the number of samples. Due to concerns about metal pollution in the ambient air, some areas have operated airborne metal-monitoring systems such as industrial complexes, and we defined this as “metal-polluted area”. In addition, KoNEHS cycle 4 asked the source of household drinking water. If it was from local underground water and/or mineral spring, not metropolitan tap water, commercial mineral bottle water and/or purifier, we classified it “Local-based water”.

KoNEHS cycle 4 was conducted with the approval of the Ethical Review Board of NIER (NIER-2018-BR-003-02), and this study was approved by the Seokyeong University Institutional Review Board (SKUIRB-2024-01-028).

Serum PFAS analysis

KoNEHS cycle 4 included the analysis of five PFAS compounds in serum samples: perfluorooctanoic acid (PFOA, CAS no. 335-67-1), perfluorooctane sulfonic acid (PFOS, CAS no. 1763-23-1), perfluorohexane sulfonic acid (PFHxS, CAS no. 355-46-4), perfluorodecanoic acid (PFDA, CAS no. 335-76-2), and perfluorononanoic acid (PFNA, CAS no. 375-95-1). The serum PFAS analysis was performed by a commercial laboratory (Smartive Co. Ltd., Gyeonggi-do, Korea) assigned by the NIER as a partner of KoNEHS. Serum samples (0.5 mL) were used for PFAS analysis. Following sampling, serum samples were stored under −70℃ until analysis. The protein precipitation method was adopted as a preprocessing step to remove proteins from the serum samples. After adding 0.01 mL of the internal standard material and 0.8 mL of acetonitrile to the sample, the mixture was stirred for 10 seconds to denature the serum proteins. After centrifugation at 13,000 rpm for 10 min, all proteins were sedimented, and 0.8 mL of the supernatant was dispensed. The dispensed sample was concentrated for 15 –20 minutes using N2 gas, and then redissolved in 0.025 mL of 50% methanol, and used for analysis. Quantitative analysis was performed using high-performance liquid chromatography-tandem mass spectrometry (Q-Sight Triple Quad, Perkin-Elmer, Waltham, MA, US) with a C18 column (2.1×100 mm).

Calibration curves were constructed using six standards, with an R2 value greater than 0.995 in all tests. Accuracy and precision were assessed through internal quality assurance and control (QAQC) schemes. NIST (National Institute of Standards and Technology) 1957 and 1958 were used for matrix reference materials in accuracy tests in the internal QAQC. Three concentrations of QC samples were applied in every batch. For external QAQC, Smartive participated in the NIER QAQC program for KoNEHS and the German External Quality Assessment Scheme (G-EQUAS), successfully passing all evaluations.

Statistical analysis

In this study, statistical analysis was divided into two. The first is descriptive statistics for deriving RVs, applied geometric means (GMs) and survey-weighting. We defined RVs as means representing the concentrations in serum samples of all investigated population and derived as representative values of whole Korean population. In addition, RV95 refers to the guidance value that distinguished high exposure groups. Given that serum PFAS concentrations showed a right-skewed distribution, GMs were used as representative values. Thus, the GMs of serum PFAS concentrations from KoNEHS cycle 4 are presented as RVs for serum PFAS in Korean adults. These RVs were calculated with survey-weighting, because KoNEHS samples were designed to calculate an official national reference value, KoNEHS surveyed based on a two-stage proportionally stratified sampling design [24]. The RVs obtained in this study were compared to those reported in the United States and Germany [25-26]. To determine high exposure groups, this study referred two guidance values – 95th percentile from the NHANES and Human Biomonitoring (HBM) values of the German Human Biomonitoring Commission [25-26]. HBM values are derived from health-related guidance values and used as advices for planning and execution of related research and policies of environmental health [26].

The second is analytical statistics to find out factors related to PFAS exposure of Korean general population. To compare serum PFAS concentrations across different general characteristics of KoNEHS participants, Student’s t-test and analysis of variance (ANOVA) were used. In addition, covariate-adjusted means were calculated using analysis of covariance (ANCOVA).

Descriptive statistics analyses for deriving used log-transferred values using “survey package” of R version 4.3.2 (R Foundation for Statistical Computing, Vienna, Austria). Analytical statistics including analyses used the same program with statistical significance set at p < 0.05.

Results

Study participants

Serum PFAS analysis in KoNEHS cycle 4 involved 2,993 participants (1,298 male; 1,695 female), representing a total of 43,863,499 Korean adults aged 20 years and older (21,848,320 male; 22,015,179 female). Among the participants, 41.3% were in their 40s and 50s, and 64.5% were never smokers. The majority of participants (71.6%) resided in urban areas (Table 1).

RVs and RV95 of serum PFAS from KoNEHS cycle 4

Table 2 presents the RVs for the concentrations of five serum PFAS compounds from the KoNEHS cycle 4. For PFOA, the GM was 6.43 μg/L, with a 95th percentile value of 16.55 μg/L, which is higher than the 4.27 μg/L reported in the United States. Notably, 81.9% and 25.9% of participants exceeded the 95th percentile of the United States NHANES (4.27 μg/L), and the HBM value (10 μg/L), respectively. The GM and 95th percentile of serum PFOA concentrations were 15.07 and 43.96 μg/L, respectively, with 42.7% of participants exceeding the 95th percentile of the United States NHANES (19.1 μg/L). Additionally, 36.9% and 30.4% of male and female participants exceeded HBM, respectively. For PFHxS, PFNA, and PFDA, which lack suggested HBM values, the GMs were 4.17, 2.06, and 0.91 μg/L, respectively, with corresponding 95th percentiles of 14.91, 5.98, and 2.40 μg/L, respectively. Between 42.6% and 74.7% of participants had levels exceeding the 95th percentiles of the United States NHANES.

Serum PFAS concentrations by general characteristics

Serum concentrations of all five PFAS compounds were significantly higher in male participants than those of female participants (GMs of female and male: 6.74 and 7.43 μg/L for PFOA; 15.71 and 18.15 μg/L for PFOS; 4.00 and 5.18 μg/L for PFHxS; 2.21 and 2.60 μg/L for PFNA; 0.98 and 1.11 μg/L for PFDA). Additionally, PFAS concentrations increased with age (GMs of 2–30s, 4–50s, and ≥60s: 4.56, 7.19, and 8.75 μg/L for PFOA; 9.83, 16.00, and 23.71 μg/L for PFOS; 2.97, 4.56, and 5.53 μg/L for PFHxS; 1.30, 2.38, and 3.32 μg/L for PFNA; 0.63, 1.02, and 1.38 μg/L for PFDA).

Serum PFAS concentrations were lower in “never-smokers” compared to “ex-“ and “current-smoker” (GMs of never-, ex-, and current-smokers: 6.79, 7.86, and 7.03 μg/L for PFOA; 16.13, 19.76, and 15.72 μg/L for PFOS; 4.10, 5.37, and 5.10 μg/L for PFHxS; 2.24, 2.89, and 2.38 μg/L for PFNA; 0.98, 1.24, and 1.00 μg/L for PFDA). Participants who frequently consumed seafood also had significantly higher PFAS concentrations, except for PFHxS (GMs of never-, monthly-, weekly-, and daily-intake: 5.47, 6.31, 7.73, and 9.44 μg/L for PFOA; 12.65, 14.88, 18.36, and 25.57 μg/L for PFOS; 3.94, 4.20, 4.69, and 5.60 μg/L for PFHxS; 1.67, 2.07, 2.68, and 3.61 μg/L for PFNA; 0.74, 0.91, 1.15, and 1.53 μg/L for PFDA). All p-values were <0.001, except for PFHxS in relation to seafood intake (Fig. 1 and Table S1).

Factors associated with serum PFAS concentrations

Comparing serum PFAS concentrations in relation to socioeconomic status (SES) revealed that higher household monthly income was correlated with increased serum PFOA concentrations, although this relationship was not statistically significant (p =0.070). In contrast, after adjusting for confounders such as sex, age, pack year, and seafood intake frequency, serum concentrations of PFOS, PFHxS, PFNA, and PFDA were significantly higher among participants with lower educational attainment (Table 3).

Participants residing in coastal areas exhibited the highest serum concentrations of PFOA, PFOS, PFNA, and PFDA. In contrast, those living in urban industrial areas showed the highest concentrations of PFHxS. In addition, those who consumed local water sources had the highest serum concentrations of PFNA and PFDA.

Discussion

This study, providing the first representative values (RVs) and guidance values (RV95) of serum PFAS concentrations in the Korean general population via the KoNEHS, revealed that PFAS concentrations in Korean population are notably high, with many participants exceeding the HBM guidelines. The RVs for PFAS concentrations in the serum of Korean adults were higher than those reported in other national and regional surveys, including the NHANES, HBM4EU, CHMS, GerES, Flemish Environment and Health Study (FLEHS), and other studies [18, 27-32]. While differences in analytical methods could partly explain these discrepancies, the fact that our study passed both the international and domestic external QA programs (G-EQUAS and NIER’s QAQC program) suggests that the differences in serum concentrations were not merely due to differences in the analytical process. This study showed that serum PFAS concentrations in the Korean population were higher than those in other countries. This elevated PFAS exposure in the Korean population may be attributed to manufacturing-based industrial structure, particularly in sectors such as semiconductors and automobiles [33]. This industrial structure contributes to both occupational and environmental exposure to PFAS. Furthermore, high PFAS exposure may be due to the increased use of contact lenses in Koreans [34-35].

Serum PFAS concentrations have been shown to increase with age, sex (male), smoking (ex-smoker), and seafood consumption, as reported in previous studies worldwide [17, 27, 29, 36-39]. Interestingly, this study found that ex-smokers had higher PFAS exposure levels than current smokers. Smoking may be related with many environmental pollutants not only for PFAS, some studies have also reported higher PFAS concentrations among the non-smoking group, indicating that the relationship between smoking status and PFAS levels remains unclear [40-41].

SES is another important factor influencing exposure to chemicals like PFAS as already reported in several studies, however [39, 42], this study did not find any relationship. The relationship between education level and PFAS levels remains unclear [42], but, a higher education level may generally reduce chemical exposure and interpret health-related information [42].

In this study, residents living coastal areas have higher serum PFAS concentrations. And this study also indicated that high PFAS exposure levels may be related to seafood consumption. In European biomonitoring studies, serum PFAS levels increased with higher consumption of fish and seafood [18, 39, 43]. Known as “forever chemicals,” PFAS can accumulate in marine ecosystems, making seafood consumption a significant contributor to PFAS exposure in the general population [44-45]. This result is thought to be related to the persistence of PFAS, and higher levels of PFAS with increasing age can be observed in this context. In contrast, the PFHxS concentration was the highest in the urban industrial area, whereas the other four compounds were the highest in the coastal area. Recently, the use of PFHxS has increased as a substitute for PFOA and/or PFOS [46]. PFHxS, a perfluorosulfonic acid (PFSA) with seven or fewer fluorinated carbons [47], and primarily detected in wastewater discharged from industrial complexes [46, 48]. In Korea, PFHxS, along with PFOA and PFOS, has been included in tap water quality inspections since 2018, following a rise in PFHxs concentrations at filtration plants near industrial complexes [49]. This study may suggest that PFHxS exposure is more likely driven by industrial pollution in drinking water rather than by seafood consumption. Although not statistically significant, the highest PFHxS concentration was found in participants using tap water as their primary drinking source. Of course, there is a limitation for this assumption in this study itself. The population consuming local water, sourced from mineral springs and groundwater, exhibited the highest concentrations of PFDA and PFNA. A previous study reported that high concentrations of PFDA were detected in subsoil samples [50]. The concentration of PFDA in the soil is generally high, and both PFNA and PFOA concentrations increase in the soil after rainfall [51]. Thus, populations relying on local water sources are likely affected by PFDA and PFNA contamination in the soil.

Establishing strong scientific evidence for the relationships between PFAS exposure in this study is challenging due to the limitations inherent in national biomonitoring, which is designed as a cross-sectional study. Furthermore, this study did not adequately consider various factors related to PFAS exposure, such as diet, consumer products, clothes, and occupational exposures.

Despite these limitations, this study suggests that PFAS exposure levels in the Korean general population are high and are related with residential environment. Therefore, PFAS exposure can be a community-based environmental health issue as we already experienced [52].

Conclusions

This study highlights the PFAS exposure levels in Korean adults, using data from a national biomonitoring program that accurately represents the general population. In addition to other known factors, seafood intake, residence, and drinking water intake may be related to PFAS exposure in the general population.

Serum PFAS concentrations by general characteristics

Notes

Acknowledgement

This work was supported by the Korea Environment Industry & Technology Institute (KEITI) through the Core Technology Development Project for Environmental Diseases Prevention and Management, funded by the Korea Ministry of Environment (MOE) [Grant No. 2480000101/ RS-2021-KE001378].

Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships.

CRediT author statement

YMC: Conceptualization, Writing-Original draft preparation, Writing-Review & Editing, Methodology, Software, Visualization, Supervision, Project administration, Funding acquisition. DH: Software, Formal analysis. JJ: Formal analysis, Writing-Original draft preparation. KHC: Writing-Review & Editing. YSH and WJK: Investigation.

Supplementary Material

This material is available online at www.eaht.org.

eaht-40-3-e2025021-Supplementary-Table-1.pdf

References

1. Saikat S, Kreis I, Davies B, Bridgman S, Kamanyire R. The impact of PFOS on health in the general population: a review. Environ Sci Process Impacts 2013;15(2):329-335 http://doi.org/10.1039/c2em30698k.

2. Wee SY, Aris AZ. Environmental impacts, exposure pathways, and health effects of PFOA and PFOS. Ecotoxicol Environ Saf 2023;267: 115663 http://doi.org/10.1016/j.ecoenv.2023.115663.

3. Mojiri A, Zhou JL, Ozaki N, KarimiDermani B, Razmi E, Kasmuri N. Occurrence of per- and polyfluoroalkyl substances in aquatic environments and their removal by advanced oxidation processes. Chemosphere 2023;330: 138666 http://doi.org/10.1016/j.chemosphere.2023.138666.

4. Domingo JL, Nadal M. Human exposure to per- and polyfluoroalkyl substances (PFAS) through drinking water: A review of the recent scientific literature. Environ Res 2019;177: 108648 http://doi.org/10.1016/j.envres.2019.108648.

5. Steenland K, Winquist A. PFAS and cancer, a scoping review of the epidemiologic evidence. Environ Res 2021;194: 110690 http://doi.org/10.1016/j.envres.2020.110690.

6. Costello E, Rock S, Stratakis N, Eckel SP, Walker DI, Valvi D, et al. Exposure to per- and polyfluoroalkyl substances and markers of liver injury: A systematic review and meta-analysis. Environ Health Perspect 2022;130(4):46001 http://doi.org/10.1289/EHP10092.

7. Zhang X, Xue L, Deji Z, Wang X, Liu P, Lu J, et al. Effects of exposure to per- and polyfluoroalkyl substances on vaccine antibodies: A systematic review and meta-analysis based on epidemiological studies. Environ Pollut 2022;306: 119442 http://doi.org/10.1016/j.envpol.2022.119442.

8. Frangione B, Birk S, Benzouak T, Rodriguez-Villamizar LA, Karim F, Dugandzic R, et al. Exposure to perfluoroalkyl and polyfluoroalkyl substances and pediatric obesity: a systematic review and meta-analysis. Int J Obes (Lond) 2024;48(2):131-146 http://doi.org/10.1038/s41366-023-01401-6.

9. Zheng Q, Yan W, Gao S, Li X. The effect of PFAS exposure on glucolipid metabolism in children and adolescents: a meta-analysis. Front Endocrinol (Lausanne) 2024;15: 1261008 http://doi.org/10.3389/fendo.2024.1261008.

10. Petersen KU, Larsen JR, Deen L, Flachs EM, Hærvig KK, Hull SD, et al. Per- and polyfluoroalkyl substances and male reproductive health: a systematic review of the epidemiological evidence. J Toxicol Environ Health B Crit Rev 2020;23(6):276-291 http://doi.org/10.1080/10937404.2020.1798315.

11. India-Aldana S, Yao M, Midya V, Colicino E, Chatzi L, Chu J, et al. PFAS exposures and the human metabolome: A systematic review of epidemiological studies. Curr Pollut Rep 2023;9(3):510-568 http://doi.org/10.1007/s40726-023-00269-4.

12. Li L, Guo Y, Ma S, Wen H, Li Y, Qiao J. Association between exposure to per- and perfluoroalkyl substances (PFAS) and reproductive hormones in human: A systematic review and meta-analysis. Environ Res 2024;241: 117553 http://doi.org/10.1016/j.envres.2023.117553.

13. DeLuca NM, Minucci JM, Mullikin A, Slover R, Hubal EAC. Human exposure pathways to poly- and perfluoroalkyl substances (PFAS) from indoor media: A systematic review. Environ Int 2022;162: 107149 http://doi.org/10.1016/j.envint.2022.107149.

14. Zahm S, Bonde JP, Chiu WA, Hoppin J, Kanno J, Abdallah M, et al. Carcinogenicity of perfluorooctanoic acid and perfluorooctanesulfonic acid. Lancet Oncol 2023;25(1):16-17 http://doi.org/10.1016/S1470-2045(23)00622-8.

15. Sassano M, Seyyedsalehi MS, Kappil EM, Zhang S, Zheng T, Boffetta P. Exposure to per- and poly-fluoroalkyl substances and lung, head and neck, and thyroid cancer: A systematic review and meta-analysis. Environ Res 2025;266: 120606 http://doi.org/10.1016/j.envres.2024.120606.

16. Schoeters G, Verheyen VJ, Colles A, Remy S, Martin LR, Govarts E, et al. Internal exposure of Flemish teenagers to environmental pollutants: Results of the Flemish Environment and Health Study 2016–2020 (FLEHS IV). Int J Hyg Environ Health 2002;242: 113972 https://doi.org/10.1016/j.ijheh.2022.113972.

17. Sonnenberg NK, Ojewole AE, Ojewole CO, Lucky OP, Kusi J. Trends in serum per- and polyfluoroalkyl substance (PFAS) concentrations in teenagers and adults, 1999-2018 NHANES. Int J Environ Res Public Health 2023;20(21):6984 https://doi.org/10.3390/ijerph20216984.

18. Uhl M, Schoeters G, Govarts E, Bil W, Fletcher T, Haug LS, et al. PFASs: What can we learn from the European Human Biomonitoring Initiative HBM4EU. Int J Hyg Environ Health 2023;250: 114168 https://doi.org/10.1016/j.ijheh.2023.114168.

19. Hoopmann M, Murawski A, Schümann M, Göen T, Apel P, Vogel N, et al. A revised concept for deriving reference values for internal exposures to chemical substances and its application to population-representative biomonitoring data in German children and adolescents 2014-2017 (GerES V). Int J Hyg Environ Health 2023;253: 114236 https://doi.org/10.1016/j.ijheh.2023.114236.

20. Alvito P, Assunção RM, Bajard L, Martins C, Mengelers MJ, Mol H, et al. Current advances, research needs and gaps in mycotoxins biomonitoring under the HBM4EU-Lessons learned and future trends. Toxins (Basel) 2022;14(12):826 https://doi.org/10.3390/toxins14120826.

21. Park C, Yu SD. Status and prospects of the Korean National Environmental Health Survey (KoNEHS). Journal of Environmental Health Sciences 2014;40(1):1-9 http://doi.org/10.5668/JEHS.2014.40.1.1 [Korean].

22. Yun J, Jang EC, Kwon SC, Min YS, Lee YJ. The association of perfluoroalkyl substances (PFAS) exposure and kidney function in Korean adolescents using data from Korean National Environmental Health Survey (KoNEHS) cycle 4 (2018-2020): a cross-sectional study. Ann Occup Environ Med 2023;35: e5. https://doi.org/10.35371/aoem.2023.35.e5.

23. Lee JH, Lee CK, Suh CH, Kang HS, Hong CP, Choi SN. Serum concentrations of per- and poly-fluoroalkyl substances and factors associated with exposure in the general adult population in South Korea. Int J Hyg Environ Health 2017;220(6):1046-1054 https://doi.org/10.1016/j.ijheh.2017.06.005.

24. Lee JY, Choi YH, Choi HI, Moon KW. Association between environmental mercury exposure and allergic disorders in Korean children: Korean National Environmental Health Survey (KoNEHS) cycles 3-4 (2015-2020). Sci Rep 2024;14(1):1472 https://doi.org/10.1038/s41598-024-51811-3.

25. United States, Centers for Disease Control and Prevention. Fourth national report on human exposure to environmental chemicals: updated tables, January 2019, Volume one. [cited Dec 6, 2024]. Available from: https://stacks.cdc.gov/view/cdc/75822.

26. Apel P, Angerer J, Wilhelm M, Kolossa-Gehring M. New HBM values for emerging substances, inventory of reference and HBM values in force, and working principles of the German Human Biomonitoring Commission. Int J Hyg Environ Health 2017;220(2 Pt A):152-166 https://doi.org/10.1016/j.ijheh.2016.09.007.

27. Colles A, Bruckers L, Hond ED, Govarts E, Morrens B, Schettgen T, et al. Perfluorinated substances in the Flemish population (Belgium): Levels and determinants of variability in exposure. Chemosphere 2020;242: 125250 https://doi.org/10.1016/j.chemosphere.2019.125250.

28. Dong Z, Wang H, Yu YY, Li YB, Naidu R, Liu Y. Using 2003-2014 U.S. NHANES data to determine the associations between per- and polyfluoroalkyl substances and cholesterol: Trend and implications. Ecotoxicol Environ Saf 2019;173: 461-468 https://doi.org/10.1016/j.ecoenv.2019.02.061.

29. Nair AS, Ma ZQ, Watkins SM, Wood SS. Demographic and exposure characteristics as predictors of serum per- and polyfluoroalkyl substances (PFASs) levels - A community-level biomonitoring project in Pennsylvania. Int J Hyg Environ Health 2021;231: 113631 https://doi.org/10.1016/j.ijheh.2020.113631.

30. Schultz AA, Stanton N, Shelton B, Pomazal R, Lange MA, Irving R, et al. Biomonitoring of perfluoroalkyl and polyfluoroalkyl substances (PFAS) from the Survey of the Health of Wisconsin (SHOW) 2014-2016 and comparison with the National Health and Nutrition Examination Survey (NHANES). J Expo Sci Environ Epidemiol 2023;33(5):766-777 https://doi.org/10.1038/s41370-023-00593-3.

31. Tewfik EL, Noisel N, Verner MA. Biomonitoring equivalents for perfluorooctanoic acid (PFOA) for the interpretation of biomonitoring data. Environ Int 2023;179: 108170 https://doi.org/10.1016/j.envint.2023.108170.

32. Yu CH, Weisel CP, Alimokhtari S, Georgopoulos PG, Fan ZT. Biomonitoring: A tool to assess PFNA body burdens and evaluate the effectiveness of drinking water intervention for communities in New Jersey. Int J Hyg Environ Health 2021;235: 113757 https://doi.org/10.1016/j.ijheh.2021.113757.

33. Yun J, Kwon SC. The association of perfluoroalkyl substance exposure and a serum liver function marker in Korean adults. Toxics 2023;11(12):965 https://doi.org/10.3390/toxics11120965.

34. Kang H, Kim DH, Choi YH. Elevated levels of serum per- and poly-fluoroalkyl substances (PFAS) in contact lens users of U.S. young adults. Chemosphere 2024;350: 141134 https://doi.org/10.1016/j.chemosphere.2024.141134.

35. Kim M, Paik JS, Kim D, Hwang HS, Han K, Na KS. Current status of contact lenses usage in Korea: A population-based cohort study 2021. PLoS One 2024;19(3):e0296279. https://doi.org/10.1371/journal.pone.0296279.

36. Christensen KY, Raymond M, Thompson BA, Anderson HA. Perfluoroalkyl substances in older male anglers in Wisconsin. Environ Int 2016;91: 312-318 https://doi.org/10.1016/j.envint.2016.03.012.

37. Daly ER, Chan BP, Talbot EA, Nassif J, Bean C, Cavallo SJ, et al. Per- and polyfluoroalkyl substance (PFAS) exposure assessment in a community exposed to contaminated drinking water, New Hampshire, 2015. Int J Hyg Environ Health 2018;221(3):569-577 https://doi.org/10.1016/j.ijheh.2018.02.007.

38. Ingelido AM, Abballe A, Gemma S, Dellatte E, Iacovella N, De Angelis G, et al. Biomonitoring of perfluorinated compounds in adults exposed to contaminated drinking water in the Veneto Region, Italy. Environ Int 2018;110: 149-159 https://doi.org/10.1016/j.envint.2017.10.026.

39. Runkel AA, Stajnko A, Tratnik JS, Mazej D, Horvat M, Přibylová P, et al. Exposure of children and adolescents from Northeastern Slovenia to per- and polyfluoroalkyl substances. Chemosphere 2023;321: 138096 https://doi.org/10.1016/j.chemosphere.2023.138096.

40. van Gerwen M, Alpert N, Alsen M, Ziadkhanpour K, Taioli E, Genden E. The impact of smoking on the association between perfluoroalkyl acids (PFAS) and thyroid hormones: A National Health and Nutrition Examination Survey Analysis. Toxics 2020;8(4):116 https://doi.org/10.3390/toxics8040116.

41. Chang CJ, Ryan PB, Smarr MM, Kannan K, Panuwet P, Dunlop AL, et al. Serum per- and polyfluoroalkyl substance (PFAS) concentrations and predictors of exposure among pregnant African American women in the Atlanta area, Georgia. Environ Res 2021;198: 110445 https://doi.org/10.1016/j.envres.2020.110445.

42. Buekers J, Colles A, Cornelis C, Morrens B, Govarts E, Schoeters G. Socio-economic status and health: Evaluation of human biomonitored chemical exposure to per- and polyfluorinated substances across status. Int J Environ Res Public Health 2018;15(12):2818 https://doi.org/10.3390/ijerph15122818.

43. Thépaut E, Dirven HAAM, Haug LS, Lindeman B, Poothong S, Andreassen M, et al. Per- and polyfluoroalkyl substances in serum and associations with food consumption and use of personal care products in the Norwegian biomonitoring study from the EU project EuroMix. Environ Res 2021;195: 110795 https://doi.org/10.1016/j.envres.2021.110795.

44. Sunderland EM, Hu XC, Dassuncao C, Tokranov AK, Wagner CC, Allen JG. A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects. J Expo Sci Environ Epidemiol 2019;29(2):131-147 https://doi.org/10.1038/s41370-018-0094-1.

45. Dassuncao C, Hu XC, Nielsen F, Weihe P, Grandjean P, Sunderland EM. Shifting global exposures to poly- and perfluoroalkyl substances (PFASs) evident in longitudinal birth cohorts from a seafood-consuming population. Environ Sci Technol 2018;52(6):3738-3747 https://doi.org/10.1021/acs.est.7b06044.

46. Lin AY, Panchangam SC, Tsai YT, Yu TH. Occurrence of perfluorinated compounds in the aquatic environment as found in science park effluent, river water, rainwater, sediments, and biotissues. Environ Monit Assess 2014;186(5):3265-3275 https://doi.org/10.1007/s10661-014-3617-9.

47. Conder JM, Hoke RA, De Wolf W, Russell MH, Buck RC. Are PFCAs bioaccumulative? A critical review and comparison with regulatory criteria and persistent lipophilic compounds. Environ Sci Technol 2008;42(4):995-1003 https://doi.org/10.1021/es070895g.

48. Eriksson U, Haglund P, Kärrman A. Contribution of precursor compounds to the release of per- and polyfluoroalkyl substances (PFASs) from waste water treatment plants (WWTPs). J Environ Sci (China) 2017;61: 80-90 https://doi.org/10.1016/j.jes.2017.05.004.

49. Ministry of Environment, Republic of Korea. Tap water quality monitoring strengthened – Governmental official statement. [cited 2024 Aug 26]. Available from: https://www.korea.kr/briefing/pressReleaseView.do?newsId=156272151.

50. Johnson GR. PFAS in soil and groundwater following historical land application of biosolids. Water Res 2022;211: 118035 https://doi.org/10.1016/j.watres.2021.118035.

51. Chen S, Jiao XC, Gai N, Li XJ, Wang XC, Lu GH, et al. Perfluorinated compounds in soil, surface water, and groundwater from rural areas in eastern China. Environ Pollut 2016;211: 124-131 https://doi.org/10.1016/j.envpol.2015.12.024.

52. Frisbee SJ, Brooks AP Jr, Maher A, Flensborg P, Arnold S, Fletcher T et al. The C8 health project: design, methods, and participants. Environ Health Perspect 2009;117(12):1873-1882 https://doi.org/10.1289/ehp.0800379.

Figure 1.

Comparisons of serum PFAS concentrations by general characteristics of KoNEHS participants (A) For sex; (B) for age; (C) for smoking status; (D) for frequencies of seafood intake

PFOA, perfluorooctanoic acid; PFOS, perfluorooctane sulfonic acid; PFHxS, perfluorohexane sulfonic acid; PFNA, perfluorononanoic acid; PFDA, perfluorodecanoic acid

Never, never or almost never; Monthly, 1-2 in a month; Weekly, 1-2 in a week; Daily, almost every day for seafood intake. y-axis of all graphs mean serum concentration of each PFAS (μg/L). All cases were statistically significant by Student’s t-test or ANOVA (p<0.05 or p<0.01) except PFHxS in relation to seafood intake (p=0.549).

Table 1.

General characteristics of KoNEHS participants.

Variable		Raw N (%)	Weighted N (%)
Sex	Male	1,298 (43.4)	21,848,320 (49.8)
Sex	Female	1,695 (56.6)	22,015,179 (50.2)
Age	20-30s	633 (21.1)	15,482,397 (35.3)
	40-50s	1,237 (41.3)	16,869,222 (38.5)
	≥60	1,123 (37.5)	11,511,880 (26.2)
Smoking	Never	1,930 (64.5)	27,549,065 (62.8)
	Ex-smoker	597 (19.9)	7,921,093 (18.1)
	Current smoker	466 (15.6)	8,393,341 (19.1)
Monthly income (Korean Won, ₩)^a	Low (<3 million)	1,353 (45.2)	16,840,294 (38.4)
	Middle (3 – 5 million)	800 (26.7)	12,828,300 (29.2)
	High (≥5 million)	837 (28.0)	14,106,447 (32.2)
Education	Low (≤middle)	811 (27.1)	8,480,093 (19.3)
	Middle (high)	896 (29.9)	11,990,867 (27.3)
	High (≥university)	1,286 (43.0)	23,392,540 (53.3)
Living area	City	2,143 (71.6)	33,590,048 (76.6)
	Rural	447 (14.9)	4,038,056 (9.2)
	Coastal	133 (4.4)	6,026,980 (13.7)
	Metal-polluted area	270 (9.0)	208,415 (0.5)
Drinking water	Tap water	825 (27.6)	11,233,817 (25.6)
	Purifier or commercially bottled water	2,036 (68.0)	31,200,230 (71.1)
	Local-based water	121 (4.0)	1,290,638 (2.9)
Seafood intake	Never	278 (9.3)	4,888,983 (11.1)
Seafood intake	Monthly	1,071 (35.8)	16,552,715 (37.7)
Seafood intake	Weekly	1,491 (49.8)	19,847,557 (45.2)
Seafood intake	Daily	153 (5.1)	2,574,245 (5.9)

^a million ₩ is approximately 700 US dollars.

Table 2.

Serum PFAS concentrations of KoNEHS participants and comparisons with other reference values (μg/L, n=2,993).

Compound	Representative values in this study		Guidance values
Compound	GM	95^th percentile	RV95	Excess rate (N, %)^d
PFOA	6.43	16.55	4.27 (US)^a	81.9 (2,450/2,993, 81.9%)
PFOA	6.43	16.55	10 (HBM)^b	25.9 (775/2,993, 25.9%)
PFOS	15.07	43.96	19.1 (US)^a	42.7 (1,279/2,993, 42.7%)
			20 (HBM for female)^c	36.9 (625/1,695, 36.9%)
			25 (HBM for male)^c	30.4 (395/1,298, 30.4%)
PFHxS	4.17	14.91	5.00 (US)^a	42.6 (1,275/2,993, 42.6%)
PFNA	2.06	5.98	1.90 (US)^a	65.8 (1,968/2,993, 65.8%)
PFDA	0.91	2.40	0.70 (US)^a	74.7 (2,236/2,993, 74.7%)

PFOA, perfluorooctanoic acid; PFOS, perfluorooctane sulfonic acid; PFHxS, perfluorohexane sulfonic acid; PFNA, perfluorononanoic acid; PFDA, perfluorodecanoic acid; GM, geometric mean.

^a 95th percentile, Age 20+ years (2015-2016) [25]

^b Upper reference value (RV95) in human plasma (women, men and children < 10 years, 2003-2007) [26]

^c Upper reference value (RV95) in human plasma (20 μg/L for women; 25 μg/L for men, 2003-2007) [26]

^d Rate of participants above the guidance levels.

Table 3.

Comparisons of serum PFAS concentrations by social economic statues and living environment of KoNEHS participants.

Variable (N)		PFOA		PFOS		PFHxS		PFNA		PFDA
Variable (N)		aMean (95% CI)	p	aMean (95% CI)	p	aMean (95% CI)	p	aMean (95% CI)	p	aMean (95% CI)	p
Monthly income	Low (1,350)	7.98 (7.72, 8.24)	0.070	20.16 (19.37, 20.94)	0.795	6.22 (5.79, 6.66)	0.242	2.80 (2.72, 2.89)	0.085	1.21 (1.17, 1.24)	0.336
	Middle (800)	8.36 (8.03, 8.68)		19.79 (18.81, 20.76)		6.64 (6.10, 7.18)		2.83 (2.72, 2.93)		1.20 (1.15, 1.24)
	High (835)	8.45 (8.13, 8.77)		20.21 (19.23, 21.18)		6.01 (5.48, 6.55)		2.95 (2.85, 3.06)		1.24 (1.20, 1.29)
Education	Low (811)	8.08 (7.70, 8.45)	0.678	21.37 (20.25, 22.50)	0.028	7.02 (6.38, 7.64)	0.007	3.06 (2.94, 3.18)	0.001	1.32 (1.27, 1.38)	<0.001
	Middle (896)	8.29 (7.99, 8.59)		19.46 (18.55, 20.37)		6.50 (6.00, 7.00)		2.78 (2.68, 2.88)		1.19 (1.14, 1.23)
	High (1286)	8.26 (7.97, 8.54)		19.72 (18.84, 20.59)		5.65 (5.17, 6.14)		2.77 (2.68, 2.87)		1.16 (1.12, 1.21)
Residential area	City (2,139)	8.21 (8.02, 8.41)	<0.001	19.50 (18.91, 20.08)	<0.001	6.62 (6.30, 6.94)	<0.001	2.76 (2.70, 2.83)	<0.001	1.18 (1.15, 1.21)	<0.001
	Rural (447)	7.45 (7.03, 7.88)		21.05 (19.77, 22.34)		4.21 (3.50, 4.92)		3.02 (2.88, 3.16)		1.32 (1.26, 1.38)
	Coastal (133)	10.67 (9.90, 11.45)		27.69 (25.35, 30.03)		4.52 (3.25, 5.84)		4.00 (3.74, 4.25)		1.57 (1.45, 1.68)
	Urban Industrial areas (269)	8.29 (7.75, 8.84)		19.43 (17.79, 21.08)		7.86 (6.95, 8.76)		2.70 (2.52, 2.88)		1.16 (1.08, 1.24)
Drinking water	Tap (824)	8.34 (8.02, 8.65)	0.674	20.56 (19.60, 21.52)	0.237	6.79 (6.26, 7.32)	0.079	2.86 (2.75, 2.96)	0.005	1.22 (1.18, 1.27)	0.001
	Purifier or mineral (2,032)	8.16 (7.96, 8.37)		19.80 (19.20, 20.41)		6.06 (5.72, 6.40)		2.82 (2.76, 2.90)		1.20 (1.17, 1.23)
	Local-based (121)	8.26 (7.44, 9.08)		21.47 (18.98, 23.95)		6.35 (4.98, 7.73)		3.29 (3.02, 3.56)		1.43 (1.31, 1.55)

PFOA, perfluorooctanoic acid; PFOS, perfluorooctane sulfonic acid; PFHxS, perfluorohexane sulfonic acid; PFNA, perfluorononanoic acid; PFDA, perfluorodecanoic acid

95% CI, 95% confidence interval for aMean. aMean, covariates-adjusted mean (covariates include sex, age, pack year and seafood intake frequency)

Monthly income Low, < 3 million Korean Won (₩); Middle, 3 – 5 million ₩; High ≥ 5 million ₩ (one million ₩ is approximately 728 US$ in April 2024).

Education Low, < middle school graduation; Middle, high schools; High ≥ University graduation.

p-values were calculated with ANCOVA.