Evaluation of the exposure to perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) through drinking water and human risk assessment

Abstract

In the present study, two most commonly used Perfluoroalkyl substances (PFASs), namely perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), were determined in 45 tap water samples from the city of Isfahan (Iran) by dispersive liquid-liquid extraction (DLLME) and liquid chromatography-mass spectrophotometry (LC-MS) analysis. Risk assessment was also performed to determine the risk to human health. The mean concentration of PFOA was 38.1 ± 26.4ng/L (min = 5.1 and max = 1056ng/L). The mean concentration of PFOS was 33.7 ± 25.09ng/L (min = 4.3 and max = 99.2ng/L). The combined concentrations of PFOA and PFOS were above the US-EPA advisory levels (70ng/L) in 48.8% of the samples. The distance between the sampling locations and the water treatment plant showed no significant correlation (p > 0.05). The results of the risk assessment showed that all calculated hazard quotients (HQ) and hazard indices (HI) are below 1, indicating that the risk to human health from exposure to PFOA and PFOS via drinking water in the city of Isfahan was not high for adults and children. These results indicate a significant contamination of Isfahan tap water by PFOA and PFOS of unknown origin. Further studies are needed on the Zayande-Roud River water as a supplier of Isfahan tap water and the efficiency of the water treatment plant and the role of the water distribution network in PFASs contamination of tap water.

Introduction

Poly- and prefluoroalkyl substances (PFASs) are an important class of emerging environmental pollutants, including about 5000 synthetic chemicals with perfluoroalkyl moieties in their chemical structure. More than 2000 PFASs are available on the global market. PFASs are categorised into three major subclasses based on the functional groups in their chemical structure and chain length, including perfluorinated carboxylic acids (PFCAs), perfluorinated sulfonic acids (PFSAs) and perfluorinated phosphonic acids (PFPAs) [1]. Strong carbon-fluorine bonds have made PFASs extremely resistant to thermal and chemical degradation. Due to their unique physical and chemical properties, PFASs have been widely used in industrial processes and commercial products since the mid-20th century [2]. Perfluorooctanoic acid (PFOA, C7F15COOH) and perfluorooctane sulfonic acid (PFOS, C8F17SO3H) are the two most widely used PFASs species belonging to the subclasses of PFCAs and PFSAs, respectively, and these two compounds have received the most research attention worldwide [3].

Various industrial products such as semiconductors, photographic films, firefighting foams, paints and stain-resistant carpets as well as numerous consumer products such as shampoos, floor polishes, alkaline cleaners, non-stick cookware, waterproof clothing, food packaging and pesticides contain significant amounts of PFASs [4]. Conventional industrial and municipal wastewater treatment processes are inefficient for the efficient elimination of PFASs from wastewater and they are usually passed through wastewater treatment plants (WWTPs) and discharged into wastewater and the environment [5]. Wastewater treatment plants are considered to be one of the most important sources of PFAS release to the environment, especially to surface waters [6].

PFASs are generally extremely resistant to environmental and biological degradation. Most PFASs are easily transported in the environment due to their high water solubility and low volatility. They have usually been detected far away from their source of release. As PFASs remain in the environment for a long time, they are referred to as persistent organic pollutants (POPs) [7]. The adsorption of PFASs by soils and aquifers is very low and they are easily transported into the environment by surface and groundwater. As a consequence of their extensive persistence in the environment and their significant industrial production, PFASs have become an important emerging water pollutant and have been detected in numerous water sources around the world [8].

PFASs have been frequently detected in water resources and drinking water can be an important source of exposure for the population. Although the presence of over than 40 PFASs in various water resources samples, were reported by several previous studies, in many cases, PFOS and PFOA were the most abundant PFASs and had the highest concentrations [4]. The concentrations of PFOS and PFOA reported by selected studies in drinking water samples from different locations and countries are shown in Table 1. In the United States alone, PFASs have been found in the drinking water of more than 16 million people in 33 states [9].

Table 1.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) concentrations in drinking tap water reported by selected studies

Year	Country	n	PFASs levels(ng/L)				Ref.
			PFOA		PFOS
			Range	Mean/Median	Range	Mean/Median
2008-9	Germany	111	˂10–68	NA/˂10	NA	NA/˂10	[12]
NA	Germany	26	NA-6.1	NA/2.6	NA-4.7	NA/1.3	[13]
2006	Italy	6	1.0-2.9	2.4/NA	6.2–9.7	8.1/NA	[14]
2008	Spain	NA	˂0.85–57.43	4.57/0.98	˂0.12–58.12	3.72/0.51	[15]
2014	Spain	29	2-140	40/41	3.8–29	14/13	[16]
2012	China	100	2.96.342	3.19/3.19	1.88–2.32	2.1/2.1	[17]
2015	China	14	5.6-115.4	26.6/18.5	˂0.5–6.67	NA/NA	[18]
2007-9	Japan	5	4.7–12	NA/6.1	1.7–11	NA/4.5	[19]
2011-2	Korea	34	NA-20.7	12.9/NA	NA-0.34	2.6/NA	[20]
2003-6	USA	25	2.5–108	20/10	NA	28/76	[21]
2010	Australia	62	˂0.50–9.66	NA/NA	˂0.66–15.6	NA/NA	[22]
2008	Brazil	26	0.35–2.82	1.17/0.95	0.58–6.70	1.7/1.09	[23]
2015	Ghana	4	68.1–190	105.8/NA	16.2–168.3	89.7/NA	[24]

In areas with highly PFOA-contaminated drinking water, elevated PFOA concentrations in human serum have been detected [8], indicating the role of water pollution in PFOA exposure of the population. PFOS and PFOA contamination of drinking water ranged from pg/L to mg/L. Some water sources near the fluorochemical production facilities contained mg/L levels of PFOA or PFOS [10]. Previous studies have shown that PFOA contamination in drinking water becomes significant at a concentration of 40ng/L or higher [8].

Increasing concerns about the environmental persistence and health effects of PFASs has led progressively stringent guidelines and regulations for PFOS and PFOA levels in drinking water. For example, the United States Environmental Protection Agency (US-EPA) has established the life time health advisory level (LHAs) of 70ng/L for individual PFOA and PFOS or their combination [11]. Other regulatory agencies in the US and some other countries have also developed criterion values for PFOA and PFOS that are lower than the values recommended by the US- EPA [5].

Toxicological studies have shown that PFASs have a wide range of adverse effects on animals and humans, including endocrine disruption, hepatotoxicity, reproductive and developmental toxicity, and toxic effects on the nervous system [25]. Associations have been demonstrated between blood levels of PFOS and PFOA and hyperuricemia [26] as well as attention-deficit/hyperactivity disorder in children [26] and reduced immune response to vaccination [27]. Disorders of thyroid hormone levels, infertility and metabolic syndrome due to PFASs exposure have been documented by epidemiological observations [28]. However, the risk of PFASs in water sources to humans and other organisms has not yet been fully investigated. To the best of our knowledge, there has been no study on the occurrence of PFASs in drinking water in Iran and the assessment of the health risk to consumers.

The metropolis of Isfahan is the third largest and most populous city in Iran with around two million inhabitants. This metropolis is located in the central plateau of Iran, which has a semi-arid and arid desert climate. These conditions, combined with strong population growth and global climate change, has led to the city struggling with water shortages and drought. Currently, providing the population of Isfahan with safe drinking water is one of the most important national concerns. The main sources of drinking water supply for Isfahan are Zayandeh-Roud River and groundwater, and the possibility of contamination of these two sources with environmental pollutants is very high [29]. Therefore, the present study focused on the determination of two main contaminants of drinking water (PFOA and PFOS) in the tap water network of Isfahan and the assessment of dietary exposure to these contaminants.

Methodology

Chemicals and standards

The standards of PFOA and PFOS were obtained from Sigma-Aldrich, Inc. (St. Louis, MO. USA). Sodium chloride, hydrochloric acid, trichloromethane and HPLC grade acetonitrile were obtained from Merck Crop. (Darmstadt, Germany). Ultrapure water with an electrical conductivity of 18.2 MΩcm was prepared using a Millipore water purification system (Millipore Corporation, Bellerica, MA, USA). N, N-Bis(trimethylsilyl)trifluoroacetamide (BSTFA) is supplied by Supelco Inc. (USA). A mixed stock solution of both PFOA and PFOS at the respective concentration of 1 mg/L was prepared by diluting the standards with methanol. The working solutions and the quality control (QC) solutions were freshly prepared by serial dilution of the stock solution with ultrapure water.

Study area and sample collection

The study was conducted in the summer of 2023 in the urban areas of the city of Isfahan in Iran. Isfahan is the second most populous and most polluted industrial city in Iran and is located in the central part of the country [30]. 45 samples were collected from tap water (100 ml) at different locations in the city covering official water monitoring points. Sampling was done after rinsing the water for 5–10 min to remove stagnant water. All water samples were placed in pre-cleaned amber glass bottles, stored in the dark at 4 °C and analyzed within 24 h of collection. A global positioning system (GPS) was used to determine the locations of the sampling points. The geographical view of the sampling points is shown in Fig. 1.

Fig. 1.

The map of sampling locations for drinking tap water in the city of Isfahan

Sample preparation and extraction

Trace concentrations of PFOA and PFOS were extracted from water samples using a dispersive liquid liquid microextraction (DLLME) method previously developed by D’Orazio et al. [31]. In brief, 7.5 mL of water sample containing 30% (w/v) sodium chloride was placed in a 10 mL screw cap glass tube with conical end and the pH was adjusted to 3.0 with 1 M hydrochloric acid. Then a mixture of 100µL trichloromethane (as extraction solvent) and 750µL acetonitrile (as dispersion solvent) was quickly injected into the aqueous sample using a 1 mL glass syringe, the sample was vortexed for 2 min and centrifuged at 4000 rpm for 5 min. The settled organic phase at the bottom of the tube was transferred to a 1 mL glass tube using a micropipette and evaporated to dryness under a gentle stream of nitrogen.

LC/MS analysis

The identification and quantification of PFOS and PFOA concentrations was carried out using high performance liquid chromatography-mass spectrometry (LC-MS). Details of the optimized analytical conditions can be found in Table 2. The selected ion monitoring mode (SIM) was applied at m/z values of 499 for PFOS and 413 for PFOA [32]. PFOA and PFOS were detected at 4.8 min and 7.3 min, respectively.

Table 2.

Optimized conditions for LC-MS quantification of PFOS and PFOA

LC		MS
Instrument	Agilent 1100 Series	Instrument: atmospheric pressure electrospray ionization (ESI) MS detector (Agilent Technologies, USA)
Column	ODS-C18 ((2.1 × 150 mm, 5 mm), Waters, USA
Mobile phase	A: CH3CN B: CH3COONH4/H2O (10mM)	Polarity mode	Negative
Elution	Linear gradient: started at 35% of A and then increased to 45% of A at 2%/min for 5 min and maintained at 45% untile the end of run time	Nebulizer	N2 (70 psi)
		Drying gas	N2 (10 L/min, 350 °C)
		Fragmenter voltage	130 V
		capillary voltage	4000 V
Flow rate	0.2 ml/min	m/z (SIM mode)	499 for PFOS 413 for PFOA
Oven temperature	Room temperature
Injection volume	20 µL	Data processing	ChemStation software
Run time	20 min

QA and QC

To avoid background contamination, only acid-washed glass containers were used for the collection, preparation, extraction and analysis of the samples. Milli-Q water and solvent blanks was prepared to assess the contamination during the analysis and background contamination of the solvents and instruments. In all blank samples, the PFOA and PFOS concentrations were below the quantification limits. The method validation parameters are listed in Table 3.

Table 3.

Main validating parameters for determination of PFOA and PFOS in drinking water

	R 2	LOD(ng/L)	LOQ (ng/L)	RSD (%)	Recovery (%)
PFOA	0.999	2.31	6.72	5.3	96.7
PFOS	0.998	3.42	11.28	4.2	98.6

Human health risk assessment

The non-carcinogenic health risks to humans from exposure to PFOA and PFOS via water consumption were assessed by comparing the measured concentrations of PFOA and PFOS in water samples with the health guidance values. PFASs are considered as emerging contaminants and few health guidelines have been established for them to date. In the present study, the oral non-carcinogenic reference dose (RfD) proposed by the US EPA for PFOA and PFOS (20ng/kg/day [33]) was used for the risk assessment. First, the estimated daily intake (EDI) of PFOA and PFOS through water consumption was calculated using equation (a) and then the hazard quotient (HQ) was calculated using equation (b) to assess the probable chronic non-carcinogenic health hazard associated with PFOA and PFOS exposure [34–36].

a

b

Where,

C: concentration of PFOA and PFOS in drinking water samples (ng/L).

Wc: the average human daily water consumption (1.8 and 2 L/Day for children and adults, respectively [37].

BW: the average human body weight of children and adults (16 and 70 kg, respectively).

To estimate the overall non-carcinogenic risk of exposure to PFOA and PFOS via drinking water, the sum of the HQ values of the individual PFAS is defined as the hazard index (HI) and calculated according to equation (c). If the HQ or HI values are ˂1, this means that there is no significant risk of non-carcinogenic effects. If these values are ≥ 1, then non-carcinogenic effects may occur, with the probability tending to increase as the HQ value increases [38].

c

Statistical analysis

The concentrations of PFOA and PFOS in water samples below the LOD were considered as 1/2 LOD in the statistical analysis. The concentration of PFOA and PFOS at each sampling point was expressed as the mean ± standard deviation (SD) of three replicates. The t-test was used to determine a significant difference in PFOA and PFOS concentration between two points. At p < 0.05, the difference was considered significant. SPSS software (version 26.0) was used for statistical analysis of the data.

Results and discussion

Presence of PFOA and PFOS in water samples

The results of the determination of PFOA and PFOS in tap water samples from the city of Isfahan are summarized in Table 4. The concentrations of both PFOA and PFOS were above the LOD in all samples and were detected in all water samples. The PFOA and PFOS concentrations ranged from 5.1 to 105.6 and 4.3 to 99.2ng/L, respectively. The combined concentration of PFOA and PFOS in the samples ranged from 8.7 to 127.06ng/L. The mean concentration of PFOA in the water samples was 38.1 ± 26.4 and for PFOS 33.7 ± 25.09ng/L. All data were found to be normally distributed. The individual and combined concentrations of PFOA and PFOS at each sampling point in the city of Isfahan are shown graphically in Fig. 1. The independent t-test showed that the concentrations of PFOA and PFOS are statistically different at many sampling sites, but no specific pattern was found for the different concentrations of these analytes at some specific sites. The combined concentrations of PFOA and PFOS at 48.8% of the sampling sites were above advisory levels by US-EPA (70ng/L).

Table 4.

PFOA and PFOS levels in drinking tap water samples, Isfahan, Iran (ng/L)

	Minimum	Maximum	Mean
PFOA	5.1	105.6	38.1 ± 26.4
PFOS	4.3	99.2	33.7 ± 25.09
PFOA + PFOS	8.7	127.06	71.9 ± 8.5

The correlation between the levels of PFOA and PFOS in water samples and the distance of the sampling points from Isfahan water treatment plant was determined by simple regression. As shown in Fig. 2, there was no significant correlation between PFOA and PFOS levels and this distance (p = 0.202 and p = 0.53, respectively).

Fig. 2.

Correlation between PFOA and PFOS levels in water samples and distance of sampling points from Isfahan water treatment plant

The detected levels of PFOA and PFOS at the tap water samples in the present study are consistent with the results of previous studies on the contamination of drinking water with PFAS in various regions and countries (see Table 1). Tanaka et al. determined the levels of PFOA and PFOS in the drinking water of 21 cities from different Asian countries. The range of PFOA and PFOS levels was 0.01 to 143.1ng/L and for PFOA 0.01 to 86.9ng/L [39]. The concentrations of PFOA and PFOS in tap water varied between 1.1 and 1.6 and 5.4 to 40.0ng/L, respectively in Germany [40] and between 0.1 and 0.7 and ˂0.1 to 0.2ng/L, respectively in Japan [41]. In another study in Germany by Skutlarek et al., PFOA was the major PFASs in tap water with a maximum concentration of 519ng/L [42]. A study by Gao et al. in China showed that the mean concentration of PFOS in drinking water samples was 2.34ng/L (accounting for 73.4% of the total detected PFASs) and the mean concentration of PFOA was 2.09ng/L [17]. In a recent study in China, PFOA was detected in 92% of the analyzed water samples from 24 cities. PFOA had the highest concentration of 9.9 ± 1.7ng/L, followed by PFOS (7.7 ± 2.1ng/L) [43]. The difference between the PFASs levels in tap water from different studies may be due to the many physical, chemical and even biological processes that take place in the tap water supply chain from the water sources to the pipelines of the water distribution network [44].

Since there are no established Iranian guidelines for safe levels of PFASs in drinking water, we compared detected levels of PFOA and PFOS in water samples with the advisory levels recommended by the US-EPA (70ng/L for PFOA, PFOS or combined). The combined level of PFOA and PFOS was above 70ng/L in 46.6% of the samples were above 70ng/L and mean combined level of PFOA and PFOS in the water samples (71.9 ± 8.5) was significantly (p˂0.05) higher than the US-EPA advisory level. Only 4 samples had PFOA levels above 70ng/L and only one sample had PFOS above this level. Based on our comprehensive literature review, PFOA and PFOS were the most frequently detected PFASs in drinking water samples and accounted for the highest portion of detected PFASs but the levels of PFOA compared to PFOS did not show a clear pattern. In some studies, PFOA showed the highest concentration in drinking water, in others PFOS (Table 1). The concentration of PFOA and PFOS in tap water depends entirely on the sources of PFASs contamination.

Possible sources of PFASs in tap water include: (A) Primary contamination of tap water suppliers (river water or groundwater), (B) Formation of PFASs during water treatment processes, especially during drinking water disinfection processes and (C) Release of PFASs from different sources into the municipal water distribution networks. The contamination of river water by PFASs has been confirmed and reported in several previous studies. For example, the mean concentrations in the main stream of the Yodo River in Japan were 3–4ng/L for PFOS and 23–33ng/L for PFOA [45]. The concentrations of PFOA and PFOS ranged from 0.53 to 8.77ng/L and ND to 2.56ng/L in the surface water of the Jin River in China [46]. In a study by Sunantha et al.. the concentrations of PFOA and PFOS ranged from 4 to 93ng/L and 3 to 29ng/L, respectively, in the surface water of Tamil Nadu, India [47]. The drinking tap water of the city of Isfahan is fed entirely from the Zayandeh-Roud River [48]. Unfortunately, there is no assessment of the PFASs pollution in the surface water of the Zayandeh-Roud and it is impossible to claim that the pollution of the tap water of Isfahan city is caused by river water or not. Therefore, further studies on the Zayandeh-Roud River are necessary.

The formation of PFOA and PFOS during drinking water treatment and disinfection processes has also been reported in previous studies [49, 50]. These studies have shown that the PFOA content in drinking water increases significantly after disinfection with ozone or chlorine. In a study by Appleman et al.., PFOA and PFOS concentrations in 15 US water treatment plants were consistently higher after chemical disinfection treatments [49]. During the chlorination of water, polyfluoroalkylamides react with free chlorine and transform into PFOA through a structural rearrangement (Hofmann type). The reaction of ozone with polyfluoroalkylsulfonamides leads to the formation of both PFOS and PFOA through direct oxidation and a radical-mediated pathway [51].

The Isfahan water treatment plant is the largest water treatment plant in Iran with a conventional treatment system (main sections included: Coagulation, flocculation, sedimentation and rapid sand filtration) that treats 12 m³/s of water from the Zayandeh-Roud River [52]. The disinfection of the treated water was mainly done by chlorination and the higher PFOA levels in the analyzed water samples could be the result of this type of disinfection. On the other hand, recent studies have shown that conventional water treatment systems may not sufficiently remove PFASs [13] and there is a high probability that river water PFASs pollution enters the municipal water distribution networks. Comprehensive assessments on the PFASs levels in input and output water of treatment plant will highlight the role of the disinfection process in tap water pollution by PFASs.

Drinking water distribution system (DWDS) by pipelines is an important part of safe drinking water supply and could strongly affect the quality of tap water. However, the impact of DWDS on the PFASs release into tap water is completely complicated and remained mainly unknown. Normally, the pipes of the water distribution systems have many leaks (due to breaks, wear and tear of the water pipes). The negative pressure in the water distribution system during the hours of water reduction causes to entrance of soil contaminants (including PFASs) into the pipes and the water distribution network. This phenomenon could be a source of PFAS and PFOS release into the tap water.

There are a few reports on the release of PFASs from polymer pips to the water in DWDS over time [53]. A recent study by Chen et al.. found a significant positive correlation between PFASs levels in tap water and the distance of the sampling point from the water treatment plant. They concluded that the content of PFAAs in tap water can be significantly influenced by the pipeline in the DWDS. Their assessments have shown that short-chain PFASs (mainly PFBA) are more stable in water and can migrate to the far distances in the water distribution system [44]. PFASs are widely used in the industrial production of polymer pipes, which can lead to the release of PFASs into tap water via the water distribution networks (transfer of water through polymer pipes and storage of water in polymer tanks) [54, 55]. Based on this assumption, a greater distance from a water treatment plant to the final water consumers in a DWDS would increase the potential of PFASs release into tap water due to prolonged contact of water with the pipes but in contrary, in the present study, we did not find a significant relationship between PFOA and PFOS levels in water samples and the distance of sampling points from the water treatment plant. It seems that several important affecting factors are neglected by Chen et al. [44], including: (A) It is very difficult to accurately calculate the distance that water travels through underground water pipes. (B) The type of water pipes and the life time of the pipes are very different in various parts of a DWDS. (C) The volume of water flowing through the pipes is very variable in different hours, days and weeks. Therefore, further studies are necessary on the PFASs sources and concentrations in tap water with a focus on the patterns of PFASs release from the water pipes.

Human risk assessment

The results of a study by Trudel et al. indicated that the majority of chronic exposure to PFOA and PFOS occurs through ingestion of food and drinking water [56]. Other studies in this area showed that tap water is the main route for human exposure to PFASs (accounting for up to 50% of PFOA exposure in adults) [20]. Therefore, a risk assessment for human exposure to PFAS via drinking water could be an appropriate tool for evaluating the hazards and health effects threatening the general population. Considering the significant difference between PFOA and PFOS concentrations at different sampling points along the city of Isfahan, Human risk assessment was performed using the mean concentrations of PFOA and PFOS from all water samples. The results of the risk assessments are presented in Table 5. As seen all HQ and HI values are below 1 indicating that human health risk for PFOA and PFOS exposure via drinking water in city of Isfahan was not high but it can be concluded that the risk for children is about 5 times higher than adults due to higher water consumption.

Table 5.

PFOA and PFOS human risk assessment for adults and children

	Mean concentrating in water samples	EDI		RfD (ng/kg/day)	HQ		HI
		Adults	children		Adults	children	Adults	children
PFOA	38.1 ng/L	0.979	4.762	20	0.044	0.238	0.087	0.444
PFOS	33.7 ng/L	0.866	4.212	20	0.043	0.206

In a survey by Jiang et al., human health risk assessment due to PFASs exposure was conducted for drinking water sources of Taiwan and the HI value for adults were reported 0.13 and 0.12 respectively [33]. In another study, the risk quotients (RQ) for all PFASs were calculated using available data form previous studies in North America, Asia and Europe. The results showed that the HQ was lower than 0.2 for all age groups, while for infants up to 6 months was higher than 1 [57]. The results of our risk assessment are in agreement with similar recent studies. Our work suggests that PFOS and PFOA levels in tap drinking water of Isfahan City pose no appreciable concern to human health. On the other hand, it should be noted that, this risk assessment is based on our cross-sectional measurement of PFOS and PFOA in drinking tap water. Continuous monitoring of these pollutants in drinking water may change the results of the measurements and risk assessment.

The present study was a cross-sectional investigation, which is the main limitation of this study. Only one-time sampling of drinking tap water and determination of PFOS and PFOA levels were performed during this study. Definitive judgment about the sources of contamination in the water distribution network and the effects of background variables, such as season and disinfection process, on PFOS and PFOA levels in drinking water is impossible by one-time assessment. It is strongly recommended that this study be continued with further comprehensive studies that include seasonal and yearly sampling of water, as well as assessment of background variable.

Conclusion

In summary, in the present study, the presence of two more important PFASs in the tap drinking water of Isfahan City (Iran) was investigated, and human health risks were assessed. Significant levels of PFOA and PFOS were detected in all the water samples. The combined concentration of PFOA and PFOS in the water samples was significantly higher than US-EPA advisory level. Inefficiency of treatment plants for removal of PFASs from the water, generation of PFASs during treatment on the disinfection process in the treatment plant, and the release of PFASs from the distribution network to the tap water are the possible sources of PFASs in the tap water samples and must be investigated in further studies. The distance of the sampling location from the water treatment plant showed no significant effect on PFOA and PFOS levels, indicating that a minor portion of PFASs was released in the water distribution network compared to other contamination sources. All Hazard indices calculated during health risk assessment for adults and children were blow 1 suggests that tap water does not present a high risk for consumers in the short term. The results of this study provide basic information about PFASs pollution in tap water in Iran for the first time and can be used in future water management programs. Urgent studies on PFASs pollution in tap waters, groundwater waters, and surface waters in other provinces of Iran are absolutely necessary. Further studies, including long-term water sampling and determination of all PFASs in drinking water, as well as repetition of risk assessment with long-term exposure values, are also recommended.

Author contributions

Zahra Manoochehri: Conceptualization, Investigation, review & editing of final manuscript. Bahareh Shoshtari-Yeganeh: Methodology, analysis of samples, review & editing of final manuscript. Leila Gheisari: sample collection and preparation, review & editing of final manuscript. Karim Ebrahimpour: Funding acquisition, Project administration, Supervision, Resources, Writing of original draft.

Funding

This study was supported by a grant from the research deputy of Isfahan University of Medical Sciences, Isfahan, Iran (Research project code: 1400495).

Declarations

Ethics approval and consent to participate

The proposal of the present study was reviewed and approved by the ethics committee of Isfahan university of medical sciences (Code: IR.MUI.RESEARCH.REC.1400.546).

Consent for publication

Not relevant.

Competing interests

The authors declare no conflicts of interest.