PFOA and PFOS Pollution in Surface Waters and Surface Water Fish

Abstract

Perfluoroalkyl and poly-fluoroalkyl substances (PFAS) are among the synthetic chemicals employed by various industries since the 1950s and the most critical persistent organic pollutants (POPs) that led to emerging concerns due to high persistency, toxicity, mobility, and environmental bioaccumulation. Although there are more than 5000 types of PFASs, perfluorooctanoic acid (PFOA) and perfluorosulfonic acid (PFOS) are the two chemicals whose employment is highly restricted and banned by the Stockholm Convention. In the present study, certain water resources in the Marmara Region, the most densely populated and industrial region in Turkey, and the waters of Turkey’s two largest drinking water reserves, Beyşehir and Eğirdir lakes, were investigated. The study was carried out in two seasons, spring and autumn. The lowest and highest PFOA concentrations were determined between 1.77 ± 0.1 and 6.71 ± 2.9 ng/L in all surface waters, and the highest PFOS concentrations were between <LOQ and 3.27 ng/L. PFOA concentrations were higher when compared to PFOS concentrations in all water sources, and PFOA and PFOS concentrations were lower in spring compared to autumn. In some commercially procured fish from water resources, 7.48 ng/g PFOS was detected in Küçükçekmece Lake pike, and 2.5 ng/g PFOA was identified in Eğirdir Lake trout. PFOA and PFOS were not detected in other fish tissues.

1. Introduction

Per- and poly-fluoroalkyl substance (PFAS) compounds have been produced or employed in various industrial processes since the 1950s [1,2]. PFAS chemicals possess unique surface-active properties, are water and oil-repellent, and are highly resistant to heat and acidity. They are widely employed in industries and consumer products due to these properties [3,4]. PFAS are employed as fire protection products, surfactants, surface protectors, food packaging, and consumer products. Since 2000, they have been investigated for potential environmental hazards due to their persistence and bio-accumulative and toxic properties [5]. These properties led to significant concerns about the use of these contaminants of emerging concerns (CECs) [6,7,8]. Thus, various regulations have been adopted to partially and gradually restrict the use of PFAS. Recently, awareness has been further raised about the negative effects of PFAS exposure on health. Four Northern European EU nations asked the European Commission to develop precautions to reduce PFAS emissions after an earlier call by the European Council on the European Commission to develop an action plan to eliminate all nonessential PFAS emissions. Recently, the European Food Safety Authority (EFSA) recommended a reduction of the tolerable weekly food intake standard. The Dutch National Institute for Public Health and Environment recommended a lower drinking water limit since human PFAS intake depends on drinking water and food consumption. Thus, not only knowledge of the presence of PFAS but also the environmental behavior of PFAS is important to understand present and future environmental and health risks [9].

PFAS assignment is based on the presence of a fully (per) or partially fluorinated (poly)alkyl chain attached to functional groups. PFAS could be classified as polymeric PFAS (fluoropolymers, side-chain fluorinated polymers, and perfluoropolyether), and non-polymeric PFAS (fluorotelomer (FT), perfluoroalkyl acids (PFAAs), per- and poly-fluoroalkyl ethers (PFPE)). Several studies have been conducted on PFAS; however, these substances have not been fully elucidated and described due to the lack of accurate, specific, and sensitive analytical standards or protocols [10]. Most global research has been conducted on two PFASs, perfluorooctanoic acid (PFOA) and perfluoro-sulfonic acid (PFOS). PFOA and PFOS are both long-chain perfluoro-carboxylic acids with eight or more carbon atoms or perfluoro-sulfonic acids with six or more carbon atoms. PFOA and PFOS are eight-carbon compounds (C8) [11]. PFOA and PFOS have been identified in surface water, groundwater, drinking and coastal waters, landfill leachates, sediments, sludge, and soil between ng/L and µg/L, or ng/g and µg/g. Toxicological studies revealed that PFOA and PFOS could lead to acute or chronic toxicity in freshwater fish, invertebrates, and liver and pancreatic tumors in laboratory animals. Due to the abovementioned factors, PFOA and PFOS were inevitably designated as significant environmental contaminants globally [12]. The US Environmental Protection Agency (USEPA) classified PFOA and PFOS as potential drinking water contaminants in 2009. The US EPA PFOS and PFOA drinking water standard is 4 ng/L [4,13,14].

Since these substances are highly soluble in water, PFOS and PFOA have been reported in most aqueous environments. In contrast with other typical POPs, PFOA and PFOS are highly mobile in aqueous systems due to their ionic nature, high solubility, and negligible vapor pressure when dissolved in water; thus, these compounds could be transferred from commercial, industrial, or domestic discharge to natural waters [15]. The present study aimed to determine PFOA and PFOS concentrations in Beyşehir and Eğirdir lakes—Turkey’s largest drinking water sources. It also aimed to determine the concentrations of these pollutants in the Marmara region surface waters, a region with the densest population and the most significant industrial development in Turkey. This study aimed to determine PFOA and PFOS concentrations in Beyşehir and Eğirdir lakes, the largest drinking water sources in Turkey. PFOS and PFOA samples were collected in autumn (October 2022) and spring (April 2023). PFOA and PFOS concentrations were also investigated in fish species procured from fish markets around the water sources.

2. Material and Method

2.1. Standards and Chemicals

Perfluoro-octane sulfonate (PFOS, 98%) was procured from Fluka Analytical (Atlanta, GA, USA), and perfluorooctanoic acid (PFOA, 96%) was procured from Alfa Aesar (Haveril, MA, USA). High-performance liquid chromatography (HPLC) grade methanol (>99.9%) was procured from Sigma-Aldrich (Taufkirchen, Germany), and ammonium acetate and Milli-Q water were procured from Merck Millipore (Darmstadt, Germany). Contaminated water samples were prepared in the laboratory with 1000 mg/L PFOA and PFOS stock solutions in pure methanol. PFOS-PFOA mixtures were prepared by diluting stock solutions with MeOH. The samples were pretreated with Oasis Wax SPE columns in 6 cc cartridges and 150 mg and 30 µm Waters (Milford, MA, USA).

2.2. Sample Collection, Pre-Treatment, and Extraction Procedures

Samples collected into 2 L polypropylene bottles from each surface water source were pairwise analyzed. In the present study, the samples were collected from the Sakarya and Ergene rivers, Terkos, Küçükçekmece, and Büyükçekmece lakes in Marmara Region, Eğirdir Lake in Mediterranean Region, and Beyşehir Lake in Central Anatolia Region the largest drinking water reserve in Turkey. Water and fish samples were transferred to the laboratory in cold chains and stored at −18 °C before the analyses. The sampling locations are presented in Figure 1.

Water samples were sieved through a 1 µm filter and filtered through a 0.45 µm nylon membrane filter (Whatman, UK) before SPE. Samples were collected and analyzed with the “Water Quality-Perfluoro-octane-sulfonate (PFOS) and Perfluoro-octanoate (PFOA) Determination Method for Unfiltered Samples with Solid Phase Extraction and Liquid Chromatography/Mass Spectrometer” as specified in international standards (BS ISO 25101-2009) [16]. Oasis WAX 6 mL Vac cartridges were installed in the Supelco Visiprep vacuum manifold. Cartridges were conditioned sequentially with 4 mL ammonia/methanol solution, 4 mL methanol, and 4 mL ultrapure water. The 500 mL samples and then 4 mL acetate buffer solution were passed through the cartridges, and eluate was discarded. The cartridges were pressurized for 2 more minutes to ensure the removal of all residue. Clean polypropylene tubes were placed in the vacuum manifold. An 8 mL eluate, obtained with 4 mL methanol and 4 mL 0.1% ammonia/methanol solution, was evaporated with nitrogen. The eluate dissolved with 0.5 mL MeOH was shaken for 2 min with a multi-vortex. The product was filtered through a nylon syringe with a 0.22 µm pore diameter and transferred into autosampler vials that included 200 µL inserts for injection [16].

For biota samples, the method developed by Ciccotelli et al. [17] was employed. Briefly, the steps of the analysis were as follows: 5 mL hexane was added to a 2 g fish tissue sample vortexed for 10 min and centrifuged at 4500 rpm for 10 min. The organic phase was discarded, and 10 mL acetonitrile was added; then, the samples were further vortexed for 5 min and centrifuged at 4500 rpm for 10 min. 2 mL supernatant was added to a flask that included 150 mg Al₂O₃, and the product was vortexed for 2 min, centrifuged at 4500 rpm for 10 min and dried with nitrogen. The residue was redissolved with 250 µL MeOH, filtered through a 0.22 µm syringe filter, and vialed. The samples were transferred to LC-MS/MS to determine the concentrations.

2.3. Ultra-High-Performance (QTRAP^® LC-MS/MS) Analysis

The ABSciex Exigent Expert Ultra LC 100 ABSciex 3200 Q-Trap (MS/MS) chromatography system with a C18 colon, Waters Acuity UPLC BEH, 1.7 µm, 50 × 2.1 mm were employed for chromatographic separation. Mobile phase A included ultrapure water and 20 mM C₂H₇NO₂, and mobile phase B included CH₃CN and 0.2% HCOOH. 20 µL sample was injected at a 0.5 mL/min flow rate. The initial mobile phase (60% A, 40% B) was kept for 2 min and then ramped to 90% B for 2 min. The mobile phase was converted to the initial status (60% A) in 4 min. The analysis lasted for 8 min. Extracted ion chromatograms that reflected the PFOA and PFOS retention times are presented in Figure 2.

3. Findings and Discussion

3.1. Methodological Performance

The limit of detection (LOD) and limit of quantification (LOQ) were 50 ng/L and 250 ng/L for PFOA, and 10 ng/L and 50 ng/L for PFOS in water samples, respectively. To determine the recovery rate, Milli Q water was spiked at two concentrations by the standards. The recovery rate was calculated as 85% for PFOA and 89% for PFOS.

Spinner fish (Vimba Vimba Tenella) was used as the indicator species, and PFOA and PFOS compounds were not identified as indicator species. Various concentrations of the standard were added to the biota, a matrix-matched calibration curve was plotted with the extracted samples, and quantitative analyses were conducted. LOQ was determined as 2.5 ng/g for PFOA and 1 ng/g for PFOS in biota (fish tissue) samples. MS/MS method parameters are presented in

Table 1. MS/MS method parameters for Perfluoroalkyl compounds.

PFC Molecule	Mass Q1 (Da)	Mass Q3 (Da)	DP (Volt)	EP (Volt)	CEP (Volt)	CE (Volt)	CXP (Volt)
PFOA 1	412.852	169	−25	−4.5	−30	−24	−2
PFOA 2	412.852	169	−25	−4.5	−30	−12	−4
PFOS 1	498.916	80	−80	−10.5	−20	−74	0
PFOS 2	498.916	98.9	−80	−10.5	−20	−62	0

.

[M-H]⁻ ions were employed as the precursor ion in tandem mass spectrometry. The two selected reaction monitoring (SRM) transitions between the precursor and the two most prevalent fragment ions were monitored for each compound. The first transition was employed for quantification, and the second was employed to confirm the identity of the target compounds. Further identification criteria in addition to the SRM transition monitoring were also employed for quantification: (i) the UHPLC retention period of the standard compound and the sample compounds were matched, and (ii) the relative content of the two selected analyte SRM transitions was compared between the sample and the standards [18].

Flow injection analysis was employed to determine the source-dependent parameter settings: ESI (-), curtain gas (CUR), 30 V, nitrogen collision gas (CAD) medium, source temperature (TEM) 450 °C, ion spray voltage 4500 V, and ion source gases GS1 and GS2 at 50 and 50 PSIG, respectively.

In the analysis, LC-MS system tubes were replaced with metal ones to prevent instrumental contamination. Furthermore, a second analytical column was added before the injector to prevent contamination from the system or solvents. PFCs were purged from all sample vials, connection elements, and other equipment [19]. All study findings include recovery figures as presented.

3.2. PFOA and PFOS in Surface Waters

The results of the analyses conducted on the samples collected from Ergene and Sakarya rivers, Küçükçekmece, Büyükçekmece, Terkos, Eğirdir, and Beyşehir lakes between October 2022 and April 2023 are presented in

Table 2. PFOA and PFOS concentrations in surface waters.

Surface Water	Sample Point Coordinates		Autumn ng/L		Spring ng/L
	Latitude (N)	Longitude (E)	PFOA	PFOS	PFOA	PFOS
Ergene River	41°21′31.92	27°81′39.82	3.7 ± 0.3	1.1 ± 0.1	2.7 ± 0.2	1.1 ± 0.1
Sakarya River	40°47′45.18	30°26′13.56	2.5 ± 0.3	1.4 ± 0.2	1.8 ± 0.1	1.0 ± 0.1
Küçükçekmece Lake	41°0′2.61	28°45′53.28	4.2 ± 0.1	3.3 ± 0.2	3.2 ± 0.7	2.2 ± 0.2
Büyükçekmece Lake	41°2′13.92	28°33′40.83	3.4 ± 0.2	1.5 ± 0.2	2.4 ± 0.1	1.5 ± 0.2
Terkos Lake	41°19′19.59	28°37′15.84	5.3 ± 1.1	0.7 ± 0.1	4.9 ± 0.3	0.9 ± 0.2
Eğirdir Lake	37°53′45.71	30°50′45.04	6.7 ± 2.9	2.6 ± 0.8	4.6 ± 0.2	2.3 ± 1.2
Beyşehir Lake	37°54′7.43	31°28′37.66	2.9 ± 0.3	<LOQ	1.8 ± 0.1	<LOQ

Note(s): <LOQ: analysis result < limit of quantification.

. PFOA and PFOS samples were not collected during winter since PFOA and PFOS concentrations could be low in autumn due to winter precipitation, and the concentrations could be <LOQ or could not be determined. Also, a study on CECs (contaminant of emerging concern) reported that water was diluted in winter [18,20].

As seen in Table 2, PFOA and PFOS were identified in all surface water samples. The highest PFOA concentration (6.1 ± 2.9 ng/L) was observed in Eğirdir Lake in autumn, while the lowest PFOA (1.8 ± 0.1 ng/L) was observed in Sakarya River in spring. The highest PFOS concentration (3.3 ± 0.2 ng/L) was observed in Küçükçekmece Lake in the autumn, and the lowest PFOS concentration (<LOQ) was observed in Beyşehir Lake in the autumn. In the autumn, the season where the highest concentrations were observed, PFOA concentrations were 6.7 ± 2.9 ng/L in Eğirdir Lake, 5.3 ± 1.1 ng/L in Terkos Lake, 4.3 ± 1.1 ng/L in Küçükçekmece Lake, 3.7 ± 0.3 ng/L in Ergene River, 3.4 ± 0.2 ng/L in Büyükçekmece Lake, 2.9 ± 0.3 ng/L in Beyşehir Lake, 2.5 ± 0.3 ng/L in Sakarya River, and PFOS concentrations were 3.3 ± 0.2 ng/L in Küçükçekmece Lake, 2.6 ± 0.8 ng/L in Eğirdir Lake, 1.5 ± 0.2 ng/L in Büyükçekmece Lake, 1.5 ± 0.2 ng/L in Sakarya River, 1.1 ± 0.1 ng/L in Ergene River, 0.7 ± 0.1 ng/L in Terkos Lake, and <LOQ in Beyşehir Lake.

In autumn, the analysis findings were generally higher than in spring. This could be due to the dilution of existing PFOA and PFOS concentrations in the receiving water environments due to winter precipitation. PFOA concentrations were higher in all water sources when compared to PFOS concentrations [20]. Seasonal PFOA and PFOS variations by surface water source are presented in Figure 3.

Although the Marmara Region is the most densely populated region with high industrial development in Turkey, the investigated surface water resources exhibited relatively lower PFOA and PFOS concentrations when compared to other countries. PFOA concentrations were 2.91 and 1.94 ng/L, and PFOS concentrations were <LOQ in autumn and spring in Lake Beyşehir, the largest drinking water reserve in Turkey located in the Central Anatolia Region. Lake Eğirdir, located in the Mediterranean Region, PFOA concentrations were 6.71 ± 2.9 and 4.64 ± 0.2 ng/L, and PFOS concentrations were 2.6 ± 0.8 and 2.3 ± 1.2 ng/L in autumn and spring, respectively. PFOA concentrations were higher than PFOS concentrations in surface water (Figure 3). This could be due to the high use of PFOA and the earlier prohibition (deprecation) of PFOS. Drinking water supplies are vulnerable to PFOA and PFOS contamination that originate in several sources. Wastewater treatment plant discharge, biodegradation of precursors during wastewater treatment, industrial discharges, and land disposal of biosolids are potential PFOA and PFOS sources in drinking water reserves [21].

The concentrations identified in the waters of certain rivers and lakes in some countries are presented in

Table 3. PFOA and PFOS concentrations in certain country rivers and lakes.

Country	Water Body	PFOA (ng/L)	PFOS (ng/L)	References
Canada	Lake Ontorio	4.4–44	3.1–37	[24]
	Grand River	6.5–9.4	10.2–20.0	[25]
	Lake Ontorio	<0.25–33	<10	[26]
USA	Hudson River	22–173	1.5–3.4	[27]
	Lake Champlain	10–46	0.8–7.7
	Lake Erie	21–47	11–39	[28]
China	Hong Lake	12.2	6.0	[29]
	Dong Lake	3.3	3.8
	Shenzhen River	30.8	10.2
	Pearl River	6.2–14.3	5.7–14.1
India	Gangs River	0.033–2.0	0.04–8.4	[30]
Japan	Tsurumi River	13.4–15.9	179.6–179.9	[31]
	Uji River	100–110	8.7–10	[32]
Spain	Catalan Rivers	0.79–9.63	1.09–9.56	[33]
	L’Albufera lake	0.03–10.90	0.10–4.80	[34]
Taiwan	Xioali River	17.3	82	[35]
	Tauchien River	10.9	48.9
	Keya River	310	5440

. The present study findings revealed lower concentrations when compared to these figures. Before 2002, US EPA published PFOS and PFOA limits in drinking water as 150 µg/L and 1 µg/L. In 2009, these limits were lowered to 0.2 µg/L for PFOS and 0.4 µg/L for PFOA, and these levels were further reduced to 70 ng/L for PFOS and PFOA in 2016 [4], and the current US EPA PFOS and PFOA drinking water standard is 4 ng/L [14]. Since PFAS toxicity is still under investigation, the 4 ng/L limit could be further reduced in the future. Thus, comprehensive studies are required on PFOA and PFOS, which are toxic, persistent, and endocrine disruptors, especially in surface waters that could be consumed as drinking water [22,23].

Takagi et al. [36] investigated drinking water treatment plants and raw surface water sources that fed these plants and determined that PFOS and PFOA concentrations were 3.7 and 48 ng/L in treatment plant effluent, 1.3 and 15 ng/L in raw river water influent, PFOS and PFOA were 2.2 and 36 ng/L in raw lake water, and <0.50 and 6.5 ng/L in the treatment plant effluent. The drinking water standard determined by the EPA for PFOA and PFOS concentrations on March 2023 was 4 ng/L [14], and various measures should be adopted for global implementation. Particularly, PFASs in drinking water sources could seriously threaten water reservoirs, aquatic ecosystems, and public health. Urgent research is required on PFASs known as forever chemicals, toxicity studies should be conducted on aquatic ecosystems in drinking water reservoirs, PFAS-contaminated water sources should be rehabilitated, and advanced treatment methods such as ion exchange, adsorption (especially granular activated carbon, GAC), nanofiltration, and reverse osmosis (NF, RO) should be included in drinking water treatment facility effluents.

3.3. PFOA and PFOS in Fish Tissue

Fish purchased from fish markets around the lakes were analyzed for PFOA and PFOS. Carp biota of the same size and weight were procured from Lake Eğirdir and Beyşehir Lake markets in 2 seasons, pike procured from Küçükçekmece Lake, and trout procured from Eğirdir Lake were available only one season. Fish samples from other water bodies were not available at fish markets at these water bodies and were not analyzed. PFOA and PFOS findings for investigated fish species are presented in

Table 4. PFOA and PFOS concentrations in fish tissue samples.

Surface Waters	ng/g
	PFOA	PFOS
Lake Küçükçekmece Pike (Esox Lucius)	<LOQ	7.5 ± 0.3
Lake Eğridir Trout (Salmo Trutta)	2.5 ± 0.1	<LOQ
Lake Eğridir 1st season (Cyprinus Carpio)	<LOQ	<LOQ
Lake Eğirdir 2nd season (Cyprinus Carpio)	<LOQ	<LOQ
Lake Beysehir Carp 1st season (Cyprinus Carpio)	<LOQ	<LOQ
Lake Beyşehir Carp 2nd season (Cyprinus Carpio)	<LOQ	<LOQ

Note(s): <LOQ: analysis result < limit of quantification.

.

PFOA and PFOS concentrations in Esox Lucius collected at Küçükçekmece Lake were <LOQ and 7.48 ng/g, respectively, while 2.5 ng/g and <LOQ concentrations were identified in Salmo Trutta collected at Eğirdir Lake. PFOA and PFOS were not identified in Cyprinus Carpio collected at Lake Eğirdir and Cyprinus Carpio collected at Lake Beyşehir in autumn and spring (Table 4). This could be because young biota of the same size and weight (fresh fish weight of about 300 g) were used to compare the two lakes.

While the tolerable daily intake limits previously set by EFSA (Panel on Contaminants in the Food Chain) were 150 ng/kg body weight for PFOS and 1500 ng/kg body weight for PFOA, in 2018, these limits were set at 13 ng/kg body weight and 6 ng/kg body weight per week. The reason for this significant decrease in the limits was the findings reported by toxicological and epidemiological studies, which demonstrated that these compounds could lead to health problems. In 2020, EFSA updated the weekly intake limit for total PFOA, PFOS, PFNA, and PFHxS compounds to 4.4 ng/kg body weight. It was determined that fish contributed 50% to the PFAS intake [37]. Paiano et al. [38] investigated the PFOA and PFOS levels in wild and farmed fish filets collected in the Mediterranean Sea and reported that the mean PFOA and PFOS concentrations were 0.19 ng/g and 1.24 ng/g for 52 wild fish species, and <0.05 ng/g and 0.05 ng/g for 13 farmed fish species, respectively. Squadrone et al. [39] studied 40 European sea bass and 50 European whitefish samples collected at Lake Maggiore in the Italian Alps and found that the highest PFOS level was 45.8 ng/g in female sea bass.

In a study that investigated PFOS, PFOA, PFNA, and PFHxS concentrations in 24 fish species and seafood in Greece, it was reported that the total PFAS concentration was between <LOQ and 20.4 ng/g, and the highest concentration was identified in butternut fish. While PFOS was identified in 50% of the analyzed samples, PFNA and PFOA were detected only in 10%, and PFHxS was not detected in any [40]. Fifty fish samples of six species in different ecosystems were screened for nine PFAS compounds, and PFOS, PFOA, and PFOSA were identified in all samples. The highest PFOS concentration was (12.83 µg/kg) in tabby fish. The mean PFOS concentration was between 0.3 and 750 µg/kg in 65 fish samples (mullet, perch, long perch) collected at a lake far from large urban centers and any pollutant source, and PFOA, PFNA, and PFHxS concentrations were below the detection limit [41]. Commercial fish are typically bred in marine fisheries. Marine fish species generally contain significantly lower PFAS concentrations when compared to freshwater fish. Thus, freshwater fish consumers are particularly at risk. Alarming levels of PFAS bioaccumulation in fish were observed even when water PFAS levels were quite low or even undetectable. This could be because instantaneous surface water samples may not represent the level that the fish were exposed to, or bioaccumulation in fish could be higher than the concentration in the water [42].

PFAS (per- and poly-fluoroalkyl substances) are considered among critical pollutant groups due to their adverse effects on human health after exposure. The most common sources of PFAS exposure include the consumption of contaminated drinking water, certain fish and shellfish, food packages that contain PFAS, transfer from stain-resistant carpets and textiles, and direct contact with industrial products that contain PFAS. Although PFAS production started in the 1940s, the sources and toxicity of these substances were initially studied in the 1990s. Due to their toxicity potential, mobility, stability (resistance to degradation in the environment), and bioaccumulation properties, PFASs are highly hazardous and often referred to as “forever chemicals” [6]. The impact of chronic exposure to low PFAS concentrations or short-term exposure to high PFAS concentrations are still not fully elucidated. When surface waters are contaminated by various substances, the consumption of PFAS-contaminated surface water through ingestion or skin contact could lead to adverse health outcomes. Health issues associated with PFAS exposure that were identified in infants, children, adults, pregnant women, and the elderly include cancer, diabetes, high blood pressure, asthma, and weak immune system. Reported health problems include kidney and testicular cancers, impaired liver function, chronic kidney damage, cardiovascular diseases, inflammatory bowel diseases, elevated cholesterol levels, osteoarthritis, thyroid and other hormonal disorders, delayed breast development, reduced fetal growth, hypertension or preeclampsia in pregnancy, high miscarriage risk, preterm birth, low birth weight, childhood obesity, emotional and behavioral disorders, and early or delayed puberty. Due to these negative health effects associated with PFAS exposure, further research could be recommended on the effects of both short-term and long-term exposure [43,44].

Research on PFASs in Turkey was conducted on PTFE-coated non-stick containers [45], food and beverages [46], and bottled and drinking water, among others [46,47]. Endirlik et al. [47] reported that the maximum PFOA concentration was 2.37 ng/L, and PFOS concentration was 1.93 ng/L in drinking water, and PFOA was 0.1 ng/L, and could not detect PFOS in bottled water in Turkey. In Turkey, PFAS contaminants should further be investigated in various environments such as food, water sources, water and wastewater treatment plants, and soil around industrial areas to determine PFAS risk levels.

4. Discussion

The investigation of PFOA and PFOS contamination in surface waters and fish allows the analysis of results. This study provides a framework within which the findings of the determination of PFOA and PFOS levels in surface waters and surface water fish can be considered. PFOA between 1.77 ± 0.1 and 6.71 ± 2.9 ng/L and PFOS between 0.7 ± 0.1 ng/L and 3.27 ± 0.2 ng/L were detected in the indicated surface water sources. In Lake Eğirdir trout tissue (Salmo Trutta) 2.5 ng/g PFOA and in Lake Küçükçekmece pike (Esox Lucius) tissue 7.48 ng/g PFOS were detected. The higher concentration of PFOS in Esox Lucius than in Kücükcekmece Lake water may be explained by the fact that the instantaneous sample taken may not be representative of the level to which the fish is exposed or that bioaccumulation in the fish occurs at a higher degree than the concentration in the water. Our findings warrant further reflection, especially on the ecological impacts of these pollutants. Some studies have shown that these pollutants, which are found at lower concentrations in surface waters, can reach higher concentrations in drinking water treatment plant effluents, while others have shown that these concentrations are lower. In particular, seasonal analyses of surface water intakes of drinking water treatment plants and various stages of drinking water treatment plants could be investigated in future studies. Despite their widespread use, PFOA and PFOS are currently restricted and banned due to their persistence, mobility, toxicity, and bioaccumulation in the food chain. Furthermore, PFOA and PFOS are the most prevalent pollutants in the environment, and the EPA was determined as 4 ng/L in drinking water in 2023. These pollutants reach surface waters through various routes such as atmospheric transport, industrial discharges, wastewater discharges, and surface runoff, pollute rivers and lakes, disrupt aquatic ecosystems, and also pose a serious global threat to all living organisms due to bioaccumulation, persistence, mobility and toxicity in the food chain. Especially water resources used as drinking water reservoirs and river waters feeding these resources should be regularly monitored for PFAS chemicals. Detection and seasonal monitoring of these chemicals, which pose a significant threat to human health, in surface water sources and drinking water treatment plants should be a requirement in every country. New processes (NF: nanofiltration, RO: reverse osmosis, etc.) should be adopted as the final treatment step in WWTPs in order to prevent the access of PFOA and PFOS to surface water sources and aquatic ecosystems, especially from wastewater treatment plants. In this context, new information should be obtained to guide decision-makers in the development of stricter regulations to control PFOA and PFOS pollution. Finally, it is important that the findings presented in this paper be taken into account by legislators in order to protect water resources and improve human health.