Occurrence and health risk assessment of peruorinated substances from water in residential areas around uorine chemical industry, China

To identify the contamination status and assess the health risk of per- and polyuoroalkyl substances (PFASs) in surface and ground water are of great signicance recently. Eighteen individual PFASs were analyzed in thirty-three surface/ground water samples from uorine industry in one period of park-A (park A) and two periods of park B. All the short chain PFASs (C < 8) and chlorinated polyuorinated ether sulfonate acid (F-53B) in the park A and B were detected with 100%. The rst three detected substances of peruorobutane sulfonate (PFBS), peruorobutanoic acid (PFBA) and peruorooctanoic acid (PFOA) were the predominant substances. The contamination status in wet season (WS) is stronger than in dry season (DS) in park B. Total concentration of PFASs( ∑ PFASs) in park A presented the increasing tendency following the groundwater ow direction whereas this rule was limited to reect in all periods of park B. Applying different relative source contribution (RSC) of 100% and 20% to assess this risk of different aged group bodies from PFASs, the result was that all PFASs (4 ≤ C ≤ 7 or 9 ≤ C ≤ 12) while peruorooctane sulfonate (PFOS) and PFOA (C = 8) were identied to the low risk quotient (RQ) contribution. Mixed RQ mix value mainly relies on the PFOA and PFOS with a larger contribution rate of 80– 90%. All assessed cases (Case 1, Case2, Case3 and Case4) to all aged groups reveal the infants were to be vulnerable to PFASs inuence, followed by the children, teenagers and adults, respectively.


Introduction
Per-and poly uoroalkyl substances (PFASs) are a class of arti cial compounds with a unique stability, surface activity, thermal stability, amphiphilic nature and have been used in various aspects of industry and household products, including surfactants, surface protectors, pesticides, lubricants, and performance chemicals derivatives have many good properties and stabilities, an increasingly crucial concern of ecological in uence and health issue has been implemented in the early 2000s, mainly based on two common individual-PFASs both per uorooctanoic acid (PFOA) and per uorooctane sulfonate (PFOS). Noticeably, PFOA, its salts and the related compounds were o cially added in Annex B of POPs in 2019 (UNEP, 2019). As regulatory restrictions of long-chain PFASs were established, new alternatives of short-chain individual-PFASs and related derivatives were continually detected. These substances with long term accumulation in environment will incur body organs to suffer a vary of diseases e.g. respiratory tract, kidney, skin, reproductive and even potentially cancer-causing (Fu et al. 2014, Li et al. 2020b, Xie et al. 2021). In addition, according to the related studies in recent years, the concentration of PFASs in environmental medium were hard to degrade by microbes or bacteria, and bio-degrade by plants. The consequence may cause that PFASs will exist in environmental system and then enter into food web, seriously affect the human health.
The ground and surface water are the most precious resource due to the fact that human usually regard it as drinking source or make use of it to irrigate vegetables and fruits. But in recent years, a large scale of aqueous environment is heavily affected by PFASs, and its concentration in waterbody environment poses the risk to human health (Gobelius et al. 2018). Different PFASs sources were frequently identi ed in which industrial production of uorine-containing have the largest distribution e.g. uorine chemical industry, uorine products manufacturing, re protection, etc. Then related to previous studies, Gobelius et al (2018) found PFASs concentrations from 41 groundwater samples were detected with the highest ∑PFASs concentration (6,400 ng L -1 ), associated with these areas of re ghting training sites including air elds and military areas. Meanwhile, irrigation water samples of 21 PFASs in 2019 were detected that the maximum concentrations of 369.9 ng·L -1 around uorine chemical park in Jiangsu province, China (Gagliano et al. 2020). Traditional wastewater equipment is di cult to completely removal the PFASs and consequently, released into receiving environment, which is a concern for the possible presence of these compounds in water used for the potable supply production (Gagliano et al. 2020, Xie et al. 2021. PFASs in water body will be ingested resulting from its abundant stability and environmental persistence.
Especially, short-chain compounds enormously strengthen many learner's attention, due to their use as an alternative to long-chain ones, and their high mobility in aquatic environment (Gobelius et  where one park has been abandoned and another one is on service now. The intensive industries have generated local PFASs contamination in relatively serve contamination degree, so the number of researches have also been implemented to focus on this area . But the surface and the ground water are only limited to study pollution status and concentration analysis without assessing water body risk to local residents, especially in groundwater as drinking source. Local residents frequently regard polluted water as drinking source though the industrial area was away from residential area, but water ow will accelerate the migration of PFASs. Thus, the health risk assessment basing on different aged groups is indispensable to evaluate the in uence of PFASs in ground water to local residents. Importantly, individual and mixed risk of PFASs including short and long chain can provide the accurate value to measure the risk degree and single out priority pollutants for prevention and control. Thus, the objective of our study is to (1) identify PFASs concentration and pro le in the surface and ground water. (2) de nite PFASs spatial distribution around regional area of two parks. (3) assess the individual and mixed of risk from short and long chain PFASs in ground water to the local residents. Through our study, it is expected to provide theoretical basis and scienti c guidance of PFASs pollution for local policies departments or makers.

Chemicals and regants
All the chemicals and standards were of chromatographically pure grade. The target PFAS analytes were purchased from Absolute Standard information and the selection of target compounds are given in the supporting information (SI).

Sample collection and analysis
All water sampling works were carried out in September (wet season, WS) and November (dry season, DS) of 2019 in the two parks of

QA/QC
The eld blank to eliminate the concentration in uencing from sampling bottle and series of laboratory Milli-Q water were added into the sampling bottle in order to determine this free blank. Procedural blanks were identi ed to every batch of samples and it will not be detected (nd) or lower than the limits of quanti cation (LOQs) in order to ensure data accuracy and method availability. LOQ were de ned as the minimum injection volume of reproducible measurement peak area within ±20% of repeated injection. The LOD and LOQ for each PFASs were given in SI. The PFASs concentrations were identi ed to a concentration series of 0, 0.01, 0.1, 1, 5, 10, 50, 100, and 500 μg·L -1 to draw the standard curve (R 2 >0.99). In addition, the IS was added to each sample to assess accuracy by the recovery of the analytes, and recoveries acceptable range needs to be less than 20%.

Heath risk assessment
To further gure out this health effect of PFASs to the local resident is so important that an original quotient method was applied in our study. The new risk quotient (RQ) methodology coming from Thomaidi et al study (2020), was applied to assess human health risk from the groundwater. This method mainly was different from the other RQ assessment method by using the relative source contribution factor (RSC, the percentage of the exposure due to the drinking water consumption, and the value for 100% and 20%, RSC 100% and RSC 20% ) . The RQ calculation of individual PFASs was given for equation (1)- (3): In our study, similarity RSC of 100% and 20% will be taken into consideration for different aged groups of infants (birth-3 months, 3 -6 months, 6-12 months, 1-2years, 2-3years), children (3-6years, 6-11years), teenagers (11-16years, 16-21years) and adults (>21years), respectively. Meanwhile, the max and mean concentration of PFASs were calculated with RSC of 100% as case 1 and case 2, then with RSC of 20% as case 3 and case 4 (Table S4)  Where ADI (μg/ kg day −1 ) is the acceptable daily intake without signi cant health risk, BW(kg) represents percentile body weight, DWI (L day −1 ) is drinking water intake in daily life, AB de nes the gastrointestinal absorption rate (assumed to be equal to 1), FOE is the frequency of exposure (350 days/365 days = 0.96) and n in Equation (4) is to assess the potential risk for human health related to mixed PFASs contamination. These parameter values can be found in (16%-63%) and C8 (34%-83%) were stronger than C>8 PFASs (≤3%) (Fig 3a). Raining activity in surface and ground system play an area, detected with serious individual concentration and ∑PFASs due to long term reception place from agricultural activities, even pesticides and fertilizers using (Fig.1, Fig. 2c and Table S7). Surface water will accelerate the migration of pollutants, and especially the supply also carries PFASs into groundwater (Chiavola et al. 2020, Feng et al. 2020. The PFOS substitute of F-53B was detected with low contamination degree, whereas concentration in surface water was higher in the groundwater. What in mentioned that long chain PFASs (C≥10) that PFDS, PFUdA, PFDoA, PFTeDA, PFTrDA and PFODA were detected certain concentration in all water body of DS without appearing in WS (nd). C4-C7 and C8 of PFASs show higher concentration contribution than C9 of PFASs in the surface and ground water of WS and DS. There was a difference that concentration rate of C4-C7 PFASs in DS (range of 64%-98%) was far lower than in WS (range of 95%-98%) (Fig. 3b,c). Time difference was better re ected on short chain PFASs than long chain PFASs. The reason was that short chain PFASs with greater hydrophobicity and lower lipophilicity will tend to be affected by season variation while Chemical groups between -SO 3 H and -COOH make PFASs in water possess the environmental behavior abundantly(Gobelius et al.

2018).
In our study, PFASs concentration have closely negative relationship with chain length in park A and B (Fig. S2). PFASs with unique physicochemical structure tend to dissolve in water body and migrate with a long distance. In addition, the functional groups are also an important factor(Liu et al. 2019). Functional groups difference between PFSAs and PFCAs are limited to affect by the water load variation in different term (Fig S1). Although other non-point sources may contribute to PFASs in surface and groundwater, the park production is the major contamination source. In addition, industrial emission in different time also affects PFASs pro les by discharge of sewage because traditional equipment is hard to removal effectively.

Spatial distribution
Page 6/15 The source of PFASs in the groundwater may be assumed to two pathways. One was that industrial waste water was directly discharged into groundwater system and another was the ground pollutant source by some environmental behavior of the surface runoff, surface water recharge and rainwater deposition, which will carry PFASs and its precursors into groundwater(Ahrens et al. In park B, this distribution of PFASs concentration was limited to be re ected, and the dominating detected substances and ∑PFASs also lack out obviously increasing or decreasing concentration tendency along with the groundwater ow direction. The concentration of PFASs in the downstream water is slightly higher than the upstream along with the groundwater ow direction but this tendency is largely weak (Fig S4).

Health risk assessment
Environmental pollutants will enter into and nally accumulate in the human body by direct drinking (Gobelius et al. 2018). In our study, the groundwater as main drinking source is a serve exposure to local residents. The short chain PFASs were mainly detected in two parks whereas part of PFASs lacks out related evaluation messages, still all individual PFASs is hard to assess the health risk. Hence, combining with the mainly detected substances and available toxicity data, PFBA(C4), PFHpA(C7), PFHxA(C6), PFHxS(C6), PFOA(C8), PFOS(C8), PFNA(C9), PFUdA(C11) and PFDoA(C12) were assessed, respectively.

Individual PFASs (C≤8)
Along with the increasing of the aged groups, the RQ value show a decreasing tendency in park A and park B-WS and DS. This reveals that PFASs risk have a more remarkable in uence on the infants and the children than the teenagers and the adults. RQ 100%/20% value has a positive relationship with PFASs concentration in the water body and the negative relationship with DWEL. In park A, the highest DWEL value appears in PFBS (17,820,547.09 -3,270,348.84 L·day -1 ), followed by PFHpA and PFHxA (654,069.01 -3,564,109.42 L·day -1 ), respectively. But these three substances lack out determining the highest health risk whereas PFOA possesses a largest RQ value, followed by PFOS (Table S8). RQ 100%/20% value of all assessed substances in park A is higher than park B and especially part of the RQ 100%/20% value in park A has exceeded 1( Table S8). The RQ 100%/20% value of PFBA, PFHpA, PFHxA and PFHxS in case 1-4 were in the reasonable range and this demonstrates that the max and the mean concentration of four substances is limited to exceed the RQ reference line of 0.2 and 1. Short chain PFASs (C≤7) in groundwater is hard to constitute the health risk to local residents. But PFOA and PFOS in part of sampling sites exceeding RQ=0.2, even RQ=1, has given rise to harm human body in case 1-4. The RQ 100%/20% value of PFOA in case 1 and case 3 were in the range of 0.26-1.44 and 1.32-7.20 for aged groups, and the range of 0.23-0.64 for birth -6years in case 4 (Fig. 4a). What counts is that total PFASs contamination degree is hard to pose health risk in case 2 for all aged groups. Causally, the water ow is the main impact to take away PFASs for the part of sampling sites with high concentration and this will dilute PFASs concentration, even decrease the toxic effect (Hongkachok et al. 2018, Ikkere et al. 2018, Jin et al. 2015. The ADI value difference between PFOS (0.15 μg/ kg day −1 ) and PFOA (1.5 μg/ kg day −1 ) has exceeded 1 orders of magnitude. However, the concentration of PFOS is 1-2 magnitude lower than PFOA which causes the RQ 100%/20% value of PFOS is hard to exceed PFOA. The RQ 100%/20% value of PFOS in case 1-2 and 4 was di cult to exceed RQ=0.2 expect for case 3, which is similar to PFOA. For different periods in park B, the degree of RQ 100%/20% value in WS is higher in DS due to the high concentration was detected in WS (Fig 4b,c and Table S8). Based on all terms of different aged groups except the case 3, only PFOA in WS exceeds the control line of RQ=0.2 but is not exceed RQ=1. The range of RQ 20% value for PFOA in case 3 was 0.22-0.62 that the max value of 0.62 for birth-3 months and the mix value of 0.22 for 3-6 years (Fig 4b,c) Long chain PFASs(C>8) were detected with lower concentration than short chain PFASs, which means the low concentration was also related to lower RQ value. Three individual-PFASs of PFNA(C9), PFUdA (C11) and PFDoA(C12) were assessed. The result reveal that three long chain PFASs is hard to pose potential risk to the local residents. The range of RQ value is that the negligible (ng)-0.002, ng-0.0001 and ng-0.006 for PFNA, PFUdA and PFDoA, respectively (Table S8). These max RQ 100%/20% value from three long chain PFASs were lower than 0.2 while the magnitude difference ranges from 1 to 3. Then in our study, extreme conditions are considered to perform operations to initially assess the risk to the human health. The group of birth-3 months can be easily affected by short chain PFASs in environmental media. If three assessed substances will cause health risk basing on the line of RQ=0.2, the concentration of 5.37, 6.53 and 0.13 ng·L -1 for PFNA, PFUdA and PFDoA were calculated, respectively. There was a huge difference of 1-2 magnitudes between the predicted and actual concentration. Thus, the long chain PFASs for assessed substances were di cult to threaten the human body.

Mixed risk of PFASs
The mixed risk assessment was increasingly concerned due to the different individual PFASs existing in the environmental media. But the related assessing method is limited to develop resulting from the complex mechanism in current environment system. The most serious situation appears in the park A of RQ mix (4≤C≤12) =8.07 for birth-3 months (Table S6). ∑PFASs (4≤C≤7) and ∑PFASs (9≤C≤12) were hard to reach the line of RQ=0.2, and RQ mix of these substances were limited to exceed that RQ=1 (Table S7). Expect for PFOS and PFOA, all PFASs (4≤C≤7 or 9≤C≤12) were analyzed with lower RQ contribution. Especially, the risk of the individual PFASs with low RQ value without exceeding RQ=0.2, then the RQ mix value was hard to possess the risk to all aged groups. In this process, PFOS and PFOA risk values determine the crucial factor to the size of RQ mix . In other words, if the risk from PFOS and PFOA can be effectively impaired, the RQ mix of all the individual-PFASs will deeply decrease. Mixed RQ mix value mainly relies on the PFOA and PFOS contribution rate (80%-90%). This indicates that PFOA and PFOS should be taken into consideration and listed as priority control.
Notably, RQ mix value from the group of teenagers (16-21 years) appears a small spike relative to two adjacent groups both 11-16 years and >21 years. In comparison with the infant and child, teenager group is the third group which is in uenced by PFASs due to the weight and drinking intake.

Conclusion
Eighteen individual PFASs were analyzed in surface water and groundwater, then the concentration pro les, spatial distribution and the health risk assessment for different aged groups was studied in two different parks. PFBS, PFBA and PFOA were the predominant substances in surface and ground water, meanwhile, ∑PFASs in park A was higher than in park B. Water loads in different periods have a crucial impact on PFASs concentration and pro les variation. PFSAs and PFCAs also appear negative concentration trend in WS or DS. In addition, ∑PFASs and part of high concentration substances(PFBA, PFBS, PFHpA, PFHxA, PFHxS, PFOA and PFPeA) appear the increasing tendency along with the groundwater ow direction in park A. However, due to the in uence of industrial process and emission, the concentration trend was limited to re ect in park B. Health risk assessment result was that short and long chain PFASs except for the PFOS and PFOA were hard to possess the serious risk to the local resident based on the line of RQ=0.2. The serious health risk from PFOS and PFOA were found with a larger contribution to the mixed RQ mix value. All assessed cases to all aged groups reveal the infants were vulnerable to the PFASs in uence, followed by the children, teenagers and adults, respectively.

Declarations
Ethics approval and consent to participate Not applicable.

Consent for publication
Not applicable.

Availability of data and materials
All data generated or analysed during this study are included in this published article and its supplementary information les.

Competing interests
The   The concentration contribution rate (%) basing on different carbon chain length of C4-C7 (short chain), C8 (long chain) and C9-C18 (long chain) in two parks of Fuxin, China