Impact of the algal monitoring and control program in Qingcaosha Reservoir on trihalomethane levels and associated health risks in the effluent of a drinking-water treatment plant in Shanghai: a decadal analysis

Abstract

The Qingcaosha Reservoir has been experiencing eutrophication, which has resulted in algal blooms. This led to heightened levels of chlorination by-products, posing a significant concern. This study evaluated the trend of trihalomethanes (THMs) in Shanghai’s drinking water before and after the reservoir’s algae monitoring program and associated health risks. The results indicated that the concentrations of total THMs, trichloromethane (CHCl₃), monochlorodibromomethane (CHBr₂Cl), dichloromonobromomethane (CHBrCl₂), and tribromomethane (CHBr₃) were below the limits stipulated by China’s standards for drinking water quality (GB 5749–2022). Total THMs concentrations also remained below the WHO and EU limits (100 µg/L) and the US EPA limit (80 µg/L). Following the intervention from 2014 to 2020, there was a significant reduction in total THMs, CHCl₃, and CHBr₂Cl in the finished water (P < 0.05), whereas CHBr₃ and CHBrCl₂ concentrations remained unchanged. By 2020, the carcinogenic risk of the total THMs was higher than 1 × 10⁻⁶ but lower than 1 × 10⁻⁴, consistent with acceptable levels recommended by the EPA, although the non-carcinogenic risk, indicated by the hazard quotient (HQ), was below 1. This study demonstrates that the algae monitoring and control program at Qingcaosha Reservoir during peak water supply periods has effectively lowered chlorinated disinfection by-product levels in the finished water of a water treatment plant in Shanghai since 2014, significantly decreasing health risks. Future efforts should focus on strengthening eutrophication and algal bloom management in water sources and improving water treatment processes to further decrease disinfection by-product content.

Introduction

Disinfection is a crucial step in drinking water treatment, which can destroy or inactivate pathogenic microorganisms, prevent the occurrence of waterborne diseases, and protect public health (Mosaferi et al., 2021). Chlorination is the most widely used disinfection method in water treatment facilities, selected for its cost-effectiveness and efficacy (Mosaferi et al., 2021). Pre- and post-chlorination are stages of the water treatment process. Pre-chlorination reduces microbial load and algae growth, facilitating coagulation, while post-chlorination ensures a chlorine residual in the distribution system (Hasan et al., 2010; Mosaferi et al., 2021). When water contains natural organic matter, such as humic and fulvic acids and amino acids, along with contaminants and bromine ions, these substances react with chlorine, forming disinfection by-products (DBPs) (Gallard et al., 2002; Ristoiu et al., 2009). To date, more than 700 DBPs have been identified in drinking water (Plewa et al., 2017). Common DBPs include trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and halogenated ketones (HKs). THMs, the primary chlorinated DBPs, are produced during disinfection and include CHCl₃, CHBr₂Cl, CHBrCl₂, and CHBr₃.

The health effects of disinfection by-products from chlorination are a significant concern. Susan’s research indicated that lifetime exposure to disinfection by-products (DBPs) elevates the risk of cancers, notably bladder and colon (Richardson et al., 2007). Rahman’s survey revealed a positive correlation between colon cancer risk and CHBr₃ levels among men in New South Wales, Australia (Rahman et al., 2014). Furthermore, THMs pose non-carcinogenic risks to vital organs including the liver, kidneys, nervous system, and reproductive system (Ristoiu et al., 2009; Sadiq et al., 2004; Woo et al., 2002). Drinking water contaminants primarily enter the body via ingestion, dermal contact, and inhalation, with ingestion being the principal pathway for exposure.

Prior to the Qingcaosha Reservoir’s completion in 2010, Shanghai’s Lujiazui water plant sourced 80% of its raw water from the Huangpu River, which suffered from water insufficiency and frequent pollution, leading to consistently poor water quality that often exceeded Class III surface water standards (Jian Wei et al., 2011). As Shanghai’s new water source, the Qingcaosha Reservoir now supplies 60% of the city’s raw water, serving approximately 10 million people with ample, high-quality water at low operational cost. However, its shallow depth and long hydraulic retention time have induced eutrophication since its operation, characterized by a high nitrogen/phosphorus ratio (16 ~ 29:1) and seasonal proliferation of cyanobacteria and Microcystis aeruginosa (Huang et al., 2014; Ou et al., 2013). Elevated algal levels provide organic precursors for THMs formation, raising THMs levels in water treatment plant effluent and posing a threat to drinking water safety.

To address these challenges, the “Algae Monitoring and Control Program for Qingcaosha Reservoir” was launched in 2013, employing real-time monitoring of algae and nutrients alongside physical-ecological technologies to prevent eutrophication. This study applies an interrupted time series (ITS) analysis—a method widely used to evaluate public health interventions such as new vaccines, legislative policies, and traffic safety measures—to assess whether the 2013 program significantly influenced THMs levels and trends in the water supply, and to evaluate associated health risks from population exposure (Dennis et al., 2013; Grundy et al., 2009; Hawton et al., 2013).

The Lujiazui water plant, selected for this study, has a long history, operational since 1937, and officially transitioned to the Qingcaosha water source from the Huangpu River at the end of 2010. The study aimed to observe the monitored levels of THMs in the effluent during the Qingcaosha reservoir’s water supply period, and using an interrupted time series (ITS) analysis, to determine if the algae control program initiated in 2013 influenced THM levels and trends, and to evaluate the health risks associated with population exposure to THMs through oral, dermal, and inhalation pathways.

Materials and methods

Sample collection

Since 2010, the Qingcaosha reservoir has served as the primary water source for the waterworks. In this study, quarterly water samples from the water plant were collected from 2011 to 2020. Samples were collected annually in February, May, August, and November, totaling 40 over the study’s duration. Samples were collected in 60 mL brown threaded-mouth sample bottles (CNW, Germany), ensuring they were filled completely without air bubbles. Samples were stored at 4 °C and promptly sent to the laboratory, with analysis completed within 24 h post-collection.

Sample processing and analysis

The samples were analyzed using capillary column gas chromatography/mass spectrometry (US EPA Method 524.2) for purgeable organic compounds in water under the following conditions (EPA, 1995). Warmed the sample to room temperature, then carefully poured the 40 mL sample into the vial against the wall, and securely tightened the headspace cap. Accurately pipetted 5.0 mL of water samples into the purge tube using a purge trap autosampler, and then used the purge trap device to elute the volatile organic compounds (VOCs) from the water samples, and trapped them in the trap tube with helium gas. After purging, the sorbent tube is heated and backflushed with helium to elute the trapped components into the capillary gas chromatography-mass spectrometry (GC-MS) system for analysis, characterized by their retention times and mass spectra, and quantified using the internal standard method. Purge and trap conditions included Tenax, silica, and charcoal as the trap materials, with a 5 mL purge injection volume at 25 °C for 11 min, followed by desorption at 220 °C for 2 min and baking at 260 °C for 2 min. Chromatographic conditions utilized an HP-5MS UI column (30 m × 0.25 mm, 0.25 μm) at an inlet temperature of 220 °C with a 20:1 split ratio, and a temperature program from 35 °C for 5 min to 100 °C at 6 °C/min, then to 210 °C at 20 °C/min, held for 1 min. Mass spectrometry conditions specified an electron ionization (EI) source at 230 °C, a transmission line temperature of 260 °C, a solvent delay of 1.6 min, full scan mode, and a mass-to-charge ratio (m/z) range of 35 to 450.

Quality control

To ensure analytical accuracy, a blank sample was tested for each batch of samples and a quality control sample was analyzed every 20 samples to maintain the relative standard deviation (RSD) below 10%. The method’s limit of detection (LOD) was 0.50 µg/L, with recoveries ranging from 90 to 110%, an RSD of less than 5%, and a linear range spanning 0.50 to 25 µg/L. Non-detectable items were assigned a value of half the LOD, which is 0.25 µg/L.

Statistical analysis

R version 3.5.2 software was utilized for descriptive and general statistical analysis. Utilizing R packages like “lmtest,” “Epi,” “tsModel,” and “vcd,” we conducted an interrupted time series (ITS) analysis on the pre- and post-program implementation monitoring data (Bernal et al., 2020). The water source algae monitoring and control program’s implementation served as an intervention event, with segmented linear regression applied to the interrupted time data to estimate two key parameters: (I) the post-intervention change in THMs levels, and (II) the post-intervention alteration in trends. The pre-intervention period spanned from 2011 to 2013, while the post-intervention period extended from 2014 to 2020.

Regression model:

$$Y_t={\beta }_0+{\beta }_{1}T+{\beta }_2{X}_t+{\beta }_3\left(T,-,T_0\right)·X_t$$ 1

where β₀ is the baseline level of THMs at the time series onset; β₁ is the pre-intervention trend of THMs level over time unit; β₂ is the level change attributable to the intervention; β₃ is the slope change due to the intervention; β₁ + β₃ is the post-intervention trend of THMs over time; T represents time, which in this study is a time unit of one quarter, and T₀ is the time when the intervention started; X_t denotes the different phases of the intervention. The study encompasses two phases: pre- and post-intervention. The ITS analysis was conducted based on 12 pre-intervention data points from 2011 to 2013 and 28 post-intervention data points from 2014 to 2020. The optimal regression model was identified using the Akaike information criterion (AIC) minimum principle to refine the model’s regression terms and enhance statistical reliability. The Durbin-Watson (DW) method was used to test for the presence of first-order autocorrelation within the series.

Health risk assessment

Exposure to THMs was calculated using chronic daily intake (CDI). The non-carcinogenic and carcinogenic health risks were assessed through three pathways: ingestion, dermal, and inhalation (Lee et al., 2004; Pardakhti et al., 2011; Siddique et al., 2015; G. S. Wang et al., 2007a, 2007b). The meanings of the parameters are shown in Table 1.

Table 1.

Parameters of health risk assessment

Parameter name	Symbol	Unit	Value	reference
THMs concentrations in water	Cw	μg/L	/	(Amjad et al., 2013)
Ingestion rate	IR	L/day	2.465	(Zhao & Duan, 2013)
Exposure frequency	EF	days/year	365	(Amjad et al., 2013)
Exposure duration	ED	year	Non-carcinogenic: 30; Carcinogenic:70	(EPA, 1989)
Exposure time	ET	h/day	0.2	(Zhao & Duan, 2013)
Body weight	BW	kg	63.5	(Zhao & Duan, 2013)
Averaging time	AT	days	Non-carcinogenic: ED × 365; Carcinogenic:70 × 365	(EPA, 1989)
Conversion factor	CF	L/cm3	0.001	(Amjad et al., 2013)
Skin surface area	SA	m2	1.7	(Zhao & Duan, 2013)
Permeability coefficient	PC	cm/h	0.00683(CHCl3);0.000402(CHBrCl2); 0.00289(CHBr2Cl); 0.0026(CHBr3)	IRIS
Slope factor (Ingestion/Dermal)	SF	(kg•day)/mg	0.031 (CHCl3);0.062(CHBrCl2); 0.084(CHBr2Cl);0.0079(CHBr3)	OEHHA IRIS
Reference dose	RfD	mg/(kg•d)	0.01(CHCl3);0.02(CHBrCl2); 0.02(CHBr2Cl); 0.02(CHBr3)	IRIS
THMs concentrations in air	Cair	mg/L	Estimated using Henry’s constant	(Little et al., 1991)
Inhalation rate	IRinh	m3/h	1.5	(Zhao & Duan, 2013)
Slope factor (Inhalation)	SF	(kg•day)/mg	8.05 × 10–5 (CHCl3);0.13(CHBrCl2);0.095 (CHBr2Cl), 0.00385 (CHBr3)	(Amjad et al., 2013)

The formulas are as follows:

$${\text{CDI}}_{\text{ing}}\text{=}\frac{C_w\times \text{EF}\times \text{ED}\times \text{IR}}{\text{AT}\times \times \mathit{BW}}$$ 2

$${\text{CDI}}_{\text{der}}\text{=}\frac{C_w\times \text{CF}\times \mathit{SA}\times \mathit{PC}\times \text{EF}\times \text{ED}\times \text{ET}}{\text{AT}\times \text{BW}}$$ 3

$${\text{CDI}}_{\text{inh}}\text{=}\frac{{\text{C}}_{\text{air}}\times \text{IR}\text{inh}\times \text{EF}\times \text{ED}\times \text{ET}}{\text{AT}\times \text{BW}}$$ 4

The hazard quotient (HQ) was used to indicate the non-carcinogenic risk and was calculated as follows:

$$HQ=\frac{\mathit{CDI}}{\mathit{RfD}}$$ 5

$$HQ=\frac{{\mathit{CDI}}_{\text{ing}}}{{Rf\text{D}}_{\mathit{ing}}}+\frac{{\mathit{CDI}}_{\text{der}}}{{\mathit{RfD}}_{\mathit{der}}}+\frac{{\mathit{CDI}}_{\text{inh}}}{{Rf\text{C}}_{\mathit{inh}}}$$ 6

The carcinogenic risk was calculated as follows:

$$\text{Risk}=\text{CDI}\times \text{SF}$$ 7

$$\text{Risk}={\text{CDI}}_{\text{ing}}\times {\text{SF}}_{\text{ing}}+{\text{CDI}}_{\text{der}}\times {\text{SF}}_{\text{der}}+{\text{CDI}}_{\text{inh}}\times {\text{SF}}_{\text{inh}}$$ 8

Results

Levels of THMs in drinking water

The monitoring data for THMs in the effluent is presented in Table 2. The median concentrations and ranges of total THMs, CHCl₃, CHBr₂Cl, CHBrCl₂, and CHBr₃ were 12.71 µg/L (3.98 ~ 34.36 µg/L), 3.65 µg/L (0.25 ~ 17.70 µg/L), 1.70 µg/L (0.25 ~ 11.10 µg/L), 4.53 µg/L (0.25 ~ 11.80 µg/L) and 0.25 µg/L (0.25 ~ 6.67 µg/L), respectively. CHCl₃ had the highest concentration, followed by CHBrCl₂, CHBr₂Cl, and CHBr₃. Figure 1 illustrates the average concentrations of each detected substance from 2011 to 2020. CHBr₃ consistently maintained a low concentration over the 10-year span. Prior to 2014, the concentrations of the total THMs and the other three THMs exhibited an upward trend, peaking at 25.97 µg/L for total THMs, while since 2014, the concentration of each substance decreased significantly, among which CHBr₃ has been at a low level during the 10 years.

Table 2.

Descriptive statistics of THMs levels in effluent (µg/L)

Items	Range	Median	P25	P75
Total THMs	3.98–34.36	12.71	6.62	19.69
CHCl3	0.25 ~ 17.70	3.65	0.25	8.84
CHBr2Cl	0.25 ~ 11.10	1.70	1.21	4.16
CHBrCl2	0.25 ~ 11.80	4.53	3.33	7.05
CHBr3	0.25 ~ 6.67	0.25	0.25	0.75

Fig. 1.

Median concentrations of THMs detected in the effluent between 2011 and 2020 (the solid red line perpendicular to the x-axis indicates algae control interventions in Qingcaosha Reservoir)

Changes of THMs pre- and post-intervention

Figure 2 illustrates the variations in THM levels in the effluent, comparing pre- and post-intervention periods. Distinct periods of intervention are indicated by shadowed and un-shadowed areas. Table 3 displays the statistical parameters for the ITS regression model. The program’s implementation and the time factor significantly affect total THM concentrations in the effluent (P < 0.05). Annual increases in total THM concentrations in the effluent were observed prior to the intervention (2011–2013). The slope shifted from positive to negative after the intervention. The total THM concentration in the effluent exhibited a downward trend, decreasing by 0.56 µg/L annually. Following the implementation of the algae control program, the actual total THM concentration (blue solid line) fell below the projected level without intervention (red dashed line). Regression model simulations indicate that the intervention reduced factory water THM concentrations by 6.31 µg/L. Before the intervention (2011–2013), the median concentration of total THMs was 18.12 µg/L, as shown in Table 4. After the implementation of the program (2014–2020), the median concentration of total THMs dropped to 8.13 µg/L, reflecting a 55.13% reduction.

Fig. 2.

ITS plots of levels and trends of THMs in effluent pre- and post-intervention

Table 3.

Estimates of ITS regression model

Items	THMs	CHCl3	CHBr2Cl
Intercept (β0)	7.77	2.93	−0.44
Time (β1)	1.56**	0.64	0.56**
Intervention (β2)	−6.31	−3.00	−1.97
Intervention: time (β3)	−2.12***	−0.90*	−0.70***

Significance codes: *P < 0.05; **P < 0.01; ***P < 0.001

Table 4.

Variation of total THMs, CHCl₃, and CHBr₂Cl concentrations in effluent pre- and post-intervention

Items	Median (μg/L)		Range (μg/L)
	Pre-	Post-	Pre-	Post-
Total THMs*	18.12	8.13	4.37–31.70	3.98–34.36
CHCl3*	7.48	0.76	0.25–17.70	0.25–15.20
CHBr2Cl*	2.25	1.64	0.25–11.10	0.56–9.80
CHBrCl2	7.06	4.29	0.25–11.00	1.50–11.80
CHBr3	0.41	0.25	0.25–6.67	0.25–4.11

*P < 0.05

We analyzed the impact of the intervention on the concentrations of four types of THMs. The results revealed that intervention and time significantly decreased CHCl₃ and CHBr₂Cl levels in the effluent, as detailed in Table 4. Post-intervention, CHCl₃ and CHBr₂Cl concentrations annually declined by 0.26 µg/L and 0.14 µg/L on average, respectively, mirroring the trend of total THMs. Median CHCl₃ and CHBr₂Cl levels dropped by 89.84% and 27.11%, respectively, while peak concentrations fell by 14.12% and 11.71% post-intervention. We also assessed CHBr₃ and CHBrCl₂ levels, finding no significant changes attributable to intervention or time (P > 0.05); thus, no graph was created for these two pollutants.

Health risk assessment

Non-carcinogenic risk

The total non-carcinogenic risk levels for three exposure routes are depicted in Fig. 3. Between 2011 and 2020, the non-carcinogenic risk from total THMs exposure via oral, dermal, and inhalation routes consistently remained below the EPA’s guidance value of HQ = 1 (Djam et al., 2020; Sharma et al., 2015). Furthermore, ingestion is the predominant route for non-carcinogenic risk among the four DBPs, accounting for 97.1% ~ 99.3%, with marginal contributions from inhalation (0.1% ~ 1.9%) and dermal pathways (0.3% ~ 0.9%). The HQ values, based on these routes, ranked as follows: CHCl₃ > CHBrCl₂ > CHBr₂Cl > CHBr₃.

Fig. 3.

Non-carcinogenic risk (HQ) through multiple routes of exposure to THMs

Carcinogenic risk

Figure 4 displays the estimated total lifetime carcinogenic risks from oral, dermal, and inhalation exposure routes. From 2011 to 2020, the annual carcinogenic risks of total THMs varied, with the highest at 6.41 × 10^–5 and the lowest at 2.06 × 10^–5. These values were higher than 1 × 10^–6 but below 1 × 10^–4,which was still within the EPA’s acceptable range. The assessment revealed ingestion as the main exposure route, contributing over 97% to the total cancer risk, followed by inhalation (0.6% ~ 1.2%) and dermal contact (0.3% ~ 0.9%). The red line in Fig. 4 indicates the initiation of algae control in the Qingcaosha reservoir. Since 2014, the lifetime carcinogenic risk for three THMs, not including CHBr₃, has notably declined, aligning with the concentration changes. Meanwhile, the carcinogenic risk values were in the order of CHBrCl₂ > CHCl₃ > CHBr₂Cl > CHBr₃, indicating that CHBrCl₂ has a higher cancer risk.

Fig. 4.

Life-time carcinogenic risk of THMs from 2011 to 2020 (the red line perpendicular to the x-axis indicates the implementation of the intervention program at Qingcaosha Reservoir)

Discussion

This study monitored THMs concentrations in the Lujiazui waterworks’ effluent from 2011 to 2020, revealing an average total THMs concentration of 13.92 µg/L. This level was lower than those found in drinking water in Bushehr Province, Iran (92.9 µg/L) (Dobaradaran et al., 2020), and Shandong Province, China (35 µg/L) (Yao et al., 2019), but similar to the Pearl River Delta’s effluent in Southern China (17.7 µg/L) (Gan et al., 2013). Utilizing the conventional “flocculation-precipitation-filtration-disinfection” water treatment process along with chlorine and chloramine disinfectants in this water plant resulted in CHCl₃ being the predominant disinfection by-product in the effluent, exhibiting the highest concentration, whereas CHBr₃ was the least concentrated, aligning with previous studies (Kargaki et al., 2020; Niu et al., 2017). In this study, the concentrations of THMs were below the permissible limits set by the Chinese drinking water hygiene standards (GB 5749–2022) (CHCl₃: 60 µg/L; CHBr₂Cl: 100 µg/L; CHBrCl₂: 60 µg/L; CHBr₃: 100 µg/L). Additionally, the total THMs concentrations were significantly below both the WHO and EU limits of 100 µg/L and the US EPA limit of 80 µg/L (Chowdhury et al., 2011). According to GB 5749–2022, the ratios of the measured concentrations of the four THMs compounds to their limit values must be calculated, ensuring the total does not surpass 1. The calculated ratio fluctuation in the effluent across seasons ranged from 0.06 to 0.48, complying with the Chinese drinking water hygiene standards.

The non-carcinogenic risks of total THMs in this study were all less than the EPA’s guidance value (HQ = 1), suggesting that exposure levels are unlikely to cause adverse reactions and do not pose a significant non-carcinogenic risk to humans. Among the four THMs, the HQ values were highest for CHCl₃, indicating a relatively higher non-carcinogenic risk for exposure to CHCl₃. According to the USEPA risk characterization handbook, if the risk ranges from 10^–6 to 10^–4, a cancer risk is considered acceptable; if the risk value is higher than 10^–4, the cancer risk is supposed to be high and remediation is required at locations (EPA, 2000). The study’s findings indicated that the carcinogenic risk values of THMs in the effluent of Lujiazui water plant fall within the range of 10^–6 ~ 10^–4. A decade of monitoring data reveals an acceptable level of carcinogenic risk for total THMs in the effluent of Shanghai Lujiazui water treatment plant (2.06 × 10^–5 ~ 6.41 × 10^–5), comparable to risks in other regions, including Canada, Thailand, and Beijing (2.19 × 10^–5 ~ 4.78 × 10^–5) (Panyakapo et al., 2008; W. Wang et al., 2007a, 2007b).

The Lujiazui Water Treatment Plant has received raw water from the Qingcaosha Reservoir since the end of 2010, and the effluent’s total THMs concentration peaked in the second quarter of 2014 at 34.36 μg/L. The Shanghai Municipal Water Affairs Bureau implemented comprehensive measures in the Qingcaosha Reservoir’s eutrophication control program, including continuous monitoring for nitrogen, phosphorus, and algae density, introduction of physical and ecological techniques, and environmental optimization around the water source. Since 2014, concentrations of THMs have steadily declined, with the average levels of all types of THMs dropping below 4 µg/L by the end of 2020, and the total THMs concentration falling below 10 µg/L—a 67.73% decrease from the peak of 25.97 µg/L. Interventions have not only reduced THMs levels in effluent but also reversed the trend from an annual increase to an annual decrease post-intervention. The trend reversal suggests that interventions effectively controlled algae proliferation in raw water, diminished precursor content for DBPs formation, and lowered DBPs levels in effluent. Furthermore, this study found that CHBrCl₂ posed the highest cancer risk among the four kinds of THMs, yet existing eutrophication controls were ineffective at mitigating its concentration. Water management agencies should continuously monitor raw water, implement effective algal pollution controls, and innovate tap water treatment processes.

The present study has some limitations. First, the sampling site for the study was located at a water plant in Pudong New District, which limits its representativeness of disinfection by-product levels in Shanghai. Second, the low monitoring frequency, occurring every 3 months, fails to capture monthly pollutant fluctuations; future studies should improve the monitoring frequency. Additionally, health risks vary by gender and age. Future assessments should target specific age groups, with a focus on vulnerable populations like children, women, and the elderly.

Conclusions

In this study, we analyzed the trends in THMs concentrations in the Lujiazui Water Treatment Plant’s effluent, both before and after the algae monitoring and control program was implemented during the Qingcaosha Reservoir’s peak water supply period. Following the intervention in 2014, there was a significant reduction in the levels of total THMs, CHCl₃, and CHBr₂Cl in the plant’s effluent. The decrease in carcinogenic and health risks suggested that the Shanghai Water Affairs Bureau’s eutrophication control measures for raw water were highly effective. Future efforts by drinking water regulatory authorities should focus on enhancing water source protection and oversight, curtailing the release of wastewater rich in phosphorus and nitrogen from upstream water sources, and innovating deep treatment processes for eutrophic raw water. This will further decrease DBP levels in drinking water, enhance water quality, and mitigate health risks for the public.

Author contributions

Yangyang Ren, Yewen Shi, and Shaofeng Sui wrote the paper. Chen Wu, Zheng Wu, and Aimin Du collected the water samples and water quality data. Yu’e Jin, Fengchan Han conducted laboratory tests and analyses. Hailei Qian made constructive suggestions for the manuscript. Shaofeng Sui conceived and designed the study. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by National Disease Control and Prevention Administration Talent Project of Field Epidemiological Investigation (No. Y2023-28B), the key projects in the 3-year plan of Shanghai municipal public health system (2023–2025) (No. GWVI-4), and Shanghai Municipal Health Commission Science and Youth Research Fund (No. 20234Y297).

Data availability

The datasets from the current study are available upon reasonable request to the corresponding author.

Declarations

Consent to participate

Not applicable.

Animal research

Not applicable.

Competing interests

The authors declare no competing interests.