Comprehensive analysis of organic contaminants in urban tap water

Zhenyu Tian, Chemistry and Chemical Biology, Northeastern University

1. Overview

Organic micropollutants in drinking water represent an emerging public health concern due to their diversity and potential for chronic health effects including endocrine disruption and carcinogenicity at trace levels.^1,2 Most of these contaminants are not regulated or even unknown.³ This research will perform comprehensive non-targeted analysis (NTA) of organic contaminants in tap water from four U.S. cities using state-of-the-art analytical methods. Our innovative approach combines NTA with dual separation techniques (reverse phase liquid chromatography, RPLC and Hydrophilic Interaction Liquid Chromatography, HILIC), enabling wider coverage of both commonly detected contaminants and persistent mobile toxicants (PMT).^4,5 Advanced data processing using SIRIUS/CSI:FingerID and GNPS molecular networking will enable confident identification of true unknowns beyond suspect screening.

Figure 1. analytical workflow for the proposed research

The Tian group at Northeastern University possesses the necessary expertise, having successfully applied NTA methods across diverse environmental matrices, with access to high-resolution mass spectrometry (HRMS) and trained personnel. All raw HRMS data, processed results, and analysis workflows will be made publicly available through MASSIVE and Zenodo repositories within six months of project completion, ensuring reproducibility and enabling broader scientific use. Northeastern's IRB has confirmed that publicly accessible tap water sampling is exempt from human subjects’ approval. The one-year project (October 2025 - September 2026) will be supported through PI startup funds. Expected outcomes include: (1) comprehensive tap water contaminant inventories with Schymanski confidence levels,⁶ (2) a prioritized list based on detection frequency, abundance, and toxicity data, and (3) evidence-based recommendations for future monitoring programs.

2. Introduction

Access to safe drinking water is fundamental to public health. Environmental factors, including water quality, contribute to 70-90% of disease risks.⁷ Tap water represents a major exposure pathway for contaminants, as adults consume 3-4 L of water daily, potentially leading to chronic exposure to any chemicals present. Despite this importance, current regulatory frameworks (e.g., Safe Drinking Water Act) monitor only a limited subset of chemicals present in drinking water, and the traditional process of identifying and regulating new contaminants is both time-consuming and costly.

Existing tap water studies have revealed concerning gaps in our understanding of drinking water quality. Disinfection byproducts (DBPs) are well-documented contaminants in treated water, yet most remain unregulated despite their known occurrence.^3,8 Additionally, polymer additives are increasingly detected in water supplies, indicating widespread leaching from polymer infrastructure/consumer products.^9,10 Of particular concern are persistent, mobile, and toxic substances (PMT) that escape conventional treatment technologies and analytical methods, representing an emerging class of drinking water contaminants. While we know the existence of these chemicals in tap water, critical knowledge gaps remain: we lack systematic data on which contaminants are most frequently detected across water suppliers, which are most abundant, and which pose the greatest toxicological risks. Comprehensive tap water analyses are needed to prioritize contaminants for regulatory action and public health protection.

Recent technological advances in high-resolution mass spectrometry (HRMS) have revolutionized our ability to detect previously unknown contaminants through non-targeted analysis (NTA) and suspect screening approaches.^11,12 Unlike conventional targeted methods that require prior knowledge/standards of specific compounds, NTA enables comprehensive chemical profiling of water samples, allowing researchers to identify emerging contaminants that might otherwise remain undetected. This analytical approach is particularly valuable for characterizing the "exposome" – the totality of chemical exposures throughout an individual's lifetime.

Despite the successful application of NTA methods to various environmental matrices, tap water remains relatively underexplored using these advanced techniques.^13,14 Our proposed research aims to address this gap by employing NTA to comprehensively characterize chemical contaminants in tap water, providing critical insights for protecting public health and identifying emerging threats to water quality.

3. Methods

Participants/Sample

We will collect tap water samples from four U.S. cities/areas (Boston, NYC, Seattle, San Diego) where we have established collaborators with expertise in environmental sampling. Our sampling design includes 3-5 sites per city, with triplicate 1L samples collected at each site using pre-cleaned amber glass bottles, yielding 36-60 total samples. Sites will have publicly accessible tap water from municipal distribution systems, and examples can be university teaching buildings, public libraries, and parks. Samples will be shipped overnight in coolers with ice packs, with field blanks included where feasible. This sample size provides >70% power to detect moderate differences (Cohen's d = 0.5) in contaminant profiles between cities while capturing within-city variability, based on comparable multi-city water quality studies.

Materials and Procedures

Sample Collection and Storage

We will collect tap water samples in triplicates (1 L each) using pre-cleaned amber glass bottles with PTFE-lined caps. Samples will be transported on icepacks and spiked with isotope-labeled internal standards upon arrival at the laboratory. All samples will be stored at 4°C and processed within 48 hours. Method blanks (LC-MS grade water) will be processed alongside each batch, with field blanks collected where possible through collaboration with participating cities.

Sample Processing

We will employ two complementary extraction methods to capture contaminants across a wide polarity range:

Solid Phase Extraction (SPE): For mid-polarity compounds, we will use Oasis HLB cartridges (150 mg, 6 mL) following established non-targeted analysis protocols. After conditioning with methanol and water, we will load triplicates of 500 mL samples at ~10 mL/min, wash with 5% methanol/water, and elute with methanol followed by acetonitrile. Combined eluates will be evaporated under nitrogen at 40°C and reconstituted in 500 μL water/methanol (90:10, v/v) for RPLC-HRMS analysis.

Evaporative Concentration (EC): For persistent and mobile toxicants (PMTs, higher polarity), we will evaporate triplicates of 100 mL aliquots to dryness using a centrifugal evaporator (GeneVac EZ-2 Elite, 40°C, 8 mbar). Residues will be reconstituted in 100 μL acetonitrile/water (90:10, v/v) and filtered (0.22 μm PTFE) for HILIC-HRMS analysis.

Instrumental Analysis

RPLC: For the SPE extracts, we will perform reversed-phase separation on a Vanquish Flex UHPLC system using a C18 column (2.1 × 100 mm, 1.7 μm) at 40°C. Mobile phases will consist of water (A) and methanol (B), both with 0.1% formic acid. The LC gradient program will follow a published work.¹⁵

HILIC: For the EC extracts, we will use Hydrophilic interaction chromatography will employ a Waters BEH Z-HILIC column (2.1 × 100 mm, 1.8 μm) at 30°C. Mobile phases will be 5 mM ammonium formate in water pH 3.5 (A) and in 95:5 acetonitrile/water (B). The gradient will decrease from 95-50% B over 12 minutes, running at 0.4 mL/min with 1 μL injections.

HRMS: We will use an Orbitrap Exploris 240 with heated ESI source, acquiring data in positive and negative ionization modes separately. Data acquisition will use data-dependent MS/MS of the top 10 ions using stepped collision energies (20, 40, 60% normalized collision energy), with resolving power at 60,000 for full scan MS and 15,000 for MS/MS.

Data Analysis

Suspect Screening: We will process raw HRMS data in Compound Dis

coverer 3.3 using optimized non-targeted workflows. ¹⁵ Suspect screening will be performed against our in-house database and published suspect lists, with tentative identifications based on accurate masses (<5 ppm), isotope patterns, and fragmentation patterns.

Non-Targeted Analysis: Unmatched features (“true unknowns”) will undergo molecular formula prediction and structural elucidation using SIRIUS (including CSI:FingerID for in source fragmentation).¹⁶ For prioritization, we will generate molecular networks in GNPS using the feature based molecular network workflow to identify compound families and clusters of interest.

Quality Control

Internal standard recoveries will be used to assess extraction efficiency across the analytical sequence. With the internal standards, we will monitor retention time stability (deviation should <0.2 min), mass accuracy (error should <5 ppm), and peak area reproducibility (RSD < 30%). Method blanks and field blanks will be used for blank subtraction (features detected in samples > 5x in the blanks will be selected for further analysis).

Ethics and Data Management

All raw HRMS data, processed results, and analysis workflows will be made publicly available through MASSIVE and Zenodo repositories within six months of project completion, ensuring reproducibility and enabling broader scientific use. Northeastern's IRB has confirmed that publicly accessible tap water sampling is exempt from human subjects’ approval.

4. Pilot Data (Optional)

My group has been developing sample preparation and instrument analytical methods for PMT in water. We have seen great performance in our quantitative method and our NTA method for detecting unknown PMT (Figure 2). The method development and drinking water application have been summarized in a manuscript (Poisson et al., submitted to Water Research).

Figure 2. a) PMT method development. b) Chromatogram of the quantitative method (Poisson et al, submitted).

Performance of developed sample preparation and analytical methods

We selected 22 PMT model compounds to develop and optimize analytical and sample preparation methods, based on: 1) detection frequency and abundance;^4,17,18 and 2) potential toxicological effects;^1,19 and 3) standard availability. It is worth noting that the most interesting PMT are usually emerging contaminants without standards, so this PMT target list is intended to guide method development. Using hydrophilic interaction liquid chromatography-high resolution mass spectrometry (HILIC-HRMS) and native/isotope-labeled standards, we established a robust and sensitive quantitative method (Figure 2a). Method limits of quantification of standard PMT range from 1.3 to 6.6 ng/L in drinking water samples. Normalized extracted ion chromatograms (EIC) are shown in Figure 2b. With water samples spiked with 500 ng/L PMT standards, we evaluated the recoveries of three extraction methods: SPE with commercial cartridge (Oasis HLB), ml-SPE (cation exchange resin, anion exchange resin, and graphite carbon black), and evaporative concentration (EC). Overall, EC had the best absolute and relative recoveries for PMT in different sample matrices (Figure 3). The median absolute recoveries were 72.4%, 65.5%, and 66.1% for tap, bottled, and surface water samples; median relative recoveries were 105%, 108%, and 101%, respectively. Because ml-SPE and HLB cartridges had lower absolute recoveries (51.7% and 24.0%, respectively), we chose EC for sample processing (matrix effect offset by internal standards).

Figure 3. Relative recoveries of evaporative concentrations for different water matrix.

PMT occurrence in drinking water samples

With good performance of the targeted PMT method, we expanded to non-targeted analysis and analyzed 10 drinking water samples (5 tap water, 4 bottled water, 1 well water), extracted by EC. We tentatively identified over 30 novel PMT in drinking water at Schymanski confidence levels 1-3,⁶ with some showing high detection frequency but never reported. To demonstrate the novelty of detected PMT, we classified them by existing knowledge (Web of Science search results: frequently investigated >50 references, rarely investigated 5-50, novel identification <5) and detection frequency. Rarely studied halogenated methanesulfonates²⁰ (Figure 4, yellow circle, level 1 standard confirmed) were present in >50% of drinking water samples, representing a first detection in both bottled waters and US drinking water. More intriguingly, 2,2-dibromo-3-nitrilopropionamide (DBNPA, Figure 4, level 2a, blue box), a biocide with known aquatic toxicity (EC₅₀ < 0.1 mg/L),^21,22 was detected in 3 of 10 drinking water samples. Similarly structured, and with likely toxicity, 2,2-bromochloro-3-nitrilopropionamide (Figure 4, level 2b, red box) is a new contaminant likely derived from DBNPA, representing the first global identification. Many PMT feature multiple polar functional groups (hydroxyl, sulfonate, amine, nitrile), making them incompatible with reverse phase columns. These PMT are likely disinfection byproducts^8,23,24 or plastic additives,¹⁰ warranting further research given their novelty, prevalence, and toxicological implications.

Figure 4. Non-target PMT in drinking water samples, classified by detection frequency and knowledge level in the literature (Poisson et al, submitted).

5. Budget

We request $35,000 as 10 months stipend for a graduate student. The graduate student is responsible for sample preparation, instrumental analysis, and data analysis in this project.
We request $12,000 to cover the instrument use of the HRMS (Exploris 240).
We request $3,000 as the cost for the supplies of sample collection and shipping.

6. References

1. Gollong, G.; Neuwald, I. J.; Kuckelkorn, J.; Junek, R.; Zahn, D., Assessing the protection gap for mobile and persistent chemicals during advanced water treatment–A study in a drinking water production and wastewater treatment plant. Water Research 2022, 221, 118847.

2. Leusch, F. D.; Neale, P. A.; Arnal, C.; Aneck-Hahn, N. H.; Balaguer, P.; Bruchet, A.; Escher, B. I.; Esperanza, M.; Grimaldi, M.; Leroy, G., Analysis of endocrine activity in drinking water, surface water and treated wastewater from six countries. Water research 2018, 139, 10-18.

3. Richardson, S. D., Tackling unknown disinfection by-products: Lessons learned. Journal of Hazardous Materials Letters 2021, 2, 100041.

4. Neuwald, I.; Muschket, M.; Zahn, D.; Berger, U.; Seiwert, B.; Meier, T.; Kuckelkorn, J.; Strobel, C.; Knepper, T. P.; Reemtsma, T., Filling the knowledge gap: A suspect screening study for 1310 potentially persistent and mobile chemicals with SFC-and HILIC-HRMS in two German river systems. Water research 2021, 204, 117645.

5. Reemtsma, T.; Berger, U.; Arp, H. P. H.; Gallard, H.; Knepper, T. P.; Neumann, M.; Quintana, J. B.; Voogt, P. d., Mind the Gap: Persistent and Mobile Organic Compounds Water Contaminants That Slip Through. In ACS Publications: 2016.

6. Schymanski, E. L.; Jeon, J.; Gulde, R.; Fenner, K.; Ruff, M.; Singer, H. P.; Hollender, J., Identifying small molecules via high resolution mass spectrometry: communicating confidence. In ACS Publications: 2014.

7. Rappaport, S. M.; Smith, M. T., Environment and disease risks. science 2010, 330, (6003), 460-461.

8. Nihemaiti, M.; Icker, M.; Seiwert, B.; Reemtsma, T., Revisiting disinfection byproducts with supercritical fluid chromatography-high resolution-mass spectrometry: identification of novel halogenated sulfonic acids in disinfected drinking water. Environmental Science & Technology 2023, 57, (9), 3527-3537.

9. Shen, K.; Kang, D.; Jang, H.; Jeon, J., Non-targeted screening of organic micropollutants in drinking water: Evidence of contamination from purification systems and plastic materials. Environment International 2025, 109685.

10. Marques dos Santos, M.; Snyder, S. A., Polymer additives to go? Occurrence of the rubber additive 1, 3-diphenylguanidine (DPG) in bottled water. Environmental Science & Technology Letters 2023, 10, (10), 937-942.

11. Hollender, J.; Schymanski, E. L.; Singer, H. P.; Ferguson, P. L., Nontarget screening with high resolution mass spectrometry in the environment: ready to go? In ACS Publications: 2017.

12. Strynar, M. J., A paradigm shift in environmental monitoring− The time for non-targeted analysis (NTA) is now. Environment International 2025, 197, 109332.

13. Newton, S. R.; McMahen, R. L.; Sobus, J. R.; Mansouri, K.; Williams, A. J.; McEachran, A. D.; Strynar, M. J., Suspect screening and non-targeted analysis of drinking water using point-of-use filters. Environmental pollution 2018, 234, 297-306.

14. Sloop, J. T.; Casey, J. S.; Liberatore, H. K.; Chao, A.; Isaacs, K. K.; Newton, S. R., Development and application of a non-targeted analysis method using GC–MS and LC-MS for identifying chemical contaminants in drinking water via point-of-use filters. Microchemical Journal 2024, 207, 112223.

15. McMinn, M. H.; Hu, X.; Poisson, K.; Berger, P.; Pimentel, P.; Zhang, X.; Ashara, P.; Greenfield, E. L.; Eig, J.; Tian, Z., Emerging investigator series: in-depth chemical profiling of tire and artificial turf crumb rubber: aging, transformation products, and transport pathways. Environmental Science: Processes & Impacts 2024, 26, (10), 1703-1715.

16. Dührkop, K.; Fleischauer, M.; Ludwig, M.; Aksenov, A. A.; Melnik, A. V.; Meusel, M.; Dorrestein, P. C.; Rousu, J.; Böcker, S., SIRIUS 4: a rapid tool for turning tandem mass spectra into metabolite structure information. Nature methods 2019, 16, (4), 299-302.

17. Schulze, S.; Zahn, D.; Montes, R.; Rodil, R.; Quintana, J. B.; Knepper, T. P.; Reemtsma, T.; Berger, U., Occurrence of emerging persistent and mobile organic contaminants in European water samples. Water research 2019, 153, 80-90.

18. Schorr, J.; Therampilly, S.; Jiao, L.; Longree, P.; Singer, H.; Hollender, J., Closing the gap: Ion chromatography coupled to high-resolution mass spectrometry to trace highly polar anionic substances in groundwater. Science of The Total Environment 2023, 889, 164170.

19. Kim, D.-H.; Bamai, Y. A.; Belova, L.; Bessems, J.; Poma, G.; Covaci, A., Human exposure to persistent and mobile chemicals: A review of sources, internal levels and health implications. Science of The Total Environment 2023, 893, 164764.

20. Zahn, D.; Frömel, T.; Knepper, T. P., Halogenated methanesulfonic acids: A new class of organic micropollutants in the water cycle. Water research 2016, 101, 292-299.

21. Wagner, T. V.; Helmus, R.; Becker, E.; Rijnaarts, H. H.; De Voogt, P.; Langenhoff, A. A.; Parsons, J. R., Impact of transformation, photodegradation and interaction with glutaraldehyde on the acute toxicity of the biocide DBNPA in cooling tower water. Environmental Science: Water Research & Technology 2020, 6, (4), 1058-1068.

22. Wagner, T. V.; Helmus, R.; Tapia, S. Q.; Rijnaarts, H. H.; de Voogt, P.; Langenhoff, A. A.; Parsons, J. R., Non-target screening reveals the mechanisms responsible for the antagonistic inhibiting effect of the biocides DBNPA and glutaraldehyde on benzoic acid biodegradation. Journal of Hazardous Materials 2020, 386, 121661.

23. Lau, S. S.; Feng, Y.; Gu, A. Z.; Russell, C.; Pope, G.; Mitch, W. A., Regulated 1–2 carbon disinfection byproducts do not correlate with cytotoxicity with increasing disinfectant contact time during chlorination, chlorination followed by chloramination or granular activated carbon followed by chlorination. Environmental Science & Technology 2024, 58, (45), 20289-20299.

24. Allen, J. M.; Plewa, M. J.; Wagner, E. D.; Wei, X.; Bokenkamp, K.; Hur, K.; Jia, A.; Liberatore, H. K.; Lee, C.-F. T.; Shirkhani, R.; Krasner, S. W.; Richardson, S. D., Drivers of disinfection byproduct cytotoxicity in US drinking water: should other DBPs be considered for regulation? Environmental science & technology 2021, 56, (1), 392-402.

Comprehensive analysis of organic contaminants in urban tap water

Comprehensive analysis of organic contaminants in urban tap water

Peer Reviews

Topics

DOI