August 9th, 2007

What is in Our Drinking Water?
Identification of New Chemical Disinfection By-products (DBPs)

What is a DBP? A drinking water disinfection by-product (DBP) is formed when the chemical used for disinfecting the drinking water reacts with natural organic matter and/or bromide/iodide in the source water.  Popular disinfectants include chlorine, ozone, chlorine dioxide, and chloramine.  Source waters include rivers, lakes, streams, groundwater, and sometimes seawater.  We have only known about DBPs since 1974, when chloroform was identified by Rook as a DBP resulting from the chlorination of tap water. Since then, hundreds of DBPs have been identified in drinking water.

So what?  Millions of people in the U.S. are exposed to these drinking water DBPs every day.  While it is vitally important to disinfect drinking water, as thousands of people died from waterborne illnesses before we started disinfection practices in the early 1900s, it is also important to minimize the chemical DBPs formed.  Several DBPs have been linked to cancer in laboratory animals, and as a result, the U.S. EPA has some of these DBPs regulated.  However, there are many more DBPs that have still not been identified and tested for toxicity or cancer effects.  Currently, we have only identified about 50% of the total organic halide (TOX) that is measured in chlorinated drinking water.  There is much less known about DBPs from the newer alternative disinfectants, such as ozone, chlorine dioxide, and chloramine, which are gaining in popularity in the U.S.  Are these alternative disinfectants safer than chlorine?  What kinds of by-products are formed?  And, what about the unidentified chlorine DBPs that people are exposed to through their drinking water--both from drinking and showering/bathing? The objective of our research is to find out what these DBPs are--to thoroughly characterize the chemicals formed in drinking water treatment--and to ultimately minimize any harmful ones that are formed.

Our research approach
• Gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), and gas chromatography/infrared spectroscopy (GC/IR) techniques are used to identify the unknown by-products 

• NIST and Wiley mass spectral databases are used first to identify any DBPs that happen to be present in these databases

• Because many DBPs are not in these databases, most of our work involves unconventional MS and IR techniques, as well as a great deal of scientific interpretation of the spectra

• High resolution MS provides empirical formula information for the unknown chemical (e.g., how many carbons, hydrogens, oxygens, nitrogens, etc. are in the chemical’s structure)

• Chemical ionization MS provides molecular weight information when this is not provided in conventional electron ionization mass spectra

• IR spectroscopy provides functional group information (e.g., whether the oxygens are due to a carboxylic acid group, a ketone, an alcohol, or an aldehyde)

• LC/MS is used to identify compounds that cannot be extracted from water (the highly polar, hydrophilic ones), as well as the high molecular weight, nonvolatile DBPs.  This is a major missing gap in our knowledge about DBPs--so far, most DBPs identified have been those that are easily extracted from water and are volatile enough to analyze by GC/MS

• Novel derivatization techniques are also applied to aid in the identification of highly polar DBPs

• Formation and fate & transport studies are conducted to better understand how certain priority DBPs are formed and transformed in treatment and distribution systems

We recently completed a major nationwide DBP occurrence study EPA/600/R-02/068 (also published in Dec. 1, 2006 issue of Environmental Science & Technology:  ES&T, 2006, 40, 7175-7185), where we sampled drinking water across the U.S. (disinfected with the different disinfectants and with different water quality, including elevated levels of bromide in the source water).  A group of >50 DBPs that resulted from a prioritization of >500 DBPs in the literature for predicted adverse health effects was quantified in these drinking waters.  Fate and transport studies were also conducted in the drinking water distribution systems to determine whether these DBPs changed in concentration or were transformed in the distribution systems. In addition to obtaining important quantitative information on these new DBPs (to help in prioritizing health effects testing), important new discoveries were made regarding the use of alternative disinfectants.  While the use of alternative disinfectants lowered the levels of the four regulated trihalomethanes and five haloacetic acids (as compared to chlorine), many of the other prioritized DBPs were formed at higher levels with these alternative disinfectants.  For example, the highest levels of iodinated DBPs were found in chloraminated drinking water, the highest levels of halonitromethanes were found in pre-ozonated drinking water, and dihaloaldehydes were highest at a plant using chloramines and ozone.

Our new work includes obtaining quantitative occurrence information on the iodo-acids that were identified for the first time in the Nationwide DBP Occurrence Study.  Chloraminated waters (where levels are expected to be highest) are targeted for this work.  In addition, a toxicity-based identification approach (using mammalian cell and medaka fish assays) will be used to ensure toxicologically important DBPs are not being missed.  The full study of the Four Lab Study is also expected to begin in 2005 (where drinking water is treated and concentrated, comprehensive DBP identifications are carried out, and drinking water concentrates are tested in a battery of in vivo and in vitro toxicity assays, with an emphasis on newer reproductive and developmental health effects).  This Four Lab Study involves the collaboration of EPA's national laboratories and centers (NHEERL, NERL, NRMRL, and NCEA).  Finally, work continues in determining how the toxicologically significant bromonitromethane DBPs are formed.  These bromonitromethanes are more genotoxic and cytotoxic to mammalian cells than most of the DBPs currently regulated and are also currently the focus of in vivo testing at NHEERL (RTP, NC) and at the National Toxicology Program (NTP, NIEHS).

Recent results
• A recent Nationwide DBP Occurrence Study (ES&T, 2006, 40, 7175-7185) has provided important new quantitative information on unregulated DBPs that have the potential to cause adverse health effects based on a structure-activity analysis (Woo et al., 2002); several of these DBPs have concentrations similar to some that are already regulated

• The use of alternative disinfectants can produce higher levels of these DBPs, as compared to chlorine

• A recent study reveals that iodoacetic acid (one of five new iodo-acids recently identified in chloraminated drinking water) is a potent cytotoxin and genotoxin in mammalian cells (Plewa et al., 2004a) (work is in progress on the toxicity of other iodo-acids)

• The presence of natural bromide in the source water  results in a tremendous shift from chlorine-containing DBPs to bromine-containing DBPs when chlorine or chloramine is used as a disinfectant (even in combination with ozone)

• New analytical methods have been developed (and are continuing to be developed) for the analysis of highly polar DBPs

• Collaborations have been forged with health effects researchers to study selected DBPs for potential adverse health effects

Gordon Research Conference on DBPs
A Gordon Research Conference on drinking water DBPs was held on August 13-18, 2006, at Mount Holyoke College in South Hadley, Massachusetts.  Title of meeting:  Drinking Water Disinfection By-products:  Integrating Occurrence and Formation, Exposure, Toxicity, and Epidemiology.  This meeting was highly successful, with a nice mix of chemists, epidemiologists, toxicologists, regulators, human exposure scientists, risk assessment scientists, clinicians, and engineers present.  Scientists from 22 countries were represented.  We were recently approved for on-going status, and will hold the next follow-up Gordon Conference on DBPs in the summer of 2009 (tentatively scheduled for early August).  Ben Blount from the Centers for Disease Control and Prevention (CDC) will be the Chair of the 2009 conference.  Contact Ben Blount ( or Susan Richardson ( for more information.

Useful publications
1. Krasner, S. W., H. S. Weinberg, S. D. Richardson, S. Pastor, R. Chinn, M. J. Sclimenti, G. Onstad, and A. D. Thruston, Jr.  2006.  The Occurrence of a New Generation of Disinfection Byproducts.  Environmental Science & Technology, 40 (23): 7175-7185.   
2. Weinberg, H. S., S. W. Krasner, S. D. Richardson, and A. D. Thruston, Jr.  The Occurrence of Disinfection By-Products (DBPs) of Health Concern in Drinking Water: Results of a Nationwide DBP Occurrence Study.  EPA/600/R02/068.  U.S. Environmental Protection Agency, National Exposure Research Laboratory, Athens, GA.  2002.
3. Muellner, M. G., E. D. Wagner, K. McCalla, S. D. Richardson, Y.-T. Wood, and M. J. Plewa. 2007.  Haloacetonitriles vs. Regulated Haloacetic Acids:  Are Nitrogen Containing DBPs More Toxic?  Environmental Science & Technology,41 (2): 645-651.
4. Zwiener, C., S. D. Richardson, D. M. DeMarini, T. Grummt, T. Glauner, and F. H. Frimmel.  2007.  Drowining in Disinfection By-Products?  Swimming Pool Water Quality Reconsidered.  Environmental Science & Technology, 41 (2): 363-372.
5. Richardson. S. D. Environmental Mass Spectrometry:  Emerging Contaminants and Current Issues.  2006.  Analytical Chemistry, 78 (12): 4021-4046. 
6. Richardson, S. D., and  T. Ternes.  2005.  Water Analysis:  Emerging Contaminants and Current Issues.  Analytical Chemistry, 77(12): 3807-3838. 
7. Richardson, S. D., C. Rav-Acha, and G. D. Simpson.  Chlorine Dioxide Chemistry, Reactions, and Disinfection By-Products.  2007.  In Chlorine Dioxide in Drinking Water Treatment, American Water Works Association Research Foundation, in press. 
8. Richardson, S. D., D. C. Wolf, M. J. Plewa, and R. Schoeny.  Occurrence, Mutagenicity, and Carcinogenicity of Emerging Disinfection By-Products in Drinking Water.  2007.  Mutation Research, in press.
9. Cemeli, E., E. D. Wagner, D. Anderson, S. D. Richardson, and M. J. Plewa.  2006.  Modulation of the Cytotoxicity and Genotoxicity of the Drinking Water DBP Iodoacetic Acid by Suppressors of Oxidative Stress. Environmental Science & Technology, 40 (6): 1878-1883.
10. Vincenti, M., S. Biazzi, N. Ghiglione, M. C. Valsania, and S. D. Richardson.  2005.  Comparison of Highly- Fluorinated Chloroformates as Direct Aqueous Sample Derivatizing Agents for Hydrophilic Analytes and Drinking Water Disinfection By-Products.  Journal of the American Society for Mass Spectrometry, 16 (6): 803-813.
11. Plewa, M. J., E. D. Wagner, S. D. Richardson, A. D. Thruston, Jr., Y.-T. Woo, and A. B. McKague.  2004.  Chemical and Biological Characterization of Newly Discovered Iodoacid Drinking Water Disinfection Byproducts.  Environmental Science & Technology, 38(18): 4713-4722.
12. Zwiener, C., and S. D. Richardson.  2005.  Drinking Water Disinfection By-Product Analysis by LC/MS and LC/MS/MS.  Trends in Analytical Chemistry, 24(7): 613-621.  (Invited review article for special thematic issue on Liquid Chromatography-Tandem Mass Spectrometry).
13.  Plewa, M. J., E. D. Wagner, P. Jazwierska, S. D. Richardson, P. H. Chen, and A. B. McKague.  2004.  Halonitromethane Drinking Water Disinfection Byproducts: Chemical Characterization and Mammalian Cell Cytotoxicity and Genotoxicity.  Environmental Science & Technology, 38(1): 62-68.
14. Kundu, B., S. D. Richardson, P. D. Swartz, P. P. Matthews, A. M. Richard, and D. M. DeMarini.  2004.  Mutagenicity in Salmonella of Halonitrometanes: A Recently Recognized Class of Disinfection By-Product in Drinking Water.  Mutation Research, 562: 39-65. 
15. Kundu, B., S. D. Richardson, C. A. Granville, D. T. Shaughnessy, N. M. Hanley, P. D. Swartz, A. M. Richard, and D. M. DeMarini.  2004.  Comparative Mutagenicity of Halomethanes and Halonitromethanes in Salmonella TA100: Structure-Activity Analysis and Mutation Spectra.  Mutation Research, 554: 335-350. 
16. Richardson, S. D.  2004.  Environmental Mass Spectrometry:  Emerging Contaminants and Current Issues.  Analytical Chemistry, 76(12): 3337-3364.
17. Simmons, J. E., L. K. Teuschler, C. Gennings, T. F. Speth, S. D. Richardson, R. J. Miltner, M. G. Narotsky, K. D. Schenck, E. S. Hunter, III, R. C. Hertzberg, III, and G. Rice.  2004.  Component-Based and Whole-Mixture Techniques for Addressing the Toxicity of Drinking Water Disinfection Byproducts Mixtures.  Journal of Toxicology & Environmental Health, 67: 741-754.
18.  Richardson, S.D., J. E. Simmons, and G. Rice.  2002.  DBPs: The Next Generation.  Environmental Science & Technology, 36(9): 198A-205A. 
19. Woo, Y.-T., D. Lai, J. L. McLain, M. K. Manibusan, and V. Dellarco.  2002.  Environmental Health Perspectives, 110 (Suppl. 1): 75-87.
20.  Richardson, S. D., A. D. Thruston, Jr., C. Rav-Acha, L. Groisman, I. Popilevsky, V. Glezer, A. B. McKague, M. J. Plewa, and E. D. Wagner.  2003.  Tribromopyrrole and Other DBPs Produced by the Disinfection of Drinking Water Rich in Bromide.  Environmental Science & Technology, 37(17): 3782-3793.
21. Richardson, S. D.  2003.  Water Analysis:  Emerging Contaminants and Current Issues.  Analytical Chemistry, 75(12): 2831-2857. 
22. Richardson, S. D.  2003.  Disinfection By-Products and Other Emerging Contaminants in Drinking Water.  Trends in Analytical Chemistry, 22(10):666-684
23.  Chen, P. H., S. D. Richardson, S. W. Krasner, G. Majetich, and G. L. Glish.  2002.  Hydrogen Abstraction and Decomposition of Tribromonitromethane and Other Trihalo Compounds by GC/MS.  Environmental Science & Technology, 36(15): 3362-3371.
24.  Simmons, J. E., S. D. Richardson, T. F. Speth, R. J. Miltner, G. Rice, K. M. Schenck, E. S. Hunter, III, and L. K. Teuschler.  2002.  Development of a Research Strategy for Integrated Technology-Based Toxicological and Chemical Evaluation of Complex Mixtures of Drinking Water Disinfection Byproducts.  Environmental Health Perspectives, 110(Supp. 6): 1013-1024.
25.  Arbuckle, T. E., S. E. Hrudey, S. W. Krasner, J. R. Nuckols, S. D. Richardson, P. Singer, P. Mendola, L. Dodds, C. Weisel, D. L. Ashley, K. L. Froese, R. A. Pegram, I. R. Schultz, J. Reif,  A. M. Bachand, F. M. Benoit, M. Lynberg, C. Poole, and K. Waller.  2002.  Assessing Exposure in Epidemiologic Studies to Disinfection By-products in Drinking Water: Report from an International Workshop.  Environmental Health Perspectives, 110 (Supp. 1): 53-60.
26.  Richardson, S. D., T. V. Caughran, T. Poiger, Y. Guo, and F. G. Crumley.  2000.  Application of DNPH Derivatization with LC/MS to the Identification of Polar Carbonyl Disinfection By-products in Drinking Water.  Ozone: Science & Engineering, 22: 653-675.
27.  Richardson, S. D., A. D. Thruston, Jr., T. V. Caughran, P. H. Chen, T. W. Collette, T. L. Floyd, K. M. Schenck, B. W. Lykins, Jr., G.-R. Sun, and G. Majetich.  1999.  Identification of New Ozone Disinfection By-products in Drinking Water.  Environmental Science & Technology, 33: 3368-3377.
28.  Richardson, S. D., A. D. Thruston, Jr., T. V. Caughran, P. H. Chen, T. W. Collette, T. L. Floyd, K. M. Schenck, B. W. Lykins, Jr., G.-R. Sun, and G. Majetich.  1999.  Identification of New Drinking Water Disinfection By-products Formed in the Presence of Bromide.  Environmental Science & Technology, 33: 3378-3383.
29.  Richardson, S. D., A. D. Thruston, Jr., T. V. Caughran, P. H. Chen, T. W. Collette, K. M.  Schenck, B. W. Lykins, Jr., C. Rav-Acha, and V. Glezer.  2000.  Identification of New Drinking Water Disinfection By-products from Ozone, Chlorine Dioxide, Chloramine, and Chlorine.  Water, Air, and Soil Pollution, 123: 95-102. 
*For more information, contact Susan Richardson at

Last updated on Thursday, August 9th, 2007.