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Microbiological and Chemical Exposure Assessment Staff

Nicholas J. Ashbolt

Title: Title 42 Senior Research Microbiologist

EPA Division: Microbiological and Chemical Exposure Assessment Research Division

Dr. Ashbolt has 25 years experience in environmental microbiology, with a focus on the fate and transport of environmental pathogens, biofilm-related pathogens in distribution systems and application of quantitative microbial risk assessment (QMRA) to drinking, reuse and recreational waters. Over the last 15 years has worked in joint Australian-Sweden and European programs developing methods to interpret pathogen data with the aid of QMRA within an urban water sustainability framework. This work has contributed to the risk-based approach adopted in the WHO recreational, drinking and reuse water guidelines and the Australia national urban water sustainability framework used by the water industry.


  • BAgSc. (Hons) 1979, Ph.D. 1984 University of Tasmania

Professional Experience:

  • Professor, School of Civil and Environmental Engineering, UNSW April 1994- January 2007
  • Principal Scientist (Microbiology), Sydney Water Corp. January 1991- April 1994
  • Section Leader (Environmental Pathogens), Sydney Water, March 1990-January 1991
  • ARC Fellow and Curator, Australian Collection of Antarctic Microorganisms, March 1989-March 1990
  • Research Fellow (Microbiology), Australian Nuclear Science and Technology Organisation, September 1987-March 1989
  • Research Microbiologist, Sugar Research Institute, Mackay, March 1984-September 1987

Professional Societies and Affiliations:

  • American Water Works Association, 1996
  • Australian Water & Wastewater Association, 1985
  • International Association Water Pollution Research Control, 1985 (now IWA)
  • IWA Special Interest Group on Health-Related Water Microbiology, 1993 (International management committee member for this SIG).
  • Australian Society for Microbiology (MASM), 1987

Select Awards and Honors:

  • Ph.D. research scholarship, University of Tasmania 1979-1983
  • University Foundation Fellowship Award for 2007, University of Tasmania
  • U.S. EPA Bronze Medal for recreational water criteria development , 2008

Select Presentations:

  • Ashbolt N.J., Schoen M.E., Soller J.A., Roser D.J. (2010). Predicting pathogen risks to aid beach management: The real value of QMRA. Paper presented at The Water Research Conference, Marriott Lisbon, Portugal, April 11-14.
  • Ashbolt N.J. (2010). Legionella in Drinking Water: Ecology, Risks & Management. Paper presented at AWWA2010 Annual Conference & Exhibition, Chicago, Illinois, June 20-24.
  • Ashbolt N.J. (2010). Emerging Pathogen Issues from Future Urban Water Services. Paper presented at International Conference on Emerging Infectious Diseases (ICEID 2010), Atlanta, GA, July 11-14.
  • Ashbolt, N.J. 2010. Aim of and Management with Novel Water Quality Indicators, WQTC 2010: STO1 – Genomics Revolution & Impact on WQ Indicators. American Water Works Association, Savannah, GA November 17th, 2010.
  • Ashbolt, N.J. (2010). Why and How Are Microbes in Drinking Water Still a Problem?, WQTC 2010: STO7 - Microbes in Drinking Water: Research, Regulation, Reduction & Risk. American Water Works Association, Savannah, GA November 18th.
  • Ashbolt, N.J. (2011). Water Futures: The Imperative for change in urban water services, ICOSSE’11 Session 11: Sustainable Water Management, International Congress on Sustainability Science and Engineering, U.S. Environmental Protection Agency, Marriott Starr, Tucson, January 12th.
  • Ashbolt, N.J. (2011). The global challenge: why & how drinking water systems still present pathogen issues 9th CECIA-IAUPR Biennial Symposium on Potable Water Issues. Inter-American University of Puerto Rico, Puerto Rico: March 9th.
  • Ashbolt, N.J. (2011). Benefits to Australia from an international perspective on microbial issues, OzWater'11 Australian Water Association, Adelaide Convention Centre, May 7th.
  • Ashbolt, N.J. (2011). An ecological context to water microbiology methods, Faecal Indicators: Problems or Solution? Royal Society of Chemistry, Edinburgh Conference Centre, June 6-8.
  • Ashbolt, N.J. (2011). The short pipe path – safe water, energy & nutrient recovery. Session 18: Zero Net Energy Facilities and the Future of Wastewater Treatment, In Proc.: Energy and Water 2011: Efficiency, Generation, Management and Climate Impact. Hyatt Regency McCormick Place, Chicago, Illinois. Water Environment Research Foundation, July 31 – August 3.
  • Ashbolt, N.J., and M.E. Schoen (2011). QMRA as an emerging tool – regulatory and operational uses, Faecal Indicators: Problems or Solution? Royal Society of Chemistry, Edinburgh Conference Centre, June 6-8.
  • Ashbolt, N. J. (2011). Legionella: Potential risks from drinking water distribution systems, Water Quality and Technology (WQTC 2011) Sunday Workshop, SUN02 - QMRA: New Applications, New Techniques, and Taking Stock of Challenges. American Water Works Association, Phoenix, AZ November 13.
  • Ashbolt, N.J. (2011). Water sustainability: EPA Approach, Water Quality and Technology (WQTC 2011) ST1MON: A Sustainability Systems Approach for Drinking Water. American Water Works Association, Phoenix, AZ November 14.
  • Ashbolt, N.J., and M.E. Schoen (2011). Legionella-like pathogens via drinking water: Role of QMRA, 21st Annual Quality Assurance Conference of Region 4, Session D. U.S. Environmental Protection Agency Region 4, 1445 Ross Ave., Dallas, TX, October 17.
PUBLICATIONS (2007-present)

Books, Chapters and Monographs (2007-present):

  • Ashbolt, N., Fujioka, R., Glymph, T., McGee, C., Schaub, S., Sobsey, M. & Toranzos, G. (2007). Pathogens, pathogen indicators and indicators of fecal contamination. In Report of the Experts Scientific Workshop on Critical Research Needs for the Development of New or Revised Recreational Water Quality Criteria. Airlie Center Warrenton, Virginia March 26-30, 2007. EPA 823-R-07-006 Washington D.C.: U. S. Environmental Protection Agency.
  • Santo Domingo, J.W. and Ashbolt, N.J. (2008). Fecal pollution of water. The Encyclopedia of Earth
  • Ashbolt, N.J. (2009). Chapter 3: The use of technologies: exposure (cross-contamination), risk assessment, and guidelines. In Research Gaps and Barriers for Providing Sustainable Water, Sanitation, and Hygiene Services, Workshop Summary ed. Coussens, C. pp.33-40. Washington, D.C.: Institute of Medicine, The National Academies Press.
  • Ashbolt, N.J. (2010). Chapter 5 Global warming and trans-boundary movement of waterborne microbial pathogens. In Adaptation and Mitigation Strategies for Climate Change, A. Sumi, K. Fukushi, and A. Hiramatsu, Editors, pp:71-82. Springer: Tokyo.
  • Sen, K., and N. J. Ashbolt (Eds.) (2011). Environmental Microbiology: Current Technology and Water Applications, Caister Academic Press, Norfolk, UK.
  • Santo Domingo, J., R. Lamendella, and N. J. Ashbolt (2011). Chapter 10 Microbial source tracking: Current and future molecular tools in microbial water quality forensics. In K. Sen and N. J. Ashbolt (eds.), pp:225-250, Environmental Microbiology: Current Technology and Water Applications, Caister Academic Press, Norfolk, UK.

Journal Articles (2007-present):

  • Ferguson, C., Davies, C.M., Kaucner, C., Krogh, M., Rodehutskors, J., Deere, D. and Ashbolt, N.J. (2007). Field scale quantification of microbial transport from bovine faeces under simulated rainfall events. Journal of Water and Health 5(1):83-95.
  • Ferguson, C.M., Croke, B.R.W., Beatson, P.J., Ashbolt, N.J. and Deere, D.A. (2007). Development of a process-based model to predict pathogen budgets for the Sydney drinking water catchment. Journal of Water and Health 5(2):187-208.
  • Lai, E., Lundie, S. & Ashbolt, N.J. (2007). A new approach to aid urban water management decision making using trade-off sacrifice modelled by fuzzy logic. Water Science and Technology 56(8):11-20.
  • Långmark, J., Storey, M.V., Ashbolt, N.J. and Stenström, T.-A. (2007). The effects of UV disinfection on distribution pipe biofilm growth and pathogen incidence within the greater Stockholm area, Sweden. Water Research 41(15):3327-3336.
  • Nilsson, P., Roser, D., Thorwaldsdotter, R., Petterson, S., Davies, C., Signor, R., Bergstedt, O. & Ashbolt, N. (2007). SCADA data and the quantification of hazardous events for QMRA. Journal of Water and Health 5(Suppl 1):99-105.
  • Petterson, S.R., Signor, R.S. & Ashbolt, N.J. (2007). Incorporating method recovery uncertainties in stochastic estimates of raw water protozoan concentrations for QMRA. Journal of Water and Health 5(Suppl 1):51-65.
  • Signor, R.S., Ashbolt, N.J. & Roser, D.J. (2007). Microbial risk implications of rainfall-induced runoff events entering a reservoir used as a drinking-water source. Journal of Water Supply - AQUA 56(8):515–531.
  • Barnes, R., Ashbolt, N., Roser, D. and Brown, P. (accepted). Implementing sustainable water and sanitation projects in rural, developing communities. Waterlines.
  • Charles, K.J., Souter, F.C., Baker, D.L., Davies, C.M., Schijven, J.F., Roser, D.J., Deere, D.A., Priscott, P.K. and Ashbolt, N.J. (2008). Fate and transport of viruses during sewage treatment in a mound system. Water Research 42(12):3047-3056.
  • Khan, S.J., Roser, D.J., Davies, C.M., Peters, G.M., Stuetz, R.M., Tucker, R. and Ashbolt, N.J. (2008). Chemical contaminants in feedlot wastes: Concentrations, effects and attenuation. Environment International 34(6):839–859.
  • Storey, M.V., Kaucner, C.E., Angles, M.L., Blackbeard, J.R. and Ashbolt, N.J. (2008). Opportunistic pathogens in drinking and recycled water distribution systems. Water, Journal of the Australian Water Association 35(1):38-45.
  • Davies, C.M., Mitchell, V.G., Petterson, S., Taylor, G., Lewis, J., Kaucner, C. and Ashbolt, N.J. (2008). Microbial challenge testing of treatment processes for quantifying stormwater recycling risks and management Water Science and Technology 57(6):843–847.
  • Lai, E., Lundie, S. and Ashbolt, N.J. (2008). Review of multi-criteria decision aid for integrated sustainability assessment of urban water systems Urban Water Journal 5(4):315-327.
  • Boehm, A.B., Ashbolt, N.J., John M. Colford, J., Dunbar, L.E., Fleming, L.E., Gold, M.A., Hansel, J.A., Hunter, P.R., Ichida, A.M., McGee, C.D., Soller, J.A. and Weisberg, S.B. (2009). A sea change ahead for recreational water quality criteria. Journal of Water and Health 7(1):9-20.
  • Jury, K.L., Khan, S.J., Vancov, T., Stuetz, R.M. and Ashbolt, N.J. (2009). Are sewage treatment plants promoting antibiotic resistance? Critical Reviews in Environmental Science and Technology (accepted).
  • Lau, H.Y. and Ashbolt, N.J. (2009). The use of Acanthamoeba as a tool for understanding Legionella pathogenesis: Implications for drinking water. Journal of Applied Microbiology 107(2):368–378.
  • Petterson, S.R., Dumoutier, N., Loret, J.F. and Ashbolt, N.J. (2009). Quantitative Bayesian predictions of source water concentration for QMRA from presence/absence data for E. coli O157:H7. Water Science and Technology 59(11):2245-2252.
  • Signor, R. and Ashbolt, N.J. (2009). Comparing probabilistic microbial risk assessments for drinking water against daily rather than annualised infection probability targets. Journal of Water and Health 7(4):535-543.
  • Ashbolt, N.J., Schoen, M.E., Soller, J.A. and Roser, D.J. (2010). Predicting pathogen risks to aid beach management: The real value of quantitative microbial risk assessment (QMRA). Water Research 44(16):4692-4703.
  • Barnes, R. and Ashbolt, N.J. (2010). Development of a planning framework for sustainable rural water supply and sanitation: Case study of a Filipino NGO. Journal of International Studies of Management and Organization 40(3):78-98.
  • Dorevitch, S., Ashbolt, N.J., Ferguson, C.M., Fujioka, R., McGee, C.D., Soller, J.A. and Whitman, R.L. (2010). Knowledge and gaps in developing microbial criteria for inland recreational waters. Environmental Health Perspectives, 118(6):871-876.
  • Klein, M., Brown, L., Tucker, R.W., Ashbolt, N.J., Stuetz, R.M. and Roser, D.J. (2010) Diversity and abundance of zoonotic pathogens and faecal indicators in manures of feedlot cattle in Australia. Applied & Environmental Microbiology 76(20):6947-6950.
  • Schoen, M.E., and Ashbolt, N. J. (2010). Assessing pathogen risk to swimmers at non-sewage impacted recreational beaches. Environmental Science and Technology 44(7):2286–2291.
  • Soller, J. A., Bartrand, T., Ashbolt, N. J., Ravenscroft, J. and Wade, T. (2010). Estimating the primary etiologic agents in freshwater recreational waters impacted by human sources of fecal contamination. Water Research, 44(16):4736-4747.
  • Soller, J.A., Schoen, M.E., Bartrand, T., Ravenscroft, J.E. and Ashbolt, N.J. (2010). Estimated human health risks from exposure to recreational waters impacted by human and non-human sources of faecal contamination. Water Research, 44(16):4674-4691.
  • Buse, H.Y., Brehm, A., Santo Domingo, J.W., and Ashbolt, N.J. (2011). Screening-level assays for potentially human-infectious environmental Legionella spp. The Journal of Microbiology, 49(2):200-207.
  • Buse, H. Y., and N. J. Ashbolt (2011). Differential growth of Legionella pneumophila strains within a range of amoebae at various temperatures associated with in-premise plumbing. Letters in Applied Microbiology, 53(2):217-224.
  • Buse, H.Y., M.E. Schoen, and N.J. Ashbolt. (Accepted). Legionellae in engineered systems and use of quantitative microbial risk assessment to predict exposure. Water Research.
  • Englehardt, J.D., N.J. Ashbolt, C. Loewenstine, E. Gadzinski, and A.Y. Ayenu-Prah Jr. (Accepted). Methods for assessing long-term mean pathogen count in drinking water and risk management implications. J Water Health.
  • Klein, M., Brown, L., Ashbolt, N. J., Stuetz, R. M., and Roser, D. (2011). Inactivation of indicators and pathogens in cattle feedlot manures and compost as determined by molecular and culture assays. FEMS Microbiology Ecology, 77(1):200-210.
  • Lu, J., H. Ryu, J. Santo Domingo, J.F. Griffith, N. Ashbolt (2011). Molecular detection of Campylobacter spp. in California Gull (Larus californicus) excreta. Applied & Environmental Microbiology, 77(13):5034-5039.
  • Lu, J., Ryu, H., Hill, S., Schoen, M., Ashbolt, N., Edge, T.A., Santo Domingo, J. (2011). Distribution and potential significance of a gull fecal marker in urban coastal and riverine areas of southern Ontario, Canada. Water Research 45(13):3960-3968.
  • Schoen, M.E., Soller, J.A. and Ashbolt, N.J. (2011) What faecal source(s) contribute to bather illness in human-impacted waters? Water Research, 45(8):2670-2680.
  • Schoen, M.E. and Ashbolt, N.J. (2011) An in-premise model for Legionella exposure during showering events. Water Research, 45(18): 5826-5836.
  • Thomas, J. M., and N. J. Ashbolt (2011). Do free-living amoebae in treated drinking water systems present an emerging health risk? Environmental Science and Technology, 45(3):860-869.
  • Van den Akker, B., V. Whiffin, P. Cox, P. Beatson, N. J. Ashbolt, and D. J. Roser (2011). Estimating the risk from sewage treatment plant effluent in the Sydney catchment area. Water Science & Technology, 63:1707-1715.
  • Buse, H.Y. and N. J. Ashbolt (2012). Counting Legionella cells within single amoeba host cells. Applied & Environmental Microbiology 78(6): 2070-7072.
  • Buse, H.Y., M. E. Schoen and N. J. Ashbolt (2012). Legionellae in engineered systems and use of quantitative microbial risk assessment to predict exposure. Water Research 46(4): 921-933.
  • Neumann, N.F., L. Villegas, and N.J. Ashbolt.(2012). The genomics revolution and its impact on water quality. Journal of the American Water Works Association, 104(1):63-65.

Published & Presented Research (1999-Present)

Contact Info:

National Exposure Research Laboratory (MD-593)
Office of Research and Development
U.S. Environmental Protection Agency
26 W. Martin Luther King Drive
Cincinnati OH 45268
Tel: 513-569 7318
Fax: 513-569 7464
Cell: 513-375-5262

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