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ENVIRONMENTAL FACTORS AND CHEMICAL AND MICROBIOLOGICAL CONSTITUENTS RELATED TO THE PRESENECE OF VIRUSES IN GROUND WATER FROM SMALL PUBLIC WATER SUPPLIES IN SOUTHEASTERN MICHIGAN
FRANCY, D. S., R. N. BUSHON, E. J. LUZANO, AND G. FOUT. ENVIRONMENTAL FACTORS AND CHEMICAL AND MICROBIOLOGICAL CONSTITUENTS RELATED TO THE PRESENECE OF VIRUSES IN GROUND WATER FROM SMALL PUBLIC WATER SUPPLIES IN SOUTHEASTERN MICHIGAN. Presented at Major Accomplishments and Future Directions in Public Health Microbiology Workshop, Columbus, OH, February 15 - 18, 2005.
Overarching Objectives and Links to Multi-Year Planning
This task directly supports the Drinking Water Research Program Multi-Year Plan's long term goal to "develop scientifically sound data and approaches to characterize and manage risks to human health posed by exposure to waterborne pathogens and chemicals" under GRPA Goal 2 (Clean and Safe Water). The overarching objective is to provide the Office of Water, Agency risk assessors and managers, academics, the scientific community, state regulators, water industry and industry spokes groups with exploratory occurrence and exposure data on human enteric viruses. These data will improve the quality of risk-based assessments and tools used by the Agency to set regulations, policies and priorities for protecting human health and allow the Agency to assure the public that the appropriate methods are being used to demonstrate that drinking water is safe from pathogenic agents.
Specific Subtask Objectives:
o Conduct an exploratory occurrence studies on emerging human waterborne pathogenic viruses and viruses on the Contaminant Candidate List (CCL) in water (Subtask A; to be completed by 9/05 in support of LTG 1 (due 2010)).
o Determine the relationship of bacterial virus indicators to human enteric virus occurrence in the above studies (Subtask A; to be completed by 9/05 in support of LTG 1 (due 2010)).
o Develop a non-invasive assay for measuring human exposure to viruses (Subtask B; to be completed by 9/05 in support of LTG 1 (due 2010)).
Thirty-eight public ground-water-supply wells serving fewer than 3,300 people were sampled from July 1999 through July 2001 in southeastern Michigan to determine (1) the occurrence of viral pathogens and microbiological indicators, (2) the adequacy of indicators as predictors of the presence of viruses, and (3) the factors that affect the presence of viruses. Samples were analyzed for enteric viruses by reverse transcriptase-polymerase chain reaction (RT-PCR), for culturable viruses by cell culture, and for the following indicators: total coliforms, E. coli, enterococci, and F-specific and somatic coliphage. Ancillary environmental and water-quality data also were collected.
A total of 169 regular samples and 32 replicate pairs were collected from 38 wells. Each well was sampled from one to five times. By use of RT-PCR, enterovirus was found in four wells (10.5 percent) and hepatitis A virus (HAV) in five wells (13.2 percent). In two of these wells, investigators found both enterovirus and HAV, but on different sampling dates. Analyses for Norwalk virus, reoviruses, and rotaviruses by RT-PCR in a subset of samples gave negative results. Culturable viruses were found once in two wells (5.9 percent), but neither of these wells was positive for viruses by RT-PCR on any sampling date. Of the 38 wells, 9 (23.7 percent) were positive for viruses by either RT-PCR or cell culture.
One or more indicators were found in 18 of 38 wells. Total coliforms, E. coli, enterococci, and F-specific and somatic coliphage were found in 34.2, 10.5, 15.8, 5.9, and 5.9 percent, respectively, of the wells tested. Only three of the indicator-positive wells were positive for an indicator on more than one date at the same well. Five out of nine (55.6 percent) virus-positive wells were also found to be positive for an indicator. Two wells with detections of viruses had a detection of total coliforms, one well had a detection of E. coli, one of enterococci, and one of F-specific coliphage.
More virus-positive samples were found at sites served by septic systems than those served by sewerlines. Sampling condition (ground water or a mixture of tank and ground water), distance to septic system, type of and distance to nearest surface-water body, well characteristics, or land use were not related to the presence of viruses or indicators. Statistically significant relations were found between total coliforms and dissolved organic carbon, iron, or chloride concentrations. Presence of nitrate was related to presence of E. coli, enterococci, coliphage, or enteric viruses but not to total coliforms. The data indicated that chloride-to-bromide (Cl:Br) ratios may be useful as a screening tool for total coliforms and enteric viruses but not for E. coli, enterococci, and F-specific and somatic coliphage.
This study provides evidence for fecal contamination of ground water at small public-supply wells and shows the importance of collecting multiple samples at each site. The study also suggests that the collection of site-characteristic data (e.g., population density, land usage, hydrogeology, well construction), data on multiple water-quality parameters (e.g., mineral and organic carbon concentrations) and data on microbiological indicators is important for making reliable predictions of the presence of enteric viruses in small public water systems. Future data collection toward this end could include repeat sampling several times a year for different indicators, measuring dissolved organic carbon, nitrate plus nitrite, and/or chloride concentrations, or determining Cl:Br ratios.