Grantee Research Project Results
2006 Progress Report: Examining Epidemiologic and Environmental Factors Associated with Microbial Risks from Drinking Water
EPA Grant Number: R831727Title: Examining Epidemiologic and Environmental Factors Associated with Microbial Risks from Drinking Water
Investigators: S. Eisenberg, Joseph N. , Moe, Christine L. , Uber, Jim
Institution: University of California - Berkeley , University of Cincinnati , Emory University
Current Institution: University of California - Berkeley , Emory University , University of Cincinnati
EPA Project Officer: Packard, Benjamin H
Project Period: December 23, 2004 through December 27, 2007 (Extended to December 27, 2009)
Project Period Covered by this Report: December 23, 2005 through December 27,2006
Project Amount: $589,806
RFA: Microbial Risk in Drinking Water (2003) RFA Text | Recipients Lists
Research Category: Nanotechnology , Drinking Water , Human Health , Water
Objective:
Results from drinking water intervention trials have provided a wide range of outcomes, ranging from no evidence of risk to attributable risk estimates as high as 35-40 percent. This range of risk estimates is problematic for regulators. One reason for this variation is because of the differing environmental conditions in each of these studies, such as source water concentrations, treatment barriers, and distribution systems. Risk models can provide insight to these epidemiologic data by interpreting the variability observed across studies. These insights then can be used to help design future studies. The objectives of this research project are to: (1) develop a population-based dynamic model that can be used to characterize drinking water risks to communities and apply this risk model to human calicivirus (HuCV), an important pathogen on the U.S. Environmental Protection Agency (EPA) Candidate Contaminant List; (2) develop an exposure model that describes the pathogen fate and transport from source water through to the distribution system for distribution systems representative of those in urban areas of the United States that will incorporate factors that have a potential role in determining human exposure; and (3) combine the models developed in Objectives 1 and 2 and conduct sensitivity studies to categorize those factors with respect to their relative importance in determining risk.
Progress Summary:
Interim Results
Progress in Year 2 of this project was impeded by the still yet completed transfer of the grant from the University of California, Berkeley (UCB) to the University of Michigan (UM). The Principal Investigator (Joseph Eisenberg) transferred from UCB to UM on April 1, 2006. The novation package was sent over to the EPA on April 15, 2006. On July 11, 2006, UCB closed the award and sent to EPA the final financial status report, with the intent that the unobligated balance was to be transferred to UM. Spending at UCB ended March 31, 2006. As of January 26, 2007, UM has not received the grant award from EPA. Because of this, spending on this project has been minimal. We have already requested and received permission to shift unused portions of the budget, due to funding delays in Year 1 (see Year 1 progress report), to fund Year 4 of the project. Given the minimal expenditure during Year 2, we will also request an extension of Year 5. Due to these funding delays, there was little progress made in Year 2.
Literature reviews
The review of Norovirus outbreaks, which began in Year 1, continued into Year 2. The database of outbreaks has been updated and systematized for ease of analysis. A literature review initiated in Year 1 on environmental occurrence of Norovirus and the effects of water treatment processes was stopped due to the funding delays but will continue in Year 3. This work was being conducted by the University of Cincinnati subcontract, which received no funds during Year 2.
Data gathering and analysis
This work was being conducted by the Emory subcontract, which also received no funds during Year 2. Their work will continue in Year 3.
Model development
The disease transmission modeling work was being conducted by the PI (now at the University of Michigan). This work was delayed by 6 months due to the funding delays. Six months of work, therefore, was completed during Year 2. The environmental model development was being conducted by the University of Cincinnati. This work was, therefore, suspended during Year 2, but will start up again in Year 3. The transmission model was developed during Year 1. In it is an individual-based stochastic model (IBM) and contains social structure; i.e., people live in houses, adults go to work, and kids go to school. During the first part of the year, we translated the modeling code from C++ to RePast. This was done because RePast is an easier format to work under, it's free, and the modeling world is increasingly using it when object-oriented code is called for. During Year 2, we focused on analysis of the following scenario: A small point source drinking water outbreak, due to a distribution system contamination event, exposed one or more daycare centers. This exposure resulted in a number of children and adult employees becoming infected with norovirus. The analysis focused on predicting the number of secondary, tertiary, etc. cases that are attributable to this outbreak and how long this norovirus strain is maintained within the community. This analysis will allow us to reformulate the way in which drinking water risks are estimated. We have recently identified a published daycare center outbreak that contains some secondary transmission data. Our goal is to analyze this outbreak using our transmission model. We have just begun to develop the necessary statistical tool for this analysis. Finally, we have begun to dialog with Jim Ubers' modeling group to begin the integration of the disease transmission model with the environmental model. This will begin as soon as our funds arrive and we can re-establish the subcontracts.
Future Activities:
Our plans for Year 3 are as they were for Year 2:
- Complete our analysis of Norovirus outbreaks.
- Complete our models of Norovirus shedding and dose-response for Norwalk virus and Snow Mountain virus.
- Complete our disease transmission model and examine ways in which secondary transmission contributes to the risks associated with outbreaks. We will use selected outbreaks as case studies.
- Complete our initial environmental models of Norovirus occurrence, fate and transport in source waters and water distribution systems, considering the effects of water treatment processes and inactivation due to the presence of free chlorine residual.
- Develop or adapt statistical models of Norovirus occurrence in surface waters used for drinking water sources.
- Develop or adapt statistical models of Norovirus removal and inactivation during common physical/chemical treatment processes and disinfection using free chlorine.
- Link the above statistical models with the distribution system transport models using the above-described EA tool developed in Year 1. Use existing data from the distribution system in Hillsborough County, Florida, to support a case study analysis.
- Include information on Norwalk virus persistence and infectivity in groundwater (funded by USEPA Cooperative Agreement 82911601-0)
- Include information on Norovirus occurrence from US studies and RIVM studies.
- Develop preliminary conceptual and mathematical models that extend these initial environmental models to incorporate processes of contamination via distribution system intrusion, and incorporation/release of infectious Norovirus to/from pipe biofilm. These models will be a focus on the exposure assessment modeling work during Year 3.
- Integrate our environmental and disease transmission models.
Journal Articles:
No journal articles submitted with this report: View all 2 publications for this projectSupplemental Keywords:
RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Water, Environmental Chemistry, Health Risk Assessment, Ecological Risk Assessment, Environmental Engineering, Drinking Water, microbial contamination, microbial risk assessment, monitoring, real time analysis, aquatic organisms, other - risk assessment, early warning, water quality, drinking water contaminants, epidemiological study, drinking water systemProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.