AWWA PATH50783

The goal of this research was to develop a framework to evaluate microbial pathogens and their importance as waterborne contaminants, specifically to sensitive subpopulations. We then apply this proposed framework to each microbial pathogen on the Contaminant Candidate List (CCL). This process will characterize the pathogens' comparative risk, delineate the data gaps for future research, and offer assessment criteria to policy makers for use in the development of regulation. The framework consists of: problem formulation; concentrations at intake; efficacy of water treatment; survival/amplification in distribution; routes of exposure; dose response; efficacy of medical treatment; secondary spread; and, chronic sequelae. Evaluations using this framework have resulted in the following findings about people who are immunocompromised or otherwise susceptible. Occurrence of illness: mycobacterium avium complex is predominantly prevalent in AIDS patients, though incidence has been steadily decreasing. On the other hand and inexplicably, the incidence in healthy people has been on the rise. Degree of morbidity and mortality: many species of adenovirus are frequently deadly in the immunocompromised; however, enteric adenovirus appears to be no more of a problem in this population than in healthy people. Role of waterborne exposure: water appears to be worth considering as a primary transmission route for calicivirus; whereas, populations most susceptible to adenovirus and echovirus tend to acquire them nosocomially. Includes 58 references.