Using quantitative microbial risk assessment to determine if health risk warrants boil water advisories in Newfoundland and Labrador : time for a new approach

Abstract

The effectiveness of Boil Water Advisories (BWAs) as a public health risk management tool is increasingly being questioned. Newfoundland and Labrador's zero-risk policy for issuing BWAs on public drinking water systems has resulted in over 210 active BWAs annually, the majority classified as long-term BWAs. BWAs are more likely to occur on small systems, in communities with low economic capacity, and in communities without a certified operator. No relationship was found relating confirmed cases of water-related illness to BWAs. Quantifiable health risk associated with BWAs was evaluated using Quantitative Microbial Risk Assessment (QMRA). Data on source water pathogen concentrations and epidemiological data was used to evaluate and calibrate the QMRA Model. The study demonstrated the application of QMRA in determining whether health risk warranted issuing a BWA. Eleven recommendations were made on how the province could adopt QMRA in establishing an alternative drinking water risk management and advisory framework.