How predictive is quantitative microbial risk assessment (QMRA)?

HUGO R. POMA; ARTI KUNDU; WUERTZ, STEFAN; RAJAL, VERONICA BEATRIZ

Salta

Simposio; III Simposio Latinoamericano de Virología Ambiental (III-SILVA 2016); 2016

Monitoring of pollution in waterways exposed to human activities is critical to protect the welfare of human populations that interact with these sources. The World Health Organization (WHO) recommends the use of QMRA to analyse the risk of viral infections from recreational waters. A critical step in this methodology is the exposure assessment, where the dose or number of pathogenic microorganisms corresponding to a given exposure is calculated. In this sense, two different methods - one proposed by Haas (Quantitative Microbial Risk Assessment, 1999) and the other using the software @Risk (Palisade, New York, EEUU) - were evaluated to fit density distributions for each data set of enteric viruses in Arenales river in Salta, Argentina. Additionally, different values were tested to represent the non-detect samples for enteric viruses: zero, sample limit of detection (SLOD), SLOD/2, the average, and the median.The distributions obtained after the risk characterization were significantly influenced by the choice of the fitting method. In general, when using the methodology proposed by Haas (1999) lower mean risk values were obtained than by calculating with @Risk. This trend was accentuated for datasets containing a greater number of non-detect samples. Implications for risk assessment are discussed.