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Health risk assessment associated with the reuse of compost, urine and greywater in agricultural field in sahelian climate.

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par Alexis Loukou BROU
Fondation 2iE - Master Environnement option Eau et Assainissement 2014

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1. Generalities on health risk assessment

1.1. Health risk assessment

According to WHO, 2006a, the risk is the probability that something with a negative impact may occur. The agent that causes the adverse effect is a hazard. Risk incorporates the probability that an event will occur with the effect that it will have on a population or the environment, considering the sociopolitical context where it takes place (WHO, 2006a). The WHO guideline for the safe use of wastewater, excreta and greywater (WHO, 2006a) gives recommendations on treatment and management in order to avoid unacceptable health risk. It is based on the Stockholm framework, which is a harmonized approach to control water-related diseases (Fidjeland, 2010). Different exposures and diseases are compared through the Disability Adjusted Life Years (DALY) unit, which is a measure of the years lost due to premature death, diseases and chronic effects. The DALY unit enables cross-sectional cost-efficiency comparison of health initiatives (WHO, 2006a); (Fidjeland, 2010). The tolerable risk which is recommended by World Health Organization is 10-6 DALY (WHO, 2006a).

Many authors have characterized the risk analysis in three principal steps: risk assessment, risk management and risk communication(WHO, 1999);(Westrell, 2004); (Metcalf & Eddy, 2007);(Fidjeland, 2010).

According to the National Research Council of USA, risk assessment can be defined broadly as the process of the probability of occurrence of an event and the probable magnitude of adverse effects on safety, health, ecology, finances over a specified time period (Metcalf & Eddy, 2007). In other words, the risk assessment is defined as the qualitative or quantitative characterization and estimation of potential adverse health effects associated with exposure of individuals or populations to hazards (here microbial agents) (Westrell, 2004); (Fidjeland, 2010). Risk assessment also includes characterization of the uncertainties inherent in the process of inferring risk.

Risk management is the process of evaluating and, if necessary, controlling sources of exposure and risk. Sound environmental risk management means weighing many different attributes of a decision and developing alternatives (Metcalf & Eddy, 2007). Risk management is anactivity much broader than technical risk analysis alone (McDowell and Lemer, 1991).

It is the interactive exchange of information and opinions concerning risk and risk management among risk assessors, risk managers, consumers, and other interested parties about the nature, magnitude, significance, or control of a risk (Metcalf & Eddy, 2007).It concerns the health risk assessment component, is the quantitative or qualitative characterization and estimation of potential adverse health effects associated with exposure of individuals or populations to hazardous materials and situations (Metcalf & Eddy, 2007). Therefore, health risk assessment can be divided into four major steps including: hazard identification, dose-responseassessment, exposure assessment, and risk characterization (WHO, 1999).Health risk assessment includes chemical and microbial risk assessment (Metcalf & Eddy, 2007), and in our case of study we will focus on microbial risk assessment.

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