Published in: 2008
WISA 2008 Conference, Sun City
Mnguni M., Ndlovu S., Gounden T., Pfaff W., Rodda N. and Buckley C.
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The eThekwini Municipality (Durban, South Africa) has adopted urine diversion (UD) dry toilets for the provision of basic, safe, dignified and sustainable sanitation in rural areas in the greater Durban region. This decision was driven by shortcomings of ventilated improved pit latrines (VIPs) in many of the areas administered by the Municipality. However, due to the urgency of the need for this intervention, it was not possible to complete scientific evaluation of UD as a sanitation solution in the greater Durban context prior to its implementation. A joint scoping workshop was held by the Pollution Research Group and eThekwini Water and Sanitation, to identify data gaps and to design specific studies to address these. One question addressed was whether quantitative microbial risk assessment could be applied productively as a decision-making tool in guiding policy decisions for sanitation implementation and community education. Studies were initiated by the Pollution Research Group to better define the extent of direct exposure of waste handlers and incidental exposure of household members to UD waste. Data generated from studies of pathogen prevalence in UD wastes, and observational studies on community practices in the operation and maintenance of the toilets, were used to develop a more regionally relevant quantitative risk assessment of the operation and maintenance of urine diversion toilets. Most likely exposure scenarios had already been defined as part of the initial PRG/eThekwini scoping workshop. The conventional steps of hazard identification, dose-response assessment, exposure assessment and risk characterisation were followed to develop probability-based distributions of risk of infection by Ascaris for the community sections identified as being most at risk. The risk estimates developed were compared to recognised guidelines for acceptable risk of infection. The effect of introducing barriers to exposure (hence to infection) on risk were evaluated. Using only two barriers to exposure (wearing gloves and washing after waste handling), it was shown that risk could be reduced to near aceptable levels.
Note: According to one of the authors (Nicola Rodda) on 22 Sept. 2014, the model assumptions of the QMRA have been superseded by the publication of a dose-response model for Ascaris, and that the risk assessment is therefore of limited value at best. The QMRA for Ascaris in UD sludge in the process of being redone with the new information. Results will be available at the end of the year.
Mnguni M., Ndlovu S., Gounden T., Pfaff W., Rodda N. and Buckley C. (2008). Health Risk Assessment of the Operation and Maintenance of Urine Diversion Toilets in eThekwini Municipality. WISA 2008 Conference, Sun City
English Peri-urban Sub-Saharan Africa Urban (entire city)
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