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Quantitative Microbial Risk Analysis
Wastewater Use in Agriculture




This page contains QMRA-Monte Carlo computer programs to calculate annual risks of infection or disease and required log unit pathogen reductions to assess the safety of using wastewater in agriculture.

► Not familiar with QMRA? See QMRA: A Beginner's Guide


There are two programs:

 QMRA-MC_UnrestrictedIrrigation_1a and QMRA-MC_RestrictedIrrigation_1a

 and a User Guide.
►These programs are based on the approach developed by Professor Hillel Shuval and colleagues in their paper Development of a risk assessment approach for evaluating wastewater reuse standards for agriculture (Water Science and Technology, 1997).

►Further details are given in our paper Health risks in wastewater irrigation: comparing estimates from quantitative microbial risk analyses and epidemiological studies (Journal of Water and Health, 2007).

These programs, and the ones below, were written by Dr Andrew Sleigh (Institute for Pathogen Control Engineering, School of Civil Engineering, University of Leeds).

►For all the programs on this page remember to ‘enable macros’ (Excel 2003) or select ‘Options’ and then check ‘Enable this content’ (Excel 2007) − otherwise the programs won’t run!


B.  New programs

1.  QMRA-MC_UnrestrictedIrrigation_2  and  QMRA-MC_RestrictedIrrigation_2
These programs are based on the improved Karavarsamis-Hamilton method to determine annual risks − see Estimators of annual probability of infection for quantitative microbial risk assessment (Journal of Water and Health, 2010).
► See the User Guide.  ► See also: Comparison of the two methods.
Grateful acknowledgements to Dr Andrew Hamilton (University of Melbourne).

2. QMRA-MC_UnrestrictedIrrigation_Norovirus_2
This program is based on Norwalk virus: How infectious is it? (Journal of Medical Virology, 2008). It incorporates the Karavarsamis-Hamilton method to determine annual risks (see #1 above). ► See the User Guide.
Grateful acknowledgements to Professor Christine Moe (Emory University, USA) and Dr Peter Teunis (RIMV, The Netherlands).
See also:
Health risks in urban agriculture when using wastewater or partially treated wastewater for crop watering (Presentation at World Bank Water Week, Washington DC, 17−19 Feb. 2009)
Estimation of norovirus infection risks to consumers of wastewater-irrigated food crops eaten raw (Journal of Water and Health, 2010)

3. QMRA-MC_UnrestrictedIrrigation_Ascaris
This program is based on Application of helminth ova infection dose curve to estimate the risks associated with biosolids application on soil (Journal of Water and Health, 2009). It also incorporates the Karavarsamis-Hamilton method to determine annual risks (see #1 above). See also: A quantitative microbial risk assessment of helminth ova in reusing sludge for agricultural production in developing countries (WIT Transactions on Information and Communication, 2008 − open access).
► See the User Guide.
Grateful acknowledgements to Professor Blanca Jiménez (UNAM, Mexico).
►Estimation of Ascaris infection risks in children under 15 from the consumption of wastewater-irrigated carrots (Journal of Water and Health, 2010)


4. QMRA-MC_RestrictedIrrigation_Norovirus_2  
    QMRA-MC_RestrictedIrrigation_Ascaris01


Further reading
Microbiological risks in food [WHO webpage]
Updating the 2006 WHO Guidelines: More Appropriate Tolerable Additional Burden of Disease, Improved Determination of Annual Risks, Norovirus and Ascaris Infection Risks, Extended Health-Protection Control Measures, Treatment and Non-treatment Options [World Health Organization, 2010]
Improving Wastewater Use in Agriculture: An Emerging Priority [World Bank Policy Research Working Paper No. 5412, September 2010] − a more detailed version of this report is: Improving Wastewater Use in Agriculture: An Emerging Priority [World Bank, June 2010] – Annex A of this report is: Development of Guidelines for Wastewater Use in Agriculture 1918−2010.
Understanding and updating the 2006 WHO guidelines for the safe use of wastewater in agriculture [Fundación Instituto Euromediterráneo del Agua, 2009]
Tools for risk analysis: Updating the 2006 WHO guidelines [Chapter 5 of Wastewater Irrigation and Health: Assessing and Mitigating Risks in Low-income Countries, 2009]
Quantifying diarrhoea infection risks [SANDEC News #10, 2009 – p. 18]
Comparing probabilistic microbial risk assessments for drinking water against daily rather than annualised infection probability targets [Journal of Water and Health, 2009]
Quantification of the health risk associated with wastewater reuse in Accra, Ghana: a contribution toward local guidelines [Journal of Water and Health, 2008] 
An approach for developing quantitative risk-based microbial standards for fresh produce [JWH,       2008]
RIRA: A tool for conducting health risk assessments for irrigation of edible crops with recycled  water [Computers & Electronics in Agriculture, 2007] [RIRA = Recycled water Irrigation Risk Analysis] − for the beta version of the computer program e-mail Andrew Hamilton (University of Melbourne).
Deterministic versus stochastic quantitative microbial risk assessment models for wastewater irrigation of food crops [Acta Horticulturae, 2008]
Managing health risks to consumers – Chapter 12 of Growing Crops with Reclaimed Wastewater [CSIRO Publishing, 2006]
Is the risk of illness through consuming vegetables irrigated with reclaimed wastewater different for different population groups? [WST, 2006 ]
Quantitative microbial risk assessment models for consumption of raw vegetables irrigated with reclaimed water  [Applied & Environmental Microbiology, 2006]
Wastewater quality and the risk of intestinal nematode infection in sewage farming families in Hyderabad, India [American Journal of Tropical Medicine and Hygiene, 2008]
A Simple Model to Include Human Excretion and Wastewater Treatment in Life Cycle Assessment of Food Products [University of Surrey, 2007]
Risk, precaution and science: towards a more constructive policy debate − Precautionary principle and risk management: which way? [EMBO Reports, 2009]
Food Quality and Safety Systems: A Training Manual on Food Hygiene and the Hazard Analysis and Critical Control Point (HACCP) System [FAO, 1998]
Food Safety Risk Analysis: A Guide for National Food Safety Authorities [FAO, 2006]

►Books:
Quantitative Microbial Risk Assessment [Wiley, 1999] – University of Leeds Library catalogue entry.
Wastewater Irrigation and Health: Assessing and Mitigating Risk in Low-income Countries [Earth- scan, 2010]
The Microbiological Risk Assessment of Food [Blackwell, 2002] – ULL catalogue entry.
Quantitative Environmental Risk Analysis for Human Health [Wiley, 2007] 
Risk Assessment for Environmental Health [Wiley, 2007] 
Biological Risk Engineering Handbook: Infection Control and Decontamination [CRC Press, 2003] – ULL catalogue entry.