Who guidelines for safe wastewater use—more than just numbers

The use of wastewater in agriculture is occurring more frequently because of water scarcity and population growth. Often the poorest households rely on this resource for their livelihood and food security needs. However, there are negative health implications of this practice that need to be addressed. WHO developed Health Guidelines for the Use of Wastewater in Agriculture and Aquaculture in 1989. The Guidelines are currently being revised based on new data from epidemiological studies, quantitative microbial risk assessments and other relevant information. WHO Guidelines contain both microbial guideline values and good practices to reduce health risks. They must be practical and offer feasible risk management solutions that will minimize health threats and allow for the beneficial use of scarce resources. It is important that the Guidelines are based on actual health risks and an evaluation of what is a tolerable risk. This will vary from country to country. WHO Guidelines, therefore, need to be adapted to the unique social, economic and environmental factors in each situation.