STOCKHOLM, Sweden, Aug. 21 (UPI) -- A survey released in Stockholm, Sweden, suggests many cities around the world use raw, untreated wastewater for agricultural purposes.
The 53-city International Water Management Institute survey showed 80 percent of those cities regularly use untreated or partially treated waste water for urban agriculture.
Officials said the practice is often critical to farmers' incomes and urban food security but raises health concerns.
"Irrigating with wastewater isn't a rare practice limited to a few of the poorest countries," said IWMI researcher Liqa Raschid-Sally, lead author of a report on the survey. "It's a widespread phenomenon, occurring on (49 million acres) across the developing world …"
Officials said wastewater is most commonly used to produce vegetables and cereals, especially rice, raising concerns about consuming uncooked vegetables. But, the survey notes, wastewater agriculture contributes importantly to urban food supplies and helps provide a livelihood for the urban poor.
"The negative and positive implications of wastewater agriculture have only recently received attention," said Colin Chartres, IWMI's director general. "This study offers the first comprehensive, cross-country analysis of the conditions that account for the practice and the difficult tradeoffs that arise from it."
Raschid-Sally's report is available at http://www.iwmi.cgiar.org/SWW2008/PDF/CA_53_city_Final_August_2008_V5.pdf.