Health risks of wastewater irrigation in Pakistan

Two thirds of all untreated wastewater in Faisalabad City, Pakistan, is used for irrigation. What benefits and hazards does this bring? Research by the International Water Management Institute shows that farmers using wastewater and their neighbours have an increased risk of Giardia infection from intestinal parasites.

Agricultural use of untreatedurban wastewater leads to an increased risk of intestinal worms, bacterial andviral infections in farm workers, their families and people who eat the cropsuncooked. Are they also at risk of infection with Giardiaduodenalis, which can cause diarrhoea?

The researchers tested 1,704people from three villages within a wastewater irrigated area and one villageoutside the area (control group) for giardia. Theyfound that:

• More than twothirds are infected with giardia. But only 3.7percent had diarrhoea in the previous week, so most infections aresymptom-free.
• Wastewaterfarming households and nearby textile labourer’s homes are more likely to beinfected than households outside the area.
• Greater risk ofinfection with Giardia is linked to the use of publicdefecation sites, no indoor toilet and poor house construction.
• Risks are lowerfor households with a motor water pump.

The wastewater villages,selected for the study, are completely surrounded by irrigated fields, sotextile labourers are exposed to contaminated soil, crops or water on the wayto work and during social activities, such as sport.

Wastewater treatment to WorldHealth Organization recommended quality levels would reduce the health risks ofirrigation. But farmers prefer the untreated wastewater because of itsreliability and high nutrient value, even if better quality water is available.Regular drug treatment can help to keep down hookworm infection. But theresearchers do not recommend regular treatment of at-risk groups with anti-giardia drugs as they would become re-infected very quicklyin this environment. A more effective approach is to extend the municipal watersupply and sewerage system to villages at risk to increase the availability ofdomestic water and improve hygiene and sanitation.