Health risks of irrigation with untreated urban wastewater in the southern Punjab, Pakistan

SUMMARY The use of wastewater for irrigation is a positiveway to dispose of urban sewage water. This watercontains a lot of nutrients and can serve asalternative water source in arid and semi-aridareas. However, wastewater contains a widespectrum of pathogens and sometimes heavymetals and organic compounds that arehazardous to the environment and human health.Therefore, the World Health Organization advisestreatment of wastewater before application to thefields, to protect farmers and crop consumers. InPakistan and many other developing countrieswastewater is used without any treatment, astreatment plants are expensive and farmers arewilling to use this nutrient rich water withouttreatment. Knowledge about costs and benefits oftreatment in developing countries is limited, as isknowledge about the actual environmental andhealth risks of irrigation with untreated urbanwastewater. Therefore, the International WaterManagement Institute started a study on benefitsand costs of irrigation with urban wastewater inPakistan. The survey described in this report waspart of this study and focussed on the health risksof irrigation with urban wastewater due tomicrobiological contamination.To estimate the health risks of irrigation withurban wastewater, wastewater samples wereanalyzed and a cross sectional study was carriedout in a farmer community that used untreatedwastewater for irrigation near the town ofHaroonabad in the Punjab Province. The healthstatus of this community was compared with afarmer community in two peri-urban villages nearthe same town that used other water sources forirrigation.The wastewater used around Haroonabadcontained far more faecal coliform bacteria andhelminth eggs than advised by the WHO. Thisposes a high health risk to farmers, their familiesand crop consumers. In the farmer communityexposed to wastewater near Haroonabad, theprevalence of diarrheal diseases and hookworminfections was very high. The prevalence of thesediseases was especially high among male farmworkers. This group was highly exposed towastewater, as they did a lot of the work in thefields manually and barefoot. In children of thesefarmers the prevalence of diarrheal diseases andhookworm was also higher than in the controlpopulation. For crop consumers the chance toacquire a hookworm infection seemed slightlyincreased.Therefore, protective measures are required forfarmers, their families and crop consumers. In thetropical climate of Pakistan treatment according tothe bacteriological guidelines of the World HealthOrganization are difficult to realize. However,appropriate treatment of wastewater for helmintheggs and faecal coliform bacteria beforeapplication on the fields is highly recommended.If treatment is not feasible according to costs andbenefits analysis, other protective measuresshould be taken. Low cost interventions couldinclude, information on hygiene behavior forfarmers, wearing of shoes and gloves whileworking in wastewater irrigated fields, regulartreatment of farmers and their families withantihelmintic drugs and crop restrictions inwastewater irrigated fields.