Abstract

Health Risks of Irrigation with Untreated Urban Wastewater in the Southern Punjab, Pakistan

by Sabiena Feenstra, Raheela Hussain & Wim van der Hoek

The use of wastewater for irrigation is a positive way to dispose of urban sewage water. This water contains a lot of nutrients and can serve as alternative water source in arid and semi-arid areas. However, wastewater contains a wide spectrum of pathogens and sometimes heavy metals and organic compounds that are hazardous to the environment and human health. Therefore, the World Health Organization advises treatment of wastewater before application to the fields, to protect farmers and crop consumers.

In Pakistan and many other developing countries wastewater is used without any treatment, as treatment plants are expensive and farmers are willing to use this nutrient rich water without treatment. Knowledge about costs and benefits of treatment in developing countries is limited, as is knowledge about the actual environmental and health risks of irrigation with untreated urban wastewater. Therefore, the International Water Management Institute started a study on benefits and costs of irrigation with urban wastewater in Pakistan. The survey described in this report was part of this study and focussed on the health risks of irrigation with urban wastewater due to microbiological contamination.

To estimate the health risks of irrigation with urban wastewater, wastewater samples were analyzed and a cross sectional study was carried out in a farmer community that used untreated wastewater for irrigation near the town of Haroonabad in the Punjab Province. The health status of this community was compared with a farmer community in two peri-urban villages near the same town that used other water sources for irrigation.

The wastewater used around Haroonabad contained far more faecal coliform bacteria and helminth eggs than advised by the WHO. This poses a high health risk to farmers, their families and crop consumers. In the farmer community exposed to wastewater near Haroonabad, the prevalence of diarrheal diseases and hookworm infections was very high. The prevalence of these diseases was especially high among male farm workers. This group was highly exposed to wastewater, as they did a lot of the work in the fields manually and barefoot. In children of these farmers the prevalence of diarrheal diseases and hookworm was also higher than in the control population. For crop consumers the chance to acquire a hookworm infection seemed slightly increased.

Therefore, protective measures are required for farmers, their families and crop consumers. In the tropical climate of Pakistan treatment according to the bacteriological guidelines of the World Health Organization are difficult to realize. However, appropriate treatment of wastewater for helminth eggs and faecal coliform bacteria before application on the fields is highly recommended. If treatment is not feasible according to costs and benefits analysis, other protective measures should be taken. Low cost interventions could include, information on hygiene behavior for farmers, wearing of shoes and gloves while working in wastewater irrigated fields, regular treatment of farmers and their families with antihelmintic drugs and crop restrictions in wastewater irrigated fields.