Of Salads and Sludge

You may want to hold your nose for this one. A new study reveals where water goes when you flush the loo—basically, in your salad. In a survey of 53 countries, the International Water Management Institute (IWMI) found that the majority of produce cultivated in urban plots is irrigated with water from polluted streams, lakes or wells. While only 10 percent of global agriculture is harvested in cities (and only part of that crop is consumed raw), some 1.1 million farmers produce greens and fruit for 4.5 million people in the areas studied. Project the numbers worldwide, and at least 200 million farmers rely on recycled water to sow 20 million hectares, an area twice the size of Hungary.

At first whiff, this all seems dire. Outbreaks of hepatitis and cholera have been traced to wastewater-contaminated food. But dirty water may provide the only way for many people to have produce at all. Nearly 200,000 residents of Accra, Ghana put food on the table thanks to wastewater irrigation and more than a quarter of Pakistan's domestic veggies are grown by the method, which also helps fertilize farms and reduce water stress.

There may be few alternatives. Where clean water is scarce, diverting it to farms is tantamount to stealing it from cups. The World Health Organization now signs off on wastewater farming in countries with scant fresh water, but presses authorities to work on better waste treatment and to educate families on washing produce. So pass the salad—just scrub it first.

© 2008