Raw waste water use on farms is ‘50% higher’ than estimated.
The global use of untreated waste water from cities to irrigate crops is much more widespread than previously estimated, says a new report.
A significant amount of that land is in countries with very limited waste water treatment, exposing 885 million urban consumers, farmers and food vendors to health risks, according to the authors.
"The area with untreated waste water is around 30 million hectares, a 50% increase on the previous estimate," said Dr Drechsel, who also leads the CGIAR Research Program on water, land and ecosystems.
The authors give the example of Ghana where across the five biggest cities, around 2,000 farmers work close to these urban centres, growing cash crops with waste water as every other water source is polluted.
The farmers often produce crops which are consumed as street food by around 800,000 people.
One of the difficulties is that farmers often prefer the raw, untreated waste water as it usually has a higher concentration of nutrients than other water sources.
In Pakistan, farmers say the treated waste water is safer but too saline for their crops.
This makes it very tricky," added Dr Drechsel.
"This can be through safer irrigation, or greater hygiene at markets and also people can effectively wash the vegetables so you can get rid of most of the pathogens – but in those countries where it is most needed, there is no risk awareness.