A study published in the journal Environmental Research Letters estimates that 139,000 square miles of cropland in or near urban areas rely heavily on untreated wastewater for irrigation, says Modern Farmer. That’s far larger than a 2004 assessment that pegged the total at 77,200 square miles.
“Much of that cropland is in countries where only a very small percentage of wastewater is treated,” says Modern Farmer. “Five countries — China, India, Mexico, Pakistan, and Iran — accounted for more than 85 percent of downstream irrigated croplands with a ‘high likelihood’ of untreated reuse, according to the study.”
A consequence of the practice can be transmission of pathogens such as salmonella or E. coli bacteria. The lead author of the study, Anne Thebo, told Phys.org, “As long as investment in wastewater treatment lags far behind population growth, large numbers of consumers eating raw produce will face heightened threats to food safety.” The study said considerable strides have been made in recent years in improving sanitation in urban areas.