The World Health Organization has unveiled new guidelines on treating wastewater for irrigating crops. Experts meeting in Beijing this week said treating wastewater properly is key to saving millions of lives around the world.
Intestinal diseases are among the biggest killers of people in developing nations killing six thousand people every day, says the World Health Organization.
Many people become sick after eating produce grown on fields irrigated with untreated wastewater. Experts say the practice is especially prevalent in parts of Asia, Africa, and Latin America where sanitation is inadequate and where access to clean water is scarce. Around two million people die each year from diarrhea, most of that caused by poor sanitation.
WHO experts say wastewater can be used safely as long as it is treated enough to remove dangerous parasites, bacteria, and toxins while leaving in nutrients.
China is the world's biggest user of raw sewage in farming. Mexico is second.
Blanca Jimenez Cisneros, an environmental researcher at the National Autonomous University of Mexico, told participants at the Beijing meeting it is difficult for farmers in poorer countries to switch from using sewage to using clean water. Scarcity of clean water is one problem in her country, but she says there are other powerful factors at work.
"Farmers living in areas that have wastewater can rent their land three times higher than farmers living in areas using clean water, which is strange," she said. "That is to say that wastewater raises the value of land, because they can produce three times per-year growth and they produce more important volume."
The problem of untreated wastewater use is a challenge to both developing and developed nations. Professor Thor-Axel Stenstroem, a researcher at the Swedish Institute for Infectious Disease Control in Stockholm, spoke of how it can disrupt trade between developing, agriculture-based economies that sell contaminated produce to industrialized nations, which then have to take defensive measures.
"There have been a lot of diseases that have been exported to other countries due to the use of untreated wastewater," he said. "This has caused international trade dilemmas and certain types of restrictions."
World Health Organization officials say raising consciousness about the dangers of using untreated sewage is key to cutting the high death rate from intestinal disease.