I learned recently that approximately 40% of the world’s food is cultivated in irrigated areas and that 10% of the world’s population consumes food irrigated with wastewater.
This realization made me wonder: how safe is it to irrigate crops with wastewater? And, after a bit of research, it appears that there are conflicting reports. After treatment, wastewater still contains an array of personal care products and medications like anti-seizure medications and antibiotics. What are the potential effects of these substances on soil, plants, and humans?
In a 2013 report, Jan Gan from the University of California-Riverside and a team of researchers studied 20 different pharmaceutical and personal care compounds to determine if they accumulated in vegetables irrigated with wastewater. While all of the crops absorbed some of the compounds, leafy vegetables took on the highest levels. But overall, the study concluded that the absorption levels were “reassuringly low.”
“These substances do not tend to accumulate in vegetables, including tomatoes and lettuce that people often eat raw,” claims Gan. The study endorsed wastewater’s reuse for irrigation purposes.
However, Alison Franklin and a team of researchers at the Pennsylvania State University recently published a 2016 study in which they evaluated compound trails from effluent to wheat plants irrigated by treated wastewater. The study once again revealed that the compounds were absorbed by plants, though none in toxic levels. The team’s research found that plants’ outer surfaces stored the majority of the compounds. Insignificant amounts were found in the edible portion, i.e., grain.
As reassuring as this may be, it makes one wonder about the cumulative effect it could have on livestock that consume large amounts of these wastewater-borne contaminants in their feed. Could it put our food supply at risk or accelerate the development of antibiotic-resistant bacteria?
This debate comes within weeks of EPA’s discovery of a superbug, carbapenem- resistant enterobacteriaceae or CRE, in Los Angeles Sewers. CRE is believed to travel into sewage facilities via hospital effluent. As sewage mixes, the antibiotics from hospital effluent kill off weaker bacteria, leaving the more lethal ones to thrive and reproduce. Sewage plants have no way of eliminating the superbug from treatment water since it is chlorine resistant. And according to the LA Times, exposure to the bacteria is lethal for half of its victims.
What happens when it’s sprayed on our fields?
With increasing water scarcity worldwide, it seems that this issue deserves further research and discussion. As consumers, policy makers, and citizens of the world, it’s imperative that we understand the cumulative effects of irrigating with wastewater and carefully manage the risks prior to adopting the practice for agricultural purposes.
What are your thoughts?
