Government Advisors Issue Warning on Reclaimed Irrigation Water

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In Germany, fresh produce intended to be eaten raw that grows close to the ground, such as lettuce, carrots, strawberries or fresh herbs, should not be irrigated with reclaimed wastewater.

The German Federal Institute for Risk Assessment (BfR) advises against this, particularly with regard to pathogenic viruses and parasites that can get onto or into the plants via this route. Current data are still insufficient for a conclusive risk assessment, however, there is evidence that certain viruses and single-celled parasites (protozoa) can defy environmental influences and cause diseases via raw fruit and vegetables.

"Reclaimed wastewater in agriculture poses a new challenge to food safety," said BfR President Andreas Hensel. "In order to reduce pathogens as much as possible, we need very good treatment and detection methods."

Climate change, unpredictable weather patterns and droughts are depleting water resources in Germany and Europe. To counteract this, Regulation (EU) 2020/741 sets minimum requirements for the use of reclaimed wastewater for agricultural irrigation. The EU regulation for water reuse applies from June 26, 2023, and is intended to protect the environment and human and animal health. The BfR has assessed possible health risks from the use of reclaimed wastewater for the irrigation of plant-based foodstuffs with regard to selected pathogenic viruses and protozoa. Particular attention was paid to fruit and vegetables that can be eaten raw, in which any pathogens that may be present are not reduced or killed by heating.

On the basis of available data, the BfR recommends not using reclaimed wastewater to irrigate plants, whose parts intended for raw consumption are growing close to or in the ground. This applies until suitable treatment processes and controls can ensure that the irrigation water does not contain pathogens, especially human-pathogenic viruses or protozoa. Pathogens can get onto or into the edible parts of the plants via all of the irrigation systems considered (subsurface drip irrigation, drip irrigation, furrow irrigation, sprinkler system, hydroponic culture) and cause illness in humans when consumed raw. Depending on the type of pathogen and the state of health of the person affected, the health impairment may vary; severe illnesses are possible in risk groups.

Further research is required with regard to the suitability of methods for inactivating or reducing pathogens during wastewater treatment.

In the opinion of the BfR, plants whose raw edible fraction grows far from the soil, for example vineyards and fruit trees, can be irrigated with reclaimed wastewater of quality class A or B, provided that direct contact of the raw edible fraction with the reclaimed wastewater (by selecting a suitable irrigation system) and the irrigated soil is excluded. Since the viruses and protozoa under consideration are heat-sensitive, no adverse health effects due to pathogens in the reclaimed wastewater are to be expected for plant foods that are sufficiently heated before consumption.

    Human pathogenic bacteria in reclaimed wastewater used for irrigation can also increase the risk of illness from fruit and vegetables consumed raw. This was already shown in a joint assessment by the BfR, the Julius Kühn Institute (JKI) and the Max Rubner Institute (MRI), published in 2020.

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