Risk assessment of irrigation water used for cultivation of vegetables, fruits and berries
Report no: 2014: 23
On request from the Norwegian Food Safety Authority (NFSA), the Norwegian Scientific Committee for Food Safety (VKM), has assessed the risk of infection from irrigation water used for cultivation of vegetables, fruits and berries. The assessment will be used for development of NFSA’s monitoring program.
Bacteria, viruses, parasites and unwanted chemical substances can cause illness if contaminated water is used for cultivation of vegetables, fruits and berries.
Low risk of infection
VKM concludes that the risk of infection, transmited from irrigation water used for cultivation of vegetables, fruits and berries, is low in Norway, because the environmental contamination is generally low in Norway.
Bacteria, virus or parasites with low infectious dose represent the highest risk of infection in humans. Infectious dose is the number of organisms needed to cause disease. Microorganisms with low infectious dose are for example enterohemorrhagic E. coli (EHEC), Campylobacter, norovirus and several parasites.
Surface water represents the highest risk of infection, especially when a spreader is used. In drip watering systems, the water is not in contact with the edible parts of vegetables, fruits and berries above ground, because the water drips from a hose on the ground directly to the roots.
VKM presumes that choice of watering method will reduce possible contamination. A quarantine period after the last watering would reduce the amount of microorganisms on vegetables, fruits and berries.
Heavy metals, environmental contaminants and plant protection products
VKM concludes that consuming vegetables, fruits and berries watered with surface water does not represent a health risk regarding heavy metals, persistent organic environmental contaminants or plant protection products.
Risk based water testing.
VKM implies that risk based water monitoring and testing should be employed. It is recommended that water tests are taken at the time the watering takes place. Tests should be done more often annually for surface water to prevent the use of contaminated water.
VKM suggests that E. coli is used as an indicator of fresh water contamination. To assess older contamination in irrigation water, VKM suggests using enterococcae as indicator.
The risk assessment method
VKM have reviewed and evaluated reports from national and international scientific organs.
The Panel on Biological Hazards is responsible for this risk assessment. The document was completed by a group consisting of members of the Panel on Biological Hazards and the Panel on Contaminants.