The Superior Council of Scientific Investigations (CSIC) has investigated the importance of irrigation water in pollutant concentrations which are detected in four vegetables: tomatoes, cauliflowers, lettuce and beans. The organization has analyzed its composition in several plots of the metropolitan area of Barcelona, two of them irrigated by the water of the Llobregat river and near the airport and several highways, and another located in the Garraf natural park that receives well water from springs .
Surprisingly, the results indicate that there are no significant differences between the irrigation source (the most polluted and the most natural), but it does depend on the vegetable in question. "Tomatoes are those that have higher concentrations of both heavy metals and organic pollutantss ". That the tomato is the one that worse stopped "It is because it is a summer crop when there is more irrigation, and, therefore, the plant ends up absorbing more water", explains Josep María Bayona, co-director of the project and researcher at the CSIC.
The reason that the contaminants in irrigation water do not reach the plants is due to the fact that it must cross numerous barriers: soil, roots and metabolism with microorganisms that degrade organic substances. But some just arrived. Among the compounds detected in vegetables are carbamezapine (anticonvulsant drug to treat eplilepsia), bisphenol A (a plasticizer present in irrigation tubes), lead or agricultural fungicides such as dimetomorf. The lead is dragged of yesteryear, "is a historical remnant that was used as an additive to gasoline, does not degrade and appears as a background pollution in areas close to roads." Bayona wants to make clear that the average levels of pollutants are low and do not pose any risk to health.
"Basically, the objective was to determine if there was an impact of the pollution of the city on crops from peripheral areas to large cities, how water could affect crops and air pollution," explains Bayona. The analysis was carried out on 33 organic substances (pesticides, surfactants, drugs, flame retardants and other products of industrial origin that reach the waters). In addition, 16 heavy metals have been controlled, which are naturally found in the soil at very low levels, such as cadmium or arsenic, but the industry has raised its concentrations.
In the studied area that irrigates the Llobregat there is agriculture since the beginning of the last century and although it has varied it maintains the traditional guidelines. In it, soil microorganisms are adapted to the type of water they receive, facilitating the degradation of contaminants. "Another issue is where you start from scratch, because the bacterial flora of the soil is not used and is not as efficient," warns Bayona.
Scientists recommend continuing research to identify the accumulation of dangerous elements and include them in the control of food as is already done with phytosanitary products. They also point out that more studies are needed to evaluate the health risk due to the presence of microorganisms (viruses and bacteria resistant to antibiotics), which have already been detected in sewage effluents.