The Spanish Higher Council for Scientific Research (CSIC) has investigated the role of irrigation water in the presence of pollutants detected in four vegetables: tomatoes, cauliflowers, lettuce and beans. The organization has analyzed their composition in several plots of the metropolitan area of Barcelona, two of them irrigated by water of the Llobregat river, near the airport and several highways, and another located in the Garraf nature reserve, which receives well water from springs.
Surprisingly, the results indicate that there are no significant differences between the most and the least polluted irrigation sources, but the pollution levels do change depending on the vegetable in question. "Tomatoes have higher concentrations of both heavy metals and organic pollutants." That tomato are the worst off "is due to the fact that it is a summer crop which needs more irrigation, and, therefore, the plant ends up absorbing more water," explains Josep María Bayona, co-director of the project and researcher of the CSIC.
The reason that pollutants in irrigation water do not reach the plants is due to them having to cross numerous barriers: soil, roots and a metabolism with microorganisms that degrade organic substances. But some still make it through. Some of the compounds detected in vegetables are carbamezapine (anticonvulsant drug used to treat epilepsy), bisphenol A (a plasticizer present in irrigation tubes), lead or agricultural fungicides, such as dimethomorph. The lead detected in the soil has been present for a very long time. "This is due to the faact that it used to be used as an additive to gasoline and does not degrade, so it is still detected as background pollution in areas close to roads." In any case, Bayona wished to stress that the average levels of pollutants are low and that they do not pose any risk to the health of consumers.
"Basically, the objective was to determine if city pollution could have an impact on crops grown in areas next to large cities, finding out how water and air pollution could affect them," explains Bayona. The analysis carried out focused on 33 organic substances (pesticides, surfactants, drugs, flame retardants and other products of industrial origin that end up in the waters). There were also checks on 16 heavy metals, such as cadmium or arsenic, which are naturally found in the soil at very low levels, but whose concentrations have been raised by the industry.
In the area under study, which is irrigated by the Llobregat river, there is agriculture since the beginning of the last century. The microorganisms in the soil have adapted to the type of water they receive, facilitating the degradation of contaminants. "Starting from scratch is a different kettle of fish, because then 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 to take them into account in food controls, as is already done with phytosanitary products. They also point out that more studies are needed to evaluate the health risk of the presence of microorganisms (viruses and bacteria resistant to antibiotics), which have already been detected in sewage effluents.
Source: elpais.com