2023-10-20 20:15:57
Lettuces are recommended for a healthy diet and if they are from kilometer 0 better for the environment, but are they safe coming from the city? And can they be used for something else?
Answering these questions is what the Prospecting and Environment (PROMEDIAM) research group from the Polytechnic University of Madrid (UPM) in Spain, together with other researchers from the University of Copenhagen in Denmark, wanted to do.
To do this, they have carried out a joint study in which lettuces were exposed to different degrees of atmospheric pollution in different places in the city of Copenhagen. According to the results obtained, the evaluation of the health risk derived from the consumption of lettuce grown in an urban environment indicates safe levels (as long as clean soil is used during planting and the lettuce is washed properly before consumption). Furthermore, lettuce grown in the areas most affected by gas emissions and particulate matter had higher concentrations of pollutants, so these can serve as a complementary system to the network of fixed air quality control stations.
In a previous study, the research team demonstrated the feasibility of using rapeseed and kale to biomonitor air quality. In this new research, some of the outstanding uncertainties have been addressed, although on this occasion using lettuce as potential bioindicators. This work arises from the need to respond to two of the challenges that humanity currently faces: global food shortages and air pollution in cities (the WHO estimates that 99% of the population is exposed to at contamination levels higher than recommended).
In this research, four objectives were set: evaluate the use of lettuce for the measurement of suspended particles, verify the reduction in the concentration of contaminants in the leaves after washing, estimate the bioavailability of the heavy metals and metalloids analyzed and determine if Lettuces grown in urban areas on clean substrate are safe to eat.
To do this, several lettuce seedlings were placed in different parts of the urban center of Copenhagen (next to a main avenue and in a park) and in the peri-urban area (in an orchard surrounded by a forest, in the garden of a house and next to a highway), as well as a climate chamber to establish reference levels. After an exposure period of one and a half months, each lettuce was divided into two halves, one of which was washed with distilled water. To determine the concentration of contaminants, two methods were used, a total extraction and a bioaccessible one (which simulates the fraction soluble in the gastrointestinal tract and available for absorption), analyzing 24 elements.
Exhibition point next to a highway in the peri-urban area. (Photo: UPM)
The results showed that there was a relationship between the concentration of accumulated elements and the exposure environment, observing an enrichment of anthropogenic contaminants in the samples located in the center of the city and near transportation routes, as well as an increase in substances typical of the marine spray at all points as it is a coastal city. Therefore, lettuces could be used as an affordable complementary system to conventional air quality monitoring networks for the measurement of suspended particles and inorganic pollutants.
Secondly, washing the samples managed to reduce the concentration of some elements associated with traffic and other industrial activities by up to 20 times, indicating that these are mainly attached to particles deposited on the surface of the leaves and have not been transferred to the fabric. vegetable. Consequently, a measure as simple as washing products grown in urban gardens before consumption can greatly limit the intake of toxic substances.
Thirdly, as the PROMEDIAM research group at the UPM had previously confirmed, the bioaccessible fraction of metals and metalloids was significantly lower than the total content. For this reason, environmental consultants and public administration should consider this parameter during the characterization of a site and the corresponding evaluation of risks to human health in order not to overestimate the value of the risk and, in this way, not undertake mitigation actions. unnecessary decontamination or, if carried out, with lower economic cost and lower environmental impact.
Finally, it was verified that the concentrations of lettuce grown on a clean substrate did not exceed the legal limits established by the European Commission for this type of food and, in addition, an estimate of the daily intake of contaminants due to its consumption did not exceed the maximum tolerable intake levels recommended by the main health agencies (EFSA and NAM). Despite this, as Miguel Izquierdo, one of the UPM researchers participating in the study, points out, “to extend these results and guarantee the suitability of foods grown in urban areas that contribute to fighting the global food crisis, it is “It should examine the contribution of other agricultural products and in cities with worse air quality indices.”
The study is titled “Assessment of lettuces grown in urban areas for human consumption and as bioindicators of atmospheric pollution.” And it has been published in the academic journal Ecotoxicology and Environmental Safety. (Source: UPM)
#Urban #gardens #air #quality #cities