Heavy Metals Accumulation in Lettuce and Cherry Tomatoes Cultivated in Cities

Vegetables cultivated in cities, carry the risk of absorbing pollutants generated by anthropogenic activities, increasing the health risk of those who consume them. Heavy metal concentrations (As, Cd, Cr, Ni and Pb) were analyzed in water, soil and in plant parts of lettuce (roots and leaves) and cherry tomatoes (roots, stem, leaves and tomato fruit) lettuce and cherry tomatoes, cultivated in urban gardens in Mexico City. In none of the studied sites was the heavy metal concentration in the soil above the permitted limits. In irrigation water, Cr surpassed the permitted limit in 5 sites and that of Cd in one site. Ni surpassed the established limit for lettuce and cherry tomato in the rank among 0.7 and 31.15 mg kg-1 in 9 sites, Cr exceeded the allowed limits 1.45-38 mg kg-1 in 11 sites, As go beyond the established limits between 5-52 mg kg-1 in 4 sites and to a lesser extent, Pb was above the allowed limits between 15.5 and 26 mg kg-1. According to the translocation factor, lettuce and cherry tomato could be an important phytoextractors of Cr and Cd respectively. The compound risk value for lettuce (TTHQ) was greater than one in three sites for lettuce and five sites for cherry tomato. Also, in gardens A, D, E and J, the Hazard Index (HI) showed a potential risk (HI>1), which reveals the danger of consuming both vegetables given the conditions of soil, water and air and taking into account all paths of exposure.

Automated summary

Vegetables cultivated in urban gardens in Mexico City were found to have heavy metal concentrations that exceeded the permitted limits for Cr, Cd, Ni, As, and Pb. Lettuce and cherry tomato were found to be potential phytoextractors of Cr and Cd, respectively. The compound risk value for lettuce (TTHQ) exceeded one in three sites and for cherry tomato in five sites. Hazard Index (HI) indicated potential risk in gardens A, D, E, and J, suggesting the danger of consuming these vegetables due to the conditions of soil, water, and air.