Assessment of Health Risks Associated with the Accumulation of Heavy Metals in Lettuce and Tomatoes Grown in the Vegetable Farming Area of the Bobo-Dioulasso Industrial Zone, Burkina Faso

Abstract

Food security and human health are increasingly threatened by soil contamination by heavy metals, particularly for vegetable crops. The main objective of this study was to assess the health risks associated with the accumulation of heavy metals in lettuce and tomatoes grown in the vegetable farming area of the industrial zone of Bobo-Dioulasso, Burkina Faso. A sampling of lettuce and tomatoes was conducted on the farming site. This was based on a reasoned and adaptive approach, taking into account the operational constraints of the field and the actual distribution of crops. Leaves were collected for lettuce, while ripe fruits were collected for tomatoes. In total, 39 plant samples were taken, consisting of 28 lettuce samples and 11 tomato samples. The results showed that regardless of the vegetable sample, the levels of As and Cd were higher than the standard (FAO). The concentrations in the vegetables ranged from 0.1 to 2.11 mg/kg. The trend in average heavy metal content in the vegetables is Zn > Ni > Cu > Pb > Cr > Cd > As. The pollution indices for As, Cd, and Pb were all significantly above 1 in the vegetables. The metal pollution index (MPI) for lettuce was 8.27, higher than that for tomatoes (6.48). Regardless of the vegetable, the results revealed that the health risk index for As, Cd, Ni, and Pb was above 1. For both heavy metals and vegetables, the health risk index for children was always higher than that for adults. The recorded hazard indices for both adults and children, whether for lettuce or tomatoes, were above 1. Therefore, there are indeed health risks associated with the consumption of these two vegetables produced in the vegetable farming area of the industrial zone of Bobo-Dioulasso, Burkina Faso. Appropriate measures must be taken to prevent contamination throughout the entire food chain.