Soil-plant transfer of heavy metals and assessment of risk to human health in crops in the state of São Paulo

Abstract

Concern about the presence and accumulation of heavy metals in soil and consequently in plants has been constant, due to the adverse effects they may cause to the environment and human health. One of the main routes of exposure to heavy metals in the majority of the population is through ingestion of food and there are few studies related to the concentrations of heavy metals in soils and plants of the humid tropics, especially in Brazil. The index most commonly used to estimate the accumulation of heavy metals in plants and the subsequent human exposure through consumption of vegetables is the bioconcentration factor (BCF), which is the ratio between the concentration of metals in edible parts of vegetables and the total concentration of metal in the soil. However, this index does not adequately describe the soil-plant transfer of metals. Thus, the use of relationships involving the main characteristics of the soils on which the availability to plants of heavy metals may explain the relationship between ground and plant. The state of São Paulo is the largest consumer market, besides being the largest and most diversified vegetable crop producers in Brazil. Thus, research is needed regarding the concentrations of heavy metals in soils and vegetables, for evaluation of their quality in relation to the limits established by law. Likewise, it is important to establish the critical limits of these elements in soils, using models of risk assessment to human health, based on results that represent the real condition of the soil of São Paulo. Our objectives are to evaluate: (i) characterize the soils and vegetables grown in areas olerículas the State of São Paulo and calculate the risk to human health by the consumption of such vegetables from these areas, (ii) evaluate soil-transfer dealings these metals plant, taking into account the physical, chemical and mineralogical soil, (iii) From the relations obtained empirically calculate the critical concentration of Cd, Cu, Ni, Pb and Zn, using models of risk assessment.