Heavy Metals in P Fertilizers Marketed in Brazil: Is This a Concern in Our Agroecosystems?

Abstract

Fertilizers are key for sustainable use of land and for intensification of crop production, especially in tropical agroecosystems, which have soil fertility constraints that hamper agricultural production on weathered soils. Heavy metals (HM) occur in fertilizers in low concentrations, as contaminants. Yet, some HM are plant nutrients and are intentionally included in fertilizer formulations. Exposure to high levels of HM (nutrient or not) could pose a health risk to humans. This risk may be estimated by collecting data on HM content in soils and plants (e.g., edible parts) in the field, as well as thru modeling. This work presents information concerning HM contents - with a focus on cadmium - in Brazilian fertilizers and agroecosystems - including agricultural products -, aiming to contribute to a better definition of safe limits of HM in phosphate fertilizers, soils, and food. These limits are key not only for food safety purposes, but also for assuring fair trade. In addition, we demonstrate the usefulness of a tool - the software EtraceProDB -, for easy calculation of risk-based concentrations (RBC) of HM in inorganic fertilizers post application, which suggest safe limits for agricultural use. The purpose of this software is to calculate values of HM concentrations in inorganic fertilizers that may, flexibly, be used by regulators to protect human and soil health. The results obtained indicate that HM do not cause harm to human health when considering post application of phosphate fertilizers in Brazil. Also, a survey of HM contents in Brazilian food and food products evidenced the safety of agricultural crops with respect to their contents of As, Cd, and Pb. Our findings concerning RBC and analyses of HM in mixed fertilizers, as well as current information published in Brazil suggest that HM contents - Cd inclusive - in major agroecosystems as well as the HM limits currently established for P fertilizers by the Brazilian legislation are safe in terms of health risk assessment. Considering the great importance of Brazil as a global food provider, such results are relevant to show that fertilizer use in Brazilian agriculture is done in such a way as to guarantee the production of healthy crops as well as adequate food quality criteria.