PERFORMANCE AND ENVIRONMENTAL IMPACT OF ANTIBIOTICS IN ANIMAL PRODUCTION IN BRAZIL

Antibiotics are used in large quantities in livestock. Many of these molecules are not fully metabolized by the animals, leaving detectable residues in soil, surface water and groundwater samples. The occurrence of these residues in the environment can favor microorganism resistance to antibiotic agents, in addition to toxic effects on certain living organisms. In general, veterinary antibiotic molecules are amphoteric with many ionizable functional groups (different pK(a) values), rather variable molar masses (172 to 916 g mol(-1)) and low volatilization potential (vapor pressure < 1.1 x 10(-11) mm Hg). In comparison to pesticides, these compounds have higher water solubility (S-w) and lower methanol-water partition coefficients (log K-ow), probably due to the presence of many ionizable functional groups, resulting in lower bioaccumulation and higher mobility potential in soils. The purpose of this paper was to evaluate antibiotic uses and importance of livestock in Brazil, to review their environmental fate in temperate climate, and finally to emphasize the need for research on the occurrence and behavior of these molecules in the predominantly highly weathered soils of tropical regions.