ENVIRONMENTAL ASSESSMENT OF AVERMECTINS BY THE UNITED-STATES-FOOD-AND-DRUG-ADMINISTRATION

The Center of Veterinary Medicine (CVM) of the Food and Drug Administr ation (FDA) is required under the National Environmental Policy Act (N EPA) to include in its decision making, an objective consideration of the potential environmental impacts associated with each contemplated action. As part of the application process for new animal drugs, detai led data must be submitted in order to develop a prediction of the env ironmental fate and effects of the drug and/or its active metabolites. Ivermectin (22,23-dihydroavermectin B] ) is a highly active antiparas itic animal drug utilized in a variety of injectable, oral and topical formulations. Residues of this drug may reach the environment through manufacturing and animal wastes and may potentially have effects on t errestrial and aquatic organisms. A comprehensive data base has been s ubmitted to the FDA in support of the environmental assessments for iv ermectin drug products. Detailed information has been submitted on the physical and chemical properties, introduction, fate and effects of t he ivermectins in the environment. These data indicate that ivermectin binds tightly to soil and is subject to photodegradation and biotrans formation to less active compounds. In contrast, ivermectin is highly toxic to certain aquatic organisms but would not be expected to partit ion into the aquatic environment. Much lower toxicity has been demonst rated toward bacteria, fungi, earthworms, plants and birds. CVM evalua ted ivermectin products based on the use pattern of the product, the m etabolism pattern in target animals, calculations of potential ivermec tin residue concentrations in the environment and data on persistence, soil sorption and acute toxicity in aquatic and terrestrial environme nts.