VETERINARY MEDICINES AND THE ENVIRONMENT

The development over the past 40 years of diverse new and modern veterinary medicines has enabled the veterinary profession to safeguard the health and welfare of livestock and companion and wild animals. These medicines also play an important role in the agricultural economy, sustainability, and production of more affordable, good-quality food for the consumer. In addition, veterinary medicines and the protection of public health are mutually dependent. During their use, however, veterinary medicines and their metabolites can be released to the environment either directly, when used as aqua-culture or pasture animal treatments, or indirectly, during the application of manure and slurry to land as a fertilizer. Like other substances, such as human medicines and plant protection products, animal health products undergo years of research and numerous trials to ensure their quality, safety, and efficacy. Before an animal health product is allowed to enter the market, it must be registered via a lengthy and complex process. In many regions, such as the United States, Europe, and Canada, an environmental assessment is now a key component of that process [1]. In the United States, environmental assessments have been required since the 1980s; in the European Union, assessments have been required from the 1990s. Over the years, a number of assessment guidelines have been developed [2], and the data from the assessments are becoming increasingly available to the scientific community. In the United States, for example, most assessments can be downloaded from the U.S. Food and Drug Administration Web site (www.fda.gov/cvm/efoi/ea/ea.htm). At the international scale, the Veterinary International Cooperation on Harmonisation in Brussels, Belgium, is currently working to harmonize the approaches for environmental risk assessment. They propose a two-phase approach. In Phase 1, the likelihood for environmental exposure is assessed [3], and for those substances moving on to Phase 2, the risks of a substance are determined by environmental fate (e.g., sorption and persistence in soils) and effects data (e.g., toxicity to fish, daphnids, algae, plants, microbes, and earthworms). Guidelines are already available for Phase 1, and Phase 2 guidelines should be finalized by the end of this year. Further details can be found at www.vich.eudra.org/htm/guidelines.htm. A number of recent monitoring studies have detected veterinary medicines in manure, soils, surface waters, and sediments [4]; generally, these data support the results of regulatory assessments that indicate exposure concentrations are well below effect concentrations from standard ecotoxicity studies. However, veterinary products contain biologically active substances that standard tests might not detect after long-term, low-level exposure. For example, sublethal effects have been reported on a range of organisms, including invertebrates and microbes at concentrations much lower than standard acute test concentrations. Certain substances can cause indirect effects on predatory species [5-8]. Studies have highlighted the potential effects of metabolites and degradation products, the effects of mixtures of substances, and the potential for environmental exposure contributing to the development of antibacterial-resistant microbes. Finally, researchers are questioning the suitability of many of the tools used to assess exposure. Veterinary medicines are often large, polar, multifunctional molecules that usually pass through an animal before being excreted and typically are released into the environment in feces. The factors affecting behavior in the environment could therefore be very different from those for other substances, such as pesticides and industrial compounds. For example, the sorption behavior of many veterinary medicines is different from that of neutral organic substances [e.g., 9]. Although a wealth of data are now available in the public domain on the behavior and effects of veterinary medicines in the environment, and the science continues to advance, much remains to be done. Numerous researchers across the world are studying the interactions of veterinary medicines with the environment, and it is timely to draw together the results of much of this work. Thus, in this issue of Environmental Toxicology and Chemistry, we have brought together a number of papers from Australia, North America, and Europe describing the behavior of veterinary medicines in the environment, their effect on aquatic and terrestrial organisms, and possible approaches for better assessing their environmental impacts in the future. We hope that this edition will encourage readers to apply their knowledge to understanding and contributing to the ongoing debate over the effects of veterinary medicines on the environment and to the development of regulatory guidelines that are based on sound science. These regulations are critical to establishing and maintaining consumer confidence in the safety, quality, and efficacy of products used in the animal health industry. We thank Dana Kolpin (U.S. Geological Survey), Jose Tarazona (INIA, Spain), and Hans Hoogland (Agency for Registration of Veterinary Medicinal Products, The Netherlands) for their help in bringing together the papers contained in this issue. We are also grateful to Susanne Zanker (IFAH) for her input to this editorial.

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