Việc phát hành thuốc thú y thủy sản vào môi trường có thể xảy ra thông qua con đường trực tiếp hoặc gián tiếp. Một ví dụ về phát hành trực tiếp là việc sử dụng thuốc trong nuôi trồng thủy sản (Armstrong và cộng sự năm 2005; Davies và cộng sự năm 1998.), Nơi các hoá chất được sử dụng để điều trị cá được bổ sung trực tiếp vào nước. Phát hành gián tiếp, trong đó thuốc thực hiện theo cách của họ để nước thông qua việc vận chuyển từ các ma trận khác, bao gồm các. | 4 Exposure Assessment of Veterinary Medicines in Aquatic Systems Chris Metcalfe Alistair Boxall Kathrin Fenner Dana Kolpin Mark Servos Eric Silberhorn and Jane Staveley INTRODUCTION The release of veterinary medicines into the aquatic environment may occur through direct or indirect pathways. An example of direct release is the use of medicines in aquaculture Armstrong et al. 2005 Davies et al. 1998 where chemicals used to treat fish are added directly to water. Indirect releases in which medicines make their way to water through transport from other matrices include the application of animal manure to land or direct excretion of residues onto pasture land from which the therapeutic chemicals may be transported into the aquatic environment J0rgensen and Halling-Sprensen 2000 Boxall et al. 2003 2004 . Veterinary medicines used to treat companion animals may also be transported into the aquatic environment through disposal of unused medicines veterinary waste or animal carcasses Daughton and Ternes 1999 Boxall et al. 2004 . The potential for a veterinary medicine to be released to the aquatic environment will be determined by several different criteria including the method of treatment agriculture or aquaculture practices environmental conditions and the properties of the veterinary medicine. During the environmental risk assessment process for veterinary medicines it is generally necessary to assess the potential for aquatic exposure to the product being assessed. For example in the VICH phase I process it is necessary to estimate aquatic exposure concentrations for aquaculture products and during the phase II process it is also necessary to determine exposure concentrations for products used in livestock treatments. Assessment of exposure must take into account the many different pathways and scenarios that influence the transport of veterinary medicines into the aquatic environment. In some cases we have a good understanding of how these exposure scenarios can
