et al.2006b). This is perhaps not surprising as data for other environmental
processes (e.g. sorption to soil) indicate that the behaviour of veterinary medicines
in the environment is poorly related to hydrophobicity but is determined by a range
of factors including H-bonding potential, cation exchange, cation bridging at clay
surfaces and complexation. Through controlled experimental studies it may be
possible in the future to begin to understand those factors and processes affecting
the uptake of veterinary medicines into plants and to develop modelling approaches
for predicting uptake.
4 Occurrence
Alongside the fate experiments described above, a series of studies have monitored
concentrations of veterinary compounds in different matrices. Veterinary medi-
cines have been measured in surface waters, groundwaters, sediments, slurry/
manure and biota. Monitoring studies have focused on veterinary products used
in sheep dips, aquaculture and as antibiotic treatments for livestock.
4.1 Aquaculture
A number of studies have explored the occurrence of veterinary medicines arising
from aquaculture treatment. For example, emamectin benzoate has been detected in
sediment, water, silt, mussels, dogfish and crab species. Oxolinic acid has been
detected in sediments surrounding wild fish populations and other marine animals
during and after the medication of cultivated fish (Bjo ̈rklund et al. 1991 ; Samuelsen
et al.1992b). Flumequine has been detected in fish tissue (Ervik et al. 1994 ).
Residues of ivermectin have been detected in sediments under and adjacent to
salmon cages (Cannavan et al. 2000 ). Finally, the environmental fate of oxytetra-
cycline following its use in aquaculture has been extensively researched (Jacobsen
and Berglind 1988 ; Bjo ̈rklund et al. 1990 , 1991 ; Samuelsen et al.1992a; Coyne
et al. 1994 ; Capone et al. 1996 ; Kerry et al. 1996 ) with the compound being
detected in wild fauna and sediments around fish farms. In selected studies (e.g.
Samuelsen et al.1992a), the environmental impacts of the treatment have been
investigated alongside the monitoring studies. Data from these studies indicate that
the use of antimicrobial compounds in aquaculture is associated with the occur-
rence of antibiotic resistant bacteria in environmental matrices.
4.2 Livestock Treatments
Several veterinary drugs have been detected in soil that has been treated with
animal manure. In three separate investigations in Germany, soil samples collected
300 A.B.A. Boxall