livestock breeding, no antibiotics were present above the limit of detection (0.02–
0.05mgl–1). Sulfonamide residues were, however, detected in four samples. Whilst
the source of contamination of two of these is considered to be attributable to
irrigation with sewage, the authors concluded that sulfamethazine, detected at
concentrations of 0.08 and 0.16mgl–1, could possibly have derived from veterinary
applications, as it is not used in human medicine.
In the investigations of Hamscher et al. (2000a) soil water was collected and
analysed from four separate areas of agricultural land, two belonging to livestock
farms and treated with animal slurry and two where no animal manure had been
applied for approximately 5 years. Chlortetracycline, oxtetracycline, tetracycline
and tylosin were all found at the limit of detection (0.1–0.3mgl–1) in water samples
collected at 80 and 120 cm depth, independent of soil treatment. In addition, no
biologically active residues could be detected with microbiological assays that had
approximately fivefold higher detection limits.
Veterinary medicines are also known to leach from landfill sites. In Denmark,
high concentrations (parts per million) of numerous sulfonamides were found in
leachates close to a landfill site where a pharmaceutical manufacturer had previ-
ously disposed of large amounts of these drugs over a 45-year period (Holm et al.
1995 ). Concentrations dropped off significantly tens of metres down gradient, most
probably due to microbial attenuation. Although this is recognised as a specific
problem, in the UK the disposal of smaller quantities of veterinary medicines to
landfill should nevertheless be considered a potential route for environmental
contamination.
5 Impacts of Veterinary Drugs in the Environment
5.1 Effects in Regulatory Studies
Guidelines are available describing how the environmental risks of veterinary
products should be assessed for a range of countries (Breton and Boxall 2003 ;de
Knecht et al. 2009 ). The approach used in Europe is based on the recommendations
of the International Co-operation on Harmonisation of Technical Requirements for
Registration of Veterinary Products (VICH) who have attempted to harmonise the
environmental risk assessment requirements of veterinary products in the USA,
Europe and Japan. The approach is a two-phase process (CVMP 2007 ). In Phase 1,
the potential for the environment to be exposed to the veterinary product is
determined. For compounds that do not pass the Phase 1 triggers, information is
required on the effects of environmental medicines on terrestrial and aquatic
organisms. Recommended aquatic studies include acute toxicity studies on daphnia
and fish with mortality as the test endpoint and short-term studies into the effects of
the compound on the growth of green or blue-green algae. Terrestrial tests are done
on earthworms (mortality) and plants (germination and growth), the effects of the
302 A.B.A. Boxall