from regions with intensive livestock production were analysed for tetracyclines
(Hamscher et al.2000a,2000b,2000c). Concentrations of up to 41.8mgkg–1were
detected in these samples. Elsewhere, American researchers detected trace amounts
(approximately 0.1–2mgkg–1) of ivermectin on the top (0–3 in.) of the soil in a
cattle feedlot, housing animals treated 28 days previously (200mgkg–1 body
weight) (Nessel et al. 1989 ). The authors suggest the concentrations detected in
the soil are probably as a result of the faeces being trampled into the mud and
subsequently being protected from light thus retarding degradation. In a recent
monitoring study in the UK, oxytetracycline, lincomycin, sulfadiazine, trimetho-
prim, ivermectin and enrofloxacin (and its metabolite ciprofloxacin) were moni-
tored in soils (Boxall et al.2006a). Concentrations of the antibacterials detected
ranged from 0.5mgkg–1(trimethoprim) to 305 (oxytetracycline)mgkg–1.
While monitoring sewage treatment work effluents and associated receiving
surface waters for antibiotic substances in Germany, residues of chloramphenicol
were detected at concentrations of 0.06 and 0.56mgl–1(Hirsch et al. 1999 ). As its
use in human medicine is extremely limited, the authors of the paper suggested that
the two positive detections were most likely from its sporadic veterinary use in
fattening farms.
In a national monitoring study in the US (Kolpin et al. 2002 ), a wide range of
medicines were monitored in watercourses. A number of substances that are used as
veterinary medicines, including sulfonamides, fluoroquinolones, tetracyclines and
macrolides were detected in the ng l^1 range. Many of these substances are also
used as human medicines so the concentrations may result from a combination of
inputs from both human and veterinary sources. Similar broad-scale monitoring
studies have been done in other regions (including Europe and Asia) and show
similar results.
The majority of surface monitoring studies involve grab sampling on a number
of occasions across a variety of sites. As inputs of many veterinary medicines are
likely to be intermittent, it is likely that concentrations reported in the studies are
significantly lower than peak concentrations. To address this, a recent UK study
used continuous monitoring of water and sediment, at farms where veterinary
medicines (including oxytetracycline, lincomycin, sulfadiazine, trimethoprim, iver-
mectin and doramectin) were known to be in use, to determine typical exposure
profiles for aquatic systems (Boxall et al.2006a). Maximum concentrations of
antibacterials in stream water ranged from 0.02mgl–1(trimethoprim) to 21.1
(lincomycin)mgl–1; the parasiticides (doramectin and ivermectin) were not
detected. Concentrations of antibacterials in sediment were 0.5–813mgkg–1and
those for doramectin and ivermectin were 2.7 and 4.9mgkg–1respectively. Gener-
ally, these concentrations are significantly lower than those required to cause effects
on organisms in the environment; this is discussed later.
There are only a few reports of veterinary medicines being detected in ground-
water (Hirsch et al. 1999 ; Hamscher et al.2000a). In an extensive monitoring study
conducted in Germany, a large number of groundwater samples were collected
from agricultural areas in order to determine the extent of contamination by
antibiotics (Hirsch et al. 1999 ). The data show that in most areas with intensive
Veterinary Medicines and the Environment 301