Abstract
The environmental risk assessment of the veterinary pharmaceutical ivermectin is receiving significant attention. This paper assesses the capacity of the MS·3 soil microcosm as a tool for targeting the environmental impact assessmentof veterinary drugs, using ivermectin as model. Two screening MS·3 were performed using different European soils; one with a soil collected in an agricultural station near to Madrid, Spain and a second with a soil collected in a farm area close to York, UK. Soils were fortified with ivermectin at the following ranges: 0.01-10 mg kg–1 and 0.1-100 mg kg–1 in the Madrid and York studies, respectively. The effects on earthworms, plants and soil microorganisms were assessed in the Madrid soil. Toxicity tests on aquatic organisms (algae, cladocerans and in vitro fish cell line RTLW1) were also conducted with the leachates. No effects were observed in earthworms and plants at any tested concentration; reduction in the respiration rate (< 5%) of soil microorganisms was detected. Earthworm/soilbioconcentration factors decreased with the increase in soil concentrations and were higher for the York soil. Effects on daphnids were observed in tested leachates; based on measured levels of ivermectin in the leachates an EC50 ofabout 0.5 μgL–1 can be estimated. Comparisons based on toxicity data and equilibrium partitioning confirmed that themain risk is expected to be related to the high sensitivity of cladocerans. The results confirm that MS·3 systems are cost-effective tools for assessing the impact of veterinary pharmaceuticals when applied to agricultural land, as previously demonstrated for antimicrobials.
Highlights
Ivermectin, an avermectin parasiticide of high environmental concern, is broadly used as endo- and ecto-antiparasitic drug for treating livestock (Nessel et al, 1989; Alvinerie et al, 1998; Edwards et al, 2001)
The main environmental concerns when treating animals with ivermectin are associated to their dung excretion, representing a potential risk to dung and soil fauna and to aquatic organisms due to runoff losses from manure or slurry applications (Halley et al, 1989; Van den Brink et al, 2005)
The concerns were considered by regulatory bodies and the International Cooperation on Harmonization of Technical Requirements for Registration of Veterinary Medicinal Products developed specific guidance (VICH, 2000, 2004), which have been implemented in the European Union (EMEA, 2008)
Summary
Ivermectin, an avermectin parasiticide of high environmental concern, is broadly used as endo- and ecto-antiparasitic drug for treating livestock (Nessel et al, 1989; Alvinerie et al, 1998; Edwards et al, 2001). The multi-species soil system (MS·3) was developed by our group as a simplified soil microcosms designed for assessing effects on agricultural land (Fernández et al, 2004; Boleas et al, 2005a,b). The system balances the benefits of standardisation with the needs for realistic conditions, combining the toxicity endpoints measured in several OECD guidelines in a cost-effective assay reproducing realistic agricultural soil conditions. This higher tier ecotoxicity test has been designed as an artificially assembled soil microcosm where soil macro-organisms, plants and invertebrates, are added into a sieved column of natural soil that provides a complex microbial community. The MS·3 ivermectin results complement our previous observations for antimicrobial drugs
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