An approach for mapping the vulnerability of European Union soils to antibiotic contamination

Release of antibiotics into the environment through the agricultural reuse of animal manure is considered a cause of chronic environmental exposure that often leads to adverse ecotoxicological effects, as well as to the introduction of antibiotic-resistant bacteria into the environment. The vulnerability of soil to antibiotic contamination plays a major role in determining the extent of the contamination and the likelihood of the emergence of antibiotic resistance and the appearance of ecotoxicological effects. It depends on soil characteristics, which vary across Europe, and antibiotic characteristics, which vary across drug classes. Understanding how soil vulnerability varies geographically for different veterinary medicinal products would be very useful for resource allocation among surveillance programmes. This paper performs risk analysis of the EU region for 12 antimicrobials using a spatial assessment performed in four steps. First, antibiotic release was estimated based on livestock density. Then exposure was estimated based on antimicrobial soil contamination. Third, consequences were modelled based on soil uses. Finally, risk was estimated by combining release, exposure and consequences using spatial multicriteria decision analysis. A final risk value for soil vulnerability was calculated for each antibiotic studied and displayed in chloropletic maps (ArcGIS 9.3). Furthermore, the Getis-Ord Gi statistic was used to identify clusters of areas at high risk for antibiotic soil contamination. Enrofloxacin was the highest-risk antibiotic in the European Union, followed by tetracyclines, tylosin and sulfodiazine. The highest risk values were found in Belgium, Ireland, Netherlands, Switzerland, Denmark, Germany and the UK. The results suggest that this methodology can be used successfully for evaluating the contamination potential of antibiotics over large areas with limited input data. This work is a preliminary step towards prioritising the use of veterinary medicinal products (VMPs), orientating monitoring studies and antimicrobial surveillance programmes, and informing sustainable decision-making for interventions designed to mitigate the risk of VMPs.