Adsorption and biodegradation of antidiabetic pharmaceuticals in soils Wojciech Mrozik ⇑ , Justyna Stefan ´ ska Department of Inorganic Chemistry, Faculty of Pharmacy, Medical University of Gdansk, Al. Hallera 107, 80-416 Gdansk, Poland highlights  Sorption and biodegradation of four antidiabetic drugs in soils was determined.  Pharmaceuticals sorbed strongly on soils rich in organic matter and higher clay content.  Sulfonylurea derivatives sorb strongly to soil whereas metformin is highly mobile.  Best biodegradation rates were obtained for metformin.  Biodegradation of antidiabetic drugs follows the first-order kinetics. article info Article history: Received 12 February 2013 Received in revised form 12 August 2013 Accepted 2 September 2013 Available online xxxx Keywords: Antidiabetic pharmaceuticals Soil Sorption Biodegradation Kinetics Sulfonylourea derivative abstract Pharmaceuticals are emerging contaminants in the natural environment. Most studies of the environ- mental fate of these chemicals focus on their behavior in wastewater treatment processes and in sewage sludge. Little is known about their behavior in soils. In this study adsorption and biodegradation of four antidiabetic pharmaceuticals – glimepiride, glibenclamide, gliclazide and metformin – were examined in three natural soils. The sorption of sulfonylurea derivatives was high (higher than sulfonylurea herbicides for example), whereas metformin showed high mobility. Desorption rates were highest for metformin. Sorption isotherms in two of three soils fitted best to the Freundlich model. Despite their high affinity to for soil surfaces, biodegradation studies revealed that transformation of the drugs occurred. Biodegra- dation results were described by pseudo-first order kinetics with half-life values from 5 to over 120 d (under aerobic conditions) and indicate that none of the tested drugs can be classified as quickly biode- gradable. Biodegradation under anoxic conditions was much slower; often degrading by less than 50% during time of the experiment. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction In recent years there has been growing interest on the preva- lence and fate of pharmaceuticals in the natural environment. Un- like pesticides, pharmaceuticals enter the natural environment wherever humans are present. Pharmaceuticals may undergo incomplete, or even resist degradation at all in traditional waste water treatment plants (WWTPs), meaning they will enter receiving waters, soils and sediments (Daughton and Ternes, 1999; Kummerer, 2008). Given the composition of environmental matrices, it is obvious that sorption and biodegradation are the most dominant fate processes. The characteristics of these two phenomena for pharmaceuticals may vary strongly in different soils. Therefore, the responsible and secure application of reclaimed water, for irrigation and groundwater recharge, as well as disposal of activated sewage sludge to agricultural land (Shore and Shemesh, 2003; Stumpe and Marschner, 2009; Li et al., 2013). Most drugs are excreted from the human body in an un- changed or only partially metabolized (hydroxylated or carboxyl- ated) form (European_Pharmacopoeia_VI, 2001). Bacterial transformation of pharmaceuticals may lead to products that are similar to human metabolites (Trautwein et al., 2008) but they may also transform excreted metabolites back to a more biologi- cally active substance (e.g. the drug in its original form) (Kummer- er, 2008). Such actions make environmental fate assessment studies more complicated. It has been estimated that about 3–5% of the human population suffers from diabetes mellitus type 2 (Kar and Holt, 2008). Since large quantities of anti-diabetic drugs are used for treatment, it is possible that huge amounts of these pharmaceuticals and their metabolites are deposited in the environment. Approved pharmaceuticals for treatment of these diseases include derivatives of: sulphonylurea (glibenclamide, gliclazide, glimepiride); biguanidine (metformin); meglitinide (repaglinide) and alpha-glucosidase inhibitors (acar- bose). The pharmaceuticals used to treat type 2 diabetes, belong to 0045-6535/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2013.09.012 ⇑ Corresponding author. Address: Department of Inorganic Chemistry, Faculty of Pharmacy, Medical University of Gdansk, Al. Gen. J. Hallera 107, 80-416 Gdansk, Poland. Tel.: +48 58 349 14 88; fax: +48 58 3493 16 24. E-mail address: wojmrozik@gumed.edu.pl (W. Mrozik). Chemosphere xxx (2013) xxx–xxx Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere Please cite this article in press as: Mrozik, W., Stefan ´ ska, J. Adsorption and biodegradation of antidiabetic pharmaceuticals in soils. Chemosphere (2013), http://dx.doi.org/10.1016/j.chemosphere.2013.09.012