Fluoroquinolones are a valuable synthetic antibacterial class widely used in the treatment of infectious diseases both in humans and animals. Until recently, it has been thought that bacterial resistance to fluoroquinolones develops very slowly. Nowadays, there are multiple studies that reveal the alarming occurrence of bacterial resistance and there is a high risk of becoming therapeutically useless. The emergence of this phenomenon comes from injudicious usage in therapy, the presence of residues and their metabolites in food of animal origin and also in sewage, compost and domestic waste, which end up in soil and water sources. In the present paper, we reviewed important issues regarding fluoroquinolones impact on the environment in connection with the development of bacterial resistance: (1) the presence of fluoroquinolones as pollutants in soil, surface waters, and food. Fluoroquinolones are persistent with high specificity to interact with soil compared to other antibiotics. Pollution of water sources raises concerns regarding the effects of small concentrations (ng L⁻¹) on human health and also of the environment. The non-therapeutic use in animal farms conducts to food pollution; the cultivated plants could concentrate the fluoroquinolones (over 100 μg L⁻¹); (2) the increase of bacterial resistance to fluoroquinolones occurring with specific mutations in the target enzymes as well by the plasmid-mediated resistance and active efflux of the cell; (3) international regulations of the fluoroquinolone residues in food that are far to encompass all compounds; (4) fluoroquinolones residues analysis with standardized methods should provide limits of detection lower than maximum residue limit values; and (5) trends and perspectives: (a) a wider process of harmonization of regulations; (b) the fluoroquinolones restriction, necessary for low levels of bacterial resistance; (c) the soil and waste water purification methods; (d) the practice of soil planting scheme as an alternative; and (e) an environmental label in order to facilitate the selection of drugs.

Recently, reports have been published on the occurrence of chlorate mainly in fruits and vegetables. Chlorate is a by-product of chlorinating agents used to disinfect water, and can be expected to be found in varying concentrations in drinking water. Data on potable water taken at 39 sampling points across Europe showed chlorate to range from < 0.003 to 0.803 mg l –¹ with a mean of 0.145 mg l –¹. Chlorate, however, can also be used as a pesticide, but authorisation was withdrawn in the European Union (EU), resulting in a default maximum residue limit (MRL) for foods of 0.01 mg kg –¹. This default MRL has now led to significant problems in the EU, where routinely disinfected water, used in the preparation of food products such as vegetables or fruits, leaves chlorate residues in excess of the default MRL, and in strict legal terms renders the food unmarketable. Due to the paucity of data on the chlorate content of prepared foods in general, we collated chlorate data on more than 3400 samples of mainly prepared foods, including dairy products, meats, fruits, vegetables and different food ingredients/additives. In total, 50.5% of the food samples contained chlorate above 0.01 mg kg –¹, albeit not due to the use of chlorate as a pesticide but mainly due to the occurrence of chlorate as an unavoidable disinfectant by-product. A further entry point of chlorate into foods may be via additives/ingredients that may contain chlorate as a by-product of the manufacturing process (e.g. electrolysis). Of the positive samples in this study, 22.4% revealed chlorate above 0.1 mg kg –¹. In the absence of EU levels for chlorate in water, any future EU regulations must consider the already available WHO guideline value of 0.7 mg l –¹ in potable water, and the continued importance of the usage of oxyhalides for disinfection purposes.