# Antibiotics in Groundwater and River Water of Bialka--A Pristine Mountain River
## 4 Discussion  
The presence of antimicrobial agents both in surface water and in groundwater is a serious problem, for a number of reasons. Threats related with water use for various purposes (including irrigation, as a source of drinking water and other urban, rural and environmental applications) and the associated toxicological implications on humans  
Figure 5: Detection of examined groups of antimicrobials at all sampling sites along with their detection by the STP (upper part of the graph) compared with their consumption in human and veterinary medicine (lower part of the graph). and animals are among the most important ones [18]. Another main concern, associated with the release of antimicrobials into the environment, is related with their impact on the development of antibiotic resistance among bacteria and the resulting reduction of therapeutic potential of antibiotics [7; 19]. In this study, the presence of 16 antimicrobial agents, classified into 10 groups, was detected in six out of seven samples, including one sample of groundwater in the pristine and protected area of the Tatra National Park. Generally, the frequency of detection and concentrations of antimicrobial agents in the aquatic environment are the result of factors such as: ubiquity of antibiotics administration for various purposes [19], their removal efficiency by the WWTPs [20] and their persistence in water, defined based on their half-life value [18]. In our study, clindamycin (lincosamides), erythromycin (macrolides), ofloxacin (fluoroquinolones), trimethoprim (antifolate) and sulfamethoxazole (sulfonamides) were most frequently detected. On the other hand, the highest concentrations were observed for oxytetracycline (tetracyclines), followed by clindamycin and netilmicin. According to [20], three out of these seven antimicrobial agents were among the ones with the highest sale in Poland in 2018: sulfamethoxazole (up to 1358 kg/month), ofloxacin (up to 829 kg/month) and clindamycin (737 kg/month). Oxytetracycline, the total concentration of which was the highest and whose concentrations were very high also in the low-impacted water samples, as well as in one of the groundwater samples, is primarily used in veterinary medicine [20]. It is widely used as a feed additive in livestock husbandry, as a preventive measure and as a therapeutic agent [21]. It has been demonstrated that its widespread use not only pollutes sewage systems, but it results in their transport further to the aquatic environment via rainwater and surface runoff [21]. Moreover, tetracyclines along with fluoroquinolones are among the most persistent antimicrobial agents in the environment; thus, they tend to easily accumulate in aquatic and soil environments [7]. Erythromycin is another example of antibiotics that are widely used in both human and veterinary medicine. In veterinary medicine, it is used for the treatment of clinical and subclinical mastitisti in cows, infectious diseases in cattle, sheep, swine and poultry and of chronic respiratory diseases in poultry [22]. Erythromycin has been reported as resistant to treatment by the STPs, resulting in its ubiquitous occurrence in final effluents [23]. Importantly, erythromycin can bind to biosolids and thus contaminate sewage sludge, which is widely used as an agricultural fertilizer. That way, this antibiotic can reach river water via surface runoff or reach groundwater [23]. [PERSON] et al. [24] suggested another three out of the most frequently detected antibiotics in this study, i.e., erythromycin, clindamycin and trimethoprim, to be among very commonly detected in the STP receiving water bodies and for this reason were recommended as of particular concern to the environment. The authors in [18] report that trimethoprim and sulfamethoxazole (which are very often used in a fixed combination) are among the most frequently detected antimicrobial agents in the European STP effluents with the detection frequency reaching around 90% of STP effluents.