Sometimes we do not realize how much industrialization and human activity interfere with and change the world around us, becoming significant pollution. As a reason, groundwater, rivers, seas, and oceans are more and more polluted. Low-quality water is dangerous not only for animals and plants but also for humankind. Have you ever wondered what kind of chemicals we can find in the water? There are more than we can even imagine. Here, we focus on the drugs that can be found in the water.
Antibiotics are used to defeat bacterial infections. They save lives and are widely used for both livestock and people. Thus, they can be easily found in the environment being a serious water pollutant that can affect living organisms. Their presence in the water has a catastrophic effect. Why? Due to their adverse effects and development of antimicrobial resistance . As a result, the antibiotics become ineffective, so once antibiotic-resistant bacteria attack the body, it can be extremely dangerous. Antibiotic resistance of bacteria leads to the spread of diseases, and as a result, we are exposed to more severe illness and even death .
In the JCR Technical Reports, “State of the Art on the Contribution of Water to Antimicrobial Resistance ” (2019) , the data from 13 countries worldwide on 45 antibiotics is collected. It was found that in the waters flowing out of the sewage treatment plant, the three most common antibiotics occur: sulfamethoxazole, trimethoprim, ciprofloxacin, levofloxacin, and B-lactam amoxicillin. All of them are used to treat broadly understood bacterial infections, such as urinary tract or middle ear. Interestingly, similar concentrations were also recorded in surface waters, although lower indications were expected due to the dilution of these substances as sewage flows into rivers and lakes . Nevertheless, it is comforting that at present, there is no risk of contamination with antibiotics in drinking water (their residues are so small that they do not pose a threat to humans) .
On the other hand, we deal with antibiotic problems in different parts of waters: surface, ground, and organic matter in sediments and shallow water both. In these cases, the most problematic aspect is bonding antibiotics into larger compounds. Thus, these components can be much more toxic than their precursors. Still, too little is known about the impact of antibiotics on bacteria resistance, determined by residues from fish farms and sediments. Nevertheless, some research suggests that dissolved organic matter in water can help to reduce the bioavailability of antibiotics for bacteria. In that case, antibiotic resistance is limited .
One of the most common antibiotics extensively used against bacterial infections in veterinarians and humans is tetracycline (TC) . This compound is widely used to treat animals and even to treat hives that are infected by bacteria. It persists in the water that is bioavailable to cross biological tissues and enter organisms or food. In this way, this antibiotic can be found even in eggs, milk, and eggs. Moreover, antibiotics which are frequently used in aquaculture can change bacteria resistance in antibiotic resistance genes (ARGs) and increase the potential for more pathogenic bacteria in humans 
Other studies carried out showed that ten typical antibiotics like tetracycline, doxycycline, ofloxacin, enrofloxacin, trimethoprim, penicillin, roxithromycin, lincomycin, sulfoxamerazine, sulfamethazole, and sulfamethazine were found in samples obtained from water supply systems and intended for treatment in water treatment plants (Tianjin). Still, their concentrations were at an acceptable level and did not pose a threat . The authors also showed that the concentrations of antibiotics in the tap water samples were higher in winter than in summer due to the disease seasons in the winter months.
Did you know that?
In Ancient Egypt, people put moldy bread on their wounds to heal them. Recent studies show that ancient civilizations used antibiotics. Some mummies have large doses of tetracycline in their bones.
One of the primary sources of antibiotics in wastewater and the environment comes from agriculture due to the broad antibiotics application for animal treatment .
The first antibiotic found by scientists was penicillin.
Some bacteria are resistant to all known antibiotics. If such dangerous bacteria infect someone, the only “last chance treatment” is based on phages (also called bacteriophages) that are viruses affecting only specific bacteria types .
aquacultures, e.g. fish farms as salmon, can deliver prevalence of more resistant bacteria in the sea environment, and antibiotic treatment is changing and increasing antibiotic resistance genes (ARGs) 
This article is a joint work or Patrycja Hejduk (Faculty of Chemistry, University of Warsaw), Ewa Borowska (The College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences (MISMaP), University of Warsaw), Weronika Urbańska (Faculty of Environmental Engineering, Wrocław University of Science and Technology), Agnieszka Pregowska (Institute of Fundamental Technological Research, Polish Academy of Sciences), and Magdalena Osial (Faculty of Chemistry, University of Warsaw).
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