The discovery of antibiotics was a real revolution in medicine. With the advent of this group of drugs, humanity has a chance to treat diseases that were previously considered fatal and incurable. Every year, biochemists create more and more new groups of antibiotics, and people use such drugs more often and in large quantities.
But these drugs also have a dark side. After antibiotics perform their function in the human body, they enter the environment, where they can remain active for a long time. The presence of these substances in the external environment stimulates the development of strains of various bacteria resistant to antibiotics.
Are antibiotics everywhere?
More than 100 tons of antibiotics are consumed annually in the world, and this figure continues to grow. As a result, more and more of these substances accumulate in the environment. Science Direct published some interesting statistics. It turns out that the concentration of antibiotics in the surface fresh waters of America reaches 15 μg / l, in Europe – more than 10 μg / l, in Africa – about 50 μg / l, and in the Asia-Pacific region, indicators of more than 450 μg / l have been found. [1].
Although these concentrations are considered relatively safe for humans, they have a detrimental effect on the aquatic ecosystem. A concentration below 10 µg/l already causes, if not death, then degeneration of bacteria contained in surface waters. Over time, microorganisms that were previously sensitive to the antibiotic develop resistance to it.
York University study
For a long time, scientists did not have a clear idea of where, in what cases and how much antibiotics enter the environment. So Alistair Boxall, a researcher and environmental chemist at the University of York (UK), and his colleagues set out to determine the extent of the problem and estimate the concentration of antibiotics in the world’s rivers.
The study was conducted by a group of scientists from different regions. A total of 711 samples were taken in 72 countries from all continents except Antarctica. Scientists collected water from the river, froze it and sent it by plane to York University for analysis. The samples were taken from the world’s most important rivers, including the Seine, Thames, Danube, Chao Phray, Mekong, Tiber and Tigris.
The resulting samples were tested for the presence of 14 types of antibiotics, the most commonly used in our time. It turned out that there is no continent where these substances would not be contained in river water. In 65% of all samples examined, scientists found traces of at least one drug. In 111 cases, the concentration of antibiotics exceeded conditionally safe levels. In the most polluted region, the indicator was 300 times higher than the norm [2].
That is, wherever people live and antibiotics are used, these substances are also present in the environment. The human body is not able to completely break down the medicine of this group. Excess drug is excreted from the body along with secretions and enters the sewer. But even the most modern treatment facilities are not able to remove the remnants of medicines from the water. In regions where there are no sewage treatment plants, antibiotics in large quantities fall directly into water bodies.
According to the results of the study, scientists said that the concentration of drugs most often exceeds the norm in Asia and Africa, although samples taken from the rivers of Europe and North and South America are also of concern. The highest levels of the antibiotic were recorded in Bangladesh, Kenya, Ghana, Pakistan and Nigeria. In Europe, the highest levels of pollution were found in water from Austria. The most polluted river in the United States was a reservoir in the city of North Liberty (Iowa), near which there are many livestock farms [3].
The results of the York study showed that the highest concentrations of antibiotics are usually found downstream of sewage treatment plants and riverside landfills, as well as in places where sewage is sent directly to the water body. Also, unsafe trends are observed in areas of political instability, including in the area of the Israeli-Palestinian conflict.
The most common antibiotic the scientists found was trimethoprim, which is commonly used to treat urinary tract infections. This substance was present in 307 out of 711 samples examined [4].
Another substance that has been found quite often in unsafe amounts by experts is ciprofloxacin, a popular broad-spectrum antibiotic. This substance exceeded the relatively safe threshold in 51 water samples. [4].
In the Danube, which is the second longest river in Europe, the researchers found 7 different types of antibiotics at once. One of them is clarithromycin, which is used to treat respiratory infections such as bronchitis. This substance was found in an amount that is 4 times the safe level.
Metronidazole, which is used to treat various infections of a bacterial nature, is found in the rivers in the most dangerous quantities. And in one of the reservoirs of Bangladesh, scientists found this substance at a concentration 300 times higher than what is considered relatively safe for the environment. [5]. In the waters of the Thames and one of its tributaries within London, the researchers found a mixture of 5 antibiotics. And this despite the fact that the Thames until that time was considered one of the cleanest rivers in Europe. In the Thames, the concentration of the antibiotic was 233 nanograms per 1 liter, while in Bangladesh, the level of chemicals in the river exceeded this figure by 170 times. [4].
Improper disposal of waste and sewage in Kenya led to the fact that in the river waters of this country the level of antibiotics was almost 100 times higher than relatively safe levels. [2]. In some Kenyan waters, extremely high levels of these substances have led to the death of fish.
A relatively safe level of antibiotics was established not so long ago by specialists from the AMR alliance, which unites more than 100 pharmaceutical and biotech companies. Depending on the type of antibacterial substance, its relatively safe amount can vary from 20 to 32 thousand ng/l. [4]. But according to microbiologist William Geise of the University of Exeter, even faint traces of antibiotics can have a big impact on the development of resistance in bacteria. [5].
In addition to antibiotics, scientists also find analgesics, hormonal and antihistamine substances, drugs used to treat mental illness, and remnants of blood-thinning drugs in the environment at environmentally hazardous concentrations.
Research in India
A similar study was conducted by experts from Banares University (India) [6]. They studied the quality of water in different parts of the Ganges. Experts took samples near the 5th ghat (stone stepped structures used for ritual ablutions of the Hindus). After careful examination of the samples, it turned out that bacteria with resistance to the most common antibiotics are abundant in the river.
This phenomenon was explained by Suresh Kumar Dubey, a professor at the Laboratory of Molecular Ecology at Banares University and the head of the study. According to him, more than 309,8 million liters of water enter the river every day in the Varanasi region alone. treated and untreated household waste. The substances contained in them, including antibiotics, contribute to the degeneration of bacteria and the development of their resistance to drugs.
Why is it dangerous
Antibiotics help treat dangerous infectious diseases, thereby saving millions of lives every year. But the populations of bacteria that are fought with antibiotics are quite viable and prone to transformation. In response to the effect of the drug, they are able to change, developing resistance to it. This means that the resistant strain becomes immune to the antibiotic, and it is very difficult or even impossible to treat the infection with such a drug.
According to Professor Dame Sally from the UK, the problem of drug resistance in bacteria is getting worse every year. If the trend continues, any of us in 20 years could end up in the hospital and, after the simplest operation, die from a common infection that will become impossible to cure with an antibiotic.
A 2016 analysis showed that around 700 people die every year worldwide from infections caused by antibiotic-resistant bacteria. According to medical experts, by 2050, drug-resistant strains will kill 1 person in the world every 3 seconds. [7].
Pollution of the environment with antibiotics affects the bacteria living there, contributes to the more rapid development of strains with drug resistance. In addition, it affects the ecological balance in rivers and streams, changing their natural bacterial composition. As a result, all kinds of ecological processes can be disturbed, including the circulation of carbon and nitrogen, which is largely dependent on bacteria.
Professor Boxall noted that the problem of antibiotic pollution is similar to the problem with plastic. According to the scientist, the root of the trouble is that modern man does not think about where they go and where the waste of our life activity accumulates.
Scientists admit they still have a lot of research to do before they understand exactly how antibiotic resistance develops. But the latest analysis shows that it is important to immediately find a solution to prevent further accumulation of antibiotics in rivers.
- Sources of
- ↑ Marie-Claire Danner, Anne Robertson, Volker Behrends, Julia Reiss – Antibiotic pollution in surface fresh waters: Occurrence and effects
- ↑↑ The Guardian – World’s rivers ‘awash with dangerous levels of antibiotics’
- ↑ Science News for Students – Antibiotics pollute many of the world’s rivers
- ↑↑↑↑ University of York – Antibiotics found in some of the world’s rivers exceed ‘safe’ levels, global study finds
- ↑↑ National Geographic – First global look finds most rivers awash with antibiotics
- ↑ Down To Earth – Antibiotic resistant bacteria found in river water
- ↑ National Geographic – Antibiotic Resistance Shows Up in Animals, Manure