I made the most of this opportunity to write  about Naturally occurring chemical product that affects the environment positively as a thematic report in my previous report. In that context, I mainly focused on Penicillin, its discovery, and its importance in the modern medicinal system.

Now I have presented my thematic report again, welcoming our two Mentor's positive comments and suggestions in my previous report.

HOW ANTIBIOTIC EXPOSURE IS AFFECTING THE ENVIRONMENT?

The capacity to battle bacterial infections with these modern medicines named antibiotics has been known as a longstanding linchpin of advance medical era. Antibiotics may be naturally occurring (e.g., Penicillin G), semi-synthetic (e.g. Ampicillin) and derived (e.g. Sulfonamides). This classification helps to know about the pharmacokinetics of the drugs.

Antibiotic exposure simply means contamination of environmental components with a significant quantity of antibiotics. This may vary according to the different nature of the drugs. There are many ways of antibiotic endangerment to the atmosphere. First, simply antibiotic residues may be exposed to outside of the manufacturing area during production and treatment. In Nepal, India and many developing countries, there are many evidences of antibiotic residues in water resources exceeding permissible concentration. Naturally occurring antibiotics like Penicillin G are degraded in a shorter time compared to other semi-synthetic and synthetics. Disposal of industrial by-products and wastages without wastewater and solid treatment and sterilization techniques is also one of the major sources of exposure to these chemicals in the environment.

For example: in Patancheru, it is reported that well water contained a significantly low concentration of antibiotic residue, which is an industrial zone located in India.

Next, If the society or country does not have well- instructed sewage treatment protocol, there may be enough chances of the microscopic drug particles to reach in the environment.  This is because human consumption of some antibiotics will be excreted via kidney and intestine which finally causes excretion of urine and feces with the residue of drugs. Most drugs are metabolized and then excreted. Some antibiotics (e.g. Aminoglycosides) are excreted by the kidney without being metabolized. There is a different concentration of excretion of these drugs through body system and common routes of excretion are urine, feces, bile, tear, sweat, respiratory system, milk, eggs, etc.

Antibiotics are widely used in animal production and treatment. This will also add exposure to the environment more easily. This mainly depends on animal species and the purpose of rearing.

Animals reared for meat, milk and egg production contain antibiotic residue up to certain days. For example, OXYTET LA 20% injection (KEPRO) is an antibiotic, has a withdrawal period for meat is 28 days and milk is 7 days. It means antibiotic residue may be seen in milk and meat after the administration of that drug up to the respective days.

Human behavior is also responsible to expose the drugs to their surroundings. Many people may not have a habit of not using proper medication which may lead to drug discards. In many countries, people are not used to of medicine take-back system, which causes discard of unused drugs. Which dumps to landfill sites. Also, many people have the habit of buying and keeping medicines for the future for health security. It is not used or expired; it is later discarded. Availability of over the counter drugs as well as some drugs without a prescription (that need prescription) makes thee medicines easily accessible for misuse. Also, not following the doctor's prescript causes excess or low dosage which later becomes harmful to the patient. Somewhere, there is a myth that high drug dosage helps in faster treatment. 

Exposure of these chemical residues have negative impacts on environmental health. Ideal antibiotics are either bacteriostatic or bactericidal which don't harm humans/ animals and the environment, but this doesn't exist. There exist billions of microorganisms in the soil for their beneficial roles. Antibiotics may harm these beneficial bacteria's biological cycle.  Although, there is no clear evidences of direct inhibition of these beneficial soil bacteria, but many scientists agree that the drug residue may later the microorganism's structural, genetic and functional diversity. This will finally lead to alteration in the enzymatic activity of soil bacteria and their carbon sources. However, this is influenced by many biotic and abiotic factors. There are many ongoing researches in the impact of antibiotic residue on soil microbiology and nitrogen cycle.

Antibiotic residues cause many side effects to the consumers. Many immunological effects, reproductive disorders, carcinogenic effects, myelotoxicity, and hypersensitivity symptoms are recorded due to excessive consumption of antibiotic residue for a long time. For example, Sulphadiazine persists carcinogenic characteristics, gentamicin causes nephrotoxicity and chloramphenicol residues may lead to bone marrow toxicity.

Environmental antibiotic pollution is a global concern as antibiotic consumption is increasing since is discovery. There is a vast mechanism of antibiotic resistance but one clear thing is bacteria is getting its strength against anti-bacterial drugs. This finally concludes in the failure of antibiotic treatment against specific bacteria which causes unimaginable loss to human and animal society.

Administration of antibiotics in poultry, fish and animal feed for better growth and disease prevention is also a major cause of antibiotic resistance. In ruminants, there are hundreds of beneficial microflorae in their gut for enough fermentation and digestion. Oral use of antibiotics may destroy these microorganisms and cause infection and immunocompromised animals.

Globally, antibiotics are used to treat and prevent bacterial diseases. The Discovery of antibiotics takes a huge amount of time and money with many resources and many environmental factors are also compromised, but antibiotic pollution in the environment appears in a relatively shorter period.  Scientists are doing their job to make the human population safe from dangerous microorganisms and this is the responsibility of we responsible citizens of this world not to take part in the path to cause antibiotic pollution. That's why it is necessary to take prescription of concerned persons before antibiotics and any medicines usage. Our small action makes a great impact o fight against antibiotic susceptibility and its exposure in the environment.

references:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6418018/

http://www.ncbi.nlm.nih.gov/pubmed/30710599

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5573035/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4034546/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6616856/

Nisha AR. Antibacterial residue-a global health hazard. Veterinary World. 2008; 1:375-377.

http://www.ncbi.nlm.nih.gov/pubmed/19560847