The human factor
In the Piedmont region of Virginia, on the southeast coast of the United States, researchers take samples of water from 59 headwater-stream sites in the local area. Analysing the samples in a lab, the scientists find significant concentrations of pharmaceutical medicines. Metformin is “pervasive”—being present in 89% of the samples and at 97% of sites—while nicotine, acetaminophen, carbamazepine, fexofenadine, lidocaine, pseudoephedrine, sulfamethoxazole and tramadol are also present in significant amounts. At least one pharmaceutical was detected at every site, with one site having concentrations of 45 different drugs present.
Within contaminated waterways across North America, diltiazem concentrations have been found in the local fish and osprey.2 Researchers found concentrations of diltiazem in fish plasma 21.6 times greater than those in water, and osprey plasma concentrations 4.71 times higher than those of fish. They have also discovered populations of male fish that have been feminised after being exposed to effluent containing synthetic oestrogen.
Antidepressants and other psychoactive drugs have made their way into aquatic ecosystems around the world. For example, elevated concentrations of sertraline and carbamazepine were “ubiquitous”in sewage-contaminated ecosystems in central Texas, US. Across the ocean to the Indian subcontinent, nearly an entire population of vultures died of kidney
failure after consuming livestock carcasses medicated with diclofenac. Not even Antarctica has escaped contamination from pharmaceuticals substances. A water sample study in the area found concentrations of 16 pharmaceuticals and recreational drugs. The highest concentrations were found for the analgesics acetaminophen, diclofenac and ibuprofen.
Looking at the research, it seems unlikely that there are places across the world that have been left untouched by our pharmaceutical drug use. With a burgeoning rise in the use of medication across all populations, humans have certainly left their mark on the planet. Pharmaceuticals enter the environment through a variety of pathways, but mainly through patient
excretion or the inappropriate disposal of unwanted pharmaceuticals. In fact, many medications are excreted from the body virtually unchanged or are only partially metabolised, and are often poorly removed by conventional wastewater treatment technologies. For example, the antidepressant fluoxetine is only partially metabolised, incompletely removed by current
wastewater treatment plant processes, and exhibits minimal degradation in sewage or soil over many months. “Conventional waste technologies treat pharmaceuticals only incidentally, resulting in ubiquitous release of pharmaceutical contaminants in effluent,” say researchers from the US Geological Survey.
Antibiotics in the environment
As awareness of antibiotic resistance due to overprescribing and overuse spreads across the world, one has to wonder: how much does the presence of antibiotics in the environment impact on helping to spread resistance? Are traces of antibiotics in the environment as ubiquitous as other medications? The answer is a resounding yes.
As with some other medications, many antibiotics are not metabolised, excreted unchanged and are environmentally persistent. While some antibiotics such as penicillins are easily degraded, others are more persistent, including fluoroquinolones and tetracyclines. This allows such antibiotics to “prevail for longer times in the environment, to spread further, and to
accumulate to higher concentrations,” explains Professor Joakim Larsson from the University of Gothenburg in Sweden. Since industrialisation, millions of tonnes of antibiotics have been released into the environment via wastewater effluents, the use of animal waste on land, treatment of crop diseases, aquaculture and animal production. Antibiotic use across livestock and aquaculture is also widespread—for example, fish infections are treated through administration of antibiotics directly into the water.
In a 2015 research article, environmental scientists Céline Roose-Amsaleg and Anniet Laverman said that improved analytical capabilities have led to the detection of antibiotic residues in virtually all natural habitats. Manure excreted by animals treated with antibiotics (for veterinary purposes or as growth promoters) is used as an agricultural fertiliser, with antibiotics seeping through the soil and entering ground water. In some areas, wastewater containing resistant bacteria and antibiotics is used for irrigation, and sewage sludge is used as fertiliser, allowing resistant bacteria to enter the food chain directly.
Large numbers of resistant bacteria that have multiplied in the gastrointestinal tracts of people and animals treated with antibiotics are also released into the environment, as are active residues of antibiotics. Antibiotic residues in the environment have been found ranging in concentrations from nanograms per litre up to low micrograms per litre.
“Although these are well below minimum inhibitory concentrations, even low concentrations provide selective advantages for certain resistant strains,” says Rita Finley and colleagues from the Public Health Agency of Canada, Ontario. Within aquatic systems, antibiotics have been found to be persistent. For example, quinolones absorb into sewage sludge, soils and sediments and are not biodegraded in tests with sediments. Discarding unused or unwanted antibiotics unsafely—for example, through the household garbage or down the toilet—is another way they find their way into the environment (see RUM Project breakout).
Source and further reading: AJP.COM.AUClean environment
Emerging Antimicrobials and Diagnostics in AMR 2019
International Matchmaking Symposium on 19-20 November, 2019 in Amsterdam, The Netherlands.