Have you ever heard of fish engaged in family planning? In the nineties, a group of UK researchers chanced upon a phenomenon in fish that lived downstream from waste- water treatment plants. The males of this piscine population became increasingly feminized, so much so, that they were busy producing eggs, in their testes. These fish were not meant to be on contraceptives, but thanks to human thoughtlessness, they were imbibing a regular dose. Such ‘cross- over’ samples are no longer strangers to the rivers and streams across the Americas and Europe. The reason-- estrogenic compounds in their habitat!
Drug RouteWhat is behind this strange phenomenon? The story begins with the multitude of drugs, masterminded in laboratories. They win approval through clinical trials, and are then mass- produced as purposeful remedies to save lives.
But the story does not end there, although the purpose is accomplished. Expired or outdated drugs are disposed by flushing them down the toilets. Drugs are also excreted by consumers. They amalgamate with the environment through treated wastewater, agricultural run-offs and manure. These drugs seep their way underground, wade their way into streams and ultimately enter the food chain.
Fishy Facts
Studies confirm that fish all over the world are being ‘slow poisoned’ with sips of estrogenic compounds besides anticonvulsants, such as carbamazepine, antidepressants, such as fluoxetine, and scores of other drugs that have been designed to brighten our lives. Carbamazepine affects the development of small insects that are savored by the fish, while fluoxetine slows development in fish and frogs.
What are the effects of these estrogenic compounds on fish? Studies on fathead minnows revealed that there was delayed sperm development in these fish and that, after a time span, the males were beginning to produce eggs. In effect they stopped reproducing. It came as no surprise, therefore that the population of these fish started to dwindle, to a point of near extinction, from the lake.
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But this eco-story is not entirely sordid; it has a fitting finish to it. It must be noted that large quantities of estrogen are not required to bring about feminization in male fish. When the estrogen in their environment was controlled, the minnows population bounced back with renewed vigor. Hence it can be safely concluded that removing estrogen from their habitat can save the fish.
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The effects of pharmaceutical pollution ramify across the environment and are not confined to the aquatic phase alone. Large- scale deaths of vultures in certain regions of Asia were traced to the rampant use of an anti-inflammatory drug, Diclofenac, among the animal stock.
Diclofenac is a drug of choice employed in the treatment of domestic cattle in India and Pakistan. When these animals die,they are feasted upon by birds of prey. It gradually came to light that the vultures that scavenged upon these carcasses suffered renal failure and visceral gout, as a result of diclofenac poisoning.
Worming Towards Food Chains
Scientists are also concerned about the huge doses of antibiotics used to treat domestic livestock and are trying to evaluate their negative effects on the environment.
Antibiotics, along with various other drugs, seep their way to the excreta of these animals, which, in turn, are used as manure in farms. These antibiotics are also accused of creating antibiotic-resistant mutant microbes.
Besides, earthworms which have set up homes in these contaminated soil, may be feeding on these drugs, specifically on trimethoprim. This is an area of concern because these humble earthworms are strategic members of nature’s food chain, as they are the prime food source of many larger organisms. Some of the adverse effects of these antibiotics in the exposed creatures are –
• Changes in feeding pattern
• Changes in mating behaviors
• Antibiotic resistance build-up
Toxic Tango
It may interest the reader to know that pharmaceuticals are but the tip of the ‘chemical’ iceberg. In terms of concentration, they represent just a fraction of all the man-made chemicals that permeate our ambiance. Ranging from pesticides, industrial effluents, and home -care products to a wide assortment of personal - care products, these chemicals have infiltrated into every nook and crevice of our lives.
Often the argument in favor of these drugs is that they seep into the environment in negligible measures. But what must be etched in our minds is the fact that these pharmaceutical compounds are designed to bring about the desired effect, even in small quantities.
Wastewater treatment often falls short of doing the needful when it comes to breaking down chemicals. For example, estrogenic compounds such as B-ethinylestradiol are eliminated in the form of sulfate conjugates and glucuronide. Bacteria that occur in the processed wastewater cleave these conjugate groups to bring back to life the parent compound.
Pharmaceutical drugs and their metabolites, meander their way from homes, health care units, farms and industries to sewage systems. It must also be kept in mind that pharmaceuticals or their metabolites may act in synchrony with a surfactant, a contaminant or with another drug.
The main concentration of scientific analysis is the parent compound, while the metabolites of these drugs are conveniently shown the blind eye. It must be noted that there are instances when the latter are more toxic than the former.
Future Steps
Are these drugs harmful to humans? Studies say ‘no’!
This is because the concentration of these drugs that reach drinking water is far too negligible, according to western reports.
In the developed countries wastewater treatment is fairly efficient. But can the same be said of the poorer countries? Treatment plants were built a long time ago and they were not designed to eliminate synthetic material from sewage waters. Hence, advanced wastewater treatment facilities need to be installed wherever required, although some may disagree.
FDA demands pharmaceuticals to undergo an evaluation for environmental risks before they enter the market. Short- term tests are performed on both terrestrial and aquatic organisms, but they do not evaluate the cumulative effect or the long- term effect of these compounds.
There is a need to ‘take back’ unused and expired drugs in a community -facilitated way. Drugs thus collected may be disposed off by methods such as incineration.
The fish episode may just be the beginning of the end if wise counsel fails to prevail. Pharmaceuticals may be capable of effects that no one can ever dream of. It therefore becomes important to set limits to the measure of drugs that we could be exposed to. More research is required towards this end to prevent a pile up of toxins in the environment.
Let us not fail in our intent or in our action to make this world a better place!
Source-Medindia
DR. REEJA THARU/L
