Published in IIPS Mumbai, ENVIS center, Volume 3, No. 2,  June 2006

 

Impact of Human Medicines on Environment – A New

Emerging Problem

*Syed Ziaur Rahman*

Man consumes drug for various medical and non-medical reasons. There are innumerable incidents where these medicines played havoc on humankind. If they are boon to man, they are also afflicting diseases. But, what about human drugs when they have an effect on environment? There has been growing concern among scientists and environmentalists about the vast amount of drugs that end up in the environment one way or another. Adverse consequences of drugs may influence socio-economic environment. These problems are encountered due to heterogeneous population, where ‘risk’ and ‘non-risk’ groups cannot be clearly identified. They adversely affect patients’ quality of life. Low levels of human medicines (pharmaceuticals) have been detected in many countries in sewage treatment plant (STP) effluents, surface waters, seawaters, groundwater and some drinking waters. For some pharmaceuticals effects on aquatic organisms have been investigated in acute toxicity assays but the chronic toxicity and potential subtle effects are only marginally known [1].

Diclofenac is turning out to be a threat to ecological balance by its swipe at vultures, nature’s scavengers, whose number is noticeably on the decline (Green RE etal, 2004). Their population had crashed during the last decade. The vulture population drastically declining and are on way to extinction for many reasons and one of them is Diclofenac Sodium commonly prescribed by veterinarians but found in the carcasses of the cattle on which the scavengers feed. The reason of their death is visceral gout and renal failure [3]. Such a drastic decline in the number of vultures meant an impending ecological disaster with the looming threat of outbreak of epidemics because of decaying carcasses. The vultures' population crash has also led to an increase in the number of feral dogs which poses a range of disease threats such as rabies [4]. Investigation, which began in 2000, was prompted by reports of a 95 percent drop in the number of Asian white-backed vultures (Gyps bengalensis), Indian vultures (Gyps indicus) and slender-billed vultures (Gyps tenuirostris). All three are now listed as critically endangered by the World Conservation Union, the international environmental agency based in Switzerland. Vultures are keystone species and their declines are having adverse effects upon other wildlife, domestic animals and people. The Peregrine Fund are all calling on the governments of countries with vulture populations, and the manufacturers of diclofenac, to ban the use of this drug in livestock. It is believed the recovery of vulture populations in southern Asia will not be effective until their exposure to diclofenac has been removed. The decline also threatened the traditions of the Parsis, a sect of Zoroastrians who have traditionally exposed their dead to the elements rather than burying or cremating them. In Bombay they had to stop putting their dead on the stone ‘Towers of Silence’ because the birds that once quickly consumed them were vanishing. Meloxicam could be an alternative medicine for veterinary use in India. 

A study by the United States Geological Survey found traces of many different pharmaceuticals and personal care products including steroids, insect repellents and many others in the American water supply [9]. The effect of these traces is unknown, but the concern is about the unexpected! So much Cocaine is being used in London that traces of the narcotic can be detected in River Thames. An estimated 2 kg of cocaine gets into the river every day after it has passed through user’s bodies and sewage plants. The Thames investigation, the first of its kind in Britain, was conducted by scientists using the latest technology. It is regarded as the most accurate large-scale drug-detection method available (UK’s Sunday Telegraph Newspaper 6 Nov. 2005). It is extrapolated that 150,000 lines of the illegal drug are snorted in the British capital every day, or 15 times higher than the official figure given by the Home Office Statistics and equates to four out of every 100 people regularly taking cocaine, or up to 250,000 of the capital's six million residents.

 

 

 

 

 

Only very little is known about long-term effects of pharmaceuticals to aquatic organisms, in particular with respect to biological targets. One laboratory study suggested that antidepressants like Prozac (Fluoxetine) could trigger spawning in some shellfish (Pallava Bagla, Jan 28,2004), thereby disturbing more natural ecological balance. For investigated pharmaceuticals chronic lowest observed effect concentrations (LOEC) in standard laboratory organisms are about two orders of magnitude higher than maximal concentrations in STP effluents. For diclofenac, the LOEC for fish toxicity was in the range of wastewater concentrations, whereas the LOEC of propranolol and fluoxetine for zooplankton and benthic organisms were near to maximal measured STP effluent concentrations. In surface water, concentrations are lower and so are the environmental risks. However, targeted ecotoxicological studies are lacking almost entirely and such investigations are needed focusing on subtle environmental effects. This will allow better and comprehensive risk assessments of pharmaceuticals in the future [1].

Many questions are still to be answered as what kind of pharmaceuticals and what concentrations occur in the aquatic environment? What is the fate in surface water and in STP? What are the modes of action of these compounds in humans and are there similar targets in lower animals? What acute and chronic ecotoxicological effects may be elicited by pharmaceuticals and by mixtures? What are the effect concentrations and how do they relate to environmental levels? In view of these newer expositions, the monitoring of adverse effects of drugs is an important component not only of good medical practice but also for environmental protection. Like pharmacovigilance and pharmacoepidemiology, it is befitting if we describe this new subject under one term for better discerning and understanding. Pharmacoenvironmentology could be one better terminology, which should mean study of drugs in terms of benefit and risk on environment. It could be a science concerned with the benefit and risk of drugs used in populations and the analysis of the outcomes of drug therapies.

 

References:

  1. Fent K, Weston AA, Caminada D. Ecotoxicology of human pharmaceuticals. Aquat Toxicol. 2006;76(2):122-59. Epub 2005 Oct 27.
  2. Green RE, Newton I, Shultz S, Cunningham AA, Gilbert M, et al. Diclofenac poisoning as a cause of vulture population declines across the Indian subcontinent. J App Ecol. 2004; 41:793–800.
  3. Oaks JL, Gilbert M, Virani MZ, Watson RT, Meteyer CU, et al. Diclofenac residues as the cause of vulture population declines in Pakistan. Nature. 2004; 427:630–633.
  4. Anon. 16th Indian Livestock Census 1997. New Delhi: Ministry of Agriculture, Department of Animal Husbandry and Dairying, Government of India; 1997.
  5. Prakash V, Pain DJ, Cunningham AA, Donald PF, Prakash N, et al. Catastrophic collapse of Indian white-backed Gyps bengalensis and long-billed Gyps indicus vulture populations. Biol Con. 2003; 109:381–390.
  6. The Peregrine Fund. Asian Vulture Population Project. 2004.
  7. Houston, DC. The use of vulture to dispose of human corpses in India and Tibet. In: Newton I, Olsen P. editors. Birds of Prey. London: Merehurst Press; 1990.
  8. Gerry Swan, Vinasan Naidoo, Richard Cuthbert, et. al. Removing the Threat of Diclofenac to Critically Endangered Asian Vultures. PLoS Biol. 2006: 4(3): e66.
  9. Pallava Bagla. Common Cure may vex vultures. Science Now. Jan 28 2004.
  10. UK's Sunday Telegraph newspaper, 6 Nov. 2005.

Note:

  1. Adverse drug reactions are those obnoxious reactions of drugs which occur at doses normally used in man (therapeutic doses) for therapy, prophylaxis, diagnosis and for any physiological modification.
  2. Pharmacovigilance is the science and activities relating to the detection, assessment, understanding and prevention of adverse drug reactions or any other drug-related problem.
  3. Pharmacoepidemiology is the study of use and effects of drugs in terms of benefit & risk in large number of population.

 

The above figure shows cocaine traces detected in River Thames

White-backed Vulture (Gyps bengalensis)