Antidepressants in the environment: combatting pharmaceutical pollution
Research by scientists at the University of Portsmouth has found that traces of clinical antidepressants present in waste water, rivers and some coastal areas may have significant consequences for underwater wildlife. Sally Turner finds out what needs to be done by prescribers, patients, government and big pharma to help combat the problem.
Around six million people in the UK – roughly 10% of the population – now regularly take antidepressant medication such as Prozac (fluoxetine) and the figure has doubled in the last decade. Detectable levels of these drugs, and other commonly used medications, have been found in the UK’s sewage, drinking water, rivers, coastal waters and animal tissues, and pose a potential threat to natural habitats and ecosystems. Pharmaceutical pollution is a major concern for environmental toxicologists with the widespread use of psychotropic medication a particular issue in high-income countries.
In a recent abstract for the British Journal of Psychiatry, experts at the University of Portsmouth have called for prescribers of antidepressants (GPs and healthcare professionals) to consider the wider implications of antidepressant use.
Professor Alex Ford, a biologist at the university and an expert in the effects of human waste on marine life says: “There is much debate about the overprescribing of antidepressant medication and hence we wanted to include an environmental aspect to that debate.”
His colleague Dr Helena Herrera, an expert in ethical pharmacology, adds: “There is a large interest within publicly funded health systems to reduce the use of medicines, both to reduce unnecessary costs and adverse effects. While these drugs have a clear place in therapy, there is debate around the risk/benefit ratio in patients with mild mental health problems. Therefore it is necessary to evaluate the wider implications as risks could extend beyond the individual to non-target organisms, particularly those in rivers and estuaries.”
Effects of pharmaceutical pollution on wildlife
The first reports of commonly prescribed drugs being found in the marine environment were in the 1960s, but it was 30 years before scientists had evidence that the contraceptive pill and hormone replacement therapy drugs in waste water could feminise fish. Since then, a growing body of research has revealed that pharmaceutical pollution is a potential threat to ecosystems, with antidepressants and anti-anxiety drugs now garnering particular interest from environmental toxicologists.
Antidepressants generally act on neurotransmitters and their transporter proteins in humans. These neurohormones and transporters are also found extensively throughout the animal kingdom, and hence, any drug designed to alter the biology of a human will also alter the biology of wildlife.
“Neurotransmitters such as serotonin and dopamine not only control behaviour as they do in humans, but also many other biological functions in animals especially invertebrates,” explains Ford. “Laboratory studies are reporting changes to growth, immunity, reproduction, metabolism, feeding habits, movement and even to the capacity to change colour. This isn’t about a one-off pollutant entering their habitat; wildlife are bathed in drugs for their entire lifecycle.”
This isn’t about a one-off pollutant entering their habitat; wildlife are bathed in drugs for their entire lifecycle.
In a previous study, Ford found Prozac in wastewater made shrimps leave their natural habitat and swim towards the light, making them more vulnerable to predators. In another study, Prozac in wastewater was found to cause some aquatic creatures to lose their ability to stick to surfaces; snails, for example, were no longer able to cling to rocks.
Previous research by Jonatan Klaminder, an ecologist at Umeå University in Sweden, also showed that another class of psychotropic drug, benzodiazepines (which includes diazepam, commonly known as Valium) can also affect the behaviour of aquatic creatures. He discovered that fish exposed to oxazepam in a lab tank (the drug had been detected in Swedish rivers) became less anxious and put more effort into feeding, which had a positive effect on their growth. However, in the wild less fearful fish might well be easy targets for predators and changes in behaviour could impact on the entire food chain.
Ford is keen to point out that many of these research findings are lab-based and there is no indication that psychotropic drug pollution is a problem in the open ocean.
“It is primarily an issue for rivers with the drugs in wastewater generally becoming more dilute as rivers flow down to the estuaries,” he says. “That said, some countries dump their sewage effluent directly into the sea sometimes several miles offshore.”
A potent cocktail
Some antidepressant medications act differently in the presence of other drugs and this potentially enhances their unwelcome effects in the environment, explains Ford.
“Effluent from wastewater treatment plants can contain over 1,000 different drugs and one of the major challenges for eco toxicologists is to determine the effects of these drug mixtures,” he comments. “We simply don't know well enough the impact of these mixtures although studies have shown that by upgrading the wastewater treatment you can get an improvement in the health of the animals downstream and the overall biodiversity.”
Effluent from wastewater treatment plants can contain over 1,000 different drugs.
Herrera adds: “Testing of these drugs as part of authorisation studies does not include looking at mixtures which are not used in clinical practice. Therefore there is no data on how drugs which are not meant to be taken together may interact at any concentration.”
How to counter the threat
There are various ways to reduce the problem of pharmaceutical waste in effluent. Top of the list is upgrading all of the UK’s wastewater treatment plants to comply with EU regulation on pollutants (the EU is particularly keen to bring synthetic oestrogens to an acceptable level).
“Second is addressing the question of whether we as a society are overprescribing or turning too quickly to antidepressants when alternatives, in particular counselling, might be more suitable,” says Ford.
Herrera also raises similar concerns: “These medicines should be provided to patients alongside other forms of support, as they have a wide range of adverse effects, but rather they are often prescribed as a ‘quicker fix’, as health systems have limited additional resources to support these patients.”
These medicines should be provided to patients alongside other forms of support, as they have a wide range of adverse effects.
Another key point is educating patients to return their waste medication to the pharmacy where it can be safely disposed of, rather than flushing it down the toilet or throwing into the rubbish bin where, in landfill later, it can leech into ground water.
“This depends on the country as to whether the pharmacy disposal service is free,” continues Ford. "There have been calls in some US states for the pharma industry to pay for the ‘take back’ programmes.”
Finally, the pharmacological industry needs to move towards a ‘cradle-to-grave’ approach with drugs that are designed and dispensed, by making it easier for them to be safely broken down. However, development of biodegradable drugs isn’t straightforward.
"It's very difficult for pharma to create ‘green’ pharmaceuticals,” concludes Ford, “as the properties required to keep them stable in the body are precisely the opposite to that required to break down in the environment.”
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