Psychiatric drugs and Fish

Psychiatric drugs used to alter behaviour in humans that find their way into aquatic systems are doing just that – altering the behaviour of the vertebrates in those systems. See the full paper here.

There is an increasing awareness and concern over the pollution of aquatic systems by pharmaceutical drugs worldwide. Anxiolytic drugs are commonly used to treat anxiety in humans, but when they enter the waterways in waste water, they are still biochemically active. This means that they persist in the system, especially since they are resistant to photodegredation (the decomposition of a compound by radiant energy from the sun). Although studies have been conducted into the effects of these chemical toxins on the biology of these systems (ecotoxicological studies), little is actually know about the ecological effects this pollution may have. Brodin et al (2013) have shown that exposure to these toxins change the behaviour and feeding rate of wild European perch – the fish show evidence of increased activity, decreased ‘sociality’ and a higher feeding rate. All these behaviours are considered important ecologically and evolutionarily because they affect how the fish interact, survive and reproduce. A change in these behaviours can lead to a change in the entire functioning of the ecosystem.

A brilliantly coloured European Perch (http://www.fishandfly.com)

This is the first study that actively shows changes in behaviour of organisms (in this case, fish) exposed to these toxins. Even though the concentrations in the natural environment are low, they are still there and are having an effect. There was a higher concentration of the drug in the tissue muscle of the fish than in the surrounding waters which indicated bioaccumulation, and leads to thoughts on the potential impacts this will have on those who consume the fish. The changes in behaviour induced by these toxins influence the aquatic community composition and thus, system function. This puts additional pressure on ecosystems already under stress from development, water extraction and other sources of pollution. It may impact the resilience of these systems to change, putting vulnerable systems at further risk along with the ecosystem services and goods these systems provide. We have to protect our freshwater sources and systems.

Fish behavioural responses to two concentrations (low: 1.8μg litre ^-1; high: 9108μg litre ^-1) of dissolved oxzazpam

compared to control treatment (08μg litre ^-1). (a) Activity, measured as level of swimming over 10 minutes (b) Boldness, measured as willingness to enter a new area during trial time (900s) (c) Sociability, measured as amount of time (seconds) spent close to another group. The error bars show standard error, and statistically significant differences between pre- and post-treatment is given by * (*p<0.05 or **p<0.001)  

[Brodin et al (2013) Science 338:814]

This study is no doubt an important one – the pollution of our freshwater systems is of major concern in the face of an increasing human population and potential future water shortages due to climate change. The study screened Swedish stream surface waters and found concentrations of oxazepam, a common anxiolytic drug, in both treated waters and in a mid-sized stream into which treated water flows. The fact that there are pharmaceutical products in these systems and that these are affecting the organisms in them can have major consequences in the potential usability of that water. No one wants to use water with psychiatric drugs still present in it! This also has major consequences for how we treat waste water, especially since these anxiolytic drugs remain biochemically active and do not decompose naturally, and thus continue to produce effects if taken into the body. The fact that these concentrations are comparable to those found in European and American waters should be cause for concern. The high demand for water in First World countries will no doubt spill over to the already water stressed Third World, with potential humanitarian issues. Pharmaceutical companies need to be made aware of this pollution, and incentives need to be devised to manufacture drugs with some foresight into where they will end up at the end of the chain. 

The strengths of this study include the neat and clean experimental design, as well as the utilisation of previously tried and tested techniques for quantifying behavioural change. However, the conclusions drawn by this study can be questioned - the concentrations of anxiolytic drugs the experimental fish were exposed were far higher than the concentrations reported out in the field. For example, the concentrations of oxazepam in Swedish streams were found to be 0.73 μg per litre in treated wastewater, and 0.58 μg per litre in a midsized stream receiving the input of treated water. Despite this, the experiment exposed fish to a “low” treatment concentration of 1.8 μg per litre, more than double that found in the wastewater effluent. The “high” exposure was at an impossible 910 μg per litre – of course the fish were going to show behavioural changes at such high dosages! There is no possible scenario where the concentrations of anxiolytic drugs will reach that level through wastewater input. 

Despite the shortcomings, this study has implications for my work as an ecologist - there is now a new factor to be considered when observing behaviour and ecosystem interactions. There are currently no studies of this sort here in South Africa, and so we don’t know what the implications of this may be on our systems. There is also no indication of the effects of this type of pollution on marine systems, but as most water systems lead to the ocean and as a large number of wastewater systems empty into the global ocean there must be some evidence, we just haven’t looked for it yet. Does the bioaccumulation of pharmaceutical products, as well as mercury, impact top marine predators such as tuna and sharks, and should we thus be cautious of consuming such fish? We do know however that anxiolytic drugs are not the only pharmaceuticals entering our waterways – the impacts of one such drug, oxazepam, on behaviour of European perch should alarm us all the more when we consider that there is a cocktail of pharmaceutical products found in waters worldwide, and that these may have direct compounding effects on behaviour and ecosystem function. The presence of pharmaceutical products in our water can be predicted to increase as they become more available for the growing human population, and thus new protocols must be implemented to determine the full impact these toxins have on our environment and ourselves.