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Antidepressants Like Prozac Harming Starling Bird Populations

A specific type of bird known as a starling tends to gravitate towards sewage treatment facilities to feed on earthworms. Many of these earthworms have already absorbed human waste, some of which contains psychotropic drugs like Prozac. A new study supports the idea that increases in the number of antidepressant prescriptions may be helping people maintain a happy mood, but may be simultaneously detrimental to the health of wildlife species – specifically starling birds.

A new study conducted by Kathryn Arnold, an ecologist at the University of New York, decided to investigate the specific impact of “environmentally relevant” levels of the SSRI antidepressant Prozac on starlings. This meant determining the concentration of Prozac within the earthworm populations near sewage treatment plants, and then using the same amount to administer to a population of starling birds. The goal was to figure out whether the traces of Prozac could be problematic for this species and to determine how it is specifically affecting them.

The findings of the study were pretty striking – starlings that consume environmentally relevant levels of Prozac don’t eat as much and the drug reduces their interest in mating. Kathryn Arnold was quoted stating, “Females who’d been on it were not interested in the male birds we introduced them to. They sat in the middle of the cage, not interested at all.” This research suggests that pharmaceutical drugs like antidepressants may be detrimentally affecting survival rates of certain wildlife.

Behavioral & Physiological Responses of Starling Birds to Environmentally Relevant Levels of Prozac

Kathryn Arnold knew that certain species were drawn to scavenge and consume food near sewage treatment facilities. The idea for the study came about when Kathryn Arnold questioned, “What about what’s in the sewage?” She stated that when we take a pill for a headache, a big portion of it ends up being unchanged. It is known that many wildlife species scavenge for food near sewage treatment facilities.

When the sewage is treated, water is then thought to be clean, and gets filtered back into the environment. Unfortunately, many water treatment plants are unable to remove pharmaceutical drug residue with their filters. It is thought that the water and spreading off sewage “sludge” for fertilization may contain drugs that are indirectly being absorbed by earthworms, which will inevitably get consumed by starlings (birds).

The amount of Prozac found within earthworms that are consumed by starling birds was significantly smaller than a standard dose taken by humans. It is estimated that the dosage was approximately 3% of a standard human dose taken for depression. To test the effects of this Prozac on starling birds, Arnold et al. fed earthworms with this same level of concentration to starlings.

Prozac-starlings vs. Control group

She monitored the behavior of 24 starling birds and compared it with a control group over the course of nearly six months. The birds given Prozac experienced some prominent side effects, specifically loss of appetite and decreased interest in mating. The problem with these effects is that they may inevitably contribute to a starling population decline. The behavior exhibited by the birds given Prozac is not optimal for ensuring survival in winter months.

Differences between Prozac birds and control group…

The study found that there were no major differences in overall activity levels between the two groups of birds. Additionally it was found that they also did not differ in evaluations of “boldness” and “exploration.” However, they did differ in how they responded to isolation – specifically regarding excrement of corticosterone metabolites.

The control group excreted significantly more corticosterone metabolites on Day 1, lost more body mass on Day 2 of isolation than birds with lower levels of corticosterone metabolites. The corticosterone metabolites and mass didn’t differ among the birds given Prozac.

  • Control group: Made a significantly greater number of visits to the food tray during important feeding periods. Female starlings that weren’t given Prozac maintained normal levels of interest in mating when placed in a cage.
  • Prozac group: Made a significantly less number of visits to the food tray during important feeding periods. It should also be noted that female starlings given Prozac were less interested in mating while in a cage compared to the control group.

This suggests that the levels of Prozac may be contributing to the demise of birds, and potentially other species. Feeding during important periods of sunrise and sunset during the winter is associated with a greater likelihood of survival. Those who don’t feed at optimal times may ultimately become weaker and more likely to die.

Note: The researchers noted that individual variability can make interpretation of this data difficult. Their data suggests that “environmentally relevant” concentrations of Prozac can result in significant changes to behavior and physiology of starlings.

How drugs like Prozac end up in the environment

It can be somewhat difficult to understand how a pharmaceutical pill like Prozac could end up contaminating the environment. Below is a step-by-step guide that you can follow for better understanding. It should also be mentioned that in addition to animals absorbing various drugs, humans also can end up getting trace levels of psychiatric drugs in their “filtered” drinking water.

  1. People take pills – When someone takes a pill, their body absorbs some of the drug, but the remaining formula gets digested and passed through urine or feces.
  2. Residue gets flushed – The unused portion of the pharmaceutical drug eventually makes its way into the toilet and gets flushed. Once its flushed, it travels into a sewage treatment facility and is processed.
  3. Water treatment – The water treatment facility essentially filters out as much residue as possible, but doesn’t filter out all residue from drugs.
  4. Discharged – The treated water is then discharged back into the environment in lakes, rivers, and reservoirs. This treated water is then ready for consumption and filtered back to consumers via drinking water.
  5. Drug residue – Most water treatment plants are unable to fully remove the drug residue. This means that traces of drugs that people took still remain in drinking water and in the environment around the treatment facilities. Many times sewage “sludge” is used as fertilizer near a sewage plant – this results in the drugs getting absorbed by earthworms.
  6. Consumption – This results in people and animals indirectly consuming various types of medications, such as Prozac in their water supply. Additionally, this means that certain types of wildlife such as birds that may scavenge near a treatment facility where the water is pumped out, may end up getting traces of the pharmaceutical chemicals.

Does this mean that Prozac and other drugs are harming birds?

In some cases, it is certainly possible that Prozac and other psychotropic drugs are affecting bird species as well as other forms of wildlife. It should be noted that this study specifically measured the effects of Prozac at an environmentally “relevant” level. Whether the level in this study was environmentally relevant could be questioned.

Important things to keep in mind…

  • Reactions may differ based on species – Just because starling birds reacted by not eating at normal feeding times and females were reported to be uninterested in mating, does not necessarily mean that all species will exhibit the same reactions. Reactions could differ based on the specific bird species as well as in other forms of wildlife.
  • Not all wildlife is exposed to antidepressants – Although it is likely that the starling population and other birds are exposed to some psychotropic medications like Prozac in minor concentrations, not all forms of wildlife will experience the same degree of exposure.
  • The specific drug – It is important to keep in mind that starlings that scavenge near sewage treatment facilities are likely exposed to more than just Prozac. Antidepressants have become popularized throughout the world, but other medications like antipsychotics, birth control pills, painkillers, etc. may also get absorbed. The accumulation of these drugs may result in a variety of effects that are difficult to track.
  • Accuracy of Prozac concentrations – Based on the way researchers estimated relevant levels of Prozac, most would agree that the amount administered was confirmed as being accurate. They used a dosing of 1.3 µg fluoxetine 5 days per week (0.92 µg d−1). Based on the factors below, researchers were able to confirm their estimation of dosing for these birds was approximately 0.92 µg d−1. Estimates were confirmed based on an analysis of worms from trickling filters, giving a mean concentration of earthworms.  This amount was determined by calculating the following:
    • Mass: The mass of Prozac prescribed in England each year.
    • Volume: Volume of wastewater per capita each year.
    • Percentage: % of the active ingredient “fluoxetine” that is excreted and unchanged.
    • Population: The entire population of England.
    • Bioconcentration: This was calculated based on the amount of Fluoxetine found in soil samples and worms. They also factored in the mass of invertebrates (worms) consumed each day by the starling population.
  • Levels of other drugs – Many people do not know the levels of drugs that get passed through treatment and work their way back into the environment. Certain drugs may be more likely to get filtered back into the environment at higher concentrations than others. Additionally, certain substances may end up causing more harm than others. It would be interesting to compare other forms of pharmaceutical drugs and attempt to gauge their impact.

Future research involves chemical residue

Since it is thought that pharmaceuticals may be contributing to the demise of the starling population, the next step for researchers is to determine whether starlings have chemical residue in their bodies. Research has shown that the starling population in the United Kingdom has declined by 50 million since the 1960s. While part of the population drop may be influenced by an array of other factors, it is important to gauge the impact of pharmaceutical drugs on this particular population.

It is important to understand that the researchers aren’t attacking the pharmaceutical industry nor are they placing blame on water treatment facilities. They are merely trying to determine the impact pharmaceuticals are having on wildlife, particularly in a species that thrives near sewage treatment plants.

  • Source: http://rstb.royalsocietypublishing.org/content/369/1656/20130575.full

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