Olsson Associates


Olsson seeks to understand pharmaceutical hazards in surface waters

Monday, May 18, 2015

Neil Wolfe, Environmental Assessment

The entirety of this research article was published in the winter 2015 issue of the Global Journal of Environmental Science and Management, which can be found here.

The majority of that pill you took this morning, be it a vitamin or an antibiotic, will pass straight through your body, unabsorbed. Further, it was only a few years ago where it was common practice to wash unused drugs down the drain. Surely a few pills down the pipes can’t hurt, can they? But all those “few pills” have to have some effect on the waters and aquatic life where they end up, right?

Not according to current research.

Pharmaceuticals have been detected in surface waters around the world. In a 2002 study, researchers sampled 139 U.S. streams and rivers and detected pharmaceuticals in 80 percent of those surface waters.

One of these bodies of water is the Tennessee River watershed, where a cocktail of 13 pharmaceuticals were consistently found. Tennessee ranks fourth in the United States for prescription drug use, making the Tennessee River watershed an ideal location to look at pharmaceutical concentrations and the hazards of those compounds. This is also the location where a study was conducted to research the effect of pharmaceuticals on freshwater zooplankton.

The study posed two questions:

  1. If these pharmaceuticals are being continuously released into surface water, at what concentration will they pose a threat for aquatic life?
  2. Is it just one pharmaceutical causing an effect or is it the mixture of pharmaceuticals?


To answer these questions and to evaluate the chronic aquatic toxicity of the pharmaceuticals that were found in the Tennessee River, a “lab rat” was needed. Zooplankton were studied for several reasons, including the following:

  • Studying zooplankton does not require special permits.
  • Zooplankton play a significant role in aquatic food webs.
  • Zooplankton can also be a helpful tool in screening for toxins in that they are sensitive to pollutants and undergo rapid reproduction.
  • They have been shown to be more susceptible to effects from pharmaceutical exposure than other aquatic organisms, including fish.

Over the course of a two-year study, the 13 pharmaceuticals consistently detected in the Tennessee River watershed ranged from caffeine (most abundant found) to the active pharmaceutical compounds in Prozac and Zoloft, as well as a handful of other antibiotics. The research looked at how the zooplankton reacted to this pharmaceutical brew to determine if the mixture had a lower Lowest Observed Effect Concentration (LOEC) than any pharmaceutical by itself, and at what concentration would we see this effect. Or, was there one (or more) of the single pharmaceuticals that was contributing significantly to reduced reproduction among the zooplankton? In a sense, was it one pharmaceutical by itself that caused zooplankton to reproduce less, or was it a mixture of the pharmaceuticals? If yes in either case, how much of the pharmaceuticals would need to be present to have an effect?

Two individual pharmaceutical tests did result in a decline (though statistically insignificant) in zooplankton reproduction. The fluoroquinolone antibiotics ciprofloxacin and levofloxacin showed a decrease in zooplankton reproduction of 87.5 percent and 88.2 percent, respectively. Fluoroquinolone are broad-spectrum antibiotics that are used to treat serious bacterial infections, especially hospital-acquired infections and others where there can be resistance to older antibacterial drugs.


Not surprisingly, the LOEC of the mixture of pharmaceuticals was found to be lower than any pharmaceutical individually—meaning that the mixture was deemed more harmful than any one pharmaceutical by itself at the same concentrations. This LOEC of the mixture was found to be 49.6 parts per million or 49.6 micrograms per liter. This means that, compared side by side, less of the mixture was needed to begin affecting the zooplankton’s reproduction. Now, while the mixture was found to be more toxic than any one pharmaceutical, the amount of the mixture had to be raised 100 times greater than what was found in the Tennessee River.

Most studies that address the ecological hazard of pharmaceuticals only account for the toxicity of single pharmaceutical exposure, usually under acute conditions (such as a catastrophic spill), and do not take into account steady, additive effects that can occur in mixtures. This is a concern given that low-level combinations of pharmaceuticals are continually released into the world’s waters on a daily basis. Aquatic environments and their species are being continually exposed over the course of their life cycles.


The purpose of this study was to determine if modern-day mixtures of hazardous pharmaceuticals had an effect on the environmentally sensitive zooplankton. The research conducted suggested that the current hazard of the 13-pharmaceutical mixture in the environment was low. However, some consideration needs to be given to future hazards that could be caused by the increasing size and age of human populations and the associated, subsequent increases in drug use.

In addition, the present research (and that of others) indicates that, as the number of pharmaceuticals added to the system increases, the potential for adverse responses is likely to increase as well. With more than 3,000 active pharmaceutical ingredients in use today, the possibility of many more pharmaceuticals in the environment cannot be ignored.

While we are, indeed, a long way from reaching the perceived hazard, it is difficult to determine how long—or if—this 100-fold safety margin could be maintained as human populations grow and we consume more pills. We must also keep in mind that there are other environmentally relative pharmaceutical mixtures that are floating around out there. Currently, science does not know at what level or what effects they might pose on different ecosystems.

If you’d like more information on this study or have further questions, please contact me at 402.458.5673 or nwolfe@olssonassociates.com.

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