Friday, March 1, 2013
It is a challenge faced by many scientists: ensuring that solutions in beakers, numbers in computer models, and cells on slides match what is happening outside the lab. And for those studying pharmaceutical pollution in waterways, it is no different. Nearly two decades of results have shown that pharmaceutical chemicals are common in lakes and rivers and that many are harmful to fish and wildlife. But most of those findings come from studies conducted in the lab–where you don't find the variability in temperatures, dissolved oxygen, and presence of other chemicals that you do in lakes and rivers–and using concentrations high above what has actually been found in waterways. Research into pharmaceutical pollution is on the rise, but it still reveals little about the risks these chemicals pose to the wildlife and humans that are exposed to them.
That is the conclusion of a new global analysis of pharmaceutical research published early this year in Environmental Science and Technology. For this report, British researchers conducted a detailed analysis of more than 200 studies focusing on pharmaceuticals in waterways that receive water from treatment plants. The studies came from 28 academic journals, 41 countries, and a dozen years of research.
Perhaps their most surprising discoveries had little to do with the results, but the process of conducting a study itself. For example, a closer look revealed that the findings of most studies cannot be reliably generalized to other water bodies, organisms, or even seasons. These studies tended to rely on 'grab sampling', a common testing method that captures only a snap-shot in time and doesn't represent what is happening in the waterway overtime. This means that the impacts of a chemical on fish living in one location in May says little about what fish are experiencing downriver or in December.
The ability to generalize results is made even more difficult by the fact that studies have clustered around a few waterways near populated areas. In the United States, this means California and the Northeastern seaboard. And on a global scale, this means that most of the world has seen little or no research on pharmaceutical pollution in receiving waters–including all of Africa.
The British researchers also discovered that the studies conducted so far are focused on a small proportion of the pharmaceuticals being prescribed–fewer than 4 percent. Most of these are antibiotics, antiepileptics, cardiovascular drugs, and painkillers. The focus on these chemicals is understandable, especially in the U.S., where cardiovascular drugs and painkillers are among the most prescribed medicines. But focusing on a few chemicals, even after numerous studies suggest that some pose no risk to wildlife, leaves a lot unknown about major classes of pharmaceuticals, including antidepressants and cancer treatments.
Hughes, S.R., Kay, P., and Brown, L.E. 2013. Global synthesis and critical evaluation of pharmaceutical data sets collected from river systems. Environmental Science and Technology (47): 661-677.
Written by: Anjanette Riley, IISG Science Writer