In most cities sewage is treated to remove most of the things that we don't want going into the environment. But, some things get through and out to sea. The Western Treatment Plant in Melbourne, which treats over 50% of Melbourne's wastewater (including my contribution), releases large amounts of nitrogen into Port Phillip Bay. Indeed, a 1996 report from the Commonwealth Scientific and Industrial Research Organisation recommended that nitrogen released from the Western Treatment Plant be reduced by 1000 tonnes per year. Nearly 20 years later they've achieved half that amount.
|The Western Treatment Plant. Covering 10,500 hectares it treats about 50% of Melbourne's wastewater.|
Nitrogen pollution is significant issue. It, along with other types of nutrient pollution, has been linked to coral and seagrass declines, and jellyfish blooms. Other things that cause problems in the ocean also slip through sewage treatments plants. From the relatively large things, like plastic fibers from clothing, to the very small, like the drugs we take.
Not all drugs remain active after they've done their job in the human body, but many do. One of the best known and most researched drugs to escape sewage treatment is ethinyl oestradiol, the active ingredient in birth control pills. Decades of research has shown that ethinyl oestradiol has negative impacts on fish and other aquatic organisms. Even very small doses can lead to male fish that produce eggs in their testes, leading to reduced fertility and potentially to population collapse (Kidd et al. 2007).
|Sections through the testis of two male fish showing developing eggs, which are the large circular cells surrounded by purple staining tissue. The smaller purple staining flecks are the sperm cells.|
Exposure to the concentrations of caffeine that are normally found in the environment probably have little or no effect on fish. Unlike caffeine, some drugs can build up in the body tissues of fish, making chronic exposure to even low concentrations a risk. Recently a study found that the concentration of a common anti-anxiety medication, oxazepam, was six times higher in the muscle of redfin perch (Perca fluviatilis) than it was in the surrounding river water (Brodin et al. 2013).
|A redfin perch, Perca fluviatilis, in an aquarium (photo Wikipedia)|
Although they scuffed their experiment a little with their choice of concentrations, they did do something that few other ecotoxicology studies do. They looked at behavioural traits that are important for the survival of fish in the wild. Too slowly are excotoxicologists moving away from testing the lethal effects of pollutants, often requiring doses that never occur in the wild. Hopefully, the publication of the Brodin et al. paper in the prestigious journal Science will encourage more researchers to examine the effects of pollutants at the levels which they typically occur and on a greater range biologically interesting traits.
Kasprzyk-Hordern, B., Dinsdale, R., & Guwy, A. (2009). The removal of pharmaceuticals, personal care products, endocrine disruptors and illicit drugs during wastewater treatment and its impact on the quality of receiving waters Water Research, 43 (2), 363-380 DOI: 10.1016/j.watres.2008.10.047
Rey, Z., Granek, E., & Buckley, B. (2011). Expression of HSP70 in Mytilus californianus following exposure to caffeine Ecotoxicology, 20 (4), 855-861 DOI: 10.1007/s10646-011-0649-6
Rodriguez del Rey, Z., Granek, E., & Sylvester, S. (2012). Occurrence and concentration of caffeine in Oregon coastal waters Marine Pollution Bulletin, 64 (7), 1417-1424 DOI: 10.1016/j.marpolbul.2012.04.015
Brodin, T., Fick, J., Jonsson, M., & Klaminder, J. (2013). Dilute Concentrations of a Psychiatric Drug Alter Behavior of Fish from Natural Populations Science, 339 (6121), 814-815 DOI: 10.1126/science.1226850