Human and veterinary medicines may be released to the environment by a number of routes. During the manufacturing process, residues may be released from the process and may ultimately enter surface waters. Following administration, human medicines may be absorbed, metabolised and then excreted to the sewer system. They will then enter a treatment works before being released to receiving waters or land during the application of sewage sludge. When used to treat pasture animals, veterinary medicines may be excreted directly to soils or surface waters. Aquaculture treatments will be released directly to surface waters. For intensive livestock treatments, the medicines are likely to enter the environment indirectly through the application of slurry and manure as fertilisers to land. Other minor routes of entry include emissions to air and through the disposal of unused medicines and containers. Once released into the environment, pharmaceuticals will be transported and distributed to air, water, soil or sediment. A range of factors and processes including the physico-chemical properties of the compound and the characteristics of the receiving environment will affect distribution.
Whilst pharmaceuticals will have been released to the environment for decades, it is only recently that attempts have been made to quantify the levels of these compounds in the environment. Using new analytical techniques such as Liquid Chromatography Tandem Mass Spectrometry (LC-MS-MS), low levels of a range of pharmaceuticals, including hormones, steroids, antibiotics and parasiticides are now being detected in soils, surface waters and groundwaters internationally (e.g., Hirsch et al. 1999; Kolpin et al. 2002). Whilst the reported concentrations are generally low (i.e., sub mgL-1 in surface waters), the substances have been observed across a wide variety of hydrological, climatic and land-use settings and many of the substances have been detected throughout the year. As a result, questions have been raised over the impacts of veterinary medicines on organisms in the environment and on human health.
Was this article helpful?