Pharmaceuticals persistence

Among pharmaceuticals, antibiotics have become of special concern in recent years. The reason is that these substances are continuously being introduced into the environment and may spread and maintain bacterial resistance in the different compartments. Sulfonamides are very commonly used antimicrobials in humans but mainly in veterinary medicine, due to their broad spectrum of activity and low cost, being the second most widely used veterinary antibiotic in the EU. Their occurrence has been reported in all kinds of water matrices their high excretion rates (after their intake by humans of livestock) and high water solubility make them very ubiquitous and persistent pollutants in the environment. 

Carbamazepine (anticonvulsant) is one of the most frequently detected pharmaceuticals in environmental and sewage treatment plant samples, known for its persistence. Its presence has been detected in treatment plants in concentration range from 1.7 ng/g in South China [56] to 120 10 ng/g in Ireland [50]. In Spain reported levels of carbamezapine ranged from 11 to 42 ng/g [130] in one study, while Radjenovic et al. [49] reported levels between 74 and 90 ng/g. 

Chenxi W, Spongberg AL, Witter JD (2008) Determination of the persistence of pharmaceuticals in biosolids using liquid-chromatography tandem mass spectrometry. Chemosphere 73 511-518... 

Citalopram and fluoxetine are antidepressant drugs widely used in human medicine and very persistent in WWTPs. However, there are few studies about the degradation of these pharmaceuticals by fungi and none of them identifies TPs. 

Apart from persistent organic pollutants considered in the monitoring programme, others compounds like pharmaceuticals [88] and drugs [89] were also analyzed in the entire Ebro river basin, and the results obtained are presented in [102, 103]. 

The high amounts in which these substances are consumed and produced have conferred illicit drugs and their human metabolites a pseudo-persistent character in the environment. Like over-the-counter and prescribed pharmaceuticals, illicit drugs are metabolized after consumption and different proportions of the parent compound and metabolic by-products are excreted via urine or feces and flushed into the sewage system toward wastewater treatment facilities, if existing. However, these substances are poorly or incompletely removed by conventional waste-water treatment processes [2, 3]. As a consequence, illicit drugs and metabolites are continuously introduced via wastewater treatment plant (WWTP) effluents into the aquatic media. In fact, this constitutes the main route of entry of this type of compounds into the environment as direct disposal is unlikely. 

Historically, organic environmental pollutants were hydrophobic, often persistent, neutral compounds. As a consequence, these substances were readily sorbed by particles and soluble in lipids. In modern times, efforts have been made to make xenobiotics more hydrophilic - often by including ionisable substituents. Presumably, these functional groups would render the compound less bioaccumulative. In particular, many pesticides and pharmaceuticals contain acidic or basic functions. However, studies on the fate and effect of organic environmental pollutants focus mainly on the neutral species [1], In the past, uptake into cells and sorption to biological membranes were often assumed to be only dependent on the neutral species. More recent studies that are reviewed in this chapter show that the ionic organic species play a role both for toxic effects and sorption of compounds to membranes. 

Gibs J, Stackelberg PE, Furlong ET, Meyer M, Zaugg SD, Lippincott RL (2007) Persistence of pharmaceuticals and other organic compounds in chlorinated drinking water as a function of time. Sci Total Environ 373 240-249... 

Stackelberg PE, Furlong ET, Meyer MT, Zaugg SD, Henderson AK, Reissman DB (2004) Persistence of pharmaceutical compounds and other organic wastewater contaminants in a conventional drinking-water-treatment plant. Sci Total Environ 329 99-113... 

According to the current knowledge, residues of pharmaceuticals and their metabolites are widespread in the aquatic systems. Surface water monitoring programmes in Europe and North America [3-8] have shown, as a result of improved analytical capabilities [9, 10], the presence of many different classes of pharmaceuticals, some of which are known to be environmentally persistent [10]. 

The Swedish Classification Scheme initiated in 2005 by the Swedish Association of Pharmacy Industries (LIF), the Swedish Medical Products Agency, Apoteket (National Corporation of Swedish Pharmacies), the Swedish Association of Local Authorities and Regions and the Stockholm County Council, take in account Persistence, Bioaccumulation and Toxicity (PBT) characteristics of pharmaceutical products. This voluntary scheme looks at the environmental hazard and the associated risk of pharmaceutical products. The environmental risk is calculated based on the ratio PEC/PNEC according to the EMEA guideline [17,124, 127]. The obtained information is only available on the website www.fss.se, since due to European restrictions it is not possible to include warning labels on the packaging of medications [17]. 

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