Photodegradation of pharmaceuticals in the aquatic environment by sunlight and UV-A, -B and -C irradiation

Abstract

-In order to investigate the effect of sunlight on the persistence and ecotoxicity of pharmaceuticals contaminating the aquatic environment, we exposed nine pharmaceuticals (acetaminophen (AA), amiodarone (AM), dapsone (DP), dexamethasone (DX), indomethacin (IM), naproxen (NP), phenytoin (PH), raloxifene (RL), and sulindac (SL)) in aqueous media to sunlight and to ultraviolet (UV) irradiation at 254, 302 or 365 nm (UV-C, UV-B or UV-A, respectively). Degradation of the pharmaceuticals was monitored by means of high-performance liquid chromatography (HPLC). Sunlight completely degraded AM, DP and DX within 6 hr, and partly degraded the other pharmaceuticals, except AA and PH, which were not degraded. Similar results were obtained with UV-B, while UV-A was less effective (both UV-A and -B are components of sunlight). All the pharmaceuticals were photodegraded by UV-C, which is used for sterilization in sewage treatment plants. Thus, the photodegradation rates of pharmaceuticals are dependent on both chemical structure and the wavelength of UV exposure. Toxicity assay using the luminescent bacteria test (ISO11348) indicated that UV irradiation reduced the toxicity of some pharmaceuticals to aquatic organisms by decreasing their amount (photodegradation) and increased the toxicity of others by generating toxic photoproduct(s). These results indicate the importance of investigating not only parent compounds, but also photoproducts in the risk assessment of pharmaceuticals in aquatic environments.

Photochemical fate and eco-genotoxicity assessment of the drug etodolac

“…Some studies, performed on the most detected NSAIDs in aquatic systems, demonstrated the low acute toxicity of such compounds in non-target organisms, with much higher short-term EC50 values than their environmental occurrence (Cleuvers, 2004;Parolini et al, 2012). Kawabata et al (2013) Although in the present study the phototrasformation process did not produce a toxic derivative, the sunlight-exposed samples show often differences in toxicity when compared to parent compound with formation of more or less hazardous derivatives for the environment and human health. Indeed, Schmitt-Jansen et al (2007) evaluated the phytotoxicity of diclofenac, a NSAID belonging to the family of carboxylic acid derivatives, after exposure to natural sunlight.…”

“…These authors demonstrated that the increasing concentration of transformation products significantly correlated with enhanced phytotoxicity. On the contrary Kawabata et al (2013) reported that the photoproducts of sulindac and indomethacin were less toxic in bacteria than parent compounds. In the present research, the photo -exposed solution was also examined to detect possible additive, synergistic or antagonistic toxic effects of the mixture photodegradation products and neither acute nor chronic toxicity was found.…”

Plant uptake of pharmaceutical and personal care products from recycled water and biosolids: a review

“…For example, after 45-day incubation, the fraction of degraded clofibric acid and diclofenac in nonsterile and sterilized agricultural soils was 88-100% (nonsterile) and 33-43% (sterilized), respectively, indicating a significant role of microorganisms in degrading these PPCPs in the soils (Xu et al, 2009). Besides biodegradation, abiotic process such as photodegradation (Kawabata et al, 2013) and hydrolysis (Mitchell et al, 2014) may also contribute to the transformations of PPCPs in the environment. During decomposition, a part of the compound in soil may undergo mineralization (i.e., converted to CO 2 ), which is viewed as complete detoxification.…”

Determination of itraconazole and its photodegradation products with kinetic evaluation by ultra‐performance liquid chromatography/tandem mass spectrometry

“…The drug concentrations as pollutants tend to increase owing to both the aging of the population and increased industrial pollutants, and their photostability plays an important role in their own pollution -low photostability causes a low environmental persistence but a complete abatement of toxicity can be attained only after their mineralization (Sammartino et al, 2013;Zuccato et al, 2000;Ternes, 1998). The outcome of photodegradation is dependent on many factors, including chemical structure, the kinds of functional groups and the wavelength of UV exposure (Kawabata et al, 2013). By comparing photolysis (without catalysts) and photocatalytic degradation of ITZ, it was found that photocatalytic degradation of this pharmaceutical was more effective than photolysis.…”