Evaluation of the photolysis of pharmaceuticals within a river by 2 year field observations and toxicity changes by sunlight

Abstract

To improve the risk assessment of pharmaceuticals, it is helpful to know how rapidly they are removed from river water. Direct photolysis by sunlight could be an important process, but so far few studies have attempted to compare modeled with actual losses in a river. Therefore, we quantified natural attenuation by monitoring 56 pharmaceuticals and personal care products over 2 full years in a 2.6 km stretch of an urban river. In addition, to screen photoproducts, we used the Microtox test with Vibrio fischeri to evaluate changes in the toxicity of two photolabile pharmaceuticals, ketoprofen and diclofenac, under sunlight. During transport along the river stretch, ketoprofen and the photolabile pharmaceutical furosemide were attenuated by median values of 77% and 39%. The observed attenuation showed good agreement with photochemical attenuation estimated by an existing method at each sampling, suggesting that the method appeared to be effective for estimating the direct photolysis of the pharmaceuticals during river transport. The toxicity of diclofenac decreased under sunlight, while that of ketoprofen increased immediately after exposure (around 12 times in EC20) and remained high, indicating the existence of toxic and photostable photoproducts of ketoprofen. Therefore, ecological risks of photolabile pharmaceuticals may increase during river transport in some cases, indicating the necessity to incorporate their photoproducts into the estimation method.

Enhanced Removal and Toxicity Decline of Diclofenac by Combining UVA Treatment and Adsorption of Photoproducts to Polyvinylidene Difluoride

“…The toxicity unit (TU = 100/EC 50% , EC 50% is the effect concentration at which 50% of effect occurs; the higher the TU, the higher the toxicity) and G L level (dilution level at which the inhibition is below 20% for the first time; the higher the G L level, the higher the toxicity) at 90 min of UVA irradiation doubles compared to an untreated diclofenac solution. The evaluation of the toxicity of diclofenac treated with UVA light is controversial discussed [ 52 , 56 , 57 , 58 ]. But the conditions (concentration of diclofenac, UVA light wavelength, UVA light intensities, additives in water, tested biological organism) do differ and lead to different transformation products and concentrations of these products.…”

“…But the conditions (concentration of diclofenac, UVA light wavelength, UVA light intensities, additives in water, tested biological organism) do differ and lead to different transformation products and concentrations of these products. Hanamoto et al [ 57 ] and Kovacic et al [ 52 ] identify a decrease of toxicity towards Vibrio fischeri after sunlight and UVA (365 nm) light treatment, respectively. Contrary, Schmitt-Jansen [ 58 ] studies showed an increase of toxicity towards the algal S. vacuolatus after day light treatment.…”

Removal of pharmaceuticals and personal care products from wastewater using algae-based technologies: a review

“…Many PPCPs have been found to be photodegradable under sunlight irradiation (Hanamoto et al 2014;Lam et al 2004;Lin et al 2006;Matamoros et al 2008). Photodegradation of PPCPs involves both direct photolysis and indirect photolysis.…”

Identification of intermediate compounds and photodegradation mechanisms of omeprazole under the system UV/O2

“…The toxicity of compounds derived from the incomplete degradation of pharmaceuticals often is greater than that of the original pharmaceutical. Photodegradation is one of the most important factors to consider in the environmental ecotoxicology of pharmaceuticals in the aquatic environment . Furthermore, some pharmaceuticals, upon photoexcitation, become phototoxins with the potential to modify biological systems.…”