Detecting Pharmaceuticals in Irrigated Crops
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A team of scientists based in Israel has quantified the uptake of pharmaceutical compounds in treated wastewater using liquid chromatography coupled to mass spectrometry (LC–MS).1 The potential health impact of using this water on crops for human consumption was also evaluated.
Pharmaceutical compounds comprise a wide range of chemicals, including prescription and over-the-counter medications, nutritional supplements, and diagnostic agents. After ingestion they are excreted out into the sewage system. Research has indicated that conventional wastewater treatment does not fully eliminate pharmaceutical compounds from the water system. This is of increasing concern as to meet mounting water demands treated wastewater has become an important source of irrigation.
Study participant Tomer Malchi commented: “This paper is part of ongoing efforts of our group at the Faculty of Agriculture of the Hebrew University to study the fate of pharmaceutical compounds in the agricultural environment. The importance of our paper lies in its experimental setup where we used lysimeter system containing three agricultural soils irrigated with treated wastewater actually used for farming, and its focus on root vegetables in realistic agricultural management.”
The team grew two root crops (sweet potato and carrot) in lysimeters that were irrigated with fresh water or treated wastewater. To ensure suitable exposure, pharmaceutical compounds were added to the treated wastewater at environmental concentrations. Malchi commented: “Our analysis is based on several steps. Extraction is accomplished through accelerated fluid extraction after which samples are evaporated, spiked with labelled compounds, and reconstituted for analysis on an LC system, coupled to a triple quadruple mass spectrometer with an ESI ion source. To attain acceptable recovery rates this process has evolved and improved over a few years. The principal difficulty has been a cleanup process to provide samples ready for LC–MS analysis without reducing recovery rates or the limit of quantification. Through method development on a wide range of crops most of the analyzed PCs have recovery rates between 80–120%.”
In both crops the nonionic pharmaceutical compounds (carbamazepine, caffeine, and lamotrigine) were detected at higher concentrations than ionic pharmaceutical compounds (metoprolol, bezafibrate, clofibric acid, diclofenac, gemfibrozil, ibuprofen, ketoprofen, naproxen, sulphamethoxazole, and sildenafil). The compounds were found at higher concentrations in the leaves than in the roots. The health risks potentially posed by this were estimated using the threshold of toxicological concern (TTC). For most of the compounds a health risk was not established. However, for two compounds (lamotrigine and 10,11-epoxycarbamazepine) a health risk was indicated. The authors’ data showed that the TTC value of lamotrigine could be reached for a child if they consume half a carrot (approximately 60 g).
Malchi concluded: “Our current research is evolving in several directions. We are currently continuing to study the fate of PCs as contaminants of emerging concern by different crops under realistic agricultural practices. In addition, our research aims to better understand the uptake, transport, and metabolism of PCs in plants in order to better assess the risks involved with introducing PCs into the environment through the use of wastewater as irrigation water and biosolids as soil amendment.” — K.M.