Comparative Exposure Assessment of Crops Grown by Urine-Derived Fertilizer and Crops Irrigated with Reclaimed Water

Abstract

Urine-derived fertilizers (UDFs) are a sustainable alternative to energy-intensive and environmentally damaging synthetic fertilizers; however, contaminant concerns must be addressed. Source-separated urine contains pharmaceutical compounds that could pose a risk to the environment and public health. While treatment technologies that address pharmaceutical contamination in UDF have been proposed, little is known about the exposure and risk to public health that UDF-fertilized crops pose. We assessed pharmaceutical uptake by lettuce exposed to UDF spiked with pharmaceuticals at two levels: the highest reported concentrations from the literature and at a level 10 times this amount to represent a worst-case scenario for UDF application. Between 0.00004% and 0.0002% of the applied pharmaceutical mass was taken up by lettuce. Exposure to pharmaceuticals through the consumption of UDF-fertilized crops is not significantly different from exposure through crops irrigated with reclaimed water (RW). Compared to therapeutic doses, the cumulative pharmaceutical ingestion associated with consuming UDF-fertilized vegetables every day over 70 years is up to 2.5% of the therapeutic dose of pharmaceuticals considered in this study. Our comparative exposure assessment reveals minimal exposures associated with the consumption of crops that are either fertilized by UDF or irrigated with RW, providing key insights for various stakeholders.

Keywords: contaminant fate; pharmaceuticals; public health; source separation; therapeutic dose.