Abstract and Introduction
Abstract
Background: Pharmaceuticals are known to contaminate tap water worldwide, but the relevant human health risks have not been assessed in China.
Objectives: We monitored 32 pharmaceuticals in Chinese tap water and evaluated the life-long human health risks of exposure in order to provide information for future prioritization and risk management.
Methods: We analyzed samples (n = 113) from 13 cities and compared detected concentrations with existing or newly-derived safety levels for assessing risk quotients (RQs) at different life stages, excluding the prenatal stage.
Results: We detected 17 pharmaceuticals in 89% of samples, with most detectable concentrations (92%) at < 50 ng/L. Caffeine (median–maximum, nanograms per liter: 24.4–564), metronidazole (1.8–19.3), salicylic acid (16.6–41.2), clofibric acid (1.2–3.3), carbamazepine (1.3–6.7), and dimetridazole (6.9–14.7) were found in ≥ 20% of samples. Cities within the Yangtze River region and Guangzhou were regarded as contamination hot spots because of elevated levels and frequent positive detections. Of the 17 pharmaceuticals detected, 13 showed very low risk levels, but 4 (i.e., dimetridazole, thiamphenicol, sulfamethazine, and clarithromycin) were found to have at least one life-stage RQ ≥ 0.01, especially for the infant and child life stages, and should be considered of high priority for management. We propose an indicator-based monitoring framework for providing information for source identification, water treatment effectiveness, and water safety management in China.
Conclusion: Chinese tap water is an additional route of human exposure to pharmaceuticals, particularly for dimetridazole, although the risk to human health is low based on current toxicity data. Pharmaceutical detection and application of the proposed monitoring framework can be used for water source protection and risk management in China and elsewhere.
Introduction
Pharmaceuticals are a group of intrinsically bioactive chemicals used in humans and animals for disease treatment and prevention and growth promotion, among other purposes. These chemicals have also been regarded as environmental contaminants in recent decades because of their potential toxicity to nontarget organisms and their ubiquitous occurrence in the environment due to extensive and continuous release from sources including municipal, hospital, agricultural, and industrial effluents (Segura et al. 2009).
Potable water sources are contaminated by human and veterinary pharmaceuticals (Huerta-Fontela et al. 2008, 2011; Watkinson et al. 2009). Incomplete removal by conventional technologies (e.g., flocculation, sedimentation, and chlorination) in drinking-water treatment plants (DWTPs) has been observed, and consequently, pharmaceuticals have been detected in tap water in several developed countries at levels of usually < 100 ng/L (Segura et al. 2009). Although pharmaceutical levels in drinking water are currently unregulated, efforts have been made to include them in environmental monitoring programs. The U.S. Environmental Protection Agency (EPA) recently added 10 active ingredients to the Third Contaminant Candidate List (CCL 3) (U.S. EPA 2009a) and proposed the inclusion of seven hormones in the third Unregulated Contaminant Monitoring Regulation (U.S. EPA 2011) as reference for future amendment of drinking-water regulations. The New York Environmental Protection Department (NYCDEP) also conducted a 1-year pilot scheme for proactive monitoring of pharmaceuticals in source water (NYCDEP 2010). Provisional safety levels for pharmaceuticals in drinking water, known as drinking-water equivalent levels (DWELs), have also been derived by a few research groups based on available chronic mammalian toxicity data, minimum inhibitory concentrations, or the lowest therapeutic doses (Bruce et al. 2010; Schwab et al. 2005). Individual pharmaceuticals are expected to pose negligible human health risks in tap water based on known levels in studied regions [World Health Organization (WHO) 2012].
Data on pharmaceutical concentrations in drinking water are available for some developed countries, but relevant information in developing countries is scarce (Segura et al. 2009). In China, human and veterinary pharmaceuticals have frequently been detected in wastewater and surface waters at concentrations of generally < 1 μg/L; levels of certain compounds, such as erythromycin-H2O, salicylic acid, and cefalexin, have been reported to be at the high end of the values reported globally (Jiang et al. 2011; Leung et al. 2012; Wei et al. 2011), and illegal use of prohibited veterinary drugs has been detected in slaughterhouse wastewater (Shao et al. 2009). However, the human health risks of pharmaceuticals in drinking water have not been evaluated to date. This information is needed for evaluating risk management and regulation with regard to pharmaceutical contamination in China.
In recognition of these concerns, the objectives of this study were a) to investigate the occurrence of 32 pharmaceutically active ingredients in drinking water in 13 cities in China; b) to assess and prioritize the potential risks of pharmaceutical exposure in the Chinese population via drinking water based on available or newly derived DWELs, with emphasis on exposure at different life stages; and c) to identify and suggest possible molecular indicators for comprehensive monitoring and for risk management of pharmaceuticals in China and elsewhere.