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Making a Case for Human Health Risk-based Ranking Nanoparticles in Water for Monitoring Purposes Arun Kumar* Department of Civil Engineering, Indian Institute of Technology, New Delhi, India disrupting chemicals in water, based on criteria, such as occurrence, treatment in water treatment plants, eco-toxicity effects and human health effects, are available,5 ranking strategies for identifying priority nanoparticles in water are lacking. Toward this, some studies have attempted to develop preliminary framework for nanoparticles, however, primarily in air media, for occupational workers inhaling NPs during NP manufacturing processes. For prioritizing NPs, approaches such as expert elicitation and mental modeling,3 multicriteria decision analysis (MCDA)-based decision support system4 has been used for ranking NPs in air medium, mostly for inhalation exposure route. Generally studies have used criteria such as NP concentration, its frequency of detection and type, toxicity information. However not many studies have used health risk as one of the criteria, which need to be considered during ranking step. Consideration of this criterion is important as inclusion of this criterion during ranking of NPs may give a different list as has been observed for the case of endocrineanoparticles (NPs) have become one of the emerging disrupting chemicals in water.5 Considering this possibility, it is water contaminants due to their reported occurrence in important to include health risk estimate as one metric to rank water environment. 1,2 For example, Westerhoff et al.2 NPs in water and to develop list of priority NPs. Further NP monitored wastewater treatment plants in the U.S. and ranking-based studies have only focused on ranking NPs in air reported titanium concentrations ranging between 181 and medium only, effort should also be required for ranking NPs in 1233 μg/L in raw sewage and below 25 μg/L concentrations in water medium as oral exposure route also leads to exposures of wastewater effluent, indicating the possibility of surface water NPs. Classification efforts for nanoparticles in water are lacking contamination with NPs. The reported presence of NPs in and warrant attention. Both of the exposure routes, inhalation water poses health risk and thus a structured framework is and oral routes, are important to consider and lists of required to properly understand identify possible effects of NPs prioritized NPs in both exposure media are required to focus and to conduct health risk assessment.3,4 Further, due to efforts on monitoring NPs in respective medium. increased use of different types of NPs in different products and There is a need to combine MCDA and human health risk possibility of their occurrence in environment, it is difficult for assessment (HHRA) methodologies with a goal of minimizing water treatment utilities to (1) properly characterize source human health risks during exposures to NPs from water drinking water for NPs presence, (2) provide adequate (termed as “NPriskrank” methodology, hereafter). Briefly, the treatment in water treatment plants to remove NPs from proposed NPriskrank methodology could base ranking of NPs water before supplying finished water for human consumption. based on human health risks which are an important step in At the same time, regulators face problems in regulating these determining if a particular NP type under consideration NPs in water primarily due to lack of information of occurrence warrants further focus or not at water treatment plant level. of rapidly increasing NPs in products. This approach uses criteria,that is, NP occurrence, toxicity, and To address this problem, it has become imperative to removal at water treatment plant level in conjunction with prioritize NPs in water to reduce number of NPs to monitor; HHRA methodology for developing a decision-making support similar to what has been done for ranking pharmaceuticals, system for ranking NPs in water. Relative significance of endocrine-disrupting chemicals and personal care products in different criteria could be obtained from expert elicitation water.5 This approach can aid water suppliers to monitor only processes as recommended in previous ranking studies.3,4 For important and few NPs in water sources before considering assessing health risks due to NPs exposures, following steps are required: (1) hazard identification (i.e., NPs considered), (2) them water sources for source drinking water. In addition, a list exposure assessment (i.e., application of different exposure of important and few NPs could also aid regulators in enforcing monitoring requirements to different water suppliers. Review of literature indicates that although prioritization Received: April 16, 2012 approaches for selecting important organic compounds, Accepted: April 18, 2012 Published: April 24, 2012 pharmaceuticals, personal care products and endocrine-
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© 2012 American Chemical Society
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dx.doi.org/10.1021/es301507j | Environ. Sci. Technol. 2012, 46, 5267−5268
Environmental Science & Technology
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scenario which might result in different human health risk estimates), (3) dose−response assessment (i.e., NP-related toxicity to different human organs; use of animal toxicity data), (4) risk characterization (i.e., risk estimate for humans under different scenarios), and (5) risk management and communication steps.5 Overall, the following steps are required to rank NPs using the NPriskrank approach: 1 Development of a priority list of NPs in source drinking water (List no. 1), 2 Quantification of human health risks due to exposures to prioritized NPs from List #1, 3 Development of a pool of human health risk-based priority NPs (List no. 2), and 4 Identification of extent of removal of NPs required at water treatment plant level. Efforts focusing on ranking NPs in water could aid water suppliers in monitoring priority NPs in water and decisionmakers in devising human health risks-based maximum allowable concentrations of nanoparticles for source drinking water to protect human health.
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AUTHOR INFORMATION
Corresponding Author
*Phone: +91-11-2659-1166; fax: +91-11-2658-1117; e-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Wiesner, M. R.; Lowry, G. V.; Alvarez, P.; Dionysiou, D.; Biswas, P. Assessing the risks of manufactured nanomaterials. Environ. Sci. Technol. 2006, 168, 4336−4345. (2) Westerhoff, P.; Song, G.; Hristovski, K.; Kiser, M. A. Occurrence and removal of titanium at full-scale wastewater treatment plants: Implications for TiO2 nanomaterials. J. Environ. Monit. 2011, 13, 1195−1203. (3) Morgan, K. Development of a preliminary framework for informing the risk analysis and risk management of nanoparticles. Risk Anal. 2005, 25 (6), 1621−1635. (4) Grieger, K. D.; Baun, A.; Owen, R. Redefining risk research priorities for nanomaterials. J. Nanopart. Res. 2010, 12, 383−392. (5) Kumar, A. 2011. Human health risk-based prioritization of endocrine-disrupting chemicals in water-A perspective. Proc. Indian Natl. Sci. Acad. 2011, 77(2): Special Issue.
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