Towards Understanding Engineered Nanomaterials for Environmental Health & Safety

[Not the senses I have but what I do with them is my kingdom. Helen Keller]

Lok Raj Pokhrel

Department of Environmental Health
College of Public Health
East Tennessee State University
Lamb Hall Room 65B
Johnson City, TN 37614, USA
E-mail: lokraj123@gmail.com; zlrp9@goldmail.etsu.edu
PO Box: 13954; Tel.: 423-439-5258(o); Fax: 423-439-5230
Company Webpage: www.etsu.edu/cph/default.aspx

EDUCATION

Ph.D. (Env. Health) East Tennessee State University, TN, USA (May 2013 due)

M.S. (Quant. Biol) East Tennessee State University, TN, USA (2009)

M.Sc. (Zool/Ecol) Degree Campus, Tribhuvan University, Nepal (2001)

B.Sc. (Zool) Mechi Multiple College, Tribhuvan University, Nepal (1999) (Valedictorian)

RESEARCH INTERESTS

Metal Nanoparticle Synthesis and Characterization
Ecotoxicology of Metal Nanoparticles to Aquatic and Terrestrial Model Organisms

E.g., E. coli, Zooplankton (D. magna), Dragonfly nymphs, Maize, Cabbage

Impact of Metal Nanoparticles on Predator-Prey Interactions in a Simple Aquatic Food Chain
Ecological and Human Health Risk Assessment of Metals and Metal-based Nanoparticles
Experimental Designs in Nanotoxicology Research
Low-dose Impacts of Glyphosate-based Herbicide on Plant Growth and Development
Leaching of Nanomaterials from Various Consumer Products
Multivariate Modeling of Physico-chemical Parameters of Nanomaterials to Develop Index for Predicting Toxicity on Various Biologic Models
Developing Predictive Models to Explain Automated Toxicological Data in an Effort to Minimize Animals Use in Understanding Toxicology of Chemicals
Population and System Dynamics Modeling

CURRENT RESEARCH

1. Rapid Screening of Metal Nanoparticles Toxicity using E. coli Bioassay

We are evaluating potential toxicity of various metal-based nanoparticles using the MetPLATE E. coli bioassay as a rapid screening tool. We are also considering potential effects of water chemistry on the toxicity of metal nanoparticles. Different types of coating materials are considered to understand the influence of surface chemistry on the toxicity of metal nanoparticles.

2. Impact of Metal Nanoparticles on the Early Development of Terrestrial Plants

Germination of Zea mays seeds

Impacts on Vascular Bundles in Zea mays

Terrestrial plants are vital components of ecosystems and serve direct source of food for humans. Soil contamination of nanomaterials can potentially affect nutrient uptake, physiology, and survival of crop plants. Biouptake of nanomaterials by plants and subsequent intake (of plants) by animals and humans may potentially affect their health and safety. We seek to understand the potential impact of metal-based nanoparticles on the growth and development of the agriculturally significant crop plant species. In particular, detailed anatomical and morphological studies conducted on the primary root cell structure, alignment, and changes in metaxylem number are expected to offer better insights into potential effects that these nanomaterials may have in plants. Generally, much information has been obtained using higher doses. Our future research will focus on low-dose applications of nanomaterials with the hope to promote growth, development and productivity of crop plants to mitigate the global hunger crisis.

3. Aquatic Toxicity Evaluation of Metal Nanoparticles using Daphnia magna Bioassay

Aqueous environment is apparently a primary disposal venue for contaminants, including the engineered nanomaterials. Little is known about the potential risk of nanoparticles to the aquatic macro-invertebrates. Here, we are using an aquatic cladoceran, Dapnia magna, to investigate the potential toxicity of nanoparticles on its behavior, survival and reproduction. Potential impacts of nanoparticles on the predator-prey (dragonfly nymph versus Daphnia) interactions may shed light on the potential short- and long-term effects on ecosystem structure and functioning.

4. Nanomaterial Leaching from Consumer Products

Engineered nanomaterials have been extensively used in various consumer products to improve their functional attributes. Metal nanoparticles, such as silver, have been used as an antimicrobial, while zinc and titanium nanoparticles have been used in sunscreens to confer protection against UV (A/B) radiation. Increasing use of nanoproducts has, on the other hand, raised concern about their potential for leaching into the environment. Standard leaching tests such as TCLP, SPLP and WET have been used to understand potential leachability of metals (in the form of ions and/or particles) from the products which have claimed to constitute metal nanoparticles in them. TCLP simulates potential leaching in the landfill environment. SPLP simulates rainfall conditions, while WET is the leaching test used in the state of California. Potential leaching analysis will enable us to estimate the potential loading of nanomaterials/ions into various environmental compartments and thus allow in parameterizing models for estimating risks. A list of commercially available nanoproducts can be found following the link: http://www.nanotechproject.org/inventoriesconsumer/browse/products/page10/.

PUBLICATIONS

1. Pokhrel LR, Dubey B. Potential impact of low-concentration silver nanoparticles on predator-prey interactions between predatory dragonfly nymphs and Daphnia magna as a prey. ACS Environmental Science & Technology 2012, 46(14):7755-7762.

2. Pokhrel LR, Dubey B, Silva T, El Badawy AM, Tolaymat TM, Scheuerman PR. Rapid screening of aquatic toxicity of several metal-based nanoparticles using the MetPLATE™ bioassay. Science of the Total Environment 2012, 426:414-422. [Winner of Adventus Americas Best Platform Presentation Award 2011]

3. Pokhrel LR, Dubey B. (2012) Global scenarios of metal mining, environmental repercussions, public policies, and sustainability: A review. Critical Reviews in Environmental Science and Technology DOI: 10.1080/10643389.2012.672086.

4. Pokhrel LR, Dubey B. Engineered nanomaterials in the waste disposal and treatment systems: Potential fate, effects and the regulatory conundrum. Journal of Environmental Monitoring (Invited Review, under review, Manuscript# EM-CRV-08-2012-030634).

5. Pokhrel LR, Karsai I, Laughlin TF, Hamed MK. Quantitative modeling of dorsal body pigmentation and sexual dimorphism in the marbled salamander Ambystoma opacum. Ethology, Ecology and Evolution (in press).[ Winner of Appalachian Student Graduate Research Award 2008]

6. Pokhrel LR, Dubey B, Scheuerman PR. (2011) Pharmaceuticals in the aquatic environment: A critical appraisal of uncertainty and knowledge gaps in human health risk assessment. Nesaj Patra 8(1):4-13.

7. Pokhrel LR, Dubey B. Untangling species sensitivity paradox in environmental research. Expert Opinion on Environmental Biology (Editorial; in press).

8. Pokhrel LR, Dubey B, Scheuerman PR. Evaluation of experimental design options in environmental nano-science research. Expert Opinion on Environmental Biology (Perspective; under review).

9. Pokhrel LR, Silva TU, Dubey B, Tolaymat TM, Maier KJ, Scheuerman PR. General Linear Model-predicted and observed toxicity of organic-coated silver nanoparticles to prokaryotic and eukaryotic organisms: Probing interactive role of particle size and surface charge. ACS Nano Letters (to be submitted).

10. Pokhrel LR, Dubey B. Silver and zinc oxide nanoparticles cause developmental anomalies in the crop plants. Science of the Total Environment (to be submitted).[Winner of AEHAP/CDC Best Student Research Competition Award 2012]

11. Pokhrel LR, Karsai I. Long-term effects of low-concentration environmental drift of Roundup herbicide on the development and fecundity of an invasive weed, Bryophyllum pinnatum. Science of the Total Environment (to be submitted).

In Preparation

1. Pokhrel LR…..Mechanistic understanding of toxicity of citrate-coated silver nanoparticles in Daphnia magna: Role of humic acid, cysteine, and trolox.

2. Pokhrel LR.…. Modulation of citrate-coated silver nanoparticle stability and antimicrobial activity by natural water chemistry: Potential role of dissolved organic carbon, pH, and hardness.

3. Pokhrel LR, Singhal N, Dubey B. Evaluation of test methods for assessing the environmental risks from road marking reflective glass beads.

Conference Presentation

1. Pokhrel LR, Silva TU, Dubey B. (2013) Modulation of silver nanoparticle toxicity by particle characteristics (size and charge) and suspension chemistry. Environmental Health 2013, Science and Policy to Protect Future Generations, 3-6 March 2013, Boston, Massachusetts, USA.

2. Pokhrel LR. (2012) How small is different: Nanomaterials in the environment. East Tennessee State University, Department of Environmental Health, Seminar series, October 30, 2012.

3. Dubey B, Pokhrel LR. (2012) Opportunities for nanoparticle research. Invited pesentation at University Consortium for Field-Focused Groundwater Contamination Research Program, Annual Progress Meeting: June 12-14, 2012, The Arboretum, University of Guelph, ON, Canada.

4. Pokhrel LR, Dubey B, Scheuerman PR. (2012) Developmental phytotoxicity of silver and zinc oxide nanoparticles to the crop plants. NEHA Conference, June 28-30, San Diego, CA. (Winner of AEHAP/CDC Student Research Competition Award 2012).

5. Pokhrel LR, Scheuerman PR, Dubey B. (2012) Ecological risk assessment of zinc oxide nanoparticles. Proceedings of the 2^nd International Conference on Environmental Pollution and Remediation, Montreal, Quebec, Canada, August 28-30.

6. Pokhrel LR, Dubey B. (2012) Metal mining industry: Global production statistics, potential environmental effects, mitigation techniques, and sustainability. 13^th Intl Symposium on Environmental Issues and Waste Management in Energy and Mineral Production SWEMP 2012, November 28-30, New Delhi, India.

7. Pokhrel LR, Dubey B. (2012) Potential developmental toxicity of silver and zinc oxide nanoparticles to the terrestrial plants. 28^th Int’l Conference on Soil, Sediment, Water, and Energy, October 15-18, Amherst, MA.

8. Pokhrel LR, Scheuerman PR, Tolaymat TM, Dubey B. (2012) Potential impacts of metal nanoparticles on the growth and development of crop plants. Appalachian Student Research Forum, April 5, Johnson City, TN.

9. Pokhrel LR, Dubey B. (2012) Silver and zinc oxide nanoparticles cause developmental anomalies in the terrestrial plants. Tennessee Environmental Conference, March 13-14, Kingsport, TN.

10. Pokhrel LR, Dubey B, Singhal N. (2012) Assessing the environmental risks from road marking glass beads. Tennessee Environmental Conference, March 13-14, Kingsport, TN.

11. Pokhrel LR, Silva T, El Badawy AM, Tolaymat TM, Dubey B. (2011) Evaluation of aquatic toxicity of nanoscale silver, zinc oxide, titanium dioxide and cadmium selenide quantum dots, and their ionic particulates to the MetPLATE™ bioassay. 27^th Int’l Conference on Soil, Sediment, Water, and Energy, October 17-20, Amherst, MA (Winner of Adventus

Americas Best Platform Presentation Award 2011).

       12. Pokhrel LR, Silva TU, El Badawy AM, Tolaymat TM, Dubey B. (2011) Evaluation of aquatic toxicity of nanoscale silver, zinc oxide, titanium dioxide and cadmium selenide quantum dots, and their ionic particulates to the MetPLATE™ bioassay. Gordon Research Conference, May 29-June 3, New Hampshire, NH.

       13. Pokhrel LR, Silva TU, El Badawy AM, Tolaymat TM, Dubey B. (2011) Evaluation of aquatic toxicity of nanoscale silver, zinc oxide, titanium dioxide and cadmium selenide quantum dots, and their ionic particulates to the MetPLATE™ bioassay. Appalachian Student Research Forum, March 24, Johnson City, TN.

       14. Pokhrel LR, Dubey B. (2011) Nanoecotoxicity and human health: Where do we stand? Appalachian Student Research Forum, March 24, Johnson City, TN.

       15. Pokhrel LR, Dubey B. (2011) Nanoecotoxicity and human health: Where do we stand? Tennessee Environmental Conference, March 15-16, Kingsport, TN.

16. Pokhrel LR, Dubey B. (2010) Investigation of the environmental fate, transport, and transformation of silver nanoparticles in the waste disposal systems. Appalachian Student Research Forum, April 8, Johnson City, TN.

17. Pokhrel LR, Karsai I. (2008) Mapping the dorsal skin pattern of spotted salamanders, Ambystoma maculatum. Appalachian Student Research Forum, April 2-3, Johnson City, TN (Winner of Graduate Research Award 2008).

In News

1. Featured on ETSU Accent, Faculty/Staff Newsletter Vol 61, No 1 July 31, 2012 (http://www.etsu.edu/univrela/accentarchives/2012/11_July_31.pdf). 2. Featured on ETSU News July 20,2012 (http://www.etsu.edu/calendar/EventList.aspx?eventidn=10067&view=EventDetails&information_id=37160). (http://www.etsu.edu/cph/NewsEventsDocuments/lokpokhrel.aspx) 3. Featured on ASPH (Association of Schools of Public Health) Friday Letters May 11, 2012 (http://fridayletter.asph.org/article_view.cfm?FLE_Index=18308&FL_Index=1725) 4. Featured on ASPH Friday Letters Oct. 22, 2011 (http://fridayletter.asph.org/article_view.cfm?FLE_Index=16822&FL_Index=1697) 5. Featured as *Outstanding Student of the Month* by Association of Environmental Health Academic Programs (AEHAP) & the National Environmental Health Science and Protection Accreditation Council (EHAC) (http://aehap.org/students/extraordinary/lokRp.htm) Sept. 6, 2011 6. Featured on ASPH Friday Letters June 17, 2011 (http://fridayletter.asph.org/article_view.cfm?FLE_Index=15800&FL_Index=1678)