Nigel Walker, Ph.D., is a staff scientist in the Toxicology Operations Branch of the Environmental Toxicology Program at the National Institute of Environmental Health Sciences (NIEHS), one of National Institutes of Health. Following postdoctoral training in environmental toxicology at the Johns Hopkins School of Hygiene and Public Health in Baltimore, Maryland, he moved to the NIEHS, where he has been since 1995.
He received a B.Sc. in biochemistry from the University of Bath, United Kingdom in 1987 and a Ph.D. in biochemistry from the University of Liverpool, United Kingdom in 1993. He joined NIEHS in 1995.
Walker is currently leading several efforts for the National Toxicology Program (NTP).
Lead Scientist for the NTP Nanotechnology Safety Initiative(http://ntp.niehs.nih.gov/go/nanotech) that is evaluating the safety of engineered nanoscale materials.
Lead Scientist for the Dioxin Toxic Equivalency Factor (TEF) Evaluation, a series of studies evaluating relative potency factors for the carcinogenicity of dioxin-like compounds in female rats.
Chairperson of the NTP Toxicogenomics faculty that leads utilization of “genomics tools” and approaches in the evaluation of toxicity of NTP nominations and research priorities.
Selected Publications
Walker NJ, Yoshizawa K, Miller RA, Brix AE, Sells DM, Jokinen MP, Wyde ME, Easterling M, Nyska A. Pulmonary lesions in female Harlan Sprague-Dawley rats following two-year oral treatment with dioxin-like compounds. Toxicologic pathology 2007 35(7):880-889. [Abstract](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=18098034)
Yoshizawa, K, Heatherly A, Malarkey DE, Walker NJ, Nyska A. A critical comparison of murine pathology and epidemiological data for TCDD, PCB126, and PeCDF. Toxicologic pathology 2007 35(7):865-879. [Abstract](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=18098033)
Xie A, Walker NJ, Wang D. (2006). Dioxin (TCDD) enhances triggered-afterdepolarizations in rat ventricular myocytes. Cardiovascular Toxicology. 2, 99-110. [Abstract](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=17303918)
Maynard, A.D, Aitken, R.J., Butz, T., Colvin, V., Donaldson, K., Oberdorster, G., Philbert, M.A., Ryan, J., Seaton, A., Stone, V., Tinkle, S.S., Tran, L., Walker, N.J., and Warheit, D.B. (2006). Safe handling of nanotechnology, Nature 444, 267-269
Walker, N.J., Wyde, M.E., Fischer, L.J., Nyska, A., and Bucher, J.R. (2006) Comparison of chronic toxicity and carcinogenicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in two-year bioassays in female Sprague-Dawley rats. Mol. Nutr. Food Res. 50, 934-944.
van den Berg, M., Birnbaum, L., Denison, M., De Vito, M., Farland, W., Feeley, M., Fiedler, H., Hakansson, H., Hanberg, A., Haws, L., Rose, M., Safe, S., Schrenk, D., Tohyama, C., Tritscher, A., Tuomisto, J., Tysklind, M., Walker, N., and Peterson, R.E. (2006). The 2005 World Health Organization Re-evaluation of Human and Mammalian Toxic Equivalency Factors for Dioxins and Dioxin-like Compounds. Toxicol Sci. 93, 223-241.
Haws, L. C., Su, S. H., Harris, M., Devito, M. J., Walker, N. J., Farland, W. H., Finley, B., and Birnbaum, L. S. (2005). Development of a Refined Database of Mammalian Relative Potency Estimates for Dioxin-like Compounds. Toxicol Sci. 89, 4-30
Holsapple, M. P., Farland, W. H., Landry, T. D., Monteiro-Riviere, N. A., Carter, J. M., Walker, N. J., and Thomas, K. V. (2005). Research Strategies for Safety Evaluation of Nanomaterials: Part 2, Toxicological and Safety Evaluation of Nanomaterials: Current Challenges and Data Needs. Toxicol Sci. 88, 12-1
Walker, N. J., Crockett, P., Nyska, A., Brix, A., Jokinen, M. P., Sells, D. M., Hailey, J. R., Easterling, M., Haseman, J. K., Yin, M., Wyde, M. E., Bucher, J. R., and Portier, C. J. (2005). Dose-additive carcinogenicity of a defined mixture of “dioxin - like compounds”. Environ Health Perspect 113, 43-48
Martinez, J. M., Baek, S. J., Mays, D. M., Tithof, P. K., Eling, T. E., and Walker, N. J. (2004). EGR1 Is a Novel Target for AhR Agonists in Human Lung Epithelial Cells. Toxicol Sci 82, 429-435.
Toyoshiba, H., Walker, N. J., Bailer, A. J., and Portier, C. J. (2004). Evaluation of toxic equivalency factors for induction of cytochromes P450 CYP1A1 and CYP1A2 enzyme activity by dioxin-like compounds. Toxicol Appl Pharmacol 194, 156-168.
Toyoshiba, H., Yamanaka, T., Sone, H., Parham, F. M., Walker, N. J., Martinez, J., and Portier, C. J. (2004). Gene interaction network suggests dioxin induces a significant linkage between aryl hydrocarbon receptor and retinoic acid receptor beta. Environ Health Perspect 112, 1217-1224.
Wyde, M. E., Braen, A. P., Hejtmancik, M., Johnson, J. D., Toft, J. D., Blake, J. C., Cooper, S. D., Mahler, J., Vallant, M., Bucher, J. R., and Walker, N. J. (2004). Oral and dermal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces cutaneous papillomas and squamous cell carcinomas in female hemizygous Tg.AC transgenic mice. Toxicol Sci 82, 34-45.
Jokinen, M. P., Walker, N. J., Brix, A. E., Sells, D. M., Haseman, J. K., and Nyska, A. (2003). Increase in cardiovascular pathology in female Sprague-Dawley rats following chronic treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3,3',4,4',5-pentachlorobiphenyl (PCB126). Cardiovascular Toxicology 3, 299-310
Kim, A. H., Kohn, M. C., Nyska, A., and Walker, N. J. (2003). Area under the curve as a dose metric for promotional responses following 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure. Toxicol Appl Pharmacol 191, 12-21.
Martinez, J. M., Afshari, C. A., Bushel, P. R., Masuda, A., Takahashi, T., and Walker, N. J. (2002) Differential toxicogenomic responses to 2,3,7,8-tetrachlorodibenzo-p-dioxin in malignant and nonmalignant human airway epithelial cells. Toxicol Sci 69, 409-426
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