Nigel J. Walker, Ph.D. | National Institute of Environmental Health Sciences Skip Navigation Nigel J. Walker, Ph.D. Close the left navigation Add Much of the work carried out by DTT is in support of the National Toxicology Program (NTP), an interagency partnership of the Food and Drug Administration, National Institute for Occupational Safety and Health, and NIEHS. Visit the NTP Website Systems Toxicology Branch Nigel J. Walker, Ph.D. Staff Scientist Tel 984-287-3204 [email protected] Nigel Walker, Ph.D., D.A.B.T., is a staff scientist in the Systems Toxicology Branch, in the Division of Translational Toxicology (DTT) at the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health (NIH). Walker leads the federal interagency Office of National Toxicology Program (NTP) Scientific Operations and Coordination (ONSOC) and in that role provides senior level scientific leadership and direction for the planning, implementation, management, and coordination of research activities of the National Toxicology Program (NTP) . The NTP is a Federal interagency program that generates, interprets, and shares toxicological information about potentially hazardous substances in our environment to provide the scientific basis for programs, activities, and policies that promote health or lead to the prevention of disease. Walker has been at the NIEHS for over 25 years and during this time has led numerous initiatives understanding the potential toxicity and carcinogenicity of compounds under investigation by NTP including nanoscale materials, dioxin-like compounds, persistent organic pollutants, environmental/occupational mixtures, endocrine disrupting compounds, and botanical dietary supplements. Walker has co-authored over 200 publications , including over 100 peer-reviewed technical reports on the toxicity and carcinogenicity of compounds studied by NTP. He received his B.Sc. in Biochemistry from the University of Bath in the U.K. and his Ph.D. in Biochemistry from the University of Liverpool, U.K. and has been board certified as a toxicologist by the American Board of Toxicology since 2007. Recent Publications Johnson V, Walker N, Luster M, Burleson G, Cora M, Baker G, Sparrow B, Germolec D. Immunotoxicity assessment of multiwalled carbon nanotubes following whole-body inhalation exposure for 30 and 90 days in B6C3F1/N mice and 30 days in HSD:Harlan Sprague Dawley SD rats. Frontiers in toxicology 2025;7:1539810. Abstract Johnson V, Walker N, Luster M, Burleson G, Cora M, Baker G, Sparrow B, Germolec D. Immunotoxicity assessment of multiwalled carbon nanotubes following whole-body inhalation exposure for 30 and 90 days in B6C3F1/N mice and 30 days in HSD:Harlan Sprague Dawley SD rats. Frontiers in toxicology. 2025 Wyde M, Capstick M, Hall S, Hooth M, Kuster N, Ladbury J, Roberts G, Shipkowski K, Shockley K, Smith-Roe S, Stout M, Walker N. Development and Testing of a Novel Whole-body Exposure System for Investigative Studies of Radiofrequency Radiation in Rodents 2025 Aug [Epub ahead of print]. Abstract Wyde M, Capstick M, Hall S, Hooth M, Kuster N, Ladbury J, Roberts G, Shipkowski K, Shockley K, Smith-Roe S, Stout M, Walker N. Development and Testing of a Novel Whole-body Exposure System for Investigative Studies of Radiofrequency Radiation in Rodents . 2025 Aug Hamm J, Hsieh J, Roberts G, Collins B, Gorospe J, Sparrow B, Walker N, Truong L, Tanguay R, Dyballa S, Miñana R, Schiavone V, Terriente J, Weiner A, Muriana A, Quevedo C, Ryan K. Interlaboratory Study on Zebrafish in Toxicology: Systematic Evaluation of the Application of Zebrafish in Toxicology's (SEAZIT's) Evaluation of Developmental Toxicity. Toxics 2024 Jan 22;12(1):. Abstract Hamm J, Hsieh J, Roberts G, Collins B, Gorospe J, Sparrow B, Walker N, Truong L, Tanguay R, Dyballa S, Miñana R, Schiavone V, Terriente J, Weiner A, Muriana A, Quevedo C, Ryan K. Interlaboratory Study on Zebrafish in Toxicology: Systematic Evaluation of the Application of Zebrafish in Toxicology's (SEAZIT's) Evaluation of Developmental Toxicity. Toxics. 2024 Jan 22 Wikoff D, Ring C, DeVito M, Walker N, Birnbaum L, Haws L. Development and application of a systematic and quantitative weighting framework to evaluate the quality and relevance of relative potency estimates for dioxin-like compounds (DLCs) for human health risk assessment. Regulatory toxicology and pharmacology : RTP 2023 Dec;145:105500. Abstract Wikoff D, Ring C, DeVito M, Walker N, Birnbaum L, Haws L. Development and application of a systematic and quantitative weighting framework to evaluate the quality and relevance of relative potency estimates for dioxin-like compounds (DLCs) for human health risk assessment. Regulatory toxicology and pharmacology : RTP. 2023 Dec Ring C, Blanchette A, Klaren W, Fitch S, Haws L, Wheeler M, DeVito M, Walker N, Wikoff D. A multi-tiered hierarchical Bayesian approach to derive toxic equivalency factors for dioxin-like compounds. Regulatory toxicology and pharmacology : RTP 2023 Sep;143:105464. Abstract Ring C, Blanchette A, Klaren W, Fitch S, Haws L, Wheeler M, DeVito M, Walker N, Wikoff D. A multi-tiered hierarchical Bayesian approach to derive toxic equivalency factors for dioxin-like compounds. Regulatory toxicology and pharmacology : RTP. 2023 Sep NTP Reports National Toxicology Program. Toxicity study of Stachybotrys chartarum (CASRN 67892-26-6) administered by inhalation to B6C3F1/N mice. Toxicity report series 2024 Oct [Epub ahead of print]. Abstract National Toxicology Program. Toxicity study of Stachybotrys chartarum (CASRN 67892-26-6) administered by inhalation to B6C3F1/N mice. Toxicity report series. 2024 Oct National Toxicology Program. Toxicology and carcinogenesis study of triclosan administered dermally to B6C3F1/N mice. National Toxicology Program technical report series 2024 May [Epub ahead of print]. Abstract National Toxicology Program. Toxicology and carcinogenesis study of triclosan administered dermally to B6C3F1/N mice. National Toxicology Program technical report series. 2024 May National Toxicology Program. Toxicology and carcinogenesis studies of black cohosh root extract (CASRN 84776-26-1) administered by gavage to Sprague Dawley (Hsd:Sprague Dawley SD) rats and female B6C3F1/N mice. National Toxicology Program technical report series 2023 Dec [Epub ahead of print]. Abstract National Toxicology Program. Toxicology and carcinogenesis studies of black cohosh root extract (CASRN 84776-26-1) administered by gavage to Sprague Dawley (Hsd:Sprague Dawley SD) rats and female B6C3F1/N mice. National Toxicology Program technical report series. 2023 Dec National Toxicology Program. Toxicology and carcinogenesis studies of an isomeric mixture of tris(chloropropyl) phosphate administered in feed to Sprague Dawley (Hsd:Sprague Dawley SD) rats and B6C3F1/N mice. National Toxicology Program technical report series 2023 Jun [Epub ahead of print]. Abstract National Toxicology Program. Toxicology and carcinogenesis studies of an isomeric mixture of tris(chloropropyl) phosphate administered in feed to Sprague Dawley (Hsd:Sprague Dawley SD) rats and B6C3F1/N mice. National Toxicology Program technical report series. 2023 Jun National Toxicology Program. Toxicity studies of acetoin and 2,3-pentanedione administered by inhalation to Wistar Han [Crl:WI(Han)] rats and B6C3F1/N mice. Toxicity report series 2023 Mar [Epub ahead of print]. Abstract National Toxicology Program. Toxicity studies of acetoin and 2,3-pentanedione administered by inhalation to Wistar Han [Crl:WI(Han)] rats and B6C3F1/N mice. Toxicity report series. 2023 Mar More Recent Publications from PubMed Back to Top Last Reviewed: December 18, 2025