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Kristen Ryan, Ph.D., DABT, is a toxicologist in the Systems Toxicology Branch of the Division of Translational Toxicology (DTT) at the National Institute of Environmental Health Sciences. As a study scientist, Ryan serves as a project leader for the toxicologic and carcinogenic assessment of agents of interest to the National Toxicology Program (NTP) as well as a subject matter expert in multidisciplinary scientific teams comprised of in-house and external scientists evaluating studies on selected chemicals. She is the currently the project leader for hazard identification and characterization studies of flame retardants [e.g., tris(chloropropyl)phosphate], botanical dietary supplements [e.g., echinacea],and alkylbenzene compounds. Ryan also is a project coordinator for zebrafish-related research ( SEAZIT ) with the aim to enable the broader adoption of zebrafish for toxicological screening.
Ryan's research interests include examining the relationship between exposure to various chemicals in the environment and developmental neurotoxicity or neurodegeneration. She participates in activities to enhance neurotoxicity testing within the DTT through the refinement of animal models as well as evaluation various new approach methodologies for the prioritization and prediction of potential neurotoxic agents.
Ryan received a B.S. in Biology from the University of Pittsburgh in 2004 and in 2012 Ryan obtained her Ph.D. in Toxicology from the University of Colorado investigating the role of mitochondrial oxidative stress and dysfunction in progressive neurological disorders such as Parkinson's disease and Temporal Lobe Epilepsy. Upon completion of her graduate work, she obtained a post-doctoral IRTA fellowship at the DTT which was completed in 2016.
Recent Publications
Truong L, Hsieh J, Ellis L, Jaka O, Muriana A, Molina-Martínez B, Del Pozo A, Schiavone V, Di Donato V, Sanz C, Tanguay R, Hessel E, Ryan K. Zebrafish behavioral assessment as a first-tier whole-organism NAM for developmental neurotoxicity: A multi-laboratory evaluation. Neurotoxicology. 2026 Sep;116:103504. [Abstract]
Johnson V, Waidyanatha S, Germolec D, Cora M, Cesta M, Shockley K, Jeffers A, Cimon K, Mutlu E, Cristy T, Pierfellice J, Luster M, Burleson G, Ryan K. Immune system evaluation of Echinacea Purpurea root extract in female Harlan Sprague Dawley (Hsd:Sprague Dawley SD) rats. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association. 2026 Sep;215:116226. [Abstract]
Konrad K, Allen-Moyer K, Ellis L, Hessel E, Jaka O, Muriana A, Martínez B, Del Pozo A, Schiavone V, Di Donato V, Sanz C, Truong L, Tanguay R, Shockley K, Ryan K, Hsieh J. Power calculations for larval zebrafish in light-dark transition test for developmental neurotoxicity. Neurotoxicology. 2026 Jan;112:103371. [Abstract]
Tandon A, Howard B, Green A, Elmore R, Shah R, Merrick A, Shockley K, Ryan K, Hsieh J. Artificial intelligence (AI)-driven morphological assessment of zebrafish larvae for developmental toxicity chemical screening. Aquatic toxicology (Amsterdam, Netherlands). 2025 Aug;285:107415. [Abstract]
Johnson V, Ryan K, Luster M, Pandiri A, Hobbie K, Cora M, Shockley K, Burleson G, Xie G, Germolec D. Developmental immunotoxicity study of tris(chloropropyl) phosphate in Hsd:Sprague Dawley SD rats exposed through dosed feed. Toxicological sciences : an official journal of the Society of Toxicology. 2025 May 01;205(1):166-179. [Abstract]
NTP Reports
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. Toxicity studies of select ionic liquids (1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-butyl-1-methylpyrrolidinium chloride, and n-butylpyridinium chloride) administered in drinking water to Sprague Dawley (Hsd:Sprague Dawley SD) rats and B6C3F1/N mice. Toxicity report series. 2022 May [Epub ahead of print]. [Abstract]
National Toxicology Program. NTP Developmental and Reproductive Toxicity Technical Report on the Prenatal Development Studies of 2-((1-(4-Phenoxyphenoxy)propan-2-yl)oxy)pyridine (CASRN 95737-68-1) in Sprague Dawley (Hsd:Sprague Dawley® SD®) Rats and New Zealand White (Hra:NZW SPF) Rabbits: DART Report 07 NTP Developmental and Reproductive Toxicity Reports. 2022 Jan [Epub ahead of print]. [Abstract]
National Toxicology Program. NTP Developmental and Reproductive Toxicity Technical Report on the Prenatal Development Studies of Dimethylaminoethanol Bitartrate (CASRN 5988-51-2) in Sprague Dawley (Hsd:Sprague Dawley® SD®) Rats (Gavage Studies): DART Report 04 NTP Developmental and Reproductive Toxicity Reports. 2020 Jun [Epub ahead of print]. [Abstract]
National Toxicology Program. NTP Developmental and Reproductive Toxicity Technical Report on the Prenatal Development Studies of 4-Methylcyclohexanemethanol (CASRN 34885-03-5) in Sprague Dawley (Hsd:Sprague Dawley® SD®) Rats (Gavage Studies): DART Report 02 NTP Developmental and Reproductive Toxicity Reports. 2020 Jun [Epub ahead of print]. [Abstract]
Related Links
NIEHS research front and center at Society of Toxicology meeting