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Shaun McCullough

Shaun D. McCullough

Senior Respiratory Scientist/Principal Investigator


PhD, Biochemistry and Molecular Genetics, University of Virginia School of Medicine
MS, Biological and Physical Sciences, University of Virginia School of Medicine
BS, Microbiology, Clemson University


Shaun D. McCullough is a Senior Respiratory Scientist/Principal Investigator at RTI where he leads RTI’s in vitro inhalation toxicology and respiratory biology program. His research program is centered around applying cell and molecular biology and in vitro toxicology to protect public health while advancing the human relevance and throughput of toxicity testing. 

Dr. McCullough’s research program requires four key areas of expertise: 

  1. Development and use of increasingly human-relevant in vitro models
  2. Use experimental in vitro exposure approaches that are anchored in real world exposure scenarios
  3. Harmonize and characterize in vitro models, exposure methods, and endpoint assays
  4. Teach, communicate, and collaborate with diverse stakeholders and partners 

Currently, Dr. McCullough leads a project to generate human health effects data for exposures to a PFAS gas. This is in response to the first Toxic Substance Control Act (TSCA) Test Order requiring the generation of in vitro respiratory tract data using human primary cell-based models. The project evaluates the effects of inhaled PFAS exposures using differentiated primary human multi-cellular in vitro models representing three different regions of the respiratory tract while maintaining physiologically relevant air-liquid interface (ALI) conditions. Exposure effects are being determined using a battery of endpoints that represent functions that are relevant to the in vivo physiology of the regions of the respiratory tract that are being modeled. 

Dr. McCullough’s work also focuses on the development and integration of new and existing in vitro models and assays for inhaled chemicals and materials safety evaluation and regulatory decision making. This work advances the human relevance and safety assessments while reducing dependence on animal testing. Dr. McCullough’s research is exploring the impact of population diversity on human in vitro models and its implications for respiratory biology research and inhalation toxicology testing.  He also currently represents RTI on the International Respiratory Tox Collaborative. As a part of this effort, Dr. McCullough is leading the development of a comprehensive protocol for the use of the trans-epithelial electrical resistance (TEER) assay to evaluate respiratory epithelial barrier integrity in in vitro systems.  He is also co-leading efforts by the Collaborative to publish consensus reporting standards for the use of TEER in inhaled chemical evaluation.

Before joining RTI in 2023, Dr. McCullough was an Expert Principal Investigator at the U.S. Environmental Protection Agency’s Public Health and Integrated Toxicology Division. He served as a subject matter expert in the use of in vitro systems for toxicity testing and toxicoepigenetics. Dr. McCullough led the Agency’s research efforts to develop and integrate in vitro models of the human respiratory tract for inhaled chemical testing. He routinely advised a broad range of government, industry, and non-profit organization stakeholders on the development and implementation of approaches to increase the human relevance and acceptance of new approach methodologies (NAMs) for chemical safety and regulatory decision making. 

Dr. McCullough is a member of the Society of Toxicology and in the presidential chain of the In Vitro and Alternative Methods (IVAM) Specialty Section. He was a past president of the Molecular and Systems Biology Specialty Section (MSBSS). Additionally, Dr. McCullough is a member of the board of directors and past president of the American Society of Cellular and Computational Toxicology. 

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