The NIH intramural research program has shifted all non-mission-critical laboratory operations to a maintenance phase in order to promote physical distancing and diminished transmission risk of COVID-19. Effective Monday, March 23, 2020, only mission-critical functions within NIH research laboratories will be supported.
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Nigel J. Walker, Ph.D.
Acting Chief, Toxicology Branch -
Tel 984-287-3204
Fax 301-451-5596
walker3@niehs.nih.govCurriculum Vitae J. Nigel Walker (328KB)
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P.O. Box 12233Mail Drop K2-02Durham, N.C. 27709
Research Summary
The Toxicology Branch provides the major reservoir of toxicological science expertise and Project Leaders for the in vivo testing program of the National Toxicology Program (NTP).

Toxicology Branch staff are responsible for the following functions:
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Design, interpretation, review, and reporting of general toxicology and carcinogenicity studies usually in rodent models as well as studies to evaluate targeted effects on the immune system, reproduction, development and interference with chromosomes and DNA for substances studied by the NTP.
- Integration of information derived from studies of absorption, metabolism, distribution and excretion of test substances within the body and the development of mathematical models that utilize this information in the extrapolation and prediction of findings across different species and exposure conditions. Branch staff also analyzes and develops models using information derived from studies of gene expression in different tissues as well as the reporting of all these specialized toxicology studies.
- Development of new methodologies for toxicological assessments.
- Guidance on the proper utilization of new types of toxicology information in hazard identification, hazard characterization and regulatory decision-making.
To facilitate these activities, the Toxicology Branch is organized into three workgroups:
- Developmental and Reproductive Toxicology Group
- General Toxicology and Cancer Group
- Systems Toxicology Group
These groups work with a variety of NTP staff to accomplish program goals.
The current portfolio of activities ranges from evaluations of the potential health impact of cell phone radiation, medicinal herbs, environmental substances that can mimic or interfere with endogenous hormones, occupational exposures, and gene therapies, to the study of mold and novel substances such as nanoscale materials.
The NTP invites interested members of the public and groups to nominate substances for possible testing. All nominations go through a formal review and selection process, which includes opportunity for public input, and studies are initiated as time and resources permit.
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