Skip Navigation
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Internet Explorer is no longer a supported browser.

This website may not display properly with Internet Explorer. For the best experience, please use a more recent browser such as the latest versions of Google Chrome, Microsoft Edge, and/or Mozilla Firefox. Thank you.

Your Environment. Your Health.

Toxicology Branch

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.

Nigel J. Walker, Ph.D., D.A.B.T.
Nigel J. Walker, Ph.D.
Acting Chief, Toxicology Branch
Tel 984-287-3204
Fax 301-451-5596
P.O. Box 12233
Mail Drop K2-02
Durham, 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 Developmental and Reproductive Toxicology Group Systems Toxicology Group General Toxicology Group

Toxicology Branch staff are responsible for the following functions:

  • 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:

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.

to Top