---

About the Division

Mission

Conduct fundamental and applied research designed to define the biological mechanisms of action underlying the toxicity of FDA-regulated products, as well as characterize the carcinogenic risks associated with chemicals of interest to the FDA.

---

2023 Select Accomplishments

The Toxicity of Triclosan

DBT scientists completed a two-year mouse bioassay elucidating the chronic dermal toxicity/carcinogenicity of triclosan. Triclosan is a widely used bacteriostatic and bactericidal agent that is present in a variety of personal care, consumer, and industrial products. Due to its extensive use, there is potential for humans in all age groups to receive lifetime exposures to triclosan, yet data on the chronic dermal toxicity/carcinogenicity of triclosan were lacking. This research, funded by an interagency agreement (IAA) between FDA and the National Institute of Environmental Health Sciences, helped address a data gap identified by FDA to assess the risk to humans from dermal exposure to triclosan and contributed to the understanding of the mechanisms of triclosan-associated toxicities. The study findings were reported in Arch Toxicol.

Effects of Cannabidiol on Male Reproductive Health

Cannabidiol (CBD), one of the major components extracted from the plant Cannabis sativa L., is an FDA-approved drug that treats specific types of seizures. CBD use has become popular within the general population in recent years due to its purported health benefits and increased availability. However, there are uncertainties regarding the safety of CBD, including reproductive toxicity. NCTR scientists in DBT and Division of Genetic and Molecular Toxicology, along with FDA’s Office of the Commissioner and Center for Food Safety and Applied Nutrition (CFSAN), examined the effects of CBD and its two main metabolites (7-carboxy-CBD and 7-hydroxy-CBD), on primary human testicular Leydig and Sertoli cells in vitro. This work was reported in Arch Toxicol and Toxicol Sci.

Skin Permeation Study of FDA-Regulated Products 

Skin permeation is a primary consideration in the safety assessment of cosmetic ingredients, topical drugs, and human users handling veterinary medicinal products. As the need for dermal absorption studies in dermatological product safety assessments grows, so does the impetus to reduce, refine, and replace (Three Rs) the use of animals in regulatory science. Researchers from NCTR’s DBT, in collaboration with scientists from FDA’s Center for Drug Evaluation and Research (CDER), CFSAN, and Center for Veterinary Medicine, the National Center for Advancing Translational Sciences, and the National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods, developed a standardized method to evaluate the suitability of alternative skin barrier models to predict skin absorption in humans. This novel multiparametric experimental approach has broad adaptability to enable the evaluation of existing and future alternative skin barrier models. This work was published in Toxicol in Vitro and was sponsored by an FDA Chief Scientist Challenge Grant. 

Breakthrough in the Study of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) has grown in global frequency to become the most common chronic liver disease, with a prevalence ranging from 25% to 48% in adults and from 8% to 12% in children. Current evidence indicates the existence of substantial interindividual heterogeneity in susceptibility to NAFLD and its severity. NCTR investigators, in collaboration with scientists from FDA’s CDER and Texas A&M University, demonstrated that extensive alterations in the expression of disease-related genes are a fundamental feature of the pathogenesis of NAFLD using a genetically diverse Collaborative Cross mouse population. These findings were published in the Am J Physiol Gastrointest Liver Physiol.

DBT Research Backs up FDA Regulations

Research conducted by DBT scientists provided important new data to support an FDA proposal to amend regulations revoking authorization for the use of brominated vegetable oil (BVO) in food due to safety concerns. BVO is a food additive used primarily to help emulsify citrus-flavored soft drinks, preventing them from separating during distribution. The rodent safety studies conducted by NCTR were published in 2022 and confirmed previous reports that dietary exposure to BVO is toxic to the thyroid and results in bioaccumulation of lipid-bound bromine in the body at doses relevant to human exposure.

---

---

Resources for You

• DBT Fact Sheet
• NCTR Grand Rounds: "Bisphenol A: Toxicology and Pharmacokenetic Data to Inform Ongoing Safety Assessments (Presentation recorded in Adobe Connect on September 13, 2018)
• Annual Reports
• Meet the Principal Investigators

---