NTP Technical Report - Toxicology and Carcinogenesis Studies of alpha-Methylstyrene (CAS No. 98-83-9) - Inhalation Studies - NTP TR 543

Sep 17, 2026

NTP Technical Report 543 documents the toxicology and carcinogenesis potential of alpha-methylstyrene (CAS No. 98-83-9) following inhalation exposure in F344/N rats and B6C3F1 mice. The report describes the purpose and scope of NTP technical reports, emphasizing that conclusions are based on results from NTP laboratory studies. It outlines the program’s study design principles, quality assurance practices, and compliance with health and safety and Good Laboratory Practice requirements, with findings prepared and evaluated by multiple contributing scientists and pathology teams.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages218

Reading Time9 h 9 min

AccessFree to download

Foreword

NTP technical report purpose and scope

Study conduct, compliance, and quality assurance

Publication availability

Contributors

Study scientists and pathologists

Pathology review and quality assessment audits

NTP TECHNICAL REPORT ON THE TOXICOLOGY AND CARCINOGENESIS STUDIES OF ALPHA-METHYLSTYRENE ( CAS NO . 98-83-9) IN F344/N RATS AND B(IF 1ATI MONI CSETUDIES) NTP TR 543 NOVEMBER 2007 NTP TECHNICAL REPORT ON THE TOXICOLOGY AND CARCINOGENESIS STUDIES OF "-METHYLSTYRENE (CAS NO. 98-83-9) IN F344/N RATS AND B6C3F1 MICE (INHALATION STUDIES) NATIONAL TOXICOLOGY PROGRAM P.O. Box 12233 Research Triangle Park, NC 27709 November 2007 NTP TR 543 NIH Publication No. 08-4474 National Institutes of Health Public Health Service U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES FOREWORD The National Toxicology Program (NTP) is an interagency program within the Public Health Service (PHS) of the Department of Health and Human Services (HHS) and is headquartered at the National Institute of Environmental Health Sciences of the National Institutes of Health (NIEHS/NIH) . Three agencies contribute resources to the program: NIEHS/NIH, the National Institute for Occupational Safety and Health of the Centers for Disease Control and Prevention (NIOSH/CDC), and the National Center for Toxicological Research of the Food and Drug Administration (NCTR/FDA) . Established in 1978, the NTP is charged with coordinating toxicological testing activities, strengthening the science base in toxicology, developing and validating improved testing methods, and providing information about potentially toxic substances to health regulatory and research agencies, scientific and medical communities, and the public. The Technical Report series began in 1976 with carcinogenesis studies conducted by the National Cancer Institute. In 1981, this bioassay program was transferred to the NTP. The studies described in the Technical Report series are designed and conducted to characterize and evaluate the toxicologic potential, including carcinogenic activity, of selected substances in laboratory animals (usually two species, rats and mice) . Substances selected for NTP toxicity and carcinogenicity studies are chosen primarily on the basis of human exposure, level of production, and chemical structure. The interpretive conclusions presented in NTP Technical Reports are based only on the results of these NTP studies. Extrapolation of these results to other species, including characterization of hazards and risks to humans, requires analyses beyond the intent of these reports. Selection per se is not an indicator of a substance’s carcinogenic potential. The NTP conducts its studies in compliance with its laboratory health and safety guidelines and FDA Good Laboratory Practice Regulations and must meet or exceed all applicable federal, state, and local health and safety regulations. Animal care and use are in accordance with the Public Health Service Policy on Humane Care and Use of Animals. Studies are subjected to retrospective quality assurance audits before being presented for public review. NTP Technical Reports are indexed in the NIH/NLM PubMed database and are available free of charge electronically on the NTP website ([http://ntp.niehs.nih.gov](http://ntp.niehs.nih.gov)) or in hardcopy upon request from the NTP Central Data Management group at cdm@niehs.nih.gov or (919) 541-3419. NTP TECHNICAL REPORT ON THE TOXICOLOGY AND CARCINOGENESIS STUDIES OF "-METHYLSTYRENE (CAS NO. 98-83-9) IN F344/N RATS AND B6C3F1 MICE (INHALATION STUDIES) NATIONAL TOXICOLOGY PROGRAM P.O. Box 12233 Research Triangle Park, NC 27709 November 2007 NTP TR 543 NIH Publication No. 08-4474 National Institutes of Health Public Health Service U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 2 CONTRIBUTORS National Toxicology Program Evaluated and interpreted results and reported findings M.E. Wyde, Ph.D., Study Scientist R.C. Sills, D.V.M., Ph.D., Study Pathologist D.W. Bristol, Ph.D. J.R. Bucher, Ph.D. L.T. Burka, Ph.D. R. S. Chhabra, Ph.D. M.L. Cunningham, Ph.D. R.A. Herbert, D.V.M., Ph.D. A.P. King-Herbert, D.V.M. G.E.

FAQs

What substance and exposure route are covered in NTP TR 543?

The report covers alpha-methylstyrene (CAS No. 98-83-9) using inhalation studies in F344/N rats and B6C3F1 mice.

Which animal models are used in the toxicology and carcinogenesis studies?

Studies are conducted in two species: F344/N rats and B6C3F1 mice.

How does the report describe the basis for its interpretive conclusions?

Interpretive conclusions are based only on results from the described NTP studies, while extrapolation to other species or human hazard/risk requires additional analyses beyond the report’s intent.

Sep 17, 2026

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