The NTP has published three draft technical reports, on the toxicology (including genotoxicity) and carcinogenicity of dietary zinc, 2,3-butanedione, and p-chloro-α,α,α-trifluorotoluene (PCBTF).

In lifetime studies, rats were administered diets containing zinc carbonate (basic), including at levels considered to be zinc-deficient. There was “equivocal evidence of carcinogenicity” in zinc-deficient male rats, based on higher incidences of pancreatic adenomas. There was “no evidence of carcinogenicity” in zinc-deficient female rats, or rats of either sex receiving excess zinc. However, exposure to diets containing excess zinc resulted in an increased incidence of non‑neoplastic lesions in the pancreas of both sexes, as well as in the testis.

There was “some evidence of carcinogenicity” of 2,3-butanedione to male and female Wistar rats exposed (whole-body) for 6 hours/day, 5 days/week, for 105 weeks. Both sexes displayed an increased incidence of carcinoma of the nose, with males also showing an increased incidence of papilloma in this tissue. There was “equivocal evidence of carcinogenicity” in female mice, based on an increased incidence of nasal adenocarcinoma, but “no evidence of carcinogenicity” in male mice. Non‑neoplastic lesions were reported in the nose, larynx, trachea, lungs and eyes of male and female mice and rats.

Inhalation exposure of male and female mice to PCBTF for 2 years caused “clear evidence of carcinogenicity”, based on increase incidences of adenoma, carcinoma and blastoma in the liver. There was “some evidence of carcinogenicity” in male and female rats, with the thyroid gland the primary site of tumour formation. Exposure also caused non‑neoplastic lesions in the lungs and liver of male and female rats and mice, as well as the uterus of female rats, the forestomach of male and female mice, and the larynx of male mice.

These reports will be peer-reviewed at the Technical Peer Review Panel meeting on 13 July 2017.

US National Toxicology Program (2017).

Technical Report on the toxicology and carcinogenesis studies of dietary zinc in Sprague Dawley rats (feed study). NTP TR 592. Draft. Scheduled peer-review date 13 July 2017. https://ntp.niehs.nih.gov/ntp/about_ntp/trpanel/2017/july/tr592_peerdraft.pdf

Technical Report on the toxicology and carcinogenesis studies of 2,3-butanedione in Wistar Han rats and B6C3F1/N mice (inhalation studies). NTP TR 593. Draft. Scheduled peer-review date 13 July 2017. https://ntp.niehs.nih.gov/ntp/about_ntp/trpanel/2017/july/tr593_peerdraft.pdf

Technical Report on the toxicology and carcinogenesis studies of p-chloro-α,α,α-trifluorotoluene in Sprague Dawley rats and B6C3F1/N mice (inhalation studies). NTP TR 594. Draft. Scheduled peer-review date 13 July 2017. https://ntp.niehs.nih.gov/ntp/about_ntp/trpanel/2017/july/tr594_peerdraft.pdf

 

The above items were taken from the June 2017 issue of Toxicology and Regulatory News which is sent automatically to members of bibra.

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