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https://ntp.niehs.nih.gov/go/8674

Isobutyl nitrite: Target Organs and Levels of Evidence for TR-448

Toxicology and Carcinogenesis Studies of Isobutyl Nitrite (CASRN 542-56-3) in F344 Rats and B6C3F1 Mice (Inhalation Studies)

Chemical (Study Title)
CASRN		Peer Review DateRoute/Exposure LevelsStudy Laboratory
Isobutyl nitrite
542-56-3		11/29/1994Inhalation
R&M: 0, 37, 75, OR 150 PPM		IIT Research Institute

Levels of Evidence

Male Rats: Clear Evidence
TypeOrgan/Tissue (Lesion)
Neoplastic Lesions
  • Lung: ALVEOLAR/BRONCHIOLAR ADENOMA 0/46 3/46 12/46 13/46 OR ALVEOLAR/BRONCHIOLAR CARCINOMA 1/46 2/46 1/46 6/46 COMBINED 1/46 5/46 13/46 15/46
Non-Neoplastic Lesions
  • LUNG: ALVEOLAR EPITHELIAL HYPERPLASIA
Other Considerations
  • HEMATOPOIETIC SYSTEM: MONONUCLEAR CELL LEUKEMIA 27/46 2/46 1/46 1/46
Female Rats: Clear Evidence
TypeOrgan/Tissue (Lesion)
Neoplastic Lesions
  • Lung: ALVEOLAR/BRONCHIOLAR ADENOMA 0/46 2/45 2/46 10/46 OR ALVEOLAR/BRONCHIOLAR CARCINOMA 0/46 1/45 0/46 1/46 COMBINED 0/46 3/45 2/46 11/46
Non-Neoplastic Lesions
  • LUNG: ALVEOLAR EPITHELIAL HYPERPLASIA
Other Considerations
  • HEMATOPOIETIC SYSTEM: MONONUCLEAR CELL LEUKEMIA 14/46 1/45 0/46 1/46
Male Mice: Some Evidence
TypeOrgan/Tissue (Lesion)
Neoplastic Lesions
  • Lung: ALVEOLAR/BRONCHIOLAR ADENOMA 7/50 12/50 13/49 17/53 OR ALVEOLAR/BRONCHIOLAR CARCINOMA 1/50 6/50 5/49 4/53 COMBINED 8/50 16/50 16/49 19/53
May Have Been Related
  • Thyroid Gland Follicular Cell: ADENOMA 1/50 0/50 0/50 5/53
Non-Neoplastic Lesions
  • LUNG: ALVEOLAR EPITHELIAL HYPERPLASIA
  • THYROID GLAND: FOLLICULAR CELL HYPERPLASIA
  • SPLEEN: HEMOSIDERIN PIGMENTATION
Female Mice: Some Evidence
TypeOrgan/Tissue (Lesion)
Neoplastic Lesions
  • Lung: ALVEOLAR/BRONCHIOLAR ADENOMA 4/51 14/51 7/50 17/50 OR ALVEOLAR/BRONCHIOLAR CARCINOMA 2/51 2/51 2/50 2/50 COMBINED 6/51 15/51 9/50 19/50
Non-Neoplastic Lesions
  • LUNG: ALVEOLAR EPITHELIAL HYPERPLASIA
  • NASAL CAVITY: SEROUS EXUDATE; OLFACTORY EPITHELIAL ATROPHY