Table 3.
Lung and trachea histopathology after exposure to AM or LA for 13 weeks
| Air control | AM 3.3 | LA 1.0 | LA 3.3 | LA 10.0 | |
|---|---|---|---|---|---|
| Lung | |||||
| Foreign Bodya | |||||
| 1 Day | 0 | 8* | 8* | 8* | 8* |
| 1 Month | 0 | 8* | 8* | 8* | 8* |
| 3 Months | 0 | 8* | 8* | 8* | 8* |
| 18 Months | 0 | 47* | 40* | 48* | 49* |
| Alveolus Inflammationb | |||||
| 1 Day | 0 | 8 (1.0)* | 8 (1.0)* | 8 (1.0)* | 8 (2.0)* |
| 1 Month | 0 | 8 (1.1)* | 8 (1.0)* | 8 (1.0)* | 8 (2.0)* |
| 3 Months | 0 | 8 (1.0)* | 8 (1.0)* | 8 (1.1)* | 8 (1.4)* |
| 18 Months | 0 | 45 (1.0)* | 40 (0.9)* | 47 (1.1)* | 48 (1.1)* |
| Alveolar Epithelial Hyperplasiac | |||||
| 1 Day | 0 | 0 | 0 | 0 | 0 |
| 1 Month | 0 | 0 | 0 | 0 | 1 (0.1) |
| 3 Months | 0 | 0 | 0 | 0 | 1 (0.1) |
| 18 Months | 1 (0.0) | 9 (0.3)* | 6 (0.2) | 6 (0.2) | 9 (0.4)*^ |
| Bronchiole Epithelial Hyperplasia | |||||
| 1 Day | 0 | 0 | 0 | 0 | 8 (1.0)* |
| 1 Month | 0 | 1 (0.1) | 0 | 0 | 8 (1.0)* |
| 3 Months | 0 | 0 | 0 | 0 | 0 |
| 18 Months | 0 | 0 | 0 | 0 | 0 |
| Bronchiolizationd | |||||
| 1 Day | 0 | 8 (1.0)* | 7 (0.9)* | 8 (1.0)* | 8 (1.0)* |
| 1 Month | 0 | 7 (0.9)* | 7 (0.9)* | 7 (0.9)* | 8 (1.4)* |
| 3 Months | 0 | 8 (1.0)* | 8 (1.0)* | 8 (1.0)* | 8 (1.0)* |
| 18 Months | 0 | 5 (0.1) | 5 (0.1) | 0 | 0 |
| Interstitial Fibrosise | |||||
| 1 Day | 0 | 8 (1.0)* | 8 (1.0)* | 8 (1.0)* | 8 (1.0)* |
| 1 Month | 0 | 8 (1.0)* | 7 (0.9)* | 8 (1.0)* | 8 (1.0)* |
| 3 Months | 0 | 8 (1.0)* | 8 (1.0)* | 8 (1.0)* | 8 (1.0)* |
| 18 Months | 0 | 42 (0.8)* | 29 (0.6)* | 43 (0.9)* | 42 (0.9)* |
| (Sub) Pleural Fibrosise | |||||
| 18 Months | 0 | 25 (0.5)* | 16 (0.3)* | 19 (0.4)* | 22 (0.4)* |
| Bronchiolar/Alveolar Adenoma | |||||
| 18 Months | 0 | 2 | 0 | 2 | 3^ |
| Bronchiolar/Alveolar Carcinoma | |||||
| 18 Months | 0 | 0 | 0 | 0 | 1 |
| Bronchiolar/Alveolar Adenoma or Carcinoma | |||||
| 18 Months | 0 | 2 | 0 | 2 | 4^ |
| Trachea | |||||
| Trachea, Chronic Inflammation | |||||
| 18 Months | 0 | 0 | 4 (0.1) | 2 (0.1) | 9 (0.2)* |
| Trachea, Squamous Metaplasia | |||||
| 18 Months | 0 | 1 (0.0) | 0 | 0 | 0 |
Rats were exposed to AM or LA for 13 weeks and evaluated at 1 day, 1 month, 3 months, or 18 months after the end of the exposure period. Column headings indicated target mass concentrations (mg/m3). Values represent the number of animals with a finding in each group (total examined n = 8 at 1 day, 1, and 3 months, and n = 49–50 at 18 months). Average lesion severity scores for all rats in each group (shown in parentheses) were graded as follows: 1 = minimal, 2 = mild, 3 = moderate, 4 = marked, and 5 = severe. *P < 0.05 vs. air control; ^P < 0.05 for trend test among LA groups. aConsistent with fibers; not graded for severity. bPredominantly macrophages with lesser numbers of neutrophils and lymphocytes, often associated with foreign bodies; occasional granulomas with rare giant cells. cProliferation of cuboidal type II alveolar cells (without evidence of significant inflammation). dPresence of cells that resemble bronchiolar epithelial cells in alveolar ducts and adjacent alveoli. eConfirmed on Masson’s trichrome stain