Table 2.
Incidences of pulmonary effects in 2-year studies of dioxin and dioxin-like compounds in female rats
| TCDD | Vehicle | 3 ng/kg | 10 ng/kg | 22 ng/kg | 46 ng/kg | 100 ng/kg | 100 ng/kg Stop | |
|---|---|---|---|---|---|---|---|---|
| Number examined | 53 | 54 | 53 | 52 | 53 | 52 | 50 | |
| Metaplasia, squamous | 1(2%a) | — | — | — | 5(9%) | 6(12%) | 3(6%) | |
| Alveolar epithelium, metaplasia, bronchiolar | 2(4%) | 19(35%) | 33(62%) | 35(67%) | 45(85%) | 46(88%) | 31(62%) | |
| Alveolar epithelium, hyperplasia | 12(23%) | — | — | — | — | — | — | |
| Cystic keratinizing epithelioma | — | — | — | — | — | 7(13%) | — | |
| Cystic keratinizing epithelioma, Multiple | — | — | — | — | — | 2(4%) | — | |
| PCB126 | vehicle | 30 ng/kg | 100 ng/kg | 175 ng/kg | 300 ng/kg | 550 ng/kg | 1000 ng/kg | 1000 ng/kg stop |
| Number examined | 53 | 55 | 53 | 53 | 53 | 51 | 51 | 50 |
| Metaplasia, squamous | 1(2%) | — | 1(2%) | 2(4%) | 3(6%) | 9(18%) | 4(8%) | — |
| Alveolar epithelium, metaplasia, Bronchiolar | — | 29(53%) | 34(64%) | 41(77%) | 39(74%) | 47(92%) | 40(78%) | 32(64%) |
| Alveolar epithelium, hyperplasia | 12(23%) | 1(2%) | — | 1(2%) | 2(4%) | — | — | — |
| Cystic keratinizing epithelioma | — | — | — | — | 1(2%) | 3(6%) | 5(10%) | — |
| Cystic keratinizing epithelioma, Multiple | — | — | — | — | — | 8(16%) | 30(59%) | — |
| Squamous cell carcinoma | — | — | — | — | — | 1(2%) | 2(4%) | — |
| PeCDF | Vehicle | 6 ng/kg | 20 ng/kg | 44 ng/kg | 92 ng/kg | 200 ng/kg | 200 ng/kg stop | |
| Number examined | 53 | 53 | 53 | 53 | 53 | 52 | 50 | |
| Metaplasia, squamous | — | — | — | 2(4%) | 4(8%) | 3(6%) | 1(2%) | |
| Alveolar epithelium, metaplasia, Bronchiolar | 5(9%) | 6(11%) | 5(9%) | 9(17%) | 23(43%) | 28(54%) | 7(14%) | |
| Alveolar epithelium, hyperplasia | 14(26%) | 17(32%) | 12(23%) | 20(38%) | 8(15%) | 3(6%) | 6(12%) | |
| Cystic keratinizing epithelioma, multiple | — | — | — | — | — | 1(2%) | — | |
| TCDD/PCB126/PeCDF | Vehicle | 10 ngTEQ/kg | 22 ngTEQ/kg | 46 ngTEQ/kg | 100 ngTEQ/kg | |||
| Number Examined | 53 | 53 | 53 | 53 | 53 | |||
| Metaplasia, squamous | 2(4%) | — | 2(4%) | 8(15%) | 11(21%) | |||
| Alveolar epithelium, metaplasia, bronchiolar | — | 20(38%) | 33(62%) | 41(77%) | 40(75%) | |||
| Alveolar epithelium, hyperplasia | 21(40%) | 25(47%) | 10(19%) | 2(4%) | 2(4%) | |||
| Cystic keratinizing epithelioma | — | — | — | 2(4%) | 9(17%) | |||
| Cystic keratinizing epithelioma, Multiple | — | — | — | — | 11(21%) |
a
Overall rate (percentage given as number of animals with lesions per number of animals examined histopathologically).
-: No incidence (0%.)