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| Endpoint | PODs (mg Mo/m3) | RDDR valuesa | HECsb (mg Mo/m3) |
|---|---|---|---|
| Squamous metaplasia of the epiglottis in male rats | 3.53 (BMCL) | 0.459 | 0.28 |
| Hyaline degeneration of the respiratory epithelium in female rats | 4.82 (BMCL) | 0.248 | 0.21 |
| Hyaline degeneration of the olfactory epithelium in female rats | 6.7 (LOAEL) | 0.248 | 0.30 |
| Squamous metaplasia of the epiglottis in female rats | 1.60 (BMCL) | 0.248 | 0.071 |
| Squamous metaplasia of the epiglottis in male mice | 1.06 (BMCL) | 0.441 | 0.08 |
| Histiocyte infiltration in the lungs of male mice | 6.7 (LOAEL) | 1.046 | 1.3 |
| Alveolar epithelial metaplasia in male mice | 6.7 (LOAEL) | 1.046 | 1.3 |
| Squamous metaplasia of the epiglottis in female mice | 6.7 (LOAEL) | 0.367 | 0.44 |
| Alveolar epithelial metaplasia in female mice | 6.7 (LOAEL) | 3.067 | 3.7 |
RDDR values specific for each region of the respiratory tract (extrathoracic, tracheobronchial, and pulmonary) were calculated using EPA’s RDDR calculator with reference body weights of 0.40, 0.25, 0.040, and 0.035 kg for male rats, female rats, male mice, and female mice, respectively, and reported particle sizes and particle size distributions.
HEC calculated by multiplying the duration-adjusted POD (POD × 6 hours/24 hours × 5 days/7days) by the RDDR value.
BMCL = 95% lower confidence limit on the benchmark concentration; HEC = human equivalent concentration; LOAEL = lowest observed adverse effect level; POD = point of departure; RDDR = regional deposited dose ratio for the specific region of the respiratory tract
From: APPENDIX A, ATSDR MINIMAL RISK LEVEL WORKSHEETS
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