ATSDR — Minimal Risk Levels for Aluminum
The US Agency for Toxic Substances and Disease Registry derived oral Minimal Risk Levels for aluminum in its September 2008 Toxicological Profile, anchored on neurotoxic effects in lifetime-exposed mice (Golub et al. 2000) (ATSDR 2008). The chronic-duration oral MRL is 1 mg Al/kg/day, the same value as the intermediate-duration oral MRL (ATSDR 2008). An acute-duration oral MRL was not derived because the available data were considered inadequate (ATSDR 2008).
Minimal Risk Levels
| Route | Duration | MRL |
|---|---|---|
| Oral | Acute (≤14 days) | Not derived (inadequate data) |
| Oral | Intermediate (15-364 days) | 1 mg Al/kg/day |
| Oral | Chronic (≥1 year) | 1 mg Al/kg/day |
For a 70-kilogram adult, the chronic oral MRL corresponds to 70 mg Al/day (ATSDR 2008).
Critical endpoint and derivation
| Parameter | Value |
|---|---|
| Critical study | Golub et al. 2000 |
| Critical effect | Decreased forelimb and hindlimb grip strength, decreased thermal sensitivity in lifetime-exposed mice |
| LOAEL | 100 mg Al/kg/day |
| Composite uncertainty factor | 100 (10 for animal-to-human extrapolation × 10 for human variability) |
| Chronic oral MRL | 100 ÷ 100 = 1 mg Al/kg/day |
Relationship to EFSA TWI
The ATSDR chronic oral MRL of 1 mg Al/kg/day is approximately 7-fold higher than the EFSA AFC TWI daily-equivalent of approximately 0.14 mg Al/kg/day (1 mg/kg/week ÷ 7). The discrepancy is methodological: ATSDR’s derivation uses the LOAEL-with-uncertainty-factor pathway from a single critical study (Golub et al. 2000); the EFSA AFC Panel 2008 integrates evidence across multiple animal endpoints with a different safety-factor structure. HMT&C calibration to the EFSA TWI is the more conservative posture; calibration to the ATSDR MRL is the more permissive.
Aluminum bioavailability context
The 2008 profile (ATSDR 2008) records aluminum gastrointestinal bioavailability ranges that constrain dose-translation:
| Source | Bioavailability |
|---|---|
| Drinking water | 0.07 to 0.39 percent |
| Diet (typical aluminum compounds) | 0.1 percent |
| Aluminum lactate (specific compound) | Higher than typical dietary forms; suggests compound-specific variation |
Typical adult dietary aluminum intake of 5 to 15 mg/day is well below the chronic oral MRL of 70 mg/day for a 70 kg adult (ATSDR 2008). Aluminum-containing antacid use (typical user: 100 to 1000 mg/day delivered) substantially exceeds the MRL on a body-weight-normalized basis (ATSDR 2008).
Sources
- ATSDR 2008 — ATSDR, September 2008. Toxicological Profile for Aluminum.