| Element | US-EPA | NOM-147-SEMARNAT/SSA1-2004 | |
| Moderately Polluted | Heavily Polluted | ||
| As | 2.0 - 8.0 | >8.0 | 22 |
| Cr | 25 - 75 | >75 | 280 |
| Pb | 20 - 200 | >200 | 400 |
| Co | ---- | ----- | ----- |
| Mn | 500 | ----- | ----- |
| Ni | ----- | ----- | 1600 |