| Heavy metal | Typical background levels for non contaminated soil (ppm) | Unsafe for leafy or root vegetables (ppm) | Unsafe for gardens and children contact (ppm) |
| Cadmium | 0.1 - 1.0 | >10 | 50 |
| Copper | 1 - 50 | >200 | 500 |
| Lead | 10 - 70 | >500 | 1000 |
| Nickel | 0.5 - 50 | >200 | 500 |
| Zinc | 9 - 125 | >200 | 500 |