Table 1.
Elements classified as heavy metals according to a density at room temperature of more than 5 g/cm3. The values for the limit in residential soils and oral reference dose were obtained from the U.S. Environmental Protection Agency (USEPA) for June 2020 [11]. The density at room temperature values was obtained from Shackelford et al. [12]. The abundance rank of the elements in the Earth’s crust was extrapolated from Anderson [13].
| Elements | Limit in Residential Soils (mg/kg) | Reference Dose (RfDo) (µg/kg/day) | Density at Room Temperature (g/cm3) | Abundance Rank |
|---|---|---|---|---|
| Antimony (metallic) | 31 | 0.40 | 6.70 | 62 |
| Arsenic | 0.77 | 0.30 | 5.73 | 55 |
| Cadmium (Diet) | 78 | 1 | 8.65 | 64 |
| Chromium (VI) | 0.31 | 3 | 7.19 | 21 |
| Cobalt | 23 | 0.30 | 8.90 | 31 |
| Copper | 3100 | 40 | 8.96 | 25 |
| Iron | 55,000 | 700 | 7.87 | 4 |
| Lead | 400 | N/A | 11.34 | 36 |
| Manganese (Non-diet) | 1900 | 24 | 7.47 | 12 |
| Mercury (elemental) | 11 | N/A | 13.53 | 66 |
| Molybdenum | 390 | 5 | 10.28 | 54 |
| Nickel (soluble salts) | 1600 | 20 | 8.91 | 23 |
| Silver | 390 | 5 | 10.49 | 65 |
| Thallium (soluble salts) | 0.78 | 0.01 | 11.85 | 60 |
| Tin | 47,000 | 600 | 7.31 | 48 |
| Tungsten | 63 | 0.80 | 19.25 | 53 |
| Uranium (soluble salts) | 16 | 0.20 | 19.05 | 50 |
| Vanadium | 390 | 5 | 6.11 | 19 |
| Zinc | 23,000 | 300 | 7.14 | 24 |
| Zirconium | 6.30 | 0.08 | 6.51 | 18 |