| Average concentration (mg∙L−1) | Contamination risk | WHO Limit Values, 1994 (mg∙L−1) | |
| Mercury (Hg) | ˂0.00033 | Low |
|
| 0.00034 - 0.00066 | Moderate |
| |
| 0.00067 - 0.001 | High | 0.001 | |
| >0.001 | Very high |
| |
| Arsenic (As) | ˂0.0033 | Low |
|
| 0.0034 - 0.0066 | Moderate | 0.01 | |
| 0.0067 - 0.001 | High |
| |
| >0.01 | Very high |
| |
| Copper (Cu) | ˂0.66 | Low |
|
| 0.67 - 1.66 | Moderate | 2.00 | |
| 1.67 - 2 | High |
| |
| >2 | Very high |
| |
| Zinc (Zn) | ˂1 | Low |
|
| 1 - 2 | Moderate | 3.00 | |
| 1 - 3 | High |
| |
| >3 | Very high |
| |