| Contaminant |
Source |
Risk |
| Dust and Ash |
Surrounding dirt and vegetation |
Moderate: can be minimized be regular roof and gutter maintenance and first flush conditions |
| Pathogenic Bacteria |
Bird and animal droppings on roof, attached to dust |
Moderate: Bacteria may be present in dust or in bird feces. Can be minimized by first flushing’s. |
| Heavy Metals |
Roof materials or dust materials from urban and industrialized area |
Low: Unless downwind of any industry or any manufacture processes like metal smelter and/or very acidic rainfall |
| Other inorganic contaminants (salt from sea spray) |
Sea spray, certain industrial discharges in air, use of unsuitable tank and/or roof |
Low: Unless downwind of any large scale industry or in very near vicinity of ocean |
| Mosquito Larvae |
Mosquitoes laying eggs in gutter |
Moderate: if tank inlet is screened and there are no gaps, risks can be minimized |
