13. References to, or to the release into water of, a substance listed in this paragraph or to its release in a quantity which, in any period of 12 months, is greater than the background quantity by an amount specified in this paragraph are to the following substances and amounts–
| Substance | Amount greater than the background quantity (in grammes) in any period of 12 months |
|---|---|
| Mercury and its compounds | 200 (expressed as metal) |
| Cadmium and its compounds | 1,000 (expressed as metal) |
| All isomers of hexachlorocyclohexane | 20 |
| All isomers of DDT | 5 |
| Pentachlorophenol and its compounds | 350 (expressed as PCP) |
| Hexachlorobenzene | 5 |
| Hexachlorobutadiene | 20 |
| Aldrin | 2 |
| Dieldrin | 2 |
| Endrin | 1 |
| Polychlorinated Biphenyls | 1 |
| Dichlorvos | 0.2 |
| 1,2 – Dichloroethane | 2,000 |
| All isomers of trichlorobenzene | 75 |
| Atrazine | 350* |
| Simazine | 350* |
| Tributyltin compounds | 4 (expressed as TBT) |
| Triphenyltin compounds | 4 (expressed as TPT) |
| Trifluralin | 20 |
| Fenitrothion | 2 |
| Azinphos-methyl | 2 |
| Malathion | 2 |
| Endosulfan | 0.5 |
*Where both Atrazine and Simazine are released, the figure for both substances in aggregate is 350 grammes.