16.—(1) The environmental hazards of a preparation shall be assessed by one or more of the following methods—
(a)by the conventional method described in paragraphs 18 and 19 using concentration limits; or
(b)by the criteria referred to in the approved classification and labelling guide in relation to the preparation for an appropriate classification and label.
(2) Where the environmental hazards have been established by both methods, the results of the method referred to in sub-paragraph (1)(b) shall be used for classifying the preparation.
(3) Subject to sub-paragraph (4), for preparations of a known composition, with the exception of plant protection products, classified in accordance with the method set out in sub-paragraph (1)(b), a new assessment of the environmental hazards shall be performed either by the method set out in sub-paragraph (1)(a) or (1)(b) whenever—
(a)changes of composition of the initial concentration, as a weight/weight or volume/volume percentage, of one or more of the dangerous constituents are introduced by the manufacturer which exceed the permitted variations set out in the following table—
| Initial concentration range of the constituent | Permitted variation in actual concentration of the constituent | |
|---|---|---|
| ≤ 2.5% | ± 30% | |
| > 2.5 | ≤ 10% | ± 20% |
| > 10 | ≤ 25% | ± 10% |
| > 25 | ≤ 100% | ± 5% |
(b)changes of composition involving the substitution or addition of one or more constituents, which may or may not be dangerous within the definitions in Schedule 1, are introduced by the manufacturer.
(4) The revised assessment required by paragraph (3) shall not be required where there is a valid scientific justification for considering that a re-evaluation of the hazard will not result in a change of classification.