Substance classification categories and criteria

Substances shall be classified as "environmentally hazardous substances (aquatic environment)", if
they satisfy the criteria for Acute 1, Chronic 1 or Chronic 2, according to Table These
criteria describe in detail the classification categories. They are diagrammatically summarized in
11 Special guidance on data interpretation is provided in Chapter 4.1 and Annex 9 of the GHS.
12 See Chapter 4.1 and Annex 9, paragraph A9. of the GHS.
Table Categories for substances hazardous to the aquatic environment (see Note 1)
(a) Acute (short-term) aquatic hazard

NOTE 1: The organisms fish, crustacea and algae are tested as surrogate species covering a range of
trophic levels and taxa, and the test methods are highly standardized. Data on other organisms may
also be considered, however, provided they represent equivalent species and test endpoints.
NOTE 2: When classifying substances as Acute 1 and/or Chronic 1 it is necessary at the same time to
indicate an appropriate M factor (see ) to apply the summation method.
NOTE 3: Where the algal toxicity ErC50 (= EC50 (growth rate)) falls more than 100 times below the
next most sensitive species and results in a classification based solely on this effect, consideration
shall be given to whether this toxicity is representative of the toxicity to aquatic plants. Where it can
be shown that this is not the case, professional judgment shall be used in deciding if classification
shall be applied. Classification shall be based on the ErC50. In circumstances where the basis of the
EC50 is not specified and no ErC50 is recorded, classification shall be based on the lowest EC50
NOTE 4: Lack of rapid degradability is based on either a lack of ready biodegradability or other
evidence of lack of rapid degradation. When no useful data on degradability are available, either
experimentally determined or estimated data, the substance shall be regarded as not rapidly
NOTE 5: Potential to bioaccumulate, based on an experimentally derived BCF ≥ 500 or, if absent,
a log Kow ≥ 4 provided log Kow is an appropriate descriptor for the bioaccumulation potential of the
substance. Measured log Kow values take precedence over estimated values and measured BCF values
take precedence over log Kow values.
Figure Categories for substances long-term hazardous to the aquatic environment


The classification scheme in Table below summarizes the classification criteria for
Table Classification scheme for substances hazardous to the aquatic environment
NOTE 1: Acute toxicity band based on L(E)C50 values in mg/l for fish, crustacea and/or algae or
other aquatic plants (or Quantitative Structure Activity Relationships (QSAR) estimation if no
experimental data13).
NOTE 2: Substances are classified in the various chronic categories unless there are adequate
chronic toxicity data available for all three trophic levels above the water solubility or above 1 mg/l.
("Adequate" means that the data sufficiently cover the endpoint of concern. Generally this would
mean measured test data, but in order to avoid unnecessary testing it can on a case by case basis also
be estimated data, e.g. (Q)SAR, or for obvious cases expert judgment).
NOTE 3: Chronic toxicity band based on NOEC or equivalent ECx values in mg/l for fish or
crustacea or other recognized measures for chronic toxicity.


Mixtures classification categories and criteria

The classification system for mixtures covers the classification categories which are used for
substances, meaning categories Acute 1 and Chronic 1 and 2. In order to make use of all available
data for purposes of classifying the aquatic environmental hazards of the mixture, the following
assumption is made and is applied where appropriate:
The "relevant ingredients" of a mixture are those which are present in a concentration equal to or
greater than 0.1% (by mass) for ingredients classified as Acute and/or Chronic 1 and equal to or
greater than 1% for other ingredients, unless there is a presumption (e.g. in the case of highly toxic
ingredients) that an ingredient present at less than 0.1% can still be relevant for classifying the mixture
for aquatic environmental hazards.

The approach for classification of aquatic environmental hazards is tiered, and is dependent upon the
type of information available for the mixture itself and for its ingredients. Elements of the tiered
approach include:
(a) Classification based on tested mixtures;
(b) Classification based on bridging principles;
(c) The use of "summation of classified ingredients" and/or an "additivity formula".
Figure below outlines the process to be followed.
13 Special guidance is provided in Chapter 4.1, paragraph and Annex 9, Section A9.6 of the GHS.
Figure Tiered approach to classification of mixtures

Classification of mixtures when toxicity data are available for the complete mixture

When the mixture as a whole has been tested to determine its aquatic toxicity, this information
shall be used for classifying the mixture according to the criteria that have been agreed for
substances. The classification is normally based on the data for fish, crustacea and algae/plants
(see and When adequate acute or chronic data for the mixture as a
whole are lacking, "bridging principles" or "summation method" shall be applied (see to

The long-term hazard classification of mixtures requires additional information on degradability
and in certain cases bioaccumulation. There are no degradability and bioaccumulation data for
mixtures as a whole. Degradability and bioaccumulation tests for mixtures are not used as they are
usually difficult to interpret, and such tests may be meaningful only for single substances.

Classification for category Acute 1

(a) When there are adequate acute toxicity test data (LC50 or EC50) available for the mixture as
a whole showing L(E)C50 ≤ 1 mg/l:
Classify the mixture as Acute 1 in accordance with Table (a);
(b) When there are acute toxicity test data (LC50(s) or EC50(s) available for the mixture as a
whole showing L(E)C50(s) > 1 mg/l, or above the water solubility:
No need to classify for acute hazard under ADR.

Classification for categories Chronic 1 and 2

(a) When there are adequate chronic toxicity data (ECx or NOEC) available for the mixture as a
whole showing ECx or NOEC of the tested mixture ≤ 1mg/l:
(i) classify the mixture as Chronic 1 or 2 in accordance with Table (b) (ii)
(rapidly degradable) if the available information allows the conclusion that all
relevant ingredients of the mixture are rapidly degradable;
(ii) classify the mixture as Chronic 1 or 2 in all other cases in accordance with Table (b) (i) (non-rapidly degradable);
(b) When there are adequate chronic toxicity data (ECx or NOEC) available for the mixture as a
whole showing ECx(s) or NOEC(s) of the tested mixture > 1mg/l or above the water
No need to classify for long-term hazard under ADR.

Classification of mixtures when toxicity data are not available for the complete mixture: bridging

Where the mixture itself has not been tested to determine its aquatic environmental hazard, but
there are sufficient data on the individual ingredients and similar tested mixtures to adequately
characterise the hazards of the mixture, these data shall be used in accordance with the following
agreed bridging rules. This ensures that the classification process uses the available data to the
greatest extent possible in characterising the hazards of the mixture without the necessity for
additional testing in animals.


Where a new mixture is formed by diluting a tested mixture or a substance with a diluent which
has an equivalent or lower aquatic hazard classification than the least toxic original ingredient and
which is not expected to affect the aquatic hazards of other ingredients, then the resulting mixture
shall be classified as equivalent to the original tested mixture or substance. Alternatively, the
method explained in may be applied.


The aquatic hazard classification of a tested production batch of a mixture shall be assumed to be
substantially equivalent to that of another untested production batch of the same commercial
product when produced by or under the control of the same manufacturer, unless there is reason to
believe there is significant variation such that the aquatic hazard classification of the untested
batch has changed. If the latter occurs, new classification is necessary.
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