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4.1.3.: Classification criteria for mixtures

4.1.3.1.

The classification system for mixtures covers all classification categories which are used for substances, i.e. categories Acute 1 and Chronic 1 to 4. In order to make use of all available data for purposes of classifying the aquatic environmental hazards of the mixture, the following is applied where appropriate:

The ‘relevant components’ of a mixture are those which are classified ‘Acute 1’or ‘Chronic 1’ and present in a concentration of 0,1 % (w/w) or greater, and those which are classified ‘Chronic 2’, ‘Chronic 3’ or ‘Chronic 4’ and present in a concentration of 1 % (w/w) or greater, unless there is a presumption (such as in the case of highly toxic components (see section 4.1.3.5.5.5)) that a component present in a lower concentration can still be relevant for classifying the mixture for aquatic environmental hazards. Generally, for substances classified as ‘Acute 1’ or ‘Chronic 1’ the concentration to be taken into account is (0,1/M) %. (For explanation M-factor see section 4.1.3.5.5.5.)

4.1.3.2.

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 components. Figure 4.1.2 outlines the process to be followed.

Elements of the tiered approach include:

 classification based on tested mixtures,

 classification based on bridging principles,

 the use of ‘summation of classified components’ and/or an ‘additivity formula’.

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Figure 4.1.2

Tiered approach to classification of mixtures for short-term (acute) and long-term (chronic) aquatic environmental hazards

image

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

4.1.3.3.1.

When the mixture as a whole has been tested to determine its aquatic toxicity, this information can 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 sections 4.1.2.7.1 and 4.1.2.7.2). When adequate acute or chronic toxicity data for the mixture as a whole are lacking, ‘bridging principles’ or ‘summation method’ should be applied (see sections 4.1.3.4 and 4.1.3.5).

4.1.3.3.2.

►M12  The long-term (chronic) hazard classification of mixtures requires additional information on degradability and in certain cases bioaccumulation. ◄ 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.

4.1.3.3.3.

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 mixture as Acute 1 in accordance with point (a) of Table 4.1.0.

(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 for normally all trophic levels:

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No need to classify for short-term (acute) hazard.

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4.1.3.3.4.

Classification for categories Chronic 1, 2 and 3

(a) When there are adequate chronic toxicity data (ECxx 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, 2 or 3 in accordance with point (b)(ii) of Table 4.1.0 as rapidly degradable if the available information allows the conclusion that all relevant components of the mixture are rapidly degradable;

(ii) Classify the mixture as Chronic 1 or 2 in all other cases in accordance with point (b)(i) of Table 4.1.0 as 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 > 1 mg/l for normally all trophic levels:

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No need to classify for long-term (chronic) hazard in categories Chronic 1, 2 or 3.

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4.1.3.3.5.

Classification for category Chronic 4

If there are nevertheless reasons for concern:

Classify the mixture as Chronic 4 (safety net classification) in accordance with Table 4.1.0.

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

4.1.3.4.1.

Where the mixture itself has not been tested to determine its aquatic environmental hazard, but there are sufficient data on the individual components and similar tested mixtures to adequately characterise the hazards of the mixture, this data shall be used in accordance with the bridging rules set out in section 1.1.3. However, in relation to application of the bridging rule for dilution, sections 4.1.3.4.2 and 4.1.3.4.3 shall be used.

4.1.3.4.2.

Dilution: if a mixture is formed by diluting another tested mixture or a substance classified for its aquatic environmental hazard with a diluent which has an equivalent or lower aquatic hazard classification than the least toxic original component and which is not expected to affect the aquatic hazards of other components, then the resulting mixture may be classified as equivalent to the original tested mixture or substance. Alternatively, the method explained in section 4.1.3.5 may be applied.

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4.1.3.4.3.

If a mixture is formed by diluting another tested mixture or substance with water or other totally non-toxic material, the toxicity of the mixture can be calculated from the original mixture or substance.

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4.1.3.5. Classification of mixtures when toxicity data are available for some or all components of the mixture

4.1.3.5.1.

The classification of a mixture is based on summation of the concentration of its classified components. The percentage of components classified as ‘Acute’ or ‘Chronic’ is fed straight in to the summation method. Details of the summation method are described in section 4.1.3.5.5.

4.1.3.5.2.

Mixtures can be made of a combination of both components that are classified (as Acute 1 and/or Chronic 1, 2, 3, 4) and others for which adequate toxicity test data is available. When adequate toxicity data are available for more than one component in the mixture, the combined toxicity of those components is calculated using the following additivity formulas (a) or (b), depending on the nature of the toxicity data:

(a) Based on acute aquatic toxicity:

image

where:

Ci

=

concentration of component i (weight percentage);

L(E)C50i

=

(mg/l) LC50 or EC50 for component i;

η

=

number of components, and i is running from 1 to n;

L(E)C50m

=

L(E) C50 of the part of the mixture with test data.

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The calculated toxicity may be used to assign that portion of the mixture a short-term (acute) hazard category which is then subsequently used in applying the summation method;

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(b) Based on chronic aquatic toxicity:

image

where:

Ci

=

concentration of component i (weight percentage) covering the rapidly degradable components;

Cj

=

concentration of component j (weight percentage) covering the non- rapidly degradable components;

NOECi

=

NOEC (or other recognised measures for chronic toxicity) for component i covering the rapidly degradable components, in mg/l;

NOECj

=

NOEC (or other recognised measures for chronic toxicity) for component j covering the non-rapidly degradable components, in mg/l;

n

=

number of components, and i and j are running from 1 to n;

EqNOECm

=

Equivalent NOEC of the part of the mixture with test data.

The equivalent toxicity thus reflects the fact that non-rapidly degrading substances are classified one hazard category level more ‘severe’ than rapidly degrading substances.

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The calculated equivalent toxicity may be used to assign that portion of the mixture a long-term (chronic) hazard category, in accordance with the criteria for rapidly degradable substances (point (b)(ii) of Table 4.1.0), which is then subsequently used in applying the summation method.

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4.1.3.5.3.

When applying the additivity formula for part of the mixture, it is preferable to calculate the toxicity of this part of the mixture using for each substance toxicity values that relate to the same taxonomic group (i.e. fish, crustacean, algae or equivalent) and then to use the highest toxicity (lowest value) obtained (i.e. use the most sensitive of the three taxonomic groups). However, when toxicity data for each component are not available in the same taxonomic group, the toxicity value of each component is selected in the same manner that toxicity values are selected for the classification of substances, i.e. the higher toxicity (from the most sensitive test organism) is used. The calculated acute and chronic toxicity is then used to assess whether this part of the mixture shall be classified as Acute 1 and/or Chronic 1, 2 or 3 using the same criteria described for substances.

4.1.3.5.4.

If a mixture is classified in more than one way, the method yielding the more conservative result shall be used.

4.1.3.5.5.

Summation method

4.1.3.5.5.1.   Rationale

4.1.3.5.5.1.1.

In case of the substance classification categories Chronic 1 to Chronic 3, the underlying toxicity criteria differ by a factor of 10 in moving from one category to another. Substances with a classification in a high toxicity band therefore contribute to the classification of a mixture in a lower band. The calculation of these classification categories therefore needs to consider the contribution of any substance classified as Chronic 1, 2 or 3.

4.1.3.5.5.1.2.

When a mixture contains components classified as Acute 1 or Chronic 1, attention must be paid to the fact that such components, when their acute toxicity is below 1 mg/l and/or chronic toxicity is below 0,1 mg/l (if non rapidly degradable) and 0,01 mg/l (if rapidly degradable) contribute to the toxicity of the mixture even at a low concentration. Active ingredients in pesticides often possess such high aquatic toxicity but also some other substances like organometallic compounds. Under these circumstances the application of the normal generic concentration limits leads to an ‘under-classification’ of the mixture. Therefore, multiplying factors shall be applied to account for highly toxic components, as described in section 4.1.3.5.5.5.

4.1.3.5.5.2.   Classification procedure

4.1.3.5.5.2.1.

In general a more severe classification for mixtures overrides a less severe classification, e.g. a classification with Chronic 1 overrides a classification with Chronic 2. As a consequence, in this example, the classification procedure is already completed if the result of the classification is Chronic 1. A more severe classification than Chronic 1 is not possible. Therefore it is not necessary to undergo the further classification procedure.

4.1.3.5.5.3.   Classification for category Acute 1

4.1.3.5.5.3.1.

First all components classified as Acute 1 are considered. If the sum of the concentrations (in %) of these components multiplied by their corresponding M-factors is greater than 25 % the whole mixture is classified as Acute 1.

4.1.3.5.5.3.2.

►M12  The classification of mixtures for short-term (acute) hazards based on this summation of classified components is summarised in Table 4.1.1. ◄



Table 4.1.1

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Classification of a mixture for short-term (acute) hazards based on summation of classified components

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Sum of components classified as:

Mixture is classified as:

Acute 1 × M () ≥ 25 %

Acute 1

(1)   For explanation of the M-factor, see 4.1.3.5.5.5.

4.1.3.5.5.4.   Classification for the categories Chronic 1, 2, 3 and 4

4.1.3.5.5.4.1.

First all components classified as Chronic 1 are considered. If the sum of the concentrations (in %) of these components multiplied by their corresponding M-factors is equal to or greater than 25 %, the mixture is classified as Chronic 1. If the result of the calculation is a classification of the mixture as Chronic 1, the classification procedure is completed.

4.1.3.5.5.4.2.

In cases where the mixture is not classified as Chronic 1, classification of the mixture as Chronic 2 is considered. A mixture is classified as Chronic 2 if 10 times the sum of the concentrations (in %) of all components classified as Chronic 1 multiplied by their corresponding M-factors plus the sum of the concentrations (in %) of all components classified as Chronic 2 is equal to or greater than 25 %. If the result of the calculation is classification of the mixture as Chronic 2, the classification process is completed.

4.1.3.5.5.4.3.

In cases where the mixture is not classified either as Chronic 1 or Chronic 2, classification of the mixture as Chronic 3 is considered. A mixture is classified as Chronic 3 if 100 times the sum of the concentrations (in %) of all components classified as Chronic 1 multiplied by their corresponding M-factors plus 10 times the sum of the concentrations (in %) of all components classified with Chronic 2 plus the sum of the concentrations (in %) of all components classified as Chronic 3 is ≥ 25 %.

4.1.3.5.5.4.4.

If the mixture is still not classified in Chronic 1, 2 or 3, classification of the mixture as Chronic 4 shall be considered. A mixture is classified as Chronic 4 if the sum of the concentrations (in %) of components classified as Chronic 1, 2, 3 and 4 is equal to or greater than 25 %.

4.1.3.5.5.4.5.

►M12  The classification of mixtures for long-term (chronic) hazards, based on this summation of the concentrations of classified components, is summarised in Table 4.1.2. ◄



Table 4.1.2

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Classification of a mixture for long-term (chronic) hazards, based on summation of the concentration of classified components

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Sum of components classified as:

Mixture is classified as:

Chronic 1 × M () ≥ 25 %

Chronic 1

(M × 10 × Chronic 1) + Chronic 2 ≥ 25 %

Chronic 2

(M × 100 × Chronic 1) + (10 × Chronic 2) + Chronic 3 ≥ 25 %

Chronic 3

Chronic 1 + Chronic 2 + Chronic 3 + Chronic 4 ≥ 25 %

Chronic 4

(1)   For explanation of the M-factor, see 4.1.3.5.5.5.

4.1.3.5.5.5.   Mixtures with highly toxic components

4.1.3.5.5.5.1.

Acute 1 and Chronic 1 components with toxicities below 1 mg/l and/or chronic toxicities below 0,1 mg/l (if non-rapidly degradable) and 0,01 mg/l (if rapidly degradable) contribute to the toxicity of the mixture even at a low concentration and shall normally be given increased weight in applying the summation of classification approach. When a mixture contains components classified as Acute or Chronic 1, one of the following shall be applied:

 the tiered approach described in sections 4.1.3.5.5.3 and 4.1.3.5.5.4 using a weighted sum by multiplying the concentrations of Acute 1 and Chronic 1 components by a factor, instead of merely adding up the percentages. This means that the concentration of ‘Acute 1’ in the left column of Table 4.1.1 and the concentration of ‘Chronic 1’ in the left column of Table 4.1.2 are multiplied by the appropriate multiplying factor. The multiplying factors to be applied to these components are defined using the toxicity value, as summarised in Table 4.1.3. Therefore, in order to classify a mixture containing Acute/Chronic 1 components, the classifier needs to be informed of the value of the M-factor in order to apply the summation method,

 the additivity formula (see section 4.1.3.5.2) provided that toxicity data are available for all highly toxic components in the mixture and there is convincing evidence that all other components, including those for which specific acute and/or chronic toxicity data are not available, are of low or no toxicity and do not significantly contribute to the environmental hazard of the mixture.

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Table 4.1.3

Multiplying factors for highly toxic components of mixtures

Acute toxicity

M factor

Chronic toxicity

M factor

L(E)C50 value (mg/l)

 

NOEC value (mg/l)

NRD () components

RD () components

0,1 < L(E)C50 ≤ 1

1

0,01 < NOEC ≤ 0,1

1

0,01 < L(E)C50 ≤ 0,1

10

0,001 < NOEC ≤ 0,01

10

1

0,001 < L(E)C50 ≤ 0,01

100

0,0001 < NOEC ≤ 0,001

100

10

0,0001 < L(E)C50 ≤ 0,001

1 000

0,00001 < NOEC ≤ 0,0001

1 000

100

0,00001 < L(E)C50 ≤ 0,0001

10 000

0,000001 < NOEC ≤ 0,00001

10 000

1 000

(continue in factor 10 intervals)

(continue in factor 10 intervals)

(1)   Non-rapidly degradable.

(2)   Rapidly degradable.

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4.1.3.6. Classification of mixtures with components without any useable information

4.1.3.6.1.

►M12  In the event that no useable information on short-term (acute) and/or long-term (chronic) aquatic hazard is available for one or more relevant components, it is concluded that the mixture cannot be attributed to one or more definitive hazard category(ies). ◄ In this situation the mixture shall be classified based on the known components only, with the additional statement on the label and in the SDS that: ‘Contains x % of components with unknown hazards to the aquatic environment’.