The classification of a mixture shall be based on summation of the concentrations of its classified ingredients. The percentage of ingredients classified as "Acute" or "Chronic" will feed straight into the summation method. Details of the summation method are described in2.2.9.1.10.4.6.1 to 2.2.9.1.10.4.6.4.

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

(a)Based on acute aquatic toxicity:

where:

Ci=concentration of ingredient i(mass percentage);

L(E)C50i=LC50or EC50for ingredient i (mg/l);

n=number of ingredients, and i is running from 1ton;

L(E)C50m=L(E)C50of the part of the mixture with test data;

The calculated toxicity shall be used to assign that portionof the mixture an acute hazard category which is then subsequently used in applying the summation method;

(b)Based on chronic aquatic toxicity:

where:

Ci=concentration of ingredient i (mass percentage) covering the rapidly degradable ingredients;

Cj=concentration of ingredient j (mass percentage) covering the non rapidly degradable ingredients;

NOECi=NOEC (or other recognized measures for chronic toxicity) for ingredient i covering the rapidly degradable ingredients, in mg/l;

NOECj=NOEC (or other recognized measures for chronic toxicity) for ingredient j covering the non-rapidly degradable ingredients, in mg/l;

n=number of ingredients, 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 degradingsubstances are classified one hazard category level more "severe" than rapidly degrading substances.

The calculated equivalent toxicity shall be used to assign that portion of the mixture a long-term hazard category, in accordance with the criteria for rapidly degradable substances (Table 2.2.9.1.10.3.1 (b) (ii)), which is then subsequently used in applying the summation method.

 

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 ingredienttoxicity values that relate to the same taxonomic group(i.e. fish, crustaceaor algae) and then to use the highest toxicity (lowest value) obtained (i.e. use the most sensitive of the three groups). However, when toxicity data for each ingredient are not available in the same taxonomic group, the toxicity value of each ingredient shall be selected inthe 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 acuteand chronictoxicity shall then be used to classify this part of the mixture as Acute 1and/or Chronic 1 or 2using the same criteria described for substances.

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

Summation method

Classification procedure

In general a more severe classification for mixtures overrides a less severe classification, e.g. a classification with Chronic 1overrides a classification with Chronic 2. As a consequence the classification procedure is already completed if the results of the classification is Chronic1. A more severe classification than Chronic 1is not possible; therefore, it is not necessary to pursue the classification procedure further.

Classification for category Acute 1

First, allingredients classified as Acute 1areconsidered. If the sum of the concentrations (in %) ofthese ingredients is greater than or equal to 25% the whole mixture shall be classified as Acute 1. If the result of the calculation is a classification of the mixture as Acute1, the classification process is completed.

The classification of mixtures for acute hazards based on this summation of the concentrations of classified ingredients is summarized in Table 2.2.9.1.10.4.6.2.2 below.

Table 2.2.9.1.10.4.6.2.2: Classification of a mixture for acute hazards based on summation of the concentrations of classified ingredients

Sum of the concentrations (in %) of ingredients classified as:

Mixture classified as:

 
 

Acute 1 x M a ≥ %25

Acute 1

 

a                      For explanation of the M factor, see 2.2.9.1.10.4.6.4.

Classification for categories Chronic 1 and 2

First, all ingredients classified as Chronic 1are considered. If the sum of the concentrations (in %) ofthese ingredients is greater than or equal to 25% the mixture shall be classified as Chronic 1. If the result of the calculation is a classification of the mixture as Chronic 1the classification procedure is completed.

In cases where the mixture is not classified as Chronic 1, classification of the mixture as Chronic 2is considered. A mixture shall be classified as Chronic 2if 10 times the sum of the concentrations (in %) ofall ingredients classified as Chronic 1plus the sum of the concentrations (in %) ofallingredients classified as Chronic 2is greater than or equal to 25%. If the result of the calculation is classification of the mixture as Chronic 2, the classification process is completed.

The classification of mixtures for long-term hazards based on this summation of the concentrations of classified ingredients is summarized in Table 2.2.9.1.10.4.6.3.3 below.

Table 2.2.9.1.10.4.6.3.3: Classification of a mixture for long-term hazards based on summation of the concentrations of classified ingredients

Sum of the concentrations (in %) of ingredients classified as:

Mixture classified as:

Chronic 1 x M a

≥ %25

Chronic 1

(M x 10 x Chronic 1) + Chronic 2

≥ %25

Chronic 2

a For explanation of the M factor, see 2.2.9.1.10.4.6.4.

Mixtures with highly toxic ingredients

Acute 1 or Chronic 1 ingredients with acute toxicities well below 1 mg/l and/or chronic toxicities well below 0.1 mg/l (if non-rapidly degradable) and 0.01 mg/l (if rapidly degradable) may influencethe toxicity of the mixture and are given increased weight in applying the summationmethod. When a mixture contains ingredients classified as acute or Chronic 1, the tiered approach described in 2.2.9.1.10.4.6.2 and 2.2.9.1.10.4.6.3 shall be applied using a weighted sum by multiplying the concentrations of Acute 1and Chronic 1 ingredients by a factor, instead of merely adding up the percentages. This means that the concentration of "Acute 1" in the left column of Table 2.2.9.1.10.4.6.2.2 and the concentration of "Chronic1" in the left column of Table 2.2.9.1.10.4.6.3.3 are multiplied by the appropriate multiplying factor. The multiplying factors to be applied tothese ingredients are defined using the toxicity value, as summarised in Table2.2.9.1.10.4.6.4 below. Therefore, in order to classify a mixture containing Acute 1and/or Chronic 1ingredients, the classifier needs to be informed of the value of the M factor in order to apply the summation method. Alternatively, the additivity formula (see2.2.9.1.10.4.5.2) may be used when toxicity data are available for all highly toxic ingredients in the mixture and there is convincing evidence that all other ingredients, including those for which specific acuteand/or chronictoxicity data are not available, are of low or no toxicity and do not significantly contribute to the environmental hazard of the mixture.

Table 2.2.9.1.10.4.6.4: Multiplying factors for highly toxic ingredients of mixtures

Acute toxicity

M factor

 Chronic toxicity

M factor

L(E)C50 value

 

NOEC value

NRD a ingredients

RD b ingredients

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)

a Non-rapidly degradable.

b Rapidly degradable.

 

Classification of mixtures with ingredients without any useable information

In the event that no useable information on acute and/or chronic aquatic toxicityis available for one or more relevant ingredients, it is concluded that the mixture cannot be attributed (a) definitive hazard category(ies). In this situation the mixture shall be classified based on the known ingredients only.

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