Substantially similar mixtures

Given the following:

(a)Two mixtures:

(i)A + B;

(ii)C + B;

(b)The concentration of ingredient B is essentially the same in both mixtures;

(c)The concentration of ingredient A in mixture (i) equals that of ingredient C in mixture(ii);

(d)Data on aquatic hazardsfor A and C are available and are substantially equivalent, i.e. theyare in the same hazard category and are not expected to affect the aquatic toxicity of B.

If mixture (i) or (ii) is already classified based on test data, then the other mixture can be assigned the same hazard category.

Classification of mixtures when toxicitydata are available for all ingredients or only for some ingredients of the mixture

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.

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

^a                      For explanation of the M factor, see 2.2.9.1.10.4.6.4.

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

^a For explanation of the M factor, see 2.2.9.1.10.4.6.4.