Mixture classification under CLP: summation method and concentration limits

Legal basis: CLP Annex I and the SEA Regulation

The rules for classifying mixtures are in Annex I of the CLP Regulation (EC) No 1272/2008 in the EU, and in its Turkish counterpart, the SEA Regulation (11/12/2013, Official Gazette No. 28848), in Türkiye. The thresholds below are the generic concentration limits of these annexes; table numbers follow CLP Annex I.

The order is as follows: if test data on the mixture itself exist, they are used; if not, the bridging principles based on similar mixtures are tried; if that is not possible either, the calculation methods in this article are used. In SMEs the third route is most often applied.

Step 1: which components count?

Not every component counts. Components below the cut-off values in CLP Annex I Table 1.1 are not included in the summation and ATE calculations:

Step 2: the summation method (skin, eye, aquatic)

Skin corrosion / irritation (Table 3.2.3)

• Σ(Skin Corr. 1) ≥ 5% → mixture is Skin Corr. 1 (H314). The sub-category is determined by the 1A/1B/1C distribution of the components.
• 1% ≤ Σ(Skin Corr. 1) < 5% → Skin Irrit. 2 (H315).
• 10 × Σ(Skin Corr. 1) + Σ(Skin Irrit. 2) ≥ 10% → Skin Irrit. 2 (H315).

Serious eye damage / eye irritation (Table 3.3.3)

• Σ(Skin Corr. 1 + Eye Dam. 1) ≥ 3% → Eye Dam. 1 (H318).
• 1% ≤ Σ(Skin Corr. 1 + Eye Dam. 1) < 3% → Eye Irrit. 2 (H319).
• 10 × Σ(Skin Corr. 1 + Eye Dam. 1) + Σ(Eye Irrit. 2) ≥ 10% → Eye Irrit. 2 (H319).

A component that is both skin corrosive and causes eye damage is counted once in the sum.

Long-term aquatic hazard (Table 4.1.2)

• Σ(Chronic 1 × M) ≥ 25% → Aquatic Chronic 1 (H410).
• 10 × Σ(Chronic 1 × M) + Σ(Chronic 2) ≥ 25% → Aquatic Chronic 2 (H411).
• 100 × Σ(Chronic 1 × M) + 10 × Σ(Chronic 2) + Σ(Chronic 3) ≥ 25% → Aquatic Chronic 3 (H412).

The M-factor is a multiplier (1, 10, 100…) that increases the weight of very toxic (acute or chronic category 1) components. If it is given in the harmonised classification, that value is used; otherwise the supplier determines it from toxicity data.

Step 3: the threshold method (sensitisers, CMR, STOT)

For these hazards there is no summation; it is enough for a single component to exceed its limit. For example, skin sensitisers (Table 3.4.5):

• Skin Sens. 1 or 1B component ≥ 1% → mixture is Skin Sens. 1 (H317).
• Skin Sens. 1A component ≥ 0.1% → mixture is Skin Sens. 1 (H317).
• Even if the mixture is not classified, EUH208 ("Contains …. May produce an allergic reaction.") is added to the label if the component is present at one tenth of these limits.

Acute toxicity: the ATE formula

For acute toxicity, the acute toxicity estimate of the mixture (ATE_mix) is calculated from the components (CLP Annex I 3.1.3.6):

100 / ATEmix = Σ ( Ci / ATEi )

If only the category of a component is known, the converted ATE value is used; for the oral route, 0.5 · 5 · 100 · 500 mg/kg for Categories 1–4 respectively (Table 3.1.2). The resulting ATE_mix falls into Category 1–4 according to the oral limits of ≤ 5 / 50 / 300 / 2000 mg/kg.

A specific concentration limit (SCL) overrides the generic limit

Some substances have their own limits in their harmonised classification (CLP Annex VI). If an SCL is defined for a component, that component is assessed with its own SCL, not with the generic limits in this article. An SCL can be lower or higher than the generic limit. A common mistake is to calculate a corrosive with an SCL using the generic 5% limit and so classify the mixture more leniently than it should be.

Worked example

A hypothetical cleaning product (no component has an SCL):

• Skin: Σ(Corr. 1) = 3% < 5%, not corrosive. 10 × 3 + 4 = 34% ≥ 10% → Skin Irrit. 2 (H315).
• Eye: Σ(Corr. 1 + Eye Dam. 1) = 3% ≥ 3% → Eye Dam. 1 (H318). Eye Irrit. 2 is not given in addition.
• Aquatic: C is above the cut-off of 0.1% / 10 = 0.01%, so it counts. Chronic 1: 0.5 × 10 = 5% < 25%. Chronic 2: 10 × 5 = 50% ≥ 25% → Aquatic Chronic 2 (H411).

Result: H315, H318, H411. Note: although the corrosive component is only at 3%, the mixture is classified for eye damage. This shows why saying "not corrosive, no problem" just by looking at component percentages is misleading.

Sources

• CLP Regulation (EC) No 1272/2008, Annex I: Tables 1.1, 3.1.2, 3.2.3, 3.3.3, 3.4.5, 4.1.2 (EUR-Lex, consolidated text).
• SEA Regulation (11/12/2013, Official Gazette No. 28848).
• ECHA, Guidance on the Application of the CLP Criteria.