CLP acute toxicity classification explained

Many factors play an important role in the CLP classification “acute toxicity”. Acute toxicity is predominantly based on LD50 values from animal experiments and the route of exposure. LD50 is the lethal dose for 50% of laboratory animals under specified experimental conditions. In contrast to specific target organ toxicity where the routes of exposure are specified in H statements, acute target organ toxicity has its own H statements for the oral, dermal and inhalative routes of exposure.

Hazard categories and statements/warnings

In Regulation (EC) No. 1272/2008 (CLP), acute toxicity has 4 categories of which category 1 is the most severe and category 4 the mildest. In this way, CLP classification differs from GHS classification which has an additional category 5.

Categories 1 and 2 each have the same safety statement that varies depending on the route of exposure (H300 – oral, H310 – dermal, H330 – inhalative). Category 3 und 4 both have different hazard warnings for each route of exposure.

CLP acute toxicity classification for mixtures

An additivity formula is used for mixture classifications on the basis of components. In the additivity formula, ATE values are used for each component. ATE stands for acute toxicity estimate

An ATE value either directly corresponds to the LD50 value of a component or is derived from the hazard category of the CLP classification for acute toxicity. The additivity formula includes the concentration and thereby the weighting of individual components. There is also a variation of the formula for mixtures with components of unknown toxicity.

The calculation result can be used to determine an ATE_mix value that corresponds to the ATE value of the mixture. This value can subsequently be used to determine the mixture classification “acute toxicity”.

Consequences of the calculated mixture classification

By using all toxicity data – depending on the route of exposure – a mixture can be classified as having acute toxicity on the basis of a mathematical calculation. This classification can differ from that of all involved components – especially when the more unfavourable additivity formula is used – because components of unknown toxicity are present.

Sources: Regulation (EC) No. 1272/2008 (CLP), consolidated version, as of 01/04/2016

Globally Harmonized System of Classification and Labelling of Chemicals (GHS), sixth revised edition, 2015 version