The GHS describes in detail how hazard categories should be assigned for each health hazard class. A summary of these methods can be found by clicking on the entries below. More detail is provided in the GHS document.

• Acute toxicity
• Skin corrosion/irritation
• Serious eye damage/eye irritation
• Respiratory or skin sensitization
• Germ cell mutagenicity
• Carcinogenicity
• Reproductive toxicity
• STOT – single exposure
• STOT – repeated exposure
• Aspiration toxicity

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Acute toxicity refers to serious adverse health effects (i.e., lethality) occurring after a single or short-term oral, dermal or inhalation exposure to a substance or mixture. This is expressed as an Acute Toxicity Estimate (ATE) referring either to an LD50-value (oral, dermal) or an LC50-value (inhalation) or expressed as a Converted value (point estimate) for Acute Toxicity.

Chapter 3.1 in the GHS describes how the classification for acute toxicity is conducted. The same classification criteria apply to both substances and for mixtures (= the pesticide formulation). Criteria are listed for the oral and dermal exposure routes, and for the inhalation route which is divided into dust, mist, and vapour, depending on the physical state of the substance.

Substances can be allocated to one of the following acute toxicity categories:

A tiered approach is used for the classification of a mixture based on the availability of data for the mixture. If a test is available for the mixture, it is possible to classify based on these test data according to the criteria used for the substance. If data are not available for the complete mixture, the mixture will have to be classified based on the ingredients of the mixture itself and by using a specific calculation formula.

Depending on the acute toxicity estimate substances can be allocated to one of five hazard categories based on the acute toxicity by the oral, dermal or inhalation route.

The labelling elements for acute toxicity are displayed in the table below including some examples of hazard statements to illustrate how they are linked to the exposure route and the severity of the effect.

For the exact classification procedure and criteria for acute toxicity, refer to Chapter 3.1 in the GHS

Skin corrosion refers to the production of irreversible damage to the skin; namely, visible necrosis through the epidermis and into the dermis occurring after exposure to a substance or mixture.

Skin irritation refers to the production of reversible damage to the skin occurring after exposure to a substance or mixture.

Chapter 3.2 in the GHS describes how classification for skin corrosion/irritation is conducted. To classify a substance or a mixture, all relevant information should be collected and assessed. Classification can be based both on standard animal test data and on human data. Classification can also be based on the chemical properties in cases where the substance has an extremely low or high pH. There is also a possibility to use non-test methods such as computer models.

Substances can be allocated to one of the following categories:

In the same way as for acute toxicity, classification of mixtures (= pesticide formulations) can either be based on data on the mixture itself if that´s available. If that´s not the case, the so-called additivity approach can be applied. That means that each skin corrosive or irritant ingredient contributes to the overall corrosive or irritant properties of the mixture in proportion to its potency and concentration.

The labelling elements for mixtures classified for skin corrosion are displayed in the table below.

For the exact classification procedure and criteria for skin corrosion/irritation, refer to Chapter 3.2 in the GHS

Serious eye damage refers to the production of tissue damage in the eye, or serious physical decay of vision, which is not fully reversible, occurring after exposure of the eye to a substance or mixture.

Eye irritation refers to the production of changes in the eye, which are fully reversible, occurring after the exposure of the eye to a substance or mixture.

Chapter 3.3 in the GHS describes how classification for serious eye damage/eye irritation is conducted. Substances are allocated to one of the categories within this hazard class, either Category 1 (serious eye damage) or Category 2 (eye irritation) which can be divided into two sub-categories, 2A and 2B.

In a tiered approach, empasis should be placed upon existing human data, followed by existing animal data, followed by in vitro data and then other sources of information. Classification is done directly when the data satisfies the criteria. In other cases, classifcation is done on the basis of the weight of evidence within the tier. In a total weight of evidence approach, all available information should be considered together, including information on skin corrosion and possible pH extreme.

Mixtures are classified using the criteria for substances when data are available for the complete mixture. When data are available for all or only for some ingredients, the additivity approach can be used, which means that each corrosive or eye damaging/eye irritant ingredient contributes to the overall serious eye damaging/eye irritation properties of the mixture in proportion to its potency and concentration.

The labelling elements for mixtures classified for serious eye damage/eye irritation are displayed below.

For the exact classification procedure and criteria for serious eye damage/eye irritation, refer to Chapter 3.3 in the GHS

Respiratory sensitization refers to hypersensitivity of the airways occurring after inhalation of a substance or a mixture.

Skin sensitization refers to an allergic response occurring after skin contact with a substance or a mixture.

Chapter 3.4 in the GHS describes how classification for respiratory or skin sensitization is conducted. Sensitization includes two phases, the first phase is the so-called induction of the specialized immunological memory in an individual by exposure to an allergen. The second phase is called elicitation, which means production of a cell-mediated or antibody-mediated allergic response by exposure of a sensitized individual to an allergen. Respiratory and skin sensitizers shall be classified in Category 1 but when so required, in one of the two sub-categories 1A (strong sensitizers) or 1B (other sensistizers), using a weight of evidence approach. The basis for the classification is reliable and good quality evidence from human cases, epidemiological studies and/or from experimental animal studies.

If good and realiable data are available for the complete mixture, the classification can be made based on the same weight of evidence approach as for substances. If data are available for all or only for some ingredients of the mixture, the mixture should be classified as a respiratory or skin sensitizer when at least one ingredient has been classified and is present at or above the cut-off value/concentration limit for the specific endpoint.

The labelling elements for mixtures classified for respiratory and skin sensitization are displayed below.

For the exact classification procedure and criteria for respiratory or skin sensitization, refer to Chapter 3.4 in the GHS

Germ cell mutagenicity refers to heritable gene mutations, including heritable structural and numerical chromosome aberrations in germ cells occurring after exposure to a substance or mixture.

Chapter 3.5 in the GHS describes how classification for germ cell mutagenicity is conducted. This hazard class is primarily concerned with chemicals that may cause mutations in the germ cells of humans that can be transmitted to the progeny. However, mutagenicity/genotoxicity tests in vitro and in mammalian somatic cells are also considered in classifying substances and mixtures within this hazard class. Two different categories of germ cell mutagens are included to accommodate for the weight of evidence approach.

Category 1 is allocated for substances which are known to induce heritable mutations or should be regarded as if they induce heritable mutations in the germ cells of humans. Depending on the weight of evidence, Category 1 can be divided into two sub-categories, 1A and 1B. Category 2 is allocated for substances which cause concern for humans owing to the possibility that they may induce heritable mutations in the germ cells of humans.

Classification of mixtures will be based on available test data for the individual ingredients using cut-off values/concentration limits for the ingredients classified as germ cell mutagens. The classification may be modified on a case-by-case basis based on the available test data for the mixture as a whole. When data are available for all or only for some ingredients, the mixture will be classified as a mutagen when at least one ingredient has been classified as a Category 1 or 2 and is present at or above the appropriate cut-off value/concentration limit.

The labelling elements for mixtures classified for germ cell mutagenicity are displayed below.

For the exact classification procedure and criteria for germ cell mutagenicity, refer to Chapter 3.5 in the GHS

Carcinogenicity refers to the induction of cancer or an increase in the incidence of cancer occurring after exposure to a substance or mixture. Substances and mixtures which have induced benign and malignant tumours in well performed experimental studies on animals are considered also to be presumed or suspected human carcinogens unless there is strong evidence that the mechanism of tumour formation is not relevant for humans.

Chapter 3.6 in the GHS describes how classification for carcinogenicity is conducted. Classification of a substance or mixture for carcinogenicity is based on its inherent properties and does not provide information on the level of the human cancer risk which the use of the substance or mixture may pose. Substances and mixtures classified as carcinogenic are allocated to one of two categories based on the strength of evidence and possible other considerations.

Category 1 is divided into two sub-categories where 1A is allocated for substances which are known to have a carcinogenic potential for humans or 1B for substances which are presumed to have a carcinogenic potential for humans. Category 2 is allocated for substances which are suspected human carcinogens. Category 1A is largely based on evidence in humans while 1B is primarily based on evidence in animals. The placing of a substance in Category 2 is done on the basis of evidence from human and/or animal studies.

Classification of mixtures will be based on available test data of the individual ingredients using cut-off values/concentration limits for those ingredients. Where the mixture itself has not been tested but where there is data available for all ingredients or only for some ingredients, the mixture will be classified as a carcinogen when at least one ingredient has been classified and is present at or above the appropriate cut-off value/concentration limit.

The labelling elements for mixtures classified as carcinogenic are displayed below.

For the exact classification procedure and criteria for carcinogenicity, refer to Chapter 3.6 in the GHS

Reproductive toxicity refers to adverse effects on sexual function and fertility in adult males and females, as well as developmental toxicity in the offspring, occurring after exposure to a substance or mixture.

Effects on or via lactation are allocated to a separate single category. Substances which are absorbed by women and have been shown to interfere with lactation, or which may be present (including metabolites) in breast milk in amounts sufficient to cause concern for the health of a breastfed child, should be classified to indicate this property hazardous to breastfed babies.

Chapter 3.7 in the GHS describes how classification for reproductive toxicity is conducted. Classification is based on the appropriate criteria and an assessment of the total weight of evidence. The classification is intended to be used for chemicals which have an intrinsic property to produce an adverse effect on reproduction. If such effects are produced as a non-specific secondary consequence to other toxic effects, the chemical should not be classified as a reproductive toxicant.

Category 1 is divided into two sub-categories where 1A is allocated for substances which are known to have produced an adverse effect on sexual funcion and fertility or on development in humans and 1B to substances which are presumed to be a human reproductive toxicant. Category 2 is allocated for substances which are suspected human reproductive toxicants. Category 1A is largely based on evidence from humans while 1B is largely based on evidence from experimental animals. The placing of a substance in Category 2 is done on the basis of evidence from humans or experimental animals. Effects on or via lacatation are allocated to a single separate category. Substances that are absorbed and interfere with lactation or may be present in breast milk in amounts sufficient to cause concern for the health of the breastfed child should be classified to indicate this property.

Classification of mixtures should be based on the available test data for the individual ingredients, using cut-off values/concentration limits for those ingredients. Where the mixture itself has not been tested but where data is available for all or only for some ingredients, the mixture will be classified as a reproductive toxicant when at least one ingredient has been classified and is present at or above the appropriate cut-off value/concentration limit. The same applies for effects on or via lactation.

The labelling elements for mixtures classified as a reproductive toxicant are displayed below.

For the exact classification procedure and criteria for reproductive toxicity, refer to Chapter 3.7 in the GHS

Specific target organ toxicity – single exposure refers to specific, non-lethal toxic effects on target organs occurring after a single exposure to a substance or mixture. All significant health effects that can impair function, both reversible and irreversible, immediate and/or delayed and not specifically addressed in GHS chapters 3.1 to 3.7 and 3.10 are included.

Chapter 3.8 in the GHS describes how classification for specific target organ toxicity after a single exposure is conducted. Classification identifies substances or mixtures as being a specific target organ toxicant and, as such, it may present a potential for adverse health effects in people who are exposed.

Classification in Category 1 is allocated to substances that have produced significant toxicity in humans, or that, on the basis of evidence from studies in experimental animals can be presumed to have the potential to produce significant toxicity in humans following single exposure. Classification in Category 2 is allocated to substances that, on the basis of evidence from studies in experimental animals can be presumed to have the potential to be harmful to human health following single exposure.

Category 3 is applied for so-called transient organ effects which are effects which adversely alter human function for a short duration after exposure but from which recovery is observed. This category only includes narcotic effects and respiratory tract irritation.

When reliable data are available from human experience or appropriate animal studies, for the complete mixture, then the mixture can be classified by a weight of evidence evaluation of these data. Where there is no reliable evidence or test data for the mixture itself, the mixture will be classified when at least one ingredient is classified in Category 1 or 2 and is present at or above the cut-off value/concentration limit. The use of expert judgement should be applied when extrapolating the toxicity of a mixture that contains Category 3 ingredients.

The labelling elements for mixtures classified as a specific target organ toxicant are displayed below.

For the exact classification procedure and criteria for specific target organ toxicity – single exposure, refer to Chapter 3.8 in the GHS

Specific target organ toxicity-repeated exposure refers to specific toxic effects on target organs occurring after repeated exposure to a substance or mixture. All significant health effects that can impair function, both reversible and irreversible, immediate and/or delayed and not specifically addressed in GHS chapters 3.1 to 3.7 and 3.10 are included.

Chapter 3.9 in GHS describes how classification for specific target organ toxicity after repeated exposure is conducted. Classification identifies substances or mixtures as being a specific target organ toxicant and, as such, it may present a potential for adverse health effects in people who are exposed.

Classification in Category 1 is allocated to substances that have produced significant toxicity in humans, or that, on the basis of evidence from studies in experimental animals can be presumed to have the potential to produce significant toxicity in humans following repeated exposure. . Classification in Category 2 is allocated to substances that, on the basis of evidence from studies in experimental animals can be presumed to have the potential to be harmful to human health following repeated exposure.

When reliable data are available from human experience or appropriate animal studies, for the complete mixture, then the mixture can be classified by a weight of evidence evaluation of these data. Where there data is available for all or for some ingredients, the mixture will be classified when at least one ingredient is classified in Category 1 or 2 and is present at or above the cut-off value/concentration limit.

The labelling elements for mixtures classified as a specific target organ toxicant are displayed below.

For the exact classification procedure and criteria for specific target organ toxicity – repeated exposure, refer to Chapter 3.9 in the GHS

Aspiration hazard refers to severe acute effects such as chemical pneumonia, pulmonary injury or death occurring after aspiration of a substance or ingestion. Aspiration means the entry of a liquid or solid chemical directly through the oral or nasal cavity, or indirectly from vomiting, into the trachea and lower respiratory system.

Chapter 3.10 in GHS describes how classification for aspiration hazards is conducted. Aspiration via vomiting may have consequences for labelling, especially if there is a recommendation that vomiting should be induced. This recommendation may have to be modified if the substance or mixture present an aspiration toxicity hazard. There is currently no standardized test methodology in animals so evidence from animal studies can only serve as a guide. Some hydrocarbons and certain chlorinated hydrocarbons have shown to pose an aspiration hazard in humans. The classification criteria refer to kinematic viscosity.

Classification in Category 1 is allocated to chemicals known to cause human aspiration toxicity hazards or to be regarded as if they cause human aspiration toxicity hazard. Classification in Category 2 is allocated to chemicals which cause concern owing to the presumption that they cause human aspiration toxicity hazard.

When data is available for the complete mixture, the mixture is classified in Category 1 based on reliable and good quality human evidence. Classification of mixtures when data are available for all ingredients or only for some ingredients of the mixture is based on the sum of the concentrations of classified ingredients and the kinematic viscosity.

The labelling elements for mixtures classified for aspiration toxicity are displayed below.

For the exact classification procedure and criteria for aspiration hazard, refer to Chapter 3.10 in the GHS

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