The GHS classification system defines and classifies the physical, health, and/or environmental hazards of a substance. Each category within the classifications has associated
pictograms to be used when applied to a material or mixture.
Physical hazards As of the 10th revision of the GHS, substances or articles are assigned to 17 different
hazard classes largely based on the
United Nations Dangerous Goods System. •
Explosives are assigned to one of four subcategories depending on the type of hazard they present, similar to the categories used in the UN Dangerous Goods System. Category 1 includes explosives not covered by the 6 Dangerous Goods categories. •
Flammable gases are assigned to one of 3 categories based on reactivity: • Category 1A includes extremely flammable gases ignitable at 20 °C and
standard pressure of 101.3 kPa,
pyrophoric gases, and chemically unstable gases that may react in the absence of oxygen. • Category 1B gases meet the flammability criteria of 1A, but are not pyrophoric or chemically unstable and have a lower flammability limit in air. • Category 2 includes gases which do not meet the above criteria but otherwise are flammable at 20 °C and standard pressure. •
Aerosols and
chemicals under pressure are categorized into one of 3 categories, but may be additionally classified as explosives or flammable gases if material properties match the previous classifications. From category 1 to 3, aerosols are classified as most to least flammable. All aerosols under these categories carry a bursting hazard. •
Oxidizing gases are any gaseous substance which contribute to combustion of other materials more than air would. There is only one category of oxidizing gases. •
Gases under pressure are categorized as compressed, liquefied, refrigerated, or dissolved gases, all of which may
explode when heated or (in the case of refrigerated gases) cause cryogenic injury, such as frostbite. •
Flammable liquids are categorized by
flammability, from Category 1 with flash point 60 °C and 2), and all other self-heating substances that only heat in large quantities are listed under Category 2. •
Substances and mixtures which, in contact with water, emit flammable gases are categorized from 1 to 3 based on the
ignitability of the gas emitted. •
Oxidizing liquids contribute to the combustion of other materials and are categorized from 1 to 3 in decreasing oxidizing potential. •
Oxidizing solids follow the same criteria as oxidizing liquids. •
Organic peroxides are unstable substances or mixtures and may be derivatives of hydrogen peroxide. They are categorized from A to G based on inherent ability to
explode or otherwise combust. •
Corrosive to metals materials may damage or destroy metals, based on tests done on aluminum and steel. The corrosion rate must be greater than 6.25 mm/year on either material to qualify under this classification. •
Desensitized explosives are materials that would otherwise be classified as explosive, but have been stabilized, or phlegmatized, to be exempted from said class.
Health hazards •
Acute toxicity includes five GHS categories from which the appropriate elements relevant to transport, consumer, worker and environment protection can be selected. Substances are assigned to one of the five
toxicity categories on the basis of LD50 (oral, dermal) or LC50 (inhalation). •
Skin corrosion means the production of irreversible damage to the skin following the application of a test substance for up to 4 hours. Substances and mixtures in this hazard class are assigned to a single harmonized corrosion category.
Skin irritation means the production of reversible damage to the skin following the application of a test substance for up to 4 hours. Substances and mixtures in this hazard class are assigned to a single
irritant category. For those authorities, such as
pesticide regulators, wanting more than one designation for skin irritation, an additional mild irritant category is provided. •
Serious eye damage means the production of tissue damage in the eye, or serious physical decay of vision, following application of a test substance to the front surface of the eye, which is not fully reversible within 21 days of application. Substances and mixtures in this hazard class are assigned to a single harmonized category.
Eye irritation means changes in the eye following the application of a test substance to the front surface of the eye, which are fully reversible within 21 days of application. Substances and mixtures in this hazard class are assigned to a single harmonized hazard category. For authorities, such as pesticide regulators, wanting more than one designation for eye irritation, one of two subcategories can be selected, depending on whether the effects are reversible in 21 or 7 days. •
Respiratory sensitizer means a substance that induces
hypersensitivity of the airways following inhalation of the substance. Substances and mixtures in this hazard class are assigned to one hazard category.
Skin sensitizer means a substance that will induce an allergic response following skin contact. The definition for "skin
sensitizer" is equivalent to "contact sensitizer". Substances and mixtures in this hazard class are assigned to one hazard category. •
Germ cell mutagenicity means an agent giving rise to an increased occurrence of
mutations in populations of cells and/or organisms. Substances and mixtures in this hazard class are assigned to one of two hazard categories. Category 1 has two subcategories. •
Carcinogenicity means a chemical substance or a mixture of chemical substances that induce
cancer or increase its incidence. Substances and mixtures in this hazard class are assigned to one of two hazard categories. Category 1 has two subcategories. •
Reproductive toxicity includes adverse effects on sexual function and
fertility in adult males and females, as well as
developmental toxicity in offspring. Substances and mixtures with reproductive and/or developmental effects are assigned to one of two hazard categories, 'known or presumed' and 'suspected'. Category 1 has two subcategories for reproductive and developmental effects. Materials which cause concern for the health of breastfed children have a separate category: effects on or via
Lactation. •
Specific target organ toxicity (STOT) category distinguishes between single and repeated exposure for
Target Organ Effects. All significant health effects, not otherwise specifically included in the GHS, that can impair function, both reversible and irreversible, immediate and/or delayed are included in the non-lethal target organ/systemic toxicity class (TOST). Narcotic effects and respiratory tract irritation are considered to be target organ systemic effects following a single exposure. Substances and mixtures of the single exposure target organ toxicity hazard class are assigned to one of three hazard categories. Substances and mixtures of the repeated exposure target organ toxicity hazard class are assigned to one of two hazard categories. •
Aspiration hazard includes severe acute effects such as
chemical pneumonia, varying degrees of
pulmonary injury or death following
aspiration. Aspiration is the entry of a liquid or solid directly through the oral or nasal cavity, or indirectly from vomiting, into the
trachea and
lower respiratory system. Substances and mixtures of this hazard class are assigned to one of two hazard categories this hazard class on the basis of
viscosity.
Environmental hazards •
Acute aquatic toxicity indicates the intrinsic property of a material of causing injury to an
aquatic organism in a short-term exposure. Substances and mixtures of this hazard class are assigned to one of three toxicity categories on the basis of acute toxicity data: LC50 (
fish) or EC50 (
crustacean) or ErC50 (for
algae or other
aquatic plants). These acute toxicity categories may be subdivided or extended for certain sectors. •
Chronic aquatic toxicity indicates the potential or actual properties of a material to cause adverse effects to aquatic organisms during exposures that are determined in relation to the lifecycle of the organism. Substances and mixtures in this hazard class are assigned to one of four toxicity categories on the basis of acute data and environmental fate data: LC50 (fish), EC50 (crustacea) ErC50 (for algae or other aquatic plants), and
degradation or
bioaccumulation. •
Ozone Depleting Potential indicates the ability of the materials to damage the Ozone Layer, determined by the
Montreal Protocol. Substances and mixtures bearing this quality have the Hazard Statement H420.
Classification of mixtures The GHS approach to the classification of mixtures for health and environmental hazards uses a tiered approach and is dependent upon the amount of information available for the mixture itself and for its components. Principles that have been developed for the classification of mixtures, drawing on existing systems such as the
European Union (EU) system for classification of preparations laid down in
Directive 1999/45/EC. The process for the classification of mixtures is based on the following steps: • Where
toxicological or
ecotoxicological test data are available for the mixture itself, the classification of the mixture will be based on that data; • Where test data are not available for the mixture itself, then the appropriate bridging principles should be applied, which uses test data for components and/or similar mixtures; • If (1) test data are not available for the mixture itself, and (2) the bridging principles cannot be applied, then use the calculation or cutoff values described in the specific endpoint to classify the mixture.
Substitute substances Companies are encouraged to replace hazardous substances with substances featuring a reduced health risk. As an assistance to assess possible substitute substances, the
Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) has developed the Column Model. On the basis of just a small amount of information on a product, substitute substances can be evaluated with the support of this table. The current version from 2020 already includes the amendments of the 12th CLP Adaptation Regulation 2019/521. ==Testing requirements==