(Updated: November 2025)

An Introduction to Chemical Hazards 

Chemicals play a significant role in our daily lives and are present in commercial products* such as soap, medicines, clothing, and food. They are also essential in various industrial processes that create the products we rely on for convenience, safety, and comfort. These chemicals are sourced

and shipped from all over the world, and differences in language and

labeling can pose serious risks. Throughout their lifecycle—from production to handling, transportation, and use—chemicals can pose dangers to human health and the environment. People of

all ages,

including children

and the elderly,

as well as those who speak different languages

To face this danger, and given the reality of the extensive global trade in chemicals and the need to develop national programs to ensure their safe use, transport and disposal, it was recognized that an internationally-harmonized approach to classification and labelling would provide the foundation for such programs. Once countries have consistent and appropriate information on or who are illiterate, are frequently exposed to hazardous substances like chemicals and pesticides. To address these risks and acknowledge the reality of global chemical trade, it’s essential to develop national programs that ensure the safe use, transport, and disposal of chemicals. An internationally harmonized approach to classification and labeling can provide the foundation for these initiatives. Once countries have access to consistent and relevant information about the chemicals they import or produce in their own countries, the infrastructure , they can establish comprehensive infrastructures to control chemical exposures exposure and protect both people and the environment can be established in a comprehensive manner.Worldwide regulations are applicable . Global regulations apply to all industrial sectors . They require and mandate that manufacturers, importers or downstream , and users of hazardous substances or mixtures to properly classify, label, and package their hazardous these chemicals appropriately before placing them on the market.before they are sold. One of the main aims primary goals of these regulations (example: Globally Harmonised System of Classification and Labelling of Chemicals (GHS) - provides an internationally recognised standard for hazard classification and communication) is to determine identify whether a substance or mixture displays has properties that lead to warrant a hazardous classification. In this contextregard, classification is serves as the starting point for effective hazard communication.

When relevant information (e.g. toxicological data) on a substance or mixture meets the classification criteria, the hazards of a substance or mixture are identified by assigning a certain hazard class and category. The hazard classes cover physical, health, environmental and additional hazards.

Once a substance or mixture is classified, the identified hazards must be communicated to other actors in the supply chain, including consumers. Hazard labelling allows the hazard classification, with labels and safety data sheets, to be communicated to the user of a substance or mixture, to alert them about the presence of a hazard and the need to manage the associated risks.

The economic impact for manufacturers is huge since they do not have to conform to different classification and labelling criteria. But most importantly, workers in all 68 countries enjoy the same level of protection thanks to universally agreed classification criteria and hazardous communication element, which includes instantly recognizable pictograms, signal words and hazard statements. These identify the degree and level of the chemical’s hazard, from that of a skin irritant to possible organ damage. So anyone who manufactures, stores, transports, handles or uses these chemicals can identify the hazards posed and apply the appropriate protection measures.

Hazard Assessment

Hazard assessment is an essential part of the risk assessment process. Hazard assessment is also referred to as characterization of effects or hazard characterization. It is the identification of adverse effects that a stressor has an inherent capacity to cause to human individuals or populations, or environmental populations or ecosystems, or natural resources.

Hazard Assessment

Hazard assessment is an essential part of the risk assessment process. Hazard assessment is also referred to as characterization of effects or hazard characterization. It is the identification of adverse effects that a stressor has an inherent capacity to cause to human individuals or populations, or environmental populations or ecosystems, or natural resources.

1/ Hazard Groups

The GHS (Globally Harmonized System) separates hazards into three groups: physical, health, and environmental.

• Physical hazards are determined by the physical and chemical properties of a substance and/or mixture and include flammability, metal corrosivity, and pyrophoricity. 
• Health hazards are determined by their potential to cause an adverse health effect to humans, such as skin irritation, respiratory sensitisation, and carcinogenicity.
• Environmental hazards are determined by their potential to cause an adverse effect on biomes or ecosystems. Environmental hazards are distinguished as acute or chronic, acute being for a short period of time and chronic being for a longer period of 20 days or greater.

2/ Hazard Classification

Classification is the starting point for hazard communication. There are pre-set criteria based on relevant information (toxicological data, ecotoxicological data, component data, etc.) for substances or mixtures to be classified within a hazard class. Further to the hazard classes, there are hazard categories that reflect the severity of the hazard; a lower category indicates a more severe hazard and vice versa.

3/ Hazard Communication

The GHS hazard communication system includes labelling, safety data sheets (SDS), and easily recognisable symbols.

The SDS and labels assure that manufacturers and importers communicate the necessary information along the entire supply chain, which in turn, ensures that substances and mixtures are used safely.

3.1. Labelling

The compulsory label elements are as follows:

• Signal words: indicate the relative level of severity of a hazard. In the GHS, the signal words ‘Warning’ and ‘Danger’ are adopted. ‘Danger’ is mostly used for the more severe hazard categories, while ‘Warning’ is used for the less severe ones.
• Pictogram: graphical representations that convey hazard information, as shown in the image below. The pictograms required depend on the hazard classification and precedence rules that dictate if certain pictograms are present, then others should not appear.

Image Added

• Hazard statements (H phrases): phrases assigned to hazard classes and categories that describe the nature and degree of severity of a hazard.
• Precautionary statements (P phrases): phrases that describe the recommended measures that should be taken to minimise or prevent adverse effects resulting from exposure to, improper storage, or handling of a hazardous product.

Each hazard and precautionary statement has an accompanying code, which is a unique identifier. The code is composed of the letter ‘H’ or ‘P’ (for ‘hazard statement’ or ‘precautionary statement’), a number indicating the hazard group (2 for physical, 3 for health, and 4 for environmental), and two numbers corresponding to the sequential numbering of hazards.

• Product identifiers: for substances, the chemical identity must be disclosed on the label. For mixtures, the chemical identities of the components that contribute to the hazard of the mixture must be disclosed on the label. In certain cases, chemical identities may be classed as confidential business information and, therefore, certain identifiers may be concealed. 
• Supplier identification: must include the name, address, and telephone number of the manufacturer or supplier of the substance or mixture.

3.2. Safety Data Sheets (SDS)

The SDS should provide comprehensive information about a substance or mixture so that those responsible for handling and storage are able to take the necessary safety precautions to prevent adverse effects to humans and the environment. 

The SDS is divided into 16 sections, of which Section 2 is dedicated to hazard(s) identification. This section must include the following information:

• Hazard classification of the substance or mixture.
• The label elements.
• Any other hazards which do not result in classification (e.g., ‘dust explosion hazard’).

The SDS format follows the Annex II of REACH and its content should be clear, understandable, be accessible to the user, be accurate,  be updated and in the official language of the country where the product is placed on the market.

• According to the REACHlegislation an SDS is mandatory (Article 31(1)) at least when:

• A substance or mixture fulfils the classification criteria as a dangerous product according to theCLP Regulation, or;
• A substance is persistent, bio-accumulative and toxic, or very persistent and very bio-accumulative, according to the criteria in Annex XIII REACH, or;
• A substance is included in the list of substances that are candidates for Authorisation (SVHC) which could possibly be subjected to Authorisation in the future according to Article 59(1) REACH.

For more information see the SDS Section by Section