Chemicals & pollution
Hazardous Substance
A substance or mixture classified as hazardous under physical, health, or environmental criteria — regulated through the UN Globally Harmonized System of classification and labelling.
Definition
A hazardous substance is a chemical substance or mixture that meets classification criteria for physical hazards (such as flammability or explosivity), health hazards (such as toxicity, carcinogenicity, or corrosivity), or environmental hazards (such as aquatic toxicity). The UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS) provides the worldwide reference rules for classifying such hazards and communicating them through labels and safety data sheets.
References
classification and communication system
Overview
What it means
Before GHS, the same chemical could be labelled carcinogenic in one country and not another; harmonised classification made hazard communication comparable across borders and supply chains. In the EU, GHS is implemented through the CLP Regulation, while REACH governs registration and risk management of substances placed on the market.
How it is used
Classification determines labelling, transport rules, workplace exposure controls, and downstream-user obligations; the term anchors chemicals management in both environmental and occupational law.
Why it matters
Common hazard language is the precondition for managing the world's chemical inventory safely.
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