Classification of Hazardous Substances
Hazards posed by hazardous substances may either be safety related or health related. The properties that make substances hazardous are related to these hazards.
The Occupational Safety and Health Administration (OSHA) defined hazardous substances in terms of health hazards and physical hazards. Health hazard is assessed as either chronic or acute.
A chronic health hazard occurs as a result of long-term exposure. On the other hand, an acute health hazard occurs rapidly as a result of short-term exposure. Similarly, a substance poses a physical hazard if there is a scientific evidence that it is a combustible liquid, flammable, explosive or reactive (i.e. unstable).
The definition of properties that renders a substance hazardous is given in Annex III of the EU Hazardous Waste Directive. This contains Fourteen (14) hazard categories (H1 – H14), and they include explosive, oxidizing, flammable, irritant, toxic, corrosive, infectious, teratogenic and mutagenic properties, among others.
A centralized system of classification of hazardous substances based on the Basel Convention (1989) identified forty–five (45) categories of hazardous substances (Y1 – Y45) including clinical, pharmaceutical, used lubrication oils, wood preservatives, wastes from petroleum refining, drilling waste, wastes containing lead, asbestos etc.
Appendix IV of this convention provides for two categories of substances requiring special consideration and they are Y46 (wastes collected from households) and Y47 (residues arising from the incineration of household wastes). These two categories are not specifically labelled “hazardous wastes‟, but their hazardous nature is implied.
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A comprehensive definition of hazardous substances will, therefore, include the following properties:
Corrosivity i.e. ability to destroy something progressively by chemical action.
Explosivity i.e. ability to explode.
Flammability i.e ability to catch fire.
Ignitability i.e. tendency to burn.
Reactivity i.e. tendency to take part in spontaneous chemical reactions.
Carcinogenicity i.e. capability to induce cancer or increase the incidence of cancer.
Infectivity i.e. ability to infect or cause infection.
Irritant properties (allergic response) i.e. causing irritation, especially physical irritation.
Mutagenicity i.e. ability to induce genetic mutation.
Toxicity (acute or chronic) i.e. capability to poison a living organism.
Radioactivity i.e. ability to emit radiation.
Teratogenicity i.e. ability to induce non-hereditary congenital malformations or increase their incidence in a developing system e.g. foetus.
Sensitization i.e. to induce undue sensitivity in somebody to a particular substance.
Hazardous substances include gents that can damage body organs and tissues such as the blood, lungs, eyes or skin etc.
Therefore, all hazardous substances are classified based on their properties. There are nine different classes which every hazardous substance must belong. The nine classes are:
Class 1: Explosives
Class 2: Gases
Class 3: Flammable and Combustible Liquids
Class 4: Flammable Solids
Class 5: Oxidizing Substances, Organic Peroxides
Class 6: Toxic Substances and Infectious Substances
Class 7: Radioactive Materials
Class 8: Corrosives
Class 9: Miscellaneous Hazardous Materials
Some of the nine hazard classes are further separated into divisions based on their physical or chemical properties.
For instance, explosive substances are further divided into mass explosive hazard, projection hazard, fire and/or minor blast /minor projection hazard, minor explosive hazard and very insensitive; no mass explosion hazard.
The same goes for the rest of the hazardous substances. Having the right information about the various hazardous materials would help in their management.
In conclusion, this article has shown how the understanding of hazardous substances, their sources, identification and classification can help in handling them. The understanding of the various categories of hazardous substances will enable people to know the appropriate precautionary measures to adopt in managing them.
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Hazardous substances take various forms–ranging from the form of gases, explosives, flammable, combustible solids to liquids. They can be found in the home or workplace, roadways, industrial or commercial areas.
They can be identified by a careful observation of their containers and/or buildings where they are kept. Hazardous substances are divided into nine major groups which also have subgroups.
