What are toxic materials?
Toxic materials are substances that may cause harm to an individual if it enters the body. Toxic materials may enter the body in different ways. These ways are called the route of exposure. The most common route of exposure is through inhalation (breathing it into the lungs). Another common route of entry is through skin contact. Some materials can easily pass through unprotected skin and enter the body. Ingestion is another, less common, route of exposure in the workplace. Ingestion often occurs accidentally through poor hygiene practices (e.g. eating food or smoking a cigarette using contaminated hands).
Toxic materials are often used in the workplace. The table below lists some common workplace materials that meet one or more of the criteria to be considered "toxic" as well as some of potential heath effects associated with that chemical. Keep in mind that toxic materials can also be found in consumer products that come into the home - always read the warning labels and safe use instructions before using any products.
|Chemical Name||Potential Health Effects/Symptoms Associated with Toxicity |
(Note: not a complete listing of symptoms
|Methylene chloride|| |
|Isopropyl alcohol (2-propanol)|| |
|Hydrogen peroxide (>35%)|| |
To prevent health effects from exposure to toxic materials, it is important to understand the potential hazards and how to protect yourself. This document discusses the hazards of toxic materials and how they are identified. For more information about working with toxic materials, see the CCOHS document "How do I Work Safely with Toxic Materials".
For definitions of some of the terms used in this document, please see the MSDS -- Glossary document.
How are toxic materials hazardous to my health?
Toxic materials can cause serious health effects in an exposed individual. The degree of hazard associated with any toxic material is related to the exact material you are exposed to, concentration of the material, the route into the body and the amount absorbed by the body (the dose). Individual susceptibility of the user also plays a role.
The health effects may occur immediately or the effects may be delayed. Health effects that occur immediately after a single exposure are called acute effects. In other cases, health effects will not occur until some point after the exposure. This is called a chronic effect. A chronic effect may occur hours, days, months or even years after exposure. Generally, acute effects are caused by a single, relatively high exposure. Chronic effects tend to occur over a longer period of time and involve lower exposures (e.g., exposure to a smaller amount over time). Some toxic materials can have both acute and chronic health effects.
It is important to remember that toxic materials can have other hazards associated with it. For example, a toxic material may also be corrosive and flammable. Always read the Material Safety Data Sheet and labels to be sure you understand what is in the product and how to work with it safely. If you do not understand the instructions, or if you are not sure, check with your supervisor.
How are toxic materials classified under WHMIS?
Under the Workplace Hazardous Materials Information System (WHMIS), toxic materials are part of Hazard Class D -- Poisonous and Infectious Materials. Since toxic materials can cause acute (short-term) health effects as well as chronic (long-term) health effects, WHMIS has a division for each. It is possible for a toxic material to be classified in both categories.
Division 1 (D1) contains "Materials Causing Immediate and Serious Toxic Effects". It is represented by the WHMIS symbol to the right. As the title suggests, these materials can cause immediate and serious health effects. Within this division, there are two additional subdivisions that separate "Toxics" and "Very Toxics". The "Very Toxics" are D1A; the "Toxics" are D1B. The main difference between D1A and D1B is the value used to determine acute toxicity (e.g. LD50, LC50). In simplest terms, D1A substances require much less material to produce a fatal effect.
Division 2 (D2) is for "Materials Causing Other Toxic Effects". It is represented by the WHMIS symbol to the right. These materials have toxic effects but these effects may be delayed. The D2 division also has two subdivisions that separate "Toxics" and "Very Toxics". The "Very Toxics" are D2A; the "Toxics" are D2B. The "Toxic" group here also includes products that produce immediate but less serious reversible effects.
Under the D2A heading of "Materials Causing Other Toxic Effects", the health effects considered for very toxic materials (D2A) include:
- severe chronic toxic effects
- reproductive toxicity (material known or suspected to cause a negative impact on reproductive functions (male or female)
- teratogenicity and embryotoxicity (material known or suspected to cause a negative impact on a developing embryo or fetus)
- carcinogenicity (material known or suspected to cause cancer)
- respiratory sensitization
Under the D2 heading of "Materials Causing Other Toxic Effects", the health effects considered for toxic materials (D2B) include:
- chronic toxic effects
- skin or eye irritation
- skin sensitization
- mutagenicity (material known or suspected to cause changes to cells)
How are toxic materials classified under GHS?
The goal of the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is to provide a harmonized approach to classifying chemical hazards as well as communicating health and safety information (e.g. through labels and safety data sheets). The intent is to have all countries using similar chemical classification, labelling and communication guidelines in order to reduce errors and misunderstandings.
Under the GHS system, there are three major hazard groupings -- physical, health and environmental. Toxic materials are categorized under the Health Hazards. Some of the toxic and very toxic materials will have characteristics that place them in more than one class or group (e.g., the same way that a material can have multiple WHMIS symbols).
The GHS system has set up a method for classifying toxic and very toxic materials using the following health hazard classes:
- acute toxicity (e.g. LD50, LC50)
- skin irritation/corrosion
- serious eye damage/eye irritation
- respiratory or skin sensitization
- mutagens (material known or suspected to cause changes to cells)
- carcinogens (material known or suspected to cause cancer)
- reproductive toxicity (material known or suspected to cause a negative impact on reproductive functions (male or female) or on a developing fetus)
- specific target organ toxicity - single exposure (materials that produce an adverse effect on one or more organ systems in the body after a single exposure)
- specific target organ toxicity - repeated exposure (materials that produce an adverse effect on one or more organ systems in the body after repeated exposure)
- aspiration hazard (a liquid or solid material that may enter the body's respiratory system directly through the nose or mouth)
- chemical mixtures
How does the GHS system and WHMIS compare regarding classification of toxics?
The GHS classification system is somewhat more complex than WHMIS and a classification of "toxic" in one system does not necessarily translate directly into the other.
While the GHS system does goes into more detail regarding the classification of toxic materials than WHMIS does, it does not change the actual hazard associated with the material. The goal of implementing the GHS system into WHMIS is to express the hazard of a particular material in a very specific and structured way globally.
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