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Hazard, Hazardous

Hazard is the potential for harmful effects. Hazardous means potentially harmful. The hazards of a material are evaluated by examining the properties of the material, such as toxicity, flammability and chemical reactivity, as well as how the material is used. How a material is used can vary greatly from workplace to workplace and, therefore, so can the hazard.

In Canada and the U.S., the term hazardous is used by many different regulatory agencies. Definitions may vary. For example, OSHA defines a "hazardous chemical" as any chemical which is a physical hazard or a health hazard according to the OSHA Hazard Communication (Hazcom) criteria.


Hazardous Combustion Products

Hazardous combustion products are chemicals which may be formed when a material burns. These chemicals may be toxic, flammable or have other hazards. The chemicals released and their amounts vary, depending upon conditions such as the temperature and the amount of air (or more specifically, oxygen) available. The combustion chemicals may be quite different from those formed by heating the same material during processing (thermal decomposition products). It is important to know which chemicals are formed by hazardous combustion in order to plan the response to a fire involving the material.


Hazard Communication Standard

The U.S. OSHA regulation that details requirements for MSDSs and labeling (29 CRF Part 1910.1200).


Hazardous Decomposition Products

Hazardous decomposition products are formed when a material decomposes (breaks down) because it is unstable, or reacts with common materials such as water or oxygen (in air). This information should be considered when planning storage and handling procedures.


Hazardous Ingredient

Under the Canadian Hazardous Products Act, a chemical must be listed in the Hazardous Ingredients Section of a Material Safety Data Sheet (MSDS) if:

  • it meets the criteria for a controlled product;
  • it is on the Ingredient Disclosure List;
  • there is no toxicological information available; or
  • the supplier has reason to believe it might be hazardous.

Certain chemicals may be exempt from disclosure on an MSDS if they meet specific criteria set out in the Hazardous Materials Information Review Act. These Acts are part of the Workplace Hazardous Materials Information System (WHMIS).


Hazardous Polymerization

See Polymerize, Polymerization.


HAZCOM

HAZCOM stands for the Hazard Communication Standard (U.S.).


Henry's Law Constant

Henry's Law Constant is a measure of the tendency of a chemical to evaporate from a solution in water. It indicates whether a chemical accumulates in water or in air at equilibrium.


Hepatotoxin

Hepatotoxins are agents that can cause toxic effects on the liver.


Highly Toxic

Under the U.S. OSHA HAZCOM Standard, there are specific criteria for materials which must be identified as toxic. The corresponding term under Canadian WHMIS is "Very Toxic" (criteria are not the same).


Hr

Hr stands for hour.


IARC

IARC stands for the International Agency for Research on Cancer. IARC evaluates information on the carcinogenicity of chemicals, groups of chemicals and chemicals associated with certain industrial processes. IARC has published lists of chemicals which are generally recognized as human carcinogens, probable human carcinogens or carcinogens in animal tests.


IATA

IATA stands for International Air Transport Association.


IDLH

IDLH stands for Immediately Dangerous to Life or Health. For the purposes of respirator selection, the National Institute for Occupational Safety and Health (NIOSH) defines the IDLH concentration as the airborne concentration that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment. The purpose of establishing an IDLH exposure concentration is to ensure that the worker can escape from a given contaminated environment in the event of failure of the respiratory protection equipment. In the event of failure of respiratory protective equipment, every effort should be made to exit immediately.


ILO

ILO stands for the International Labour Office.


Impervious

Impervious is a term used to describe protective gloves and other protective clothing. If a material is impervious to a chemical, then that chemical cannot readily penetrate through the material or damage the material. Different materials are impervious (resistant) to different chemicals. No single material is impervious to all chemicals. If an Material Safety Data Sheet recommends wearing impervious gloves, you need to know the type of material from which the gloves should be made.


Incompatible Materials

Incompatible materials can react with the product or with components of the product and may:

  • destroy the structure or function of a product;
  • cause a fire, explosion or violent reaction; or
  • cause the release of hazardous chemicals.

Inert Ingredient

An inert ingredient is anything other than the active ingredient of a product. It may be a solvent, colorant, filler or dispersing agent. In some cases, inert ingredients may be hazardous.


Ingestion

Ingestion means taking a material into the body by mouth (swallowing).


Inhalation

Inhalation means taking a material into the body by breathing it in.


Irritancy, Irritation

Irritancy is the ability of a material to irritate the skin, eyes, nose, throat or any other part of the body that it contacts. Signs and symptoms of irritation include tearing in the eyes and reddening, swelling, itching and pain of the affected part of the body.

Irritancy is often described as mild, moderate or severe, depending on the degree of irritation caused by a specific amount of the material. Irritancy may also be described by a number on a scale of 0 to 4, where 0 indicates no irritation and 4 means severe irritation. Irritancy is usually determined in animal experiments.

The Canadian Controlled Products Regulations [part of the Workplace Hazardous Materials Information System (WHMIS)] and the U.S. OSHA Hazcom Standard describe technical criteria for identifying materials which are skin or eye irritants for the purposes of each regulation.


ISO

ISO stands for the International Organization for Standardization.


Kg

Kg stands for kilogram


Kow

Kow stands for octanol/water partition coefficient.


LC50

LC stands for lethal concentration. LC50 is the concentration of a material in air which causes the death of 50% (one half) of a group of test animals. The material is inhaled over a set period of time, usually 1 or 4 hours. The LC50 helps determine the short-term poisoning potential of a material.


LD50

LD stands for lethal dose. LD50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals. The LD50 can be determined for any route of entry, but dermal (applied to skin) and oral (given by mouth) LD50's are most common. The LD50 is one measure of the short-term poisoning potential of a material. (See also LC50.)


LCLO

LCLO stands for lowest lethal airborne concentration tested. (See also LC50 and LD50.)


LDLO

LDLO stands for lowest lethal dose tested. (See also LC50 and LD50.)


LEL

See Explosive Limits.


LFL

See Explosive Limits.


Local Exhaust Ventilation

Local exhaust ventilation is the removal of contaminated air directly at its source. This type of ventilation can help reduce worker exposure to airborne materials more effectively than general ventilation. This is because it does not allow the material to enter the work environment. It is usually recommended for hazardous airborne materials. (See also Mechanical Ventilation and Ventilation.)


Lower Explosion Limit

See Explosive Limits.


Lower Explosive Limit

See Explosive Limits.


Lower Flammable Limit

See Explosive Limits.


Material Causing Immediate And Serious Toxic Effects

The Canadian Controlled Products Regulations describe technical criteria for identifying materials which cause immediate and serious toxic effects. These criteria use information such as the LD50 or LC50 for a material. Based on the specific information, a material may be identified as toxic or very toxic in the class D - Poisonous and Infectious Material.

The Canadian Controlled Products Regulations are part of the Workplace Hazardous Materials Information System (WHMIS).


Material Causing Other Toxic Effects

The Canadian Controlled Products Regulations describe technical criteria for identifying materials which cause toxic effects such as skin or respiratory sensitization, mutagenicity and carcinogenicity. Based on the specific information, a material may be identified as toxic or very toxic in the class D - Poisonous and Infectious Material.

The Canadian Controlled Products Regulations are part of the Workplace Hazardous Materials Information System (WHMIS).


Means Of Extinction

See Extinguishing Media.


Mechanical Ventilation

Mechanical ventilation is the movement of air by mechanical means (for example, a wall fan). There are two kinds of mechanical ventilation: general ventilation and local exhaust ventilation. (See also Ventilation.)


Melting Point

The melting point is the temperature at which a solid material becomes a liquid. The freezing point is the temperature at which a liquid material becomes a solid. Usually one value or the other is given on the Material Safety Data Sheet.

It is important to know the freezing or melting point for storage and handling purposes. For example, a frozen or melted material may burst a container. As well, a change of physical state could alter the hazards of the material.


MESA

MESA stands for Mining Enforcement and Safety Administration. MESA was the U.S. government agency responsible for enforcing the health and safety regulations and standards for American miners. It was replaced by MSHA in 1978.


mg/m3

The abbreviation mg/m3 stands for milligrams (mg) of a material per cubic metre (m3) of air. It is a unit of metric measurement for concentration (weight/volume). The concentrations of any airborne chemical can be measured in mg/m3, whether it is a solid, liquid, gas or vapour.


MIN

MIN can stand for minute or minimum.


Miscible

Miscible means able to be mixed. Two liquids are said to be miscible if they are partially or completely soluble in each other. Commonly, the term miscible is understood to mean that the two liquids are completely soluble in each other. (See also Solubility.)


Mist

A mist is a collection of liquid droplets suspended in air. A mist can be formed when spraying or splashing a liquid. It can also be formed when a vapour condenses into liquid droplets in the air. (See also Aerosol.)


mL

mL stands for millilitres (mL).


mm Hg

The abbreviation mm Hg stands for millimeters (mm) of mercury (Hg). It is a common unit of measurement for the pressure exerted by gases such as air. Normal atmospheric pressure is 760 mm Hg.


Molecular Formula

See Chemical Formula.


Molecular Weight

The molecular weight of a chemical is a number showing how heavy one molecule (or unit) of the chemical is compared to the lightest element, hydrogen, which has a weight of 1. The molecular weight has various technical uses, such as calculating conversions from parts per million (ppm) to milligrams per cubic metre (mg/m3) in air.


MSDS

MSDS stands for Material Safety Data Sheet. The MSDS is a document that contains information on the potential health effects of exposure and how to work safely with the material it is written about. It is an essential starting point to a health and safety program. It contains hazard evaluations on the use, storage, handling, and emergency procedures all related to the material.

In Canada, all products or material covered by the Controlled Products Regulations require an MSDS before the product or material can be used in the workplace. The Controlled Products Regulations are part of the Workplace Hazardous Materials Information System (WHMIS).


MSHA

MSHA stands for Mine Safety and Health Administration. MSHA is the U.S. government agency responsible for enforcing the health and safety regulations and standards for American miners. It replaced MESA in 1978.


Mutagen, Mutagenic, Mutagenicity

A mutagen is a substance which can cause changes in the DNA of cells (mutations). Mutagenic means able to cause mutations. Mutagenicity is the ability of a substance to cause mutations.

DNA determines the characteristics that children inherit from their parents. DNA also determines how cells in the body divide or reproduce.

A number of mutagenicity tests are used to screen chemicals for possible carcinogenicity or reproductive effects. This is because there is some evidence that mutations may increase the risk of cancer and reproductive problems such as infertility or birth defects. However, mutagenicity test results are not very reliable predictors of these effects. One reason for this is that the human body can repair mutations while most mutagenicity tests cannot.

Mutagenicity is included on Material Safety Data Sheets because it is an early indicator of potential hazard, and often there is very little other evidence available on possible carcinogenic or reproductive effects. The Canadian Controlled Products Regulations describes technical criteria for identifying materials which are mutagenic. The Canadian Controlled Products Regulations are part of the Workplace Hazardous Materials Information System (WHMIS). The U.S. OSHA HAZCOM Standard includes mutagenic effects as reproductive target organ effects.

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Document last updated on June 6, 2006

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