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Workplace Hazards: FAQs

  • Content last reviewed: October 2013

What is an occupational hazard?

An occupational hazard is a thing or situation with the potential to harm a worker. Occupational hazards can be divided into two categories: safety hazards that cause accidents that physically injure workers, and health hazards which result in the development of disease. It is important to note that a "hazard" only represents a potential to cause harm. Whether it actually does cause harm will depend on circumstances, such as the toxicity of the health hazard, exposure amount, and duration. Hazards can also be rated according to the severity of the harm they cause - a significant hazard being one with the potential to cause a critical injury or death.

The Ministry publishes a series of hazard alerts, outlining precautions against hazards known to have injured Ontario workers. Other hazard alerts are also issued by Canadian government agencies and the U.S. National Institute for Occupational Safety and Health (NIOSH).

What is a risk? How is it different from a hazard?

The hazard posed by some material or situation is its potential to cause harm. Risk is the probability, or chance, that it actually will harm someone. For example, crossing the Atlantic Ocean by plane or rowboat exposes the traveller to the same hazard of drowning, but the risk of drowning is immeasurably higher in the rowboat. It is the risk of drowning (among other things!) not the hazard that discourages people from rowing across the Atlantic.

Removing occupational hazards is only one way of improving worker protection. What is often more practical is the control or management of the risks that hazards pose. Sometimes, in addition to the probability of a hazard causing harm, risk includes a consideration of the seriousness of the hazard.

The consequences of exposure to some hazards may be so harmful that, even if there is little chance of a worker being exposed, the risk is so great that extreme precautions must be taken to prevent even that small possibility.

How should workplace health and safety hazards be dealt with?

There is a three-step process for dealing with workplace hazards. First they must be recognized; then they must be assessed; and finally, if necessary, they must be controlled. Recognition involves both identifying a hazard and determining if there is a possibility of workers being affected by it. If there is such a possibility, it must be assessed and if it is found to be significant, the hazard must be controlled.

Control can be applied at the source of the hazard, along the path between the source and the worker, or at the worker. Control at the source is preferred. Hazard recognition is an important role of the Joint Health and Safety Committee; the control of hazards is a general duty for employers under OHSA Section 25(2)(h).

Are there Ontario laws requiring the control of exposure to specific workplace hazards?

Regulations made under OHSA may be sector, work or hazard specific.

Legal requirements governing exposure to various safety hazards can be found in the sector-specific regulations under OHSA. which apply to the following sectors:

Certain types of hazardous work are covered by their own regulations:

Health hazards are either covered by the sector regulations or separate hazard-specific regulations, including:

There is also a fourth set of regulations that do not fall into these categories. Some clarify requirements in OHSA, such as defining "critical injury", or specifying that the employer must pay for JHSC member certification training. Others extend the application of OHSA; examples are the regulations for farming operations, or for teachers and for university academics and teaching assistants. The most far-reaching of these regulations is the Workplace Hazardous Materials Information System (WHMIS) regulation.

What are the legal requirements for personal protective equipment (PPE)?

PPE should be provided to workers wherever there are health (or safety) risks that cannot be adequately controlled in other ways. PPE can reduce or prevent a worker's exposure to a health hazard in the workplace and can include respirators, hearing protectors, protective clothing, footwear and face and eye shields.

PPE is also required in specific situations and dealt with in regulations made under OHSA. For example:

What is an occupational health hazard?

The term "hazard" refers to the potential to cause harm. In the case of a workplace health hazard, the harm is to a worker's health and usually takes the form of an illness. Occupational illness is defined in OHSA Section 1 as a condition that results from exposure in a workplace to a physical, chemical or biological agent to the extent that the normal physiological mechanisms are affected and the health of the worker is impaired.

Hazards also include an occupational disease for which a worker is entitled to benefits under the Workplace Safety and Insurance Act, 1997. An occupational health hazard can therefore be thought of as something in the workplace that is capable of making a worker sick. The "sickness" can vary in severity from a headache or skin rash to a fatal illness such as cancer.

What kind of health effects can exposure to workplace hazards lead to?

Most workplace health hazards target a particular part of the body such as the lungs, skin or liver. A large number of workplace diseases and disease agents are recognized. Virtually any part of the body can be affected in some way by some workplace health hazard. An important consideration is how exposure occurs.

For some hazards, there can be one type of effect from a single, high exposure (an acute effect) and a quite different result when exposure is at a low level, but repeated regularly over a prolonged time period (chronic effect). Acute effects depend on the degree of exposure.

It is therefore relatively easy to control exposure (keep it at a low enough level) to avoid acute effects. Or, to put it another way, if workers are experiencing acute effects, they know exposure to the hazard is not being properly controlled. With chronic effects there is no immediate warning. Where long-term exposure is known to cause disease without any warning of the hazard, it may be necessary to control worker exposure through regulations that prescribe occupational exposure limits (OELs).

How can the risks posed by health hazards be controlled?

The best methods of controlling exposure to a particular hazard will depend on what it is. In general, methods of control can be placed in four categories:

  • Engineering controls are methods of designing or modifying plants, processes and equipment so as to minimize workers' exposure to the hazard. They are preferred because they work independently of workers.
  • Work and hygiene practices are on-the-job activities that reduce the potential for exposure.
  • Administrative controls are things like job rotation schedules, work-rest cycles and timing of maintenance procedures, which can be used to limit the amount of time an individual is exposed to a hazard.
  • Personal protective equipment includes items like respirators, hearing protectors, safety clothing and protective clothing. It can reduce a worker's exposure but must be used properly to be effective.

What are engineering controls?

Engineering controls are the preferred method of controlling exposure to workplace hazards. They can be placed in three categories:

  • Substitution includes the use of a less hazardous material, a change in the process equipment used, or a change in the process itself. Care must be taken to ensure that the substitution actually does result in less hazardous conditions.
  • Isolation is a method of limiting exposure to those employees who are working directly with the hazard, often by enclosing them within a containment structure. While isolation will reduce the risk to those outside the isolated area, it should be accompanied by appropriate controls to ensure that those within are not faced with an increased exposure to the hazard.
  • Ventilation is most important for the control of airborne hazards. It involves the removal (from the workplace) of air that contains a hazardous contaminant and its replacement with uncontaminated outside air. There are two types: local exhaust and general dilution. A properly designed local exhaust system can capture a contaminant where it is generated and remove it before it is dispersed into the work environment.

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