Physical Hazards

After reading this chapter, you will be able to:

• ➤ Define physical hazards and explain how they operate.
• ➤ Describe root and proximate causes of physical hazards and how they affect hazard control.
• ➤ Identify techniques to control workplace noise.
• ➤ Explain why vibration is a hazard and consider control options.
• ➤ Discuss why radiation and temperature extremes are hazards and consider control options.
• ➤ Outline the longer-term health effects of work design and the principles of ergonomics.

On Christmas Eve, 2009, six employees of Metron Construction were repairing balconies at a Toronto high-rise apartment. All the men were newcomers to Canada, hailing from Latvia, Uzbekistan, and Ukraine. They were on a swing-stage scaffolding (the type of suspended scaffolding you often see on the outside of tall buildings) working on a 13th- floor balcony. Their project manager, Vadim Kazenelson, was on the balcony handing them tools. As Shohruh Tojiddinov, one of the workers on the scaffolding, later reported, Kazenelson decided to climb on to the scaffolding. “He said ‘where is the lifeline’ and [the site supervisor Fayzullo] Fazilov said ‘don’t worry’. . . .[Kazenelson] jumped onto the stage and the stage broke.” Tojiddinov was wearing a harness and when the stage broke he was left hanging in mid-air. “I looked up and I saw Vadim pulling me up. . . . I saw four deaths and one was still alive. I vomited.”1

As Kazenelson landed on the scaffolding, it split in two. Kazenelson was able to scramble back onto the balcony. The other five men fell to the ground, instantly killing four (Alesandrs Bondarevs, Aleksey Blumberg, Vladamir Korostin, and Fazilov). The fifth, Dilshod Marupov, was left permanently disabled. The scaffolding had only two lifelines available for the seven men and Tojiddinov was the only one using the fall protection. The scaffolding had been provided to Metron by Swing N Scaff Inc., a scaffolding supply company.

The investigation that followed the incident revealed that the scaffold was faulty and had not been designed or inspected properly by Swing N Scaff. It also found that the men, whose knowledge of English was limited, were not provided with any training about working at heights or using fall protection.2 There was insufficient fall protection gear available to secure all the men. Subsequently, Kazenelson attempted to cover up the incident. He told Tojiddinov to say that Kazenelson had been on the ground and he gave him a safety manual on fall protection (in English, which Tojiddinov could not read), instructing him to say he had received it before the incident.3

This incident dramatically demonstrates what can happen when an employer fails to protect their workers from physical hazards. In this case, the employer failed to provide the workers with safety training and equipment to protect them from the primary hazard (falling from a height). The danger of the hazard was compounded by the workers’ limited ability to enforce their safety rights due to their limited language skills, minimal knowledge of health and safety laws, and weak negotiating position as new Canadians.

As we saw in Chapter 3, a hazard (which is sometimes called an agent) is anything that might harm, damage, or adversely affect any person or thing under certain conditions at work. It can be an object, process, context, person, or set of circumstances that has the potential to create negative health and safety outcomes. In this chapter, we will focus our attention on physical hazards. A physical hazard typically (but not always) entails a transfer of energy that results in an injury, such as box falling off a shelf and hitting a worker or a worker falling from a scaffold and hitting the ground.

Physical hazards are the most widely recognized hazards and include contact with equipment or other objects, working at heights, and slipping. This category also includes noise, vibration, temperature, electricity, atmospheric conditions, radiation, and lasers. More recently, OHS practitioners have also included the design of work and the workplace as physical hazards, suggesting it is important to attend to the ergonomic effects of work. This chapter discusses how to identify physical hazards and to determine ways to control some of the more common physical hazards. In discussing physical hazards, it is important to keep in mind that non-traditional work relations, such as the one highlighted in the opening vignette, can compound the risk associated with a physical hazard. We discuss the health and safety implications of non-traditional work relations more fully in Chapter 7.

In 2023, over 80% of all WCB time-loss injuries in Canada were caused by physical hazards. Injuries caused by overexertion and bodily reaction, including excessive effort and repetitive movements, were the most common type of injury, followed by contact with an object/machine and falls. Injuries caused by physical hazards are both overrepresented and underestimated in mainstream OHS. As we saw in Chapter 1, physical hazards are overrepresented in media portrayals of workplace incidents because they conform to commonly held views of safety hazards.4 Hazards such as a slippery floor or an unguarded saw blade are easy to understand and their effects on workers’ health are clear and direct.

At the same time, employers often underestimate the prevalence of (and thus fail to control) physical hazards. For example, an extension cord lying across a hallway floor is often seen as no big deal because it is a readily apparent and easily understood tripping hazard that we expect workers to avoid as a matter of course (“pick up your feet!”). When such hazards result in an injury, we often blame the worker for their inattention to the hazard rather than examine why the hazard was present and not controlled. The loose extension cord, for example, could have been eliminated as a hazard by re-running the wiring through the ceiling or moving the powered device closer to the plug in.

This example is a reminder that the definition of cause affects decisions about injury control. If worker carelessness or inattention is deemed to be the cause of an incident, then the controls will focus on correcting the worker rather than removing the hazard. Indeed, often the nature of physical hazards lends itself to devising “simple” solutions designed to alter worker behaviour rather than controlling the hazard itself. For example, the contact hazard posed by a doorway with unusually low clearance may be addressed by posting a sign saying “caution: low doorway” and expecting workers to duck as they pass through it. A more effective (but costlier) solution is to increase the doorway’s height.

Physical hazards also sometimes hide in plain sight. Often a hazard is so pervasive or workers’ behaviours to avoid the hazard are so routinized that the hazard is rendered almost invisible. For example, workers in a kitchen may use a dishtowel when opening an oven door to prevent the hot handle from burning them. Habitually turning a dishtowel into PPE prevents the injury and renders the hazard invisible. The dishtowel is a poor control. If a worker forgets to use it or uses it incorrectly, then the worker will get burned. A more effective control would be insulating the handle. This engineering control prevents the worker from contacting the hot handle. When identifying physical hazards, it is important to adopt the outlook of someone new to the workplace to bring back into view any hazards that have become invisible over time.

Noise and vibration are related physical hazards that are treated very differently in OHS regulation and management. Noise has been well studied and there is a long (albeit incomplete) list of rules for controlling noise hazards. By contrast, less than half of Canadian jurisdictions have any regulations governing vibration exposure. This section examines the nature of each hazard, their health effects, and briefly considers effective control options.

Noise is simply defined as sound energy that moves through the medium of the air. More scientifically, sound consists of small air-pressure changes caused by the vibration of molecules. The energy from the molecules exerts influence on neighbouring molecules, causing the sound to disperse throughout an area. Human eardrums are designed to detect the small pressure changes and then transfer them through a network of three bones to the inner ear where tiny hair-like cells turn the vibrations into electrical impulses interpreted by the brain. Noise is always present around us.

Noise can damage the structures of our ears and lead to hearing loss. Noise can also cause other health effects (see below). Three characteristics of noise affect whether it becomes a hazard: frequency, duration, and loudness.

• Frequency is vibration of the medium (e.g., air molecules) through which sound energy moves. We measure frequency in Hertz (Hz) (i.e., the number of vibrations per second). We experience sound frequency as the pitch of noise. Fast vibration yields a higher-pitched noise than slow vibration. We can normally hear sounds with frequencies between 20 Hz and 20,000 Hz. Sounds extending beyond the low and high end of our hearing range are not registered by our brains (i.e., we cannot hear them), but they can still harm our ears.
• Duration is the length of time a worker is exposed to noise. How long a worker is exposed to noise is important. Yet, as discussed below, even short-term exposure can cause damage, especially if the noise is sudden and at a high frequency.
• Loudness (or intensity) is the amount of energy that is being carried through the medium. Loudness is measured in decibels (dB). The key feature of decibels is that they are a logarithmic scale. Unlike linear scales (where each step on the scale represents the same increase, such as a car’s speedometer), each increase on a logarithmic scale is an order of magnitude greater than the previous increase. For example, a sound measured at 10dB is 10 times more intense than a sound measured at 0dB (the lowest audible sound). But a sound measured at 20dB is 100 times more intense than the sound measured at 0dB. Noise over 85dB is generally considered hazardous for human hearing.

The most widely accepted health effect of noise exposure is hearing loss. If the loss is temporary, such as after a music concert, it is called a temporary threshold shift (TTS), meaning the normal range of human hearing has been reduced. This effect usually reverses itself over a short period of time. Nevertheless, TTS is a signal that the noise exposure was harmful and that continual or repeated exposure can accumulate and lead to permanent threshold shift (PTS). Men typically have higher rates of PTS. Some of this gender effect is due to job segregation (i.e., men typically work in louder workplaces than women). It is also possible that some of this effect reflects physicians failing to link female hearing loss to occupational exposures. Women are often exposed to noise in food, bottling, and textile factories as well as service industry jobs.10

Extended exposure to noise hazards can lead to non-hearing health effects as well. It can induce a sensitive startled response to sound and cause changes in endocrine and biochemical systems, along with cardiovascular disease, hypertensions, speech issues, sleep disturbances, nausea and headaches.11 Sound can also create health effects without prolonged exposure. Acoustic trauma is caused by a short, intense exposure to noise, usually of high frequency (see Box 4.2). Exposure to this hazard can lead to a series of short- and long-term health effects. Short-term effects include a full sensation in the ears, sharp pain around the ear, nausea, or dizziness. Longer-term effects can include headaches, fatigue, anxiety, and hypersensitivity to sound.12

All jurisdictions in Canada regulate workers’ exposure to noise. Most jurisdictions utilize an exposure model that factors in duration and loudness, known as a time-weighted average (TWA). Government regulations use dB(A), which is a weighted measure of loudness that factors in the frequency of the noise. Lower-frequency noises are weighted in the calculation so that their dB(A) is lower than their unadjusted dB. This reflects a belief that lower-frequency noises are less harmful than higher-frequency noises.

The regulations establish an occupational exposure limit (OEL) that aims to restrict workers’ noise exposure to no more than 85dB(A) during an 8-hour shift and a 40-hour workweek. The duration of acceptable exposure declines by half for every 3dB(A) increase. So acceptable worker exposure drops to 4 hours at 88dB(A), 2 hours at 91dB(A), and so forth. The logic of TWA leads to a ceiling of noise exposure at approximately 115dB(A). Box 4.3 provides some real life examples of these noise levels.

Just over half of jurisdictions also regulate impulse or impact noise, which includes short and intense sounds that can cause acoustic trauma. These limits typically focus on maximum peak pressure level (dB(peak)), with most jurisdictions legislating a 140 dB(peak) limit. However, most jurisdictions do not specify a maximum number of impact noises, even at peak level, that a worker can be exposed to over the course of a work shift.14

There are significant shortcomings in this approach to regulating noise exposure. First, there is insufficient evidence to determine if an exposure at 85dB every day over a period of many years is safe. Second, the rules do not account for individual variation. Research has established that people possess different degrees of sensitivity to noise. Some have greater physiological and psychological reactions to lower levels of noise, while others appear to be more tolerant.15 As with other types of hazards (e.g., carcinogenic substances), some individuals appear to be more susceptible to harm than others. Third, this approach treats noise as an isolated hazard and overlooks its interactions with other hazards, such as vibration, heat stress, chemicals, and rotating shift work.16 Workers exposed to a combination of hazards can face greater risk at lower exposure levels.17 Fourth, many people treat OELs as the line between safe and unsafe exposure or the maximum acceptable exposure for a worker. This interpretation of OELs is inaccurate. The best approach remains keeping exposure to all hazards as low as possible. The reasons are complex, but a universal standard designed to address the so-called “average” person will leave some workers inadequately protected from noise hazards.

Vibration is the oscillating movement of a particle around its stationary reference position. In the workplace, a mechanical process usually causes vibration. Vibration becomes a hazard when workers come into contact with the vibration, causing energy to be transferred to the worker. Two types of workplace vibration are important for OHS. Whole-body vibration occurs when a worker’s entire body experiences shaking caused by contact with the vibration. This is most common with low-frequency vibration (below 15 Hz), as when driving in a car or working near a large machine, such as an air compressor. The health effects of whole-body vibration include a general ill feeling, nausea, motion sickness, and increased heart rate. Extended exposure to whole-body vibration can lead to lower-spine damage and, sometimes, internal organ damage.

Segmental vibration occurs when only parts of the body are affected by the vibration. This is usually caused by higher-frequency vibration. The most common and concerning form of segmental vibration is hand-arm vibration. Hand-arm vibration results from gripping power tools such as jackhammers, saws, and hammer drills. An important aspect of hand-arm vibration is that a tight grip is required to control the vibrating tool. The tighter the worker grips the source of vibration, the worse are its effects. Hand-arm vibration syndrome (sometimes called Raynaud’s phenomenon or “white finger”) is caused by restriction of blood and oxygen supply to fingers and hands, which causes damage to blood vessels and nervous systems. The first symptoms are tingling in the fingers, loss of sensation, loss of grip strength, and whitening of the fingers when exposed to cold. Initially, these effects are reversible, but over time they become permanent.19 Because vibration, as the movement of particles, is closely linked to noise, it is frequently encountered alongside noise exposure. When combined, noise and vibration can significantly increase the risk of ill health for workers.20 Additionally, noise can mask the effects of vibration, causing workers and employers to underestimate its impact, especially in environments with high levels of noise.

As with noise, individual susceptibility to vibration exposure effects varies. How hard the worker grips the tool, their posture, their sensitivity to motion sickness, and other factors can shape how the exposure manifests itself, which can make it difficult to ascertain the seriousness of the health risk. Men most often manifest vibration-related injuries, reflecting occupational segregation. That said, women in some female-dominated occupations (e.g., dental hygiene) frequently report vibration-related injuries.21 Exposure to vibration, while widely recognized as a safety hazard, is largely unregulated. The few provinces that do restrict exposure to vibration adopt a time-weighted average approach similar to that used for noise regulations.

Noise and vibration are measured in similar ways. Both require a specialized meter to reliably detect the intensity of the molecular movement. These meters can provide accurate measurements of real-time levels. Nevertheless, the meters cannot assess the susceptibility of a worker to noise/vibration exposure, nor the degree of damage sustained by the exposure. This means that, even if vibration standards are established, workers may still be harmed by these hazards. OHS regulations also require that workers exposed to noise undergo regular audiometric testing to detect any threshold shift (there are no equivalent requirements for vibration exposure).

Controlling noise and vibration hazards is a complex undertaking. In both cases, the most effective way to control the hazard is elimination, substitution, or engineering controls. Such controls can be expensive, as they require replacing machinery, altering processes, or eliminating tasks from the workplace. Controls along the path can also be implemented by erecting sound barriers to muffle noise or installing vibration resistant material on tool handles. The most common, yet least effective, controls for noise and vibration are time restrictions and PPE. Restricting workers’ exposure to noise or vibration can reduce the effect of these hazards but does not address the full range of risk to the worker.

Humans are a temperature-sensitive species and have evolved a finely tuned system that regulates our internal temperature. Under normal circumstances, the body interacts with its environment to maintain a core body temperature at about 37 degrees Celsius. When the environment becomes too cold or hot, our bodies have difficulty generating or shedding sufficient heat to maintain temperature homeostasis, which is the state of maintaining a steady core temperature.

When temperature extremes prevent our bodies from properly self-regulating, we experience thermal stress. Temperatures that are too high can lead to heat stroke. Early signs of heat stroke include fatigue, dizziness, confusion, lightheadedness, nausea, and sudden, unexplained mood swings. People often struggle to recognize these symptoms in themselves and commonly rely on co-workers to identify the issue and help them to seek medical attention. Prolonged exposure leads to fainting and death. Heat stroke can cause damage to muscles, the heart, kidneys, and the brain. Humidity interferes with the body’s ability to shed heat (through sweating) and, therefore, can lower the temperature at which thermal stress occurs. Conversely, when temperatures are too low, we can experience hypothermia. Initial symptoms of hypothermia include dizziness, fatigue, nausea, sudden euphoria, or irritability. Pain in extremities and severe shivering may also occur. Advanced hypothermia can lead to frostbite and frozen extremities, and unconsciousness leading to death. Wind and humidity can intensify the effects of cold, as they strip heat away from the body.

Exposures to extreme temperature are most common among workers working outdoors, although thermal stress can occur in some indoor locations (e.g., a meat cooler or a non-air-conditioned office on a hot summer day). Employers should also pay attention to thermal comfort. Thermal comfort is the condition in which a person wearing normal clothing feels neither too cold nor too warm. It is a function of temperature, humidity, and air movement within an indoor workplace. A lack of thermal comfort may not pose a direct health risk, but it can exacerbate existing hazards or be a factor that increases risk of an incident occurring. For example, thermal discomfort may lead to rushing, heat-induced fatigue, or mental distraction.22

Extreme temperature is unevenly regulated in Canada. For instance, in Alberta, there are no OHS provisions specifically addressing extreme heat and cold. In contrast, some provinces have implemented temperature limits based on recommendations from external agencies for at least some workplaces as either guides or regulations. A minority of jurisdictions provide general duties to employers aimed at preventing thermal stress in the workplace. Gender-based job segregation can affect heat and cold exposures on worksites. For example, Karen Messing’s study of meat processing found that, while women did not work in the extreme cold of meat freezers, their work required them to stay relatively immobile at their work stations, where temperatures hovered around 4 degrees Celsius. Men in the study experienced significant lower temperatures working in the meat freezers, but their work was more active and the additional body heat generated by this activity attenuated the effects of the cold.23

Temperature poses a unique OHS challenge in that it is often not possible for an employer to control the hazard at the source (since the weather is out of our control). The most effective control for preventing thermal stress is to limit workers’ exposure to hazardous temperatures. It can, however, be difficult to determine what temperature is too hot or cold for work to occur. There are many factors, including wind chill and humidity, individual temperature sensitivity, and the nature of the work being performed (light or heavy effort) that shape when a worker is at risk of thermal stress. Compounding these issues is that of variability. Weather conditions and work tasks change over time and often rapidly. This instability in working conditions requires closer monitoring of changes in the hazard than is the case with most other physical hazards. Box 4.4 explores how climate change affects the hazard posed by temperature.

The American Conference of Governmental Industrial Hygienists (ACGIH), an industry group of OHS professionals working in government, has established a matrix for determining when work should be reduced and, ultimately, ceased.24 For example, the ACGIH recommends that work cease completely at temperatures between −32 and −43 Celsius, depending on wind chill. On the warm end, the limits are more complicated due to humidity effects, but temperatures above 30 Celsius require work reduction or cessation. Within the recommended maximum and minimum, the degree of exposure is dependent upon clothing and other factors, such as access to fluids, degree of exertion, and rest breaks to warm/cool. Thus the need to establish controls extends beyond the extremes to ensure workers are shielded from the effect of hot or cold temperatures. Other controls include relocating work, installing heating/cooling devices or shelters, work-rest cycles, preventing working alone, and minimizing manual effort.

Radiation is any energy emitted from a source, including heat, light, X-rays, microwaves and other waves, and particles. Radiation is categorized into two forms: ionizing and non-ionizing. Ionizing radiation is radiation with enough strength to remove electrons from a molecule as it passes through. The electron loss causes the molecule to become positively charged (called an ion). Examples of ionizing radiation include X-rays, gamma rays, alpha particles, and neutrons. Non-ionizing radiation is unable to ionize molecules but may have other effects, and includes microwaves and radio waves as well as ultraviolet, visible, and infrared light.

Ionizing radiation can occur naturally at low levels from a variety of sources but is uncommon in workplaces. It is most often found in medical, nuclear, and research facilities. When ionizing radiation is present in a workplace, it poses a significant safety hazard. Both short exposures to high levels of radiation and long-term exposure to lower levels have serious health consequences. In Canada, it is estimated that people are exposed to approximately 1.8 millisieverts (mSv, a standard measure of radiation) of naturally occurring radiation per year.30 Short-term exposure of 10,000 mSv will lead to death within a few days or weeks. An exposure as low as 100 mSv will lead to significant increase in the risk of cancer later in life.

Long-term, lower-level exposure is also a concern as it, too, can lead to increased risk of cancer. The recommended annual exposure limit for the general public is 1 mSv. Nevertheless, the Canadian Centre for Occupational Health and Safety recommends an annual limit for radiation workers of 20 mSv, averaged over five years, a figure much higher than public health limits.31 Controls for ionizing radiation are quite expensive and technical, requiring significant engineering controls. Specialized training is also required, and exposure to ionizing radiation should never be taken lightly.

Non-ionizing radiation, in comparison, has less dire health effects, but should not be ignored. Longer-wave non-ionizing radiation (such as microwaves) can cause deep tissue damage, cataracts and other eye issues, and skin rashes as well as interfere with the operation of pacemakers. Infrared radiation can lead to corneal and retinal burns and other eye injuries.

The most common non-ionizing radiation exposure is ultraviolet light (UV). UV radiation damages our skin, leading to burns and permanent skin darkening as well as heightened risk of skin cancer. It also damages our eyes and can cause pain and swelling in the eye and blurred vision, a condition variously called snow blindness, welder’s flash, or flash burn. The sun is the most common source of UV radiation, but UV radiation can also be produced by welding equipment, black light lamps, mercury lamps, counterfeit currency detectors, fluorescent tubes, and nail-curing lamps. Outdoor workers often have more UV exposure than recommended, placing them at higher risk of developing skin cancer.34 Other workers at greater risk of UV exposure include those with fair skin, young people, and those on certain medications that make skin more sensitive, such as antidepressants, antibiotics, oral contraceptives, diabetes medication, and immunosuppressants.35

Controls for non-ionizing radiation should include replacing radiating equipment, proper maintenance to prevent fugitive radiation (such as with microwave ovens), separating workers from the radiation source, reducing exposure time to low levels, and using UV-blocking PPE (e.g., hats, clothing, sunscreen).

Laser is an acronym for “light amplification by stimulated emission of radiation” and a form of non-ionizing radiation. The light emitted by a laser will be a specific wavelength, measured in nanometres, and can be different parts of ultraviolet, visible light, and infrared spectrum. Unlike conventional light sources, such as flashlights, lasers emit highly focused beams in which photons or particles move uniformly in a singular direction, resulting in significantly higher radiant power. Sources of light such as flashlights will spread light over a larger area. Lasers are categorized into different classes, ranging from Class 1 for lasers that have limited hazards to skin and eyes with normal use to Class 4 lasers that include those capable of causing immediate damage to skin and eyes. Class 4 lasers are generally used in surgery, welding, and cutting. Manufacturers and importers are responsible for classifying and labelling lasers in Canada.36

There are two types of hazards associated with lasers. The first type of hazard is associated with the laser beam, which can cause burns to the skin or eyes depending on factors such as power, wavelength, and duration of exposure. Some lasers are so powerful that blinking to protect our eyes is not fast enough to prevent damage. Other lasers can produce a beam that is invisible to the human eye and do not trigger a blinking reflex or pupil constriction. A laser beam can also cause a fire if it comes into contact with combustible materials or chemicals, including materials such as intestinal gases in medical settings.37

Lasers also entail non-beam hazards, such as electrical hazards from the high voltage that they use. Additionally, laser plumes, which consist of particles emitted from the laser connecting with another material, can pose health risks. Plumes can appear as small puffs of smoke, but their composition varies depending on the laser used and the material that it contacts. These plumes can contain viruses, bacteria, blood fragments, or cellular debris in health-care settings, and other environments can encounter gases, chemicals, or dust. Exposure to laser plumes can lead to short-term effects such as eye and respiratory irritation as well as long-term health issues depending on the composition of the plume.

Mitigation efforts for lasers tend to focus on worker training, equipment maintenance, and PPE such as eye protection, protective clothing, and respirators. Engineering controls can include proper ventilation or plume scavenging systems along with fail-safes that automatically shut down lasers in the event of malfunctions. Additionally, engineering controls include removing reflective materials that can bounce a beam around or adding materials to a room that can absorb scattered laser beams.38 Workplaces that use lasers in Class 3B or 4 must have a laser safety officer given additional legal duties on behalf of the employer.

Ergonomics is the study of how workers and the work environment interact. It is a broad-based approach to OHS that considers how the design of work affects the human body and its health. Ideally, ergonomics starts with job design. Job design comprises the decisions employers make about what tasks will be performed by workers and how that work will be performed.

Job design includes establishing the physical dimensions of work. This includes the size and location of the workspace, and what furniture, tools, and equipment will be used, as well as the temperature or lighting of the workspace. Job design also determines the nature of the tasks, including their complexity, pace, and duration and how individual tasks and jobs relate to one another. Finally, job design often includes making decisions and assumptions about the characteristics of the workers who will perform the work, including their height, weight, sex, and other physical and mental abilities.

The decisions made during job design can have significant effects on workers’ health and safety. Poor work design has negative effects on worker health. For example, if you have ever worked at a job where, at the end of the day, your eyes hurt (due to poor lighting) or your back was sore (because of standing on a cement floor), you have experienced ill health caused by poor ergonomics.

A core principle of ergonomics is “fit the job to the worker, not the worker to the job.” More specifically, ergonomics seeks to ensure that the design of work matches the anatomical, physiological, and psychological needs of the worker. Yet some ergonomic hazards are easier to “see” than others. For example, back pain from heavy lifting is easier to identify than fatigue to due poor shift rotation design. The broad acceptance of lifting as hazardous and requiring control shows that the relationship between the hazard and the injury is both direct and well accepted. By contrast, there are many factors contributing to worker fatigue. This makes it difficult to definitively prove that shift rotation is an important factor in worker fatigue (or, as we’ll see in Chapter 5, cancer).

The aspects of ergonomics that have been more readily adopted are the design of tools, equipment, and workspaces. For example, we have seen an increase in more appropriately designed keyboards, workstations, retail scanners, and other equipment. There has also been greater attention paid to minimizing manual lifting and handling of loads. Buildings are being constructed with better climate and air-quality control.

Employers have been more reluctant to address other ergonomic issues because the required changes affect the work process or may impede management’s ability to direct work. For example, providing a better-designed chair to prevent spinal deterioration is easier and cheaper than altering the workflow to reduce the mechanical forces exerted on workers’ spines by twisting to reach objects. This reluctance to address some ergonomic hazards echoes employers’ preference for PPE over engineering and administrative changes that we saw in Chapter 3. As well, government OHS regulations tend to address only small pockets of ergonomics, such as manual lifting, while remaining silent on many other aspects.

A common health effect of poor ergonomic design is repetitive strain injury (RSI). As we saw in Chapter 1, RSIs (which are sometimes called cumulative trauma disorders) are injuries to muscles, nerves, tendons, or bones caused by repetitive movement, forceful exertions and overuse, vibration, and sustained or awkward positions. RSIs frequently occur in the hands, wrists, and arms but can also afflict legs and other key joints. Carpal tunnel syndrome, frozen shoulder, trigger finger, tendonitis, bursitis, and (more recently) trigger thumb are all examples of RSIs.

Any task that requires either the same movement over and over again or puts the body in an awkward position can lead to RSIs, especially if repeated over a long period of time. RSIs have only gained acceptance as the outcome of workplace hazards over the past 20 years. They were first acknowledged in factories with workers on assembly lines. Even today workers in some occupations, such as retail clerks, typists, and restaurant servers (notably occupations dominated by women), still have greater difficulty having RSI claims accepted. Among the reasons for the slow acceptance of RSIs is the murky causality of the disease: did you get it from keyboarding at work or playing tennis on your own time? RSIs may also worsen even after the hazardous tasks are eliminated and can appear as a result of work not normally associated with repetition. There has been inadequate epidemiological research into the full range of factors that lead to RSIs.39

Engineering controls are the best way to address ergonomic hazards. Wrist supports, rest breaks, and other controls-at-the-worker fail to address the root cause of the hazard and do not effectively prevent the onset of injury. Ergonomic principles require that the design of the work be altered to better fit the needs of the workers in question. What those specific controls look like is highly dependent upon the nature of the work and the demographics of the worker.

Returning to our opening vignette, the owner of Metron Construction, scaffold supplier Swing N Scaff, and project manager Vadim Kazenelson were all convicted of offences after the Toronto scaffolding collapse. Metron and its director were fined $750,000 for offences under the Ontario OHS Act. Swing N Scaff and its director were ordered to pay $400,000, also under the OHS Act. In June 2015, Kazenelson was convicted under the Criminal Code for criminal negligence causing death and criminal negligence causing bodily harm. He was sentenced to three and a half years in prison. This conviction and sentence were upheld upon appeal. As we saw in Chapter 2, criminal prosecution is rare in Canada (there have been only nine successful cases across three provinces since the Westray amendments were enacted in 2004) and so Kazenelson’s conviction is noteworthy.

These convictions may have brought some solace to the families of the four killed workers. Yet, given the number of annual injuries in Canadian workplaces, clearly many hazards—including obvious physical hazards—remain uncontrolled in Canadian workplaces. While this situation may, in part, reflect the fact that some hazards are difficult to identify and control, we also need to be cognizant that employers often have a financial incentive to cut corners on safety.

Write a definition for each bold italic word in this chapter.

Select a workplace with which you are familiar and identify a job task performed by a worker that exposes them to a physical hazard. For example, you might select a restaurant kitchen and identify that washing dishes exposes a worker to sharp edges.

Using the HRAC process set out in Chapter 3, perform a hazard assessment for this task. Your completed hazard assessment should include:

• ➤ A description of the workplace and the work being assessed.
• ➤ A description of the hazard, which injury it might cause the workers, and the mechanism of the injury.
• ➤ The risk of injury that the hazard poses to the workers, including probability, exposure, and consequences.
• ➤ Three ways to control the hazard. For each potential control, identify which kind of control it is on the hierarchy of controls, how it would be implemented, and the expected cost and effectiveness of the control.
• ➤ A recommended control or controls based on your analysis, including a justification for why you recommended this control instead of the other options that you developed.

Briefly discuss with a partner or write 250-word responses to the following questions:

1. Why are some physical hazards difficult to identify?
2. How are noise hazards identified, and what are the shortcomings of current approaches to controlling them?
3. Which hazard control strategies exist to address thermal stress? Which controls are the most effective? Why might an employer be reluctant to enact such controls?
4. What is the core principle of ergonomics, and why have OHS practitioners been slow to adopt it?
5. Which physical hazards does a cashier at a grocery store face, and how would you control each hazard?

Write 250-word responses to the following questions:

1. What are three physical hazards that you have faced in a workplace?
2. Which of these hazards posed the highest risk to you and why?
3. How did your employer control the most dangerous hazard? How could your employer have made that work safer?
4. What do you think would happen if you refused to do the work because it was unsafe?
5. Which strategies did (or could) you or other workers use to make the work safer?