The Pareto principle states that about 80% of all effects come from 20% of causes. A classic example is from the world of business, where it's said that 80% of a company's sales come from 20% of its clients. The idea is that focusing on those 20% of clients gives you a much better return on investment than focusing on the majority of clients who account for only a fifth of your sales.

There's something similar when it comes to workplace safety. If we apply the Pareto principle to the workplace, we can assume that roughly 80% of injuries are caused by 20% of known hazards. Focusing our efforts on controlling those 20% could drastically reduce the injury rate for our workforce.

In this case, the 80/20 split might be a bit generous, but it's not far off. OSHA has determined that 65% of all fatalities in construction can be traced back to just four hazards, which it has dubbed the Fatal Four. The amount of non-fatal injuries from these four hazards is likely even higher.

When we're looking to improve our safety performance, it makes sense to prioritize the hazards that are most likely to injure workers or most likely to injure them severely. If you're responsible for the safety of construction workers, that means tackling the Fatal Four.

OSHA's Fatal Four and What to Do About Them

The Fatal Four, ranked in decreasing order of frequency, are:

  • Falls from height
  • Struck by object
  • Electrocution
  • Caught-in or between

Many safety professionals think that safety training is the answer to every safety issue. So, it comes as no surprise OSHA offers programs (Outreach Training Program - Construction Focus Four Training) to private training facilities and employers who are hoping to decrease the rate of death and injury.

Despite all these training efforts, however, a 2016 report shows an increase in workplace fatalities, including deaths resulting from the Fatal Four. This is supported by several studies that have concluded that training is not the most cost-effective way to increase occupational health and safety (it comes in fifth place).

I know that some of you will counter that there is no cost too steep for our employees' safety, but the reality is that companies have limited resources. To get better results with the resources we have available, we need to return to the Pareto principle. If we can identify the safety activities that have the highest return on investment, then we should focus our efforts on these.

So, if we're not going to go all in on training, what should we do instead? For these four hazards, the most effective controls (in order of effectiveness) are:

  • Hazards prevention and control
  • Management leadership and involvement
  • The concurrence of the bargaining agent
  • Worksite analysis
  • Health and safety training
  • Documentation review

The first two outweigh the rest by an order of magnitude in terms of efficiency. We should, therefore, focus more of our efforts on them.

Fall Hazards

Fall hazards are by far the biggest culprit for workplace fatalities and have been for many years in a row. While it might be convenient to say that employee involved in a fall had not been properly trained or did not pay attention, the root cause of falls can usually be traced back to not having the proper equipment. Unprotected edges, inadequate fall protection equipment, open holes, substandard scaffolding, and ladders are all leading causes of falls and deaths for workers at height (learn more about Fall Protection and Leading Edges).

The best thing we can do is to not be satisfied with the fact that we have (or think we have) fall protection equipment in place. Our best options for preventing falls are:

  • Minimizing the amount of work done at heights – If any of the tasks can be accomplished from the ground, then those tasks should be done on the ground. There is no need to increase the amount of time employees are exposed to fall hazards.
  • Guardrails – These prevent falls from occurring. They keep employees inside the safe perimeter and physically stop them from going over the edge if they lose their balance or walk backward unaware of how close they are to the edge.
  • Safety nets and fall protection equipment – Unlike guardrails, these do not prevent falls from happening. What they do instead is protect workers who have fallen by minimizing the impact of the fall on their bodies. Safety nets should extend a minimum of eight feet from the work surface but should extend more if there is potential for a longer fall. OSHA provides a formula to help us calculate how much a net should extend.
  • Scaffolding – When installed correctly, these platforms provide a comfortable working surface, avoiding the loss of balance and overreaching, while allowing employees to place tools and materials that would otherwise place stress on their body. It should be installed by a competent person and have proper components (bracing, planks minimum 18 inches wide, proper access).
  • Ladders – Choose a proper ladder for the task, place it at 1:4 angle (or about 75 degrees), and ensure it extends three feet beyond the point of landing and that it is tied at the top and bottom. Provide means for lifting equipment and tools to the working surface, such as ropes, hoists, and cranes (learn the Keys to Safe Ladder Use).
  • Housekeeping – Keeping the work area clean reduces the risk of tripping and falling. Employees should clean the work surface as they work, not leave it for the end of the day.
  • Access to health and safety professionals – Occupational health and safety professionals can monitor and advise your employees when implementing these methods. They can be dedicated professionals or can be (properly trained) supervisors or foremen.

Struck by Object Hazards

Struck-by hazards refer to equipment, tools, materials, and other objects that pose a risk of injury or fatality caused by the impact between the employee and that object. This is a fairly wide class and includes employees being struck by:

  • Flying objects
  • Falling objects
  • Swinging objects
  • Rolling objects or equipment

A major difficulty in protecting employees from these hazards is that, more often than not, the injured employees are not involved in the task that resulted in the object flying or falling.

As with other hazards, the best way to deal with these is to prevent them from happening in the first place. When the tasks cannot be avoided, prevention and controls should include:

  • Weighing or tying down materials that can be lifted by the wind, such as plywood and OSB boards, glass panels, insulation, and tarps.
  • Ensuring safeguards on tools that discharge a projectile (like framing and roofing nailers or powder actuated tools) to avoid misfiring when not set against the working surface.
  • When working with the above-mentioned tools, barricade or tape off the area on the opposite side (behind the wall, under the roof) to keep unaware employees away and to avoid hurting them if the projectile passes through the working surface.
  • Providing lanyards to secure tools to the worker and prevent a dropped tool from falling and hitting employees working below (learn The 3 T's of Dropped Object Prevention).
  • Installing minimum 4" toeboards/kickboards around elevated working surfaces, such as rooftops, unprotected building edges, and scaffolds.
  • Restricting employee access to the areas where lifting operations occur or where objects might drop by using barricades or hazard tape.
  • Ensuring only qualified and competent personnel operate lifting equipment or do rigging.
  • Blocking materials that can roll, such as pipes or logs, with appropriate blocks and barricades.
  • Installing cameras and audible backup alarms on equipment to mitigate blind spot hazards.

PPE, such as safety glasses and hard hats are usually mandatory on most construction sites, but we should be aware of their limitations. While they offer some degree of protection against objects, they are the last line of defense against struck-by hazards and should not be considered a sufficient control measure.

Electrocution Hazards

Death by electrocution accounts for over 8% of all workplace fatalities. Electricity flows through wires and looks for the path of least resistance to complete a circuit. Unfortunately, our bodies are electrical conductors, so when we come into contact with the electric current, we become the path that completes the circuit, resulting in severe electrical burns or a stopped heart.

Electrical fatalities also include deaths that are indirectly caused by contact with electricity. When it's not the contact with an electric current that proves fatal, it is often the fire, explosion, or fall that results from the electricity.

Here are some ways to avoid and control for electrocution hazards:

  • Stay away from power lines. The distance should be dictated by OSHA's guidelines, based on the voltage of the line. This applies to people as well as equipment. When using equipment, make sure that your swing radius does not encroach within the distance of approach. Place markers and use spotters to ensure enough separation from the power line. If you must operate equipment within this area, ask the utility company to de-energize the line. (Do not touch a power line if you do not know whether it has been de-energized.)
  • Call the utility company to report any downed power lines. If you downed a power line with your equipment or if a power line falls on your equipment, keep driving and do not exit your vehicle.
  • Get a ground disturbance permit and locate underground lines before digging. Do not dig with mechanical tools in the immediate proximity of buried electrical lines.
  • When working on electric equipment, follow lockout/tagout procedures. Lock the circuit and ensure it is disabled by trying to start the equipment.
  • When working close to live power lines, even outside of the hazardous area, use nonconducive equipment, such as fiberglass ladders. The same goes for PPE. Hard hats should be type E, rated for electrical work, and gloves should provide the proper degree of insulation for the voltage being handled (learn the Hard Hat Requirements You Need to Know).
  • Inspect all electrical tools before use. Do not use damaged equipment (frayed cords, broken casing, ungrounded tools).
  • Do not run electrical cables through water or in wet locations. Drain wet areas or route the electrical cables above the head. Don't operate any electrical equipment while standing in water.
  • Use only Ground Fault Circuit Interrupter receptacles for your power tools. Test the receptacle and then reset.
  • Lockout defective tools and send them to be inspected and repaired by a qualified person. Do not attempt to fix your tools if you are not qualified.

Caught-in and Caught Between Hazards

Caught-in and caught between hazards sound very similar to struck-by hazards, but the difference is that it is not the initial impact that causes the injury or fatality in a caught-in/between accident. Rather, it is being pulled in or under the equipment and crushed (for related reading, see First Aid for Major Trauma: Crushes, Amputations, Impalement).

Examples of this type of accident include being caught in the moving parts of machinery, being buried by a caving trench, and getting pinned to a wall by a heavy piece of equipment.

Here are a few of the prevention and control measures you can take for these hazards:

  • Install guards on any equipment that can create pinch or crush points. Never remove the guards or render them inoperational (see 6 Things to Look for When Selecting Machine Guards for more advice).
  • Major pieces of equipment should be equipped with automatic shut off devices when their guards are removed. Do not disable automatic shut off.
  • Lockout and tagout equipment before servicing it (read about Lockout Tagout: 6 Essential Elements).
  • Do not wear loose clothing, hoodies, or any accessories that could get caught in machinery around equipment with moving parts.
  • Laser or pressure sensors are ideal for deactivating equipment if your employees come to close to hazardous areas.
  • Install cameras and audible backup alarms on equipment to mitigate blind spot hazards. Buggy whips, beacons, or projecting blue lights are also great for creating awareness to heavy equipment approach.
  • Know the limitations of heavy equipment to avoid pushing it beyond its limits and rolling.
  • If equipment could roll over, install rollover protective structure (ROPS).
  • Slope a trench or an excavation at an appropriate angle, according to the type of soil.
  • Protect trenches deeper than five feet with protective devices. Trenches over 20 feet deep should have engineered protective devices, such as aluminum hydraulics.
  • Use trench boxes to prevent cave-ins.

Management's Role in Tackling the Fatal Four

All of these prevention and control measures are worth pursuing, but their existence and application are guided by management and how involved company leaders are in the safety of the workplace.

Management should:

  • Determine what policies are needed to protect workers
  • Provide the proper prevention and control measures
  • Ensure these measures are properly used
  • Participate in the hazard assessment process
  • Have an active presence on site
  • Demonstrate and encourage safe behavior

Management is essential in setting the organizational culture and guiding it in a direction that is conducive to the health and safety of the workers.

Making the Construction Site Safer

There is no single, all-encompassing solution to address all of the Fatal Four simultaneously. We should, therefore, institute a code of practice for activities subject to these hazards. Studies, moreover, show that hazard assessment and involvement provide the highest ratio of benefits to costs. Keeping workers safe on the construction site, then, requires a combination of strong hazard assessment, management leadership, and employee involvement.