Tree Worker Safety Update By the Numbers: Another Us vs. Them

Proper fall protection is a must when working in an aerial-lift bucket. Too often, aerial-lift operators die from a fall after they choose not to wear fall protection. Here, a Harrison McPhee employee puts on a safety harness prior to working. Photo by Richard May.

Another year, and arboricultural operations are still among the leading industrial activities for fatal and nonfatal injuries. Compared to all industries, tree workers have at least 15 times the fatality rate (Bureau of Labor Statistics 2020a) and three times the nonfatal rate (BLS 2018). You might take some comfort in the nonfatal rate being “only” three times that of all industries, but consider its meaning. Our incidents are so severe that we die.

The BLS places tree workers within the Standard Occupational Classification (SOC) 37-1031 Tree Trimmers and Pruners, and defines these as workers who “cut away dead or excess branches from trees or shrubs to maintain rights-of-way for roads, sidewalks or utilities or to improve the appearance, health and value of trees” (BLS 2020b). They estimate a total workforce in this category to be about 52,000 workers.

This is an underestimate of the workforce, considering there are more than 80,000 tree care establishments in the U.S. (O’Bryan et al. 2007). There may be as many as 289,000 tree workers, many of whom are self-employed and may do more than tree care. This article focuses on tree-related incidents that happened to paid workers (so helping a neighbor remove a tree for beer is exempt) who work either for themselves or a company and are involved in ground maintenance, landscaping or tree care (including line-clearance tree pruning and removal).

Improper use of pole saws or pole pruners can result in struck-by incidents, electrocutions and soft- tissue injuries. Photo courtesy of John Ball.

So, what has been happening? Any new trends in incidents? This article will cover some of the most common recent incidents and their hazard sources. These incidents are covered within the appropriate BLS event categories. Since these incidents could be significantly reduced if a few simple work practices were followed, they are noted here with the appropriate Z133-2017 standard in parentheses.

Falls, Slips and Trips (40% of fatal incidents)

Falls were the most common fatal incident. This event category vies with Contact with Objects and Equipment for the most-recorded annual arboricultural-operation fatalities. One year the leading event category is Falls, the next Contact. Some years there is a 10% gap between the two, other years they are almost tied. Regardless, Falls and Contact are the two event categories which, combined, account for about three out of four tree-worker deaths each year.

Climbers should use two tie-in points while working aloft. The problem with severing a climbing line (either with a chain saw or handsaw) could be almost eliminated if 6.36 was followed – and if it applied to handsaws. Photo courtesy of Brandenberger Tree Care.

Climber falls

Not surprisingly, climbers experienced the most falls, though falls involving aerial lifts are beginning to close the gap. The climber falls were of two types: the climber fell from the tree or fell with the tree. The most common was falling from the tree, so we will focus on this type of incident.

The sources for, or activities related to, most climber falls were either tie-in-point/anchor failure, disconnecting from the climbing system or severing the climbing line with a saw. Tie-in-point/anchor failures are found with either moving-rope or stationary-rope systems. It does not matter which system you use; any time you have isolated your line to a single branch, it had better hold. Unfortunately, sometimes they do not. They often fail as the climber ascends, even after the climber first subjects the anchor point to a load “double” their weight (8.1.11) to test it. We need to do a better job of selecting and inspecting our anchor points. Trying to get an anchor to fail before we climb on it is not a safe practice.

The anchor point must be inspected from the ground (81.11), but we do not define what to inspect or consider. Lilly and Julius (2021) listed the criteria as a living, healthy limb with no sign of decay and about 4 inches in diameter. Admittedly, examining a potential anchor 50 feet in the air is not going to reveal all defects, but at least stick with the basics – if you cannot clearly see it, do not use it.

Disconnecting from the climbing system has been a source of incidents ever since we started climbing with a line attached to a rope snap or carabiner. It becomes too easy to just unclip “for a second” when isolating the climbing line or transferring a system, but that second is when you slip. One of the many things I like about traditional climbing with students is, once they are tied into their place on the line, they cannot untie it. The tie-in is through the two hard points on the harness, not a carabiner. I am not advocating this for tree climbing; we need to reposition lines throughout our climb. But we must carry a second means of being secured (8.1.4) so we are never unsecured (8.1.6). And that leads us to the third type of fall incident, severing a climbing line.

The problem with severing a climbing line (either with a chain saw or handsaw) could be almost eliminated if 6.36 was followed (and if it applied to handsaws) and a second means of being secured was used in addition to the climbing line. Every year, climbers sever their single means of being secure with a saw and fall.

Aerial-lift-operator falls

As climbers are becoming less common and aerial lifts more versatile, we are seeing more use of mechanized means of accessing tree canopies and, consequently, more fall incidents related to them. Falls involving aerial-lift operators are also of two types: the aerial-lift operator falls from the lift or with the lift. The majority are falls out of the bucket, either from over-reaching while cutting with a chain saw and tumbling out or, more commonly, catapulting out when the boom is struck by a falling branch, treetop, whole tree or even a crane. I will focus here on falls from lifts.

Too often, aerial-lift operators die from a fall after they choose not to wear fall protection. Fall protection is part of our PPE, and the reason we wear PPE is because it is our final measure of protection. You need PPE when everything else has gone wrong. It seems flying lifts without wearing fall protection is almost as common as drivers not wearing seat belts was back in the 1980s. Some older readers will remember the argument that you did not want to wear seat belts because it was safer to be thrown free of the burning car (myth). You never want to be thrown free from the bucket.

We probably will need to go the way of car manufacturers and expand the use of audible-warning devices and kill switches to keep the boom from operating when someone does not clip in before the boom operates. Unfortunately, just like car drivers who override the restraint system by clipping in but sitting on the straps, there will be lift operators who just leave a snap attached and fly without fall protection – it is hard to fix stupid.

One other analogy to car restraint systems – both have to be worn properly. Too many car drivers (and their passengers) wear the lap belt too high, across the stomach, and the shoulder belt too low, under the arm. Wearing the belts wrong can kill or injure the wearer. So can improperly wearing fall-arrest harnesses.

Read and follow the manufacturer’s instructions on the care and use of your fall protection. The one time you need it to work, it must work properly! We have documentation where workers have been flung out of the bucket and suffered no more than a few aches from the experience because of their fall protection. Attachment should be between the shoulder blades, not at the center of your back. An operator should be able to slide only the flat fingers on his or her hand between their clothes and the harness straps, not a fist. Snug is safe.

Here’s another tip for those who planned to clip in but forgot. This is another good use for a command-and-
response system (even with an alarm or switch), but instead of protecting the responder, it is for the benefit of the caller, the aerial-lift operator. The lift operator says, “I am clipped to the boom,” (or similar phrase), but they do not lift the boom until a specific ground worker affirms this with a reply, “You are good,” (or similar phrase). Remember, safety means teamwork.

Contact with Objects or Equipment (38% of fatal incidents)

The event category with the second-highest number of fatalities is Contact with Objects and Equipment. This category includes many hazard sources, from being struck by a falling tree to being compressed by the feed rollers of a chipper. The sources for most fatal incidents in this category are falling trees or limbs.

Struck by a falling tree: One of the most common Contact incidents is being struck by a falling tree, and the injuries from this event are almost equally divided between the chain-saw operators and other ground workers. Unfortunately, this is also the activity during which we kill or injure bystanders or homeowners.

One way to reduce these incidents is by paying attention to the location of workers during manual tree falling. No other worker, except the chain-saw operator, shall be within one-and-one-half (1.5) times the tree’s height during the felling (8.6.4). The only workers permitted to be as close as one-and-one-half times the tree’s height are those assisting in the felling, by holding a pull line, for example. All other workers and bystanders must remain at least two (2) times the tree’s height away.

The second way to reduce incidents is for operators to be moving once the tree begins to fall. The chain-saw operator must have the saw shut off and be moving away from the trunk once the back cut is completed and begins to open (look where you are cutting, not just at the top of the tree) ( The farther along the retreat path, the lower the risk of being struck by a snapped limb or a trunk that kicks back. The first 10 feet from the trunk is where most struck-by incidents happen to the chain-saw operator, so follow the 5-20 rule. It takes about five seconds for a tree to fall once the back cut is completed. The chain-saw operator can be 20 feet away in that time. It is also a good idea for the pull crew to retreat to twice the height, where the other workers are stationed, once the tree begins to fall. We all have witnessed debris flying farther than expected.

Struck by a falling limb: There are struck-by incidents every year to workers standing beneath the tree while workers are aloft. The climber or aerial-lift operator cuts a branch, and it falls on an unsuspecting ground worker. Establishing a drop zone (3.4.6) and using a command-and-respond communication system (8.5.11) are excellent means of reducing the frequency of these incidents. Another good rule of thumb is to place the chipper outside the drop zone. It is a longer haul with the brush, but we see incidents every year when the chipper operator is struck by a falling limb.

Chain saws, chippers and stump grinders: All this equipment is designed to plane through or shred wood, and has no difficulty slicing through human flesh and bone. Chipper incidents are either compressed-by, i.e., the operator is pulled into the chipper, or struck-by, in which the worker is struck by a rope pulled into the chipper. The struck-by incidents are increasing, so crews should practice good housekeeping on their work sites. Everything – ropes, saws, harnesses, etc. – should be in its place (I use a tarp) when not in use. This way ropes are not just scattered over the site where they can be snagged by a branch and pulled into the chipper.

Chain saws and stump grinders are the sources of far more nonfatal than fatal injuries. Chain-saw fatal incidents to climbers and aerial-lift operators often involve cutting with one hand, a practice not allowed by our standards (6.3.5). These fatalities are at 40 feet and higher due to the difficulty of reaching the worker. The victim bleeds out before aid arrives. Climbers often carry first-aid kits with them, but these often contain a few bandages and blood stopper. Neither are much help with a deep chain-saw cut, and a climber might want to consider including a soft tourniquet in their aerial first-aid pouch (and know how to use one).

Always use both hands when using a chain saw. Chain-saw fatal incidents to climbers and aerial-lift operators often involve cutting with one hand, a practice not allowed by our standards (6.3.5). Photo courtesy of Brandenberger Tree Care.

Finally, while not many incidents involve stump grinders, they seem to be increasing. The worker stands near the grinding wheel to kick debris away or just walks by too closely. There even have been workers injured after a rope is snagged by the stump grinder and it pulls the worker to the grinding wheel.

Exposure to Harmful Substances or Environments (15% of fatal incidents)

Electrocutions, i.e., deaths from electric shock, are one of the most common fatal incidents in the United States. Most contacts are indirect – the result of contacting an overhead power line with a conductive object. The conductive object is frequently a metal pole pruner or pole saw. The other common occurrence is when a living branch that has just been cut and is still being held contacts the power line. If tree workers did not carry metal pole saws into trees near wires and did not allow cut branches to sweep lines, we could reduce the electrocutions almost in half.

We have three categories of tree workers regarding working near electrical hazards: the unqualified worker, the incidental line-clearance arborist and the qualified line-clearance arborist. If unqualified tree workers stayed out of any trees that had branches within 10 feet of their canopies, we could eliminate most of these fatalities. These workers lack the training and experience to work near power lines, and they frequently are the ones who make poor decisions around conductors because they are unaware of the hazards.

Temperature-related injuries are in this event category, and most of our temperature-related fatalities are heat strokes. These occur most often when the heat indexes are above 105, and frequently to new hires who are not used to working in the heat.

Other Fatal Events (7% of fatal incidents)

These big-three fatal events involve contact, falls and exposure – but two other event categories have fatal incidents every year. Traffic incidents are about 5% of our fatalities. Assaults and Violent Acts by Persons and Animals are fewer, 1%, and these involve people or bees annoyed with our activity. One has a firearm and the other a stinger – both can kill.

Nonfatal incidents

The nonfatal injuries are defined here as those resulting in at least one day out of work. They happen from the same sources that kill us and for the same reasons. I will focus on the most common injuries, ones we rarely think about until dealing with workers’-compensation insurance – sprains or strains. A sprain is an injury to the ligaments, the tissue that connects bones. A strain is injury to either a muscle or a tendon, the tissue that connects muscles to bone. These soft-tissue injuries account for about a third of all the non-fatal injuries.

These soft-tissue injuries are from two sources. A common source for strains is picking up logs that are either too heavy or outside the power zone (the safe lift zone between mid-thigh and mid-chest). Another source of strains is twisting the body while climbing and reaching out. Falls are responsible for many sprains. A worker steps in a divot or trips over a log and twists an ankle. Another source is sliding on an oil spill on the truck and falling.


Another year gone, and we continue to lose tree workers. Every occupational death is a tragedy, and one is too many. But there are few occupations that have no deaths during a year (“college administrator” came close, only one). We still are far above the all-industry average, and it has remained high despite our improvement in equipment and practices.

Almost 20 years ago, Shane Vosberg and I wrote a safety update for TCI Magazine (“How Accidents Occur – and Why,” August 2003), and we mentioned that “the biggest hazard, representing about 40% of all fatalities, is contact with an object. The number-two source, at about 35%, is a fall. The third is electricity, accounting for 15% of the fatalities.” Neither the number of incidents nor their sources has changed much over the past two decades.


Ball, J., Vosberg S. 2003. “How Accidents Happen and Why.” Tree Care Industry 14(8): 50-54.

[BLS] Bureau of Labor Statistics. 2018. Survey of occupational injuries and illnesses. Table R100. Incident rates for nonfatal occupational injuries involving days away from work per 10,000 full-time workers.

[BLS] Bureau of Labor Statistics. 2020(a). Survey of injuries, illnesses and fatalities. Table A-5. Fatal occupational injuries by occupation and event or exposure, all United States.

[BLS] Bureau of Labor Statistics. 2020(b). Occupational Employment and Wages: 37-3031 tree trimmers and pruners.

Lilly S.J,. Julius A.K. 2021. Tree Climbers’ Guide, 4th ed. Atlanta (GA, USA) International Society of Arboriculture. 272 p.

O’Bryan C.M., Staka T.J., Templeton S.R., Caldwell JD. 2007. Economic patterns in U.S. arboriculture. Arboriculture & Urban Forestry 33:292-299.

John Ball, Ph.D., BCMA, CTSP, A-NREMT (Advanced – National Registry of Emergency Medical Technicians), is professor of forestry at South Dakota State University and a Board Certified Master Arborist.

Leave a Reply

Your email address will not be published. Required fields are marked *

Click to listen highlighted text!