Slips, Trips, and Falls

March 14th, 2010 by Andrea Bennett

The Center for Injury Epidemiology identifies risks, and what we can do about them.

Brought to you by Liberty Mutual's
The Responsibility Project


A keystone of public health research, the practice of injury epidemiology uses research to identify occupational injury risk factors. In other words, injury epidemiologists are on the front lines of identifying who’s at risk for what, and provide the logic for interventions designed to prevent injury.

Liberty Mutual’s Center for Injury Epidemiology conducts massive field data collection efforts, and collaborates with organizations such as the Harvard School of Public Health, the U.S. Consumer Products Safety Commission, University of Massachusetts-Lowell, and occupational safety and health institutions in Vietnam and Finland (among others) to amass data sets. They’re also behind the Workplace Safety Index, a report that combines a huge amount of collected data to index the leading causes and costs of the most disabling workplace injuries in the United States.

Like the other centers at the Liberty Mutual Research Institute for Safety, everything the CIE does is eventually published, in peer-reviewed journals as well as the Institute’s own publication, “From Research to Reality.” We sat down with Ted Courtney, Director of The Center for Injury Epidemiology to get some insight into the index, newly published work, and what’s on the center’s radar right now.

For a decade now, your center at the Institute has been indexing the leading causes of the most disabling workplace injuries in the U.S. What does this involve?

The Workplace Safety Index is essentially a report of the causes of the worst injuries — and what they cost U.S. businesses. We combine data from various sources, including Liberty Mutual claims, data from the U.S. Department of Labor’s Bureau of Labor Statistics, and the National Academy of Social Insurance. But it’s not just gathering the data; indexing it can take up to 18 months, because we’re looking at how recent the data is and assessing what the true cost of the injuries is. Just waiting for claims to process can take that much time.

Are there ever dramatic shifts in the most disabling workplace injuries?

Not usually. You might, for instance, see some of the lower ranking causes replace each other; for instance, workers who were injured by striking against an object [such as walking into a door] constituted 5.1 percent of the injuries in 2006 [indexed in the 2008 study] but we saw that percentage decrease compared with repetitive motion and highway incidents in the 2009 study. The top five most disabling injuries were the same: overexertion, falls on the same level, falls to a lower level, bodily reaction [such as slips or trips without falling], and being struck by an object. It all amounts to a large sum of money — around $52 billion in direct U.S. worker compensation costs.

What are some of the interesting discoveries that the CIE has made recently?

Our findings from a study reporting on slips-and-falls issues among fast food restaurant workers have been pretty robust. One thing we’ve been looking at in particular are the slips and falls among workers who have been wearing shoes that were advertised to be slip resistant. There’s no standard for slip resistant footwear, but we did find that employees who weren’t wearing it slipped three times as much as those who didn’t. That was from a CIE field study of 475 workers from across chains. There’s a scientific interest in developing a standard, but the question is, “Who develops it?” This data we’re generating says that at least slip resistant footwear is effective. We did the biomechanics, but the field studies help you test the reality of the conditions.

What are some of the most unusual results of the slips, trips and falls studies?

Interestingly, the average levels of conditions of slipperiness on restaurant floors weren’t that bad. The average coefficient of friction was between .4 and .8; we consider a solid floor that you wouldn’t slip too much on to be about a .5. But here’s where it gets interesting: If you took the most slippery restaurant floor and simply lowered the risk, improving its coefficient by classic housekeeping techniques like removing grease, oil, water and contaminants, you could improve the coefficient of friction by fivefold.

We found that simply training people to use their materials could have an effect. Many restaurants are now using enzyme-based cleaners. But using very hot water actually neutralizes the effects of some enzymes, so the old rule – that hot water is better – doesn’t apply. When we issued recommendations that would have restaurants dispense the water at the right temperature for the cleaner, we found that they actually reported a lower workforce injury rate.

How were you able to get the results?

We set up an interactive voice response system, or they could use an Internet-based system, reporting in to us once a week on how they slipped, and which slips resulted in falls.

What’s in the works right now?

We have a few projects that are wrapping up in writing right now. For instance, a study on ladder injury cases was informed by a study we did. Before you can simulate things in a lab, you have to understand how people are getting injured. We’ve collaborated with the U.S. Consumer Product Safety Commission, the National Institute for Occupational Safety and Health, the Center for Construction Research and Training, and the Harvard School of Public Health to study the risk factors that can trigger falls from portable ladders. The study essentially revealed that most ladder injuries were happening when people were doing work on a ladder or attempting to do something while standing on a ladder — not while going up or coming down. This led to the simulations that the Research Institute’s Center for Physical Ergonomics is working on now, which measures the stability of people reaching at different heights from a ladder. One of the components of that study measures whether that old commonplace rule — the so-called “belt buckle rule” or “belly button rule,” which says that the top of the ladder should hit at your belly button — actually works. One of the reasons to watch this study is that the most frequent injury in a ladder-related event is a fracture, although fractures are some of the most infrequent work-related injuries. It tells us that the ladder cases are more severe than many others.

Are there projects on the drawing board you can talk about yet?

We have two projects that are especially interesting. We are working with data from Vietnam to study the injury risks of working multiple jobs. What tends to happen there is that people might have a family job, but then everything shuts down at harvest time so people can pitch in. As people switch jobs, they’re changing their risk profiles; the risk is most often coming from the secondary job. We’re looking at how those secondary jobs feed into the risks. Say I work as Joe Repairman; once I go to that secondary job, I’m changing my total working hours, I have sleep loss — you can see how the risk is shifting. Most of our systems in the U.S. still look at people like they have one circa-1950 General Motors job. Populations like contingent workers and immigrant workers just aren’t well accounted for. We’re hiring a demographer to strategically evaluate the changes in work over time. That’s our forward-thinking work.

We’re also doing the natural extensions to work we have already in progress. For instance, we are taking the results of those slips, trips, and falls studies from the fast food restaurants and considering what we call “limited service” restaurants - casual dining places - where you have employees on the floor, intermixed with customers, so there’s a higher risk of collision. We want to see if that scientific paradigm from the fast food study holds up, and what are the other risk factors involved.