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Popular Woodworking Magazine, 2011.
When the debate over table saw safety gets heated, numbers are brought out to bolster one side or the other. This happened the other day when USA Today published the headline: “CPSC wants to stop daily table saw amputations,” followed by a mention in the second paragraph of 10 amputations a day. That sounds pretty serious, maybe somebody should do something about it. Or maybe we should
look at where these numbers come from, how they are used, and how they fit in the big picture of modern life.
The source of these statistics is the National Electronic Injury Surveillance System. NEISS is a database used by the Consumer Product
Safety Commission to track injuries caused by products ranging from abrasive cleaners to zip lines. For any safety issue, we as individuals and as a society need to do a cost/benefit analysis. As much as we would like to keep anyone from ever getting hurt, the value of using anything needs to be compared to the risks involved and the costs of eliminating those risks, and if that isn’t possible the cost of minimizing them. As individuals, we can eliminate risks entirely by choosing not to use something. Beyond the personal level, decisions become far more complicated and difficult.
There are so many things that can hurt us in so many ways that even assessing the risks is an expensive and daunting task. Rather than record every instance of every injury to every individual in the United States, the NEISS uses a small sample of cases from about 100 emergency rooms to project statistics to the population at large. Doctors in these ERs make notes and enter product, injury, body part and diagnostic codes and the results are weighted and projected. It works in a similar way to exit polls during elections; a small sample that’s easy to manage and count is examined and applied to the entire population. It’s a useful tool, but it isn’t perfect and the numbers that come out at the far end are predictions, not facts.
Let’s look at the table saw amputation numbers for 2009, the latest year with available statistics. If you want to follow along at home, the NEISS database is online, and the product code for table saws is 841. The number of samples that mention table saws is 783, and the database suggests that this reflects a total of 35,624 injuries. If the phrase “table saw” appears anywhere in the doctors notes or the product code, the accident is counted as a “table saw accident”. There aren’t many of them, but the numbers include instances where somebody fell off a ladder and hit his head on a table saw, or someone hurt their back moving a table saw.
The same effect occurs if the word “amputation” appears. In 2009 for example, 117 reported cases were projected to arrive at an estimate of 4211 finger amputations. A look at the actual notes reveals that four cases weren’t table saws after all, and six were near amputations. That’s only ten instances, but ten out of 117 is 8.5 percent. The projected numbers are weighted, so you can’t simply multiply, but you can safely say that the total number is overstated.
When the word amputation appears, it’s often followed by a phrase such as “life-altering” that was quoted in the USA Today story. I don’t want to minimize anyone’s pain or suffering, but analyzing injuries and possible solutions is by nature a heartless, dollars and cents exercise. Mangle your hand at work, and your disability claim will be based on how many parts of how many fingers are gone. Losing a thumb, means losing the ability to grip and that loss will make many things more difficult for the rest of your life. That is indeed life-changing.
Of the table saw amputation cases from 2009, about half involved the loss of one or more complete digits. The largest segment of that portion, 37 percent of the total amputations, were one finger or one thumb. Of the remainder, the listings were almost evenly divided between partial amputations, or the loss of a fingertip. In the cases listed as amputations, 23 per cent involved the loss of the tip of one digit. Losing the tip of a pinky will hurt for a while, but unless you’re a musician, it won’t make much difference in your overall abilities or the quality of your life.
With an estimating system such as the NEISS, there is a confidence number assigned that reflects the probable accuracy of the projected numbers. If you were to count every case that occurred in a given year, you could be quite sure of the numbers. The smaller the sample, the less accurate the results, so the confidence number reflects a greater possible variation. The database will reach a point where the number of actual reports is too small to give a reliable projection. When the sample is that small, the NEISS database won’t make an estimate of overall cases. In cases involving commercial woodworking operations, saw operators under 18 years of age or schools, there aren’t enough samples in the database to project a total number of accidents.
This doesn’t mean that cabinetmakers on the job or high school kids in shop class don’t get injured. But it does mean that the number is quite small, compared to the total number of injuries. And where does the number of table saw accidents, particularly amputations of fingers fit in the big picture of the population of table saw users, and in society as a whole? There isn’t a reliable count of table saws in use in the United States. Estimates range between 6 million and 10 million. If we pick from the middle and use 8 million, the estimates suggest that in any particular year, about one table saw in 229 will be in an accident that sends someone to the emergency room, and that one in about 2,076 saws will result in an accident with an amputation as the result. The number of saws in accidents that result in the complete loss of one or more digits is about half that, or one in 4,152.
In the context of the general population of 310 million Americans, about one in 9,000 will go to the emergency room in any given year after tangling with their table saw, one in 80,000 will have a medical report that lists the word “amputation” and one in 160,000 will lose one or more fingers or a thumb. If you, or someone close to you are that “one” you’ll look at this differently than everyone else. For those charged with writing rules and regulations, the task will be to decide if this is a problem that happens often enough for action.
While reviewing the numbers, I wondered about how the figures on table saws compared to other items. In 2009, there was an estimated total of about 22,000 finger amputations due to accidents of all kinds in the United States. There is no doubt that table saws are a significant portion of that number. Once again, the database sample is too small to provide estimates for many other items, but there was one item that caused about the same number of finger amputations as table saws, and about 10 times the number of total accidents. In addition, this product caused enough finger amputations among children under the age of 18 to generate an
estimate of total occurrences, about 45 percent of the total. Five children a day are enduring finger amputations due to this hazard. The
name of this product? The door.
Table saw injuries are a serious matter, and many if not most, could be prevented. The Consumer Product Safety Commission is considering rules that might help in reducing the number and the severity of these injuries. These rules would likely change the number and types of choices we have, and they would almost certainly raise the price of the tool that is central in most of our shops. There are two big questions here: Are table saw injuries prevalent enough to require government action and are there other solutions?
This post is part of a series of articles that will look at this issue in depth. I’ll do my best to put my opinions, emotions and agendas on the shelf so as a group, woodworkers will have better information about the frequency, causes and possible solutions to table saw injuries. In upcoming posts I’ll be reporting on the real costs of these injuries, the history of this issue from all sides, and most important what woodworkers tend to do to injure themselves and how they can prevent those injuries. Stay tuned, and sign up for the RSS feed to receive these articles as they appear. Your comments are welcome, or you can send me email.
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