giant Cypress

Dust thou breathe, and unto dust thou lungs shalt return

So here’s my real contribution to Safety Week 2010.

Dust. We all have it in our shops. It’s bad for our lungs. It’s not pleasant stuff, nor is it fun to think about and deal with. As a result, there’s a lot of sloppy thinking about dust, and a lot of discussion revolves around what a “safe” level of dust exposure might be for a woodworker, and decisions are then made on how much dust collection you need for your shop based on that level.

The problem is, there really isn’t a “safe” level of dust exposure. One factor that contributes to this train of thought is that there are various regulatory agencies here in the U.S. and abroad that have set limits regarding wood dust exposure in working environments. If the dust levels are below that limit, the working environment is in compliance with regulations. If the dust level is above that level, then that’s bad.

Where this sort of thinking goes awry is that to state that there is an acceptable limit on dust exposure leads many to erroneously believe that there is a step-like relationship between dust exposure and disease — that if you keep your exposure below some level, your health will be just fine, and you only have to worry once you go over that line. That’s just not the case.

In several studies on the health effects of wood dust exposure on woodworkers published in peer-reviewed medical journals, it was found that decreased lung function worsened with the length of exposure (time spent working in the industry). This indicates that there is a dose-response relationship for wood dust exposure and loss of lung function. In other words, the more dust you are exposed to, the worse your lung function gets. This means that there is no “safe” level of wood dust exposure. Once you start breathing it in, your lungs start to deteriorate.

I happen to be a pediatric oncologist as my day job, and there is an example that directly impacts my patients that hopefully will make this a little more clear. There is a chemotherapy drug called daunorubicin that we use for many pediatric cancers. A side effect of daunorubicin can be weakening of the heart muscle so that your heart will not be able to pump as effectively as it used to, and this can lead to heart failure. There is a dose of daunorubicin that is considered “safe”, but “safe” is not really an accurate term. I know that if I measure heart function in my patients as they get successive doses of daunorubicin, then I will be able to see a real decrease in the strength of their heart. Not so much that it will cause heart failure, but the difference will be there. I also know that for some patients, they will go into heart failure after only one dose of daunorubicin.

So the question is whether or not my patients have heart disease from exposure to “safe” levels of daunorubicin. If you only define disease in terms of having heart failure or not, then no, these kids will not have disease. But as a group all of them will have a measurable decrease in heart function compared to kids that did not receive this drug. So from that standpoint, these patients have diseased hearts.

Does it matter if my patients have decreased heart function, but not heart failure? It depends. These kids clearly have decreased reserve compared to normal kids. For a couch potato/Playstation playing kid, it probably won’t matter. On the other hand, I have taken care of teenage athletes who tell me that after their treatment is done, that they can’t perform at the same level they used to. Maybe it’s because their heart took a hit from daunorubicin, and this group of kids notice the difference because they put more stress on their heart. The thing I’m worried about is not what happens to these kids now, but 20-30 years from now, if it turns out that the damage done to their heart from daunorubicin gives them all heart failure in their 30’s-40’s.

Of course, I continue to use daunorubicin because the alternative is not treating the cancer, in which case the kid will die. But this is an extreme example.

Let’s go back to wood dust and lung function. Wood dust exposure causes a measurable decrease in lung function that is related to the amount of exposure. Again, to suggest that there is a “safe” level presupposes that there is some level of dust that you can breathe in that causes no harm. And again, this is not true. If you breathe in wood dust, measurable acute decreases in lung function can be demonstrated. If your definition of lung disease is limited to the presence or absence of pulmonary fibrosis, then one could say that one does not have lung disease. But like my cancer patients and their heart dysfunction due to daunorubicin, the bottom line is that your lungs can be affected by a single exposure to wood dust. And like my cancer patients, it might not matter now, but it may matter 20 years from now.

Given this information, I feel comfortable saying that wood dust exposure can cause lung disease and that given the dose-response behavior of this phenomenon that there is no “safe” dose. And from a lung function standpoint, I’m also comfortable saying that all who work in a woodworking environment will have some measurable lung dysfunction.

It all comes down to whether one is willing to take the risk or not. I, for one, am willing to take that risk, otherwise I wouldn’t have taken on woodworking as a hobby, nor would I have set up a workshop in what is probably the worst possible location from a dust control standpoint: a basement with no windows and no possibility of ventilation to the outside. But I also made sure that my dust collection and my air cleaning capacity are at a level that I am comfortable with, which is what we all should do. I would only stress that you should not think in terms of a “safe” level of dust when thinking about this. One does not need to stop woodworking to deal with wood dust, any more than one would need to stop driving because of the risk of dying in an accident.

That’s also one reason why I try to do as much with hand tools as possible. There’s a lot less dust that way.

And don’t worry. I’ll get back to wacko Japanese tool esoterica, I promise.