As I stated in my twin cradle series, I used MDF to build my templates. I have tried not to use a lot of MDF in my shop, mostly because my wife hates the stuff and gives me lectures every time I mention the three letters.
My wife, who we’ll call “Ellen” (since that’s her name), is a production designer for film and television. That means she designs the scenery and deals with the carpentry shops that build it. Most of the scenic shops will not use MDF and the unions strongly discourage it’s use due to the health concerns. I was shocked to read a recent article in Fine Woodworking, that while it recommended using dust protection, it did not mention anything regarding any potential health risks. Pretty irresponsible. Present the information and let the reader decide, but please don’t ignore the obvious potential risks.
I found it frustrating, however, that this commonly used, extremely flat and useful material was getting such a bad wrap (even if not in FN). So I decided I needed to do my homework and find out what the story really is. So here is what I found:
MDF or Medium-Density Fiberboard is made from wood fibers glued together under heat and pressure. It is commonly used in mass produced furniture, for a veneering substrate, as well as moulding for kitchens and baths, plus you and I like to use it for templates and shop jigs.
It has many qualities that make it an ideal replacement for plywood or particle board. It is dense, flat, stiff, has no knots and is easily machined. Unlike most plywoods, MDF also contains no voids and will deliver sharp edges without tearout. However, MDF is not entirely isotropic, since the fibers are pressed tight together throughout the sheet. Like natural wood, MDF may split when woodscrews are installed without pilot holes, it can however be glued, doweled or laminated, but smooth shank nails do not hold well.
In spite of its many positives, medium density fiberboard does have some drawbacks. Its comparatively high density makes it heavy and difficult to move. It dulls more quickly than other wood options, and it is somewhat susceptible to chipping and denting. More seriously, the glue used to bind the wood fibers in MDF contains urea formaldehyde, which the US Environmental Protection Agency classifies as a probable carcinogen. The cancer-causer is released in sawdust particles when MDF is machined, and these can quite dangerous to inhale in large quantities. This gives rise to health concerns for workers who produce it and cut it, but these risks can be minimized by wearing goggles and masks and by using saws that cut the board more cleanly. For the average person working with MDF, sawdust can be avoided by gluing pieces together with wood glue instead of nailing them. Alternatively, boards of MDF can be connected with wood-joints or pins. Yet, even when it is not being cut, MDF is constantly releasing urea formaldehyde at a slow rate, so it is important that its entire surface be coated in a finish to trap in the poisonous chemical. Wax and oil finishes are acceptable, but the most effective seal is an even layer of paint. Properly coated, well-maintained MDF poses no health threat, but consumers should be aware of the risk of cancer from unfinished products. 1
MDF Was developed in the US in the Early 1960’s based on the design of Hardboard, a similar product invented by William Mason in 1925. Mason Attempted to turn woodchips discarded by Lumber mills into affordable insulation, but when he forgot to turn down his machine one evening, his machine continued working, turning the wood chips into a thin durable sheet. 2.
Perhaps MDF should be considered one of the greenest products in woodworking as it is all recycled materials (or perhaps not due to the use of Rainforest wood!). The most common raw materials are wood chips and saw dust, but some manufacturers add other materials such as corn silk and wasted paper such as telephone directories, old newspapers, and cardboard. The raw material that goes into MDF must do through a process before it is able to be used. A large magnet is used to remove any impurities and separate the material by size. The materials are then compressed to remove water and then fed into a refiner, which shreds them into small pieces. Resin is then added to help the fibers bond. The mixture is put into a very large dryer and heated by gas or oil. This dry combination is run through a drum compressor equipped with computerized controls to guarantee proper density and strength. The resulting pieces are then cut to the correct sizes with an industrial saw while they are still warm. 2.
Here is a cool video on how MDF is made.
Now for the Health Concerns:
MDF has a reputation for it’s health risks. The International Agency for Research on Cancer (IARC) classified all wood dust as a human carcinogen and the substantial dust produced by MDF has been connected to other health problems such as asthma. One of the affordable resins used as a binding agent in MDF is urea-formaldehyde. Formaldehyde is also classified as a likely carcinogen on the Agency for Toxic Substances and Disease Registry. Prolonged exposure to formaldehyde can result in cancer, including nasal and sinus cancer and leukemia. These cancers take several years or decades to develop (usually 10-15 years). Working eight hours daily for 40 years at the level of the government standard would give you a risk of about 2 in a thousand for getting cancer (based on the OSHA standard of 0.75 ppm and 1991 USEPA estimates). When formaldehyde is present in the air, some individuals may experience adverse effects such as watery eyes; burning sensations in the eyes, nose, and throat; coughing; wheezing; nausea; and skin irritation. Repeated exposure to formaldehyde may cause bronchitis or skin and asthma-like allergy. Some people are very sensitive to formaldehyde, whereas others have no reaction to the same level of exposure. There is limited evidence that formaldehyde may damage the developing fetus and affect female fertility.
The OSHA Formaldehyde Standard requires employers to conduct air monitoring or have other documentation that shows exposure limits will not be exceeded. Workers’ average daily and peak exposure must be below 0.75 parts per million (ppm) and the peak exposure must be below 2 ppm. If greater than 0.1 ppm in the air is expected, then the employer must enforce labeling, education and Material Safety Data Sheet (MSDS) requirements of the OSHA Hazard Communications standard. OSHA does not have a wood dust or urea formaldehyde standard. OSHA may rely on The American Conference of Governmental and Industrial Hygienists (ACGIH) guidelines for wood dust when evaluating a wood dust hazard. ACGIH recommends average exposure to inhalable wood dust be kept below 1 milligram per cubic meter (mg/m3); and half that amount for western red cedar. 3.
Precautions and Options:
What are the recommended special precautions should you take while handling MDF? 1) always wear a protective face mask such as a respirator 2) always wear eye protection, 3) Only saw in a well ventilated room with adequate dust collection, 4) wear gloves to avoid formaldehyde coming in contact with the skin. Does any of this stuff sound familiar? Don’t we do that already in our shops? Well maybe not the glove/formaldehyde thing…but you get the point. It’s all common sense. Remember: Sawdust is a known carcinogen! If your not comfortable using the stuff, then don’t, or at least find a product that you are comfortable with. Some companies, especially due to California law, are replacing the resins with phenolic resins, such as Medex or Ultra Stock-Free. Check em out and see where you can source them locally.
So, if you haven’t figured it out by now: I’m no doctor, no OSHA consultant, and no chemical engineer. I don’t pretend to have all the answers, I’m just searching for them and sharing what I’ve found.This is one of those topics, like SawStop, that could be debated for days in the forums. The truth is, even as a hobbyist, you need to educate yourself and take what steps you feel are necessary for a healthy work environment. Like anything we use in the shop, it is important to know the risks and potential hazards. People work in extremely dangerous work environments every day, but they are safe when they take the appropriate precautions.
Some other options for MDF with no added urea formaldehyde: