Q) My husband is a keen DIYer, and has been making new cabinets for our lounge out of MDF. I've heard that MDF is dangerous, and I'm concerned not just for his health, but also for the heath of the rest of the family. He says there's nothing to worry about. Who is right?-E.B., Essex
A) AMDF (medium-density fibreboard) is a widely used cheap alternative to wood that is easily machined and sanded. However, the dust it produces has been fingered as the cause of health problems such as asthma and even cancer. Some even callit the 'new asbestos', but officialdom says that's nonsense.
What are the facts? MDF is mostly finely chopped waste-wood fibres that have been pressed and glued together into flat sheets of variable thicknesses. You'll now find MDF in practically every home-as kitchen units, cabinets, skirting boards and architraves. When painted, it's indistinguishable from machined wood.
However, since MDF first came onto the market 20 years ago, carpenters have complained about the large amount of dust it creates when sawn or sanded. In Australia, factories that routinely work with MDF have been tested for dust production, and the results show that working with MDF does indeed produce comparatively high levels of dust. Indeed, sanding MDF creates five times more dust than with wood, and often with finer particles.
Is MDF harmful to health? No, says the UK's Health & Safety Executive (HSE), claiming there's no evidence of any specific health hazards. Yet, over a decade ago, the Inter-national Agency for Research on Cancer (IARC) classified wood dust as a human carcinogen after a score of studies had shown that joinery industry workers had an increased rate of nasopharyngeal carcinoma, a rare cancer of thenose and throat (IARC Monogr Eval Carcinog Risks Hum, 1995; 62: 35-215). So, the HSE does impose the same exposure limits on MDF dust as they do on wood dust-5 mg of dust/m3.
Nevertheless, in practice, this may be difficult to achieve. The University of Paisley in Scotland found that MDF dust levels in a typical joinery peaked at over 90 mg/m3 (Int J Environ Health Res, 2004; 14: 323-6).
Another reason to doubt that MDF is equivalent to ordinary wood in terms of safety is that, unlike wood, MDF contains large amounts of formaldehyde. The binder usedin MDF is called 'ureaformaldehyde', the vapour of which is toxic. At the very least, formaldehyde is an irritant to the eyes and throat. But studies of industrial workers have also shown that the vapour can cause myeloid leukaemia and cancer of the nose and throat, prostate, lung and pancreas (Am J Epidemiol, 2004; 159: 1117-30). What's more worrying about MDF is that the formaldehyde is attached to the dust, which is not easily expelled from the respiratory tract and, instead, may become lodged in the nose and lungs.
As yet, there's no hard evidence that MDF itself is more harmful than ordinary wood, but there are already straws in the wind. One study in manufactured-timber workers inNew Zealand found that workers were nearly twice as likely to have asthma as the general population, and four times more likely to suffer if exposed to high levels of formaldehyde (Ann Occup Hyg, 2003; 47: 287-95). When French doctors carried out a similar analysis-adjusting for wood-dust health effects-using pooled data from timber-factory workers across seven countries, they found a threefold increase in sinonasal cancer, all directly attributable to formaldehyde (Cancer Causes Control, 2002; 13: 147-57).
There's now growing concern that the 5 mg/m3 safety limits of MDF dust exposure is too low. A recent report by Finnish researchers found high levels of nasal, eye and skin symptoms among MDF workers-even in those exposed to a mere 1.2 mg/m3 (J Occup Environ Hygiene, 2004; 1: 738-44).
Clearly, this is not good news for DIY enthusiasts like your husband, but there's probably no reason to panic for those who work with MDF only occasionally. However, you and your husband may nonetheless wish to take some sensible precautions (see box below).
It's too early to tell if MDF is truly the new asbestos, in part because cancers such as asbestosis or mesothelioma (coalminer's disease) usually take decades to show up. Wood-dust cancers are the same. Sinonasal cancer has been found to have a long 'latency period'-as much as 48 years in at least one case (Rhinology, 2000; 38: 204-5). Nevertheless, given the strong evidence of MDF's carcinogenic potential, your husband may prefer to work with plain old wood whenever the DIY urge takes him.
Be safe with MDF
- Never work on MDF inside the house, but use a carport or open garage instead
- Hose the dust down afterwards
- If you have a workshop, use an extractor fan very close to where you're working
- Wear a good-quality, well-fitting dust mask; unlike sawdust, MDF dust is extremely fine
- Keep others away while you are working
- Paint all naked MDF panels to prevent formaldehyde outgassing
- After installation inside your home, ventilate for up to three days. If your house appears to be particularly full of outgassing materials, do a 'bake-out': heat it up to a high temperature, usually 38 degrees C
(100 degrees F), to speed up the release of toxic chemicals, while keeping the windows open and ventilation system running at full capacity. Repeat this process for two or three days.