Are we playing with fibre?

Builders have known about the dangers of MDF for years. Jeff Howell gives some professional advice

In The past week Medium Density Fibreboard, or MDF, a common building material popular with do-it-yourself enthusiasts, has come under scrutiny. This follows growing doubts among academics and trade unionists about its safety. It has been described as "vile and pernicious" and "the asbestos of the Nineties". There have been calls for the material to be taken out of the DIY sector, outlawed for use in bedroom furniture, or even banned outright. The British authorities have been criticised for allowing occupational exposure levels 20 times greater than those of other countries. Should we be concerned?

MDF, a strong, smooth timber board material, has been manufactured for more than 30 years. It is prized by carpenters and furniture makers for its strength and for the smooth finish to which it can be worked, though there have long been reservations about the health implications of the formaldehyde resins used to bond all timber board materials and the dust generated when they are machined.

However, it was not clear whether MDF posed more of a problem than any other timber product until the early 1990s, when workers in factories producing MDF were found to be suffering from acute health problems. Subsequent research pinpointed the combination of the fine dust particles, capable of being breathed deep into the lungs, and their coating with urea formaldehyde - a suspected carcinogen - as the culprit.

Since then there have been moves to treat MDF with greater caution. The very small size of the dust particles given off by the material means that conventional dust masks are ineffective; workshops using MDF are recommended to use air extraction equipment and workers need to wear special fine filter masks. Exposure limits for formaldehyde were also cut, to 0.5 parts per million (ppm) in the United States, and 0.1 ppm in Sweden and Germany. Recommended limits in the UK remain 20 times higher than this, at 2 ppm.

The outcry that has brought the MDF hazard to public attention has been instigated by workers in the theatre, film and exhibitions industry. MDF is widely used for stage and film scenery, which involves carpenters working in less-than-perfect conditions. Roy Lockett, deputy general secretary of the Broadcasting, Entertainment, Cinematographic and Theatre Union, BECTU, made a blistering attack on MDF at this year's TUC conference, in which he called it the "asbestos of the Nineties". Mr Lockett is convinced that using MDF is damaging his members' health, and is furious that the health and safety conditions in British industry are lagging behind the rest of Europe.

As far as the dust problem is concerned, this may not be too difficult to achieve. Suitable breathing equipment is available, and most power tools can be adapted for dust extraction, at a price. The formaldehyde problem remains, however; formaldehyde is a colourless gas with a strong pungent odour that has been linked with a number of health concerns. The difficulty is that formaldehyde continues to be emitted from the MDF for some months after manufacture - the so-called out-gassing problem. One possibility is for MDF to be stored for some time before use, until out-gassing has fallen to an acceptable level.

But a more satisfactory solution is available; MDF bonded with safer resins is manufactured, and complies with the stringent German "E1" safety standard. Mick Holder, an occupational health worker with the London Hazards Centre, says: "Safer building boards are available, but they are more expensive to produce. Manufacturers will not change unless they are forced to do so by legislation."

Dr Andrew Watterson, of De Montfort University, has investigated the hazards of MDF and is concerned that the material continues to be used despite the safety issue.

Few home-improvement enthusiasts are likely to use the material regularly enough for health problems to become an issue, although people with multiple chemical sensitivities or allergies can be badly affected by even low levels of formaldehyde or wood dust.

Any MDF furniture or fittings already in the home can probably be safely left in place, as out-gassing of the free formaldehyde will already have taken place. Certainly, MDF products seem to represent a far lower risk in the home than, say, timber treatment chemicals, which are designed to be toxic and long-lasting.