Medium Density Fibreboard (MDF) is an engineered wood-based sheet material made by bonding together wood fibres with a synthetic resin adhesive. MDF is extremely versatile and can be machined and finished to a high standard. As a result, MDF has replaced solid timber as a low-cost alternative in a wide range of applications across industry.
The majority of MDF is mainly composed of softwood, although some brands may contain a higher percentage of temperate hardwood if this is locally available to the manufacturer. High levels of hardwood can be found in MDF board from outside the UK and Ireland.
The most common binder for boards intended for dry environments is urea-formaldehyde. Other binders may be used depending on the grade of board and its intended end-use. For example, melamine urea-formaldehyde, phenolic resins and polymeric diphenylmethane diisocyanate (PMDI) are generally used in boards that require an improved moisture resistance. PMDI binder is not formaldehyde-based and consequently does not emit any formaldehyde. The exact constituents of an MDF board will vary from product to product.
The atmosphere created by machining or sanding MDF board contains a mixture of softwood dust and hardwood dust (if it is present). In addition, there will also be free formaldehyde, dust particles onto which formaldehyde is adsorbed and potentially, the resin binder itself and its derivatives. However, the levels of free formaldehyde in boards made within the EU at levels of formaldehyde class E1 are thought to be insignificant. This is because at these levels the resin is fully reacted (polymerised) – see Q.4 & Q.5 for information on standards and classes.
Under current legislation softwood dust, hardwood dust and formaldehyde are considered to be hazardous to health. Both softwood and hardwood dusts are known to be respiratory sensitisers and may cause asthma and other respiratory problems. Hardwood dust can also cause a rare form of nasal cancer.
Formaldehyde is classified in the UK, and in the European Union as a carcinogen and it carries the hazard statement ‘suspected of causing cancer’.
Because of the additional presence of formaldehyde in MDF the simple precautions detailed in Q.7 and Q.8 should be followed.
Formaldehyde is a simple but essential organic chemical that occurs naturally in most forms of life, including people, some foods we eat and trees. All products made from wood will therefore emit some naturally occurring formaldehyde. It is widely used in the manufacture of numerous products including shampoos, plastics, carpets, clothing, resins and glues etc.
A range of materials found in the home or workplace may therefore release formaldehyde. The US Consumer Products Safety Commission provides the following information on formaldehyde on their website.
Formaldehyde is normally present at low levels, usually less than 0.03 ppm,(parts per million) in both outdoor and indoor air. The outdoor air in rural areas has lower concentrations while urban areas have higher concentrations. Residences or offices that contain products that release formaldehyde to the air can have formaldehyde levels of greater than 0.03 ppm. Products that may add formaldehyde to the air include particleboard used as flooring underlayment, shelving, furniture and cabinets; MDF in cabinets and furniture; hardwood plywood wall panels, and urea-formaldehyde foam used as insulation.
Similar levels are quoted in the World Health Organisation (WHO) report WHO guidelines for indoor air quality: selected pollutants, published in December 2010. This states for buildings, some of which contain wood based panels, ‘levels on the average are less than 0.05 mg/m3 (0.04ppm) in homes and about half that in public buildings’. It is important to note that these levels are from all sources, not just building products.
MDF boards manufactured in Europe for construction purposes must meet the appropriate European standards. These are BS EN 622-1:2003 Fibreboards-Specifications - Part 1: General requirements and BS EN 622-5:2009 Fibreboards - Specifications - Part 5: Requirements for dry process boards (MDF). There are two European formaldehyde classes, E1 and E2, depending on levels of formaldehyde emission measured. The release of formaldehyde from E1 boards is less than 0.1 ppm (parts per million) and for E2 boards it is between 0.1 ppm and 0.3 ppm.
In Europe, the majority of manufacturers produce only low emission boards. There are some boards available on the market with extremely low formaldehyde emissions and some with ‘no added formaldehyde’, for example those using formaldehyde free binders such as PMDI, i.e. these boards will only have the naturally occurring emissions from the wood itself. Manufacturers from outside Europe may however produce boards that have higher emissions.
Wood based panels, such as MDF, that are used in construction should be CE marked according to – Characteristics, evaluation of conformity and marking. In complying with this standard, formaldehyde levels will have to be tested on a regular basis and a class will have to be declared (E1 or E2).
Other than compliance with the Construction Products Directive via CE marking (soon to be superseded by the Construction Products Regulation), there are no regulatory compliance schemes in the UK for emissions of formaldehyde.
There are a limited number of third party labelling schemes that do operate in the UK which specify amongst other things, maximum formaldehyde limits as part of their requirements. Such schemes include BREEAM (Building Research Establishment Environmental Assessment Method) for the assessment of buildings and for furniture products and the Furniture Industry Research Association ’FIRA Gold’ scheme.
Around the world there are certification and labelling schemes for products that can be specific to formaldehyde release, such as the Californian Air Resources Board (CARB) scheme or other schemes where a range of emissions may be considered, such as the AgBB scheme in Germany.
HSE is not aware of any countries in the world where MDF is banned.
Employers have duties under the Control of Substances Hazardous to Health Regulations 2002 (COSHH) to control risks to employees’ health arising from work activities. This means they need to ensure exposures to wood dust and formaldehyde are kept as far below the Workplace Exposure Limits (WELs) as reasonably practicable.
WELs are the concentrations of hazardous material in the air averaged over a specified time period – called the Time Weighted Average (TWA).
Two periods are used, long-term (8 hours) and short-term (15 mins) – the long-term representing a working day and the short-term to help prevent effects such as eye irritation which may occur after only a few minutes exposure.
The WELs for hardwood dust, softwood dust and formaldehyde are expressed in the number of milligrams (mg) of material in one cubic metre of air (m3). Levels of formaldehyde are also expressed in parts per million (ppm). The current WELs are:
To control exposures, employers should follow the ‘hierarchy of control’ set out in the COSHH Regulations. This means:
RPE should not be used as the only means of control as it should complement other control measures such as a dust extraction system. Where you need to use RPE you should:
RPE comes in three types FFP1 (4x protection), FFP2 (10x protection) and FFP3 (20x protection).
FFP3 is the most advisable type to have if you are exposed to high levels of dust and one combined with an organic vapour filter will also provide protection against any formaldehyde vapours that are present.