Wood based boards are used almost everywhere. Workers complain of the dust produced by the boards but few workers know what the boards are made of or the hazards.

Boards are categorised into three main groups, laminated boards, particle boards or fibre boards.

Laminates or wood particles are glued or bonded together by formaldehyde resins. Most boards will be glued by urea formaldehyde but exterior, "WBP", or marine quality boards will be glued by stronger glues, normally phenol formaldehyde or possibly resorcinol formaldehyde. Water resistant boards may have melamine mixed with the glue.

Rumours that medium density fibre board (MDF) is banned in the USA are untrue. Emissions of formaldehyde from board products are, however, regulated in the USA and Germany, and are expected to be regulated throughout the European Community (EC) in the future.

Formaldehyde emissions at work in the UK are controlled by standards set in the Control Of Substances Hazardous to Health Regulations (see factsheet Daily Hazard No. 24) and the occupational exposure standards set out in HSE Guidance note EH40.

In the UK, board manufacturers are advertising low formaldehyde or zero formaldehyde emission boards made to the stringent German "E1" standard. This appears to be because manufacturers feel the EC is very likely to adopt this standard in the future.

Some boards are finished with laminated plastic sheet (melamine), foil (PVC) or wood veneer. Boards may be treated with flame retardant chemicals.

Hazards

Polyurea resin, urea formaldehyde resin

Formaldehyde Resins are used to bond the constituent parts together (in some particleboards and all fibreboards). Irritant at low levels to eyes, mucous membranes, nose and throat. Can sensitise skin (dermatitis) and respiratory system (asthma and rhinitis). Increases risk of cancer. Some evidence of reproductive hazards and ability to damage a fetus. Formaldehyde resin continues to emit vapour after it has hardened. (See LHC factsheet, Formaldehyde, Daily Hazard 25).

Melamine

An eye, skin and mucous membrane irritant, causes dermatitis, and is an experimental carcinogen.

Paraffin and mineral wax

Petroleum derivatives which can cause dermatitis. If not solvent refined may contain small amounts of hazardous impurities such as benzene.

Wood dust

Hardwood dust can cause nasal cancer, with a small number of woods being directly implicated (beech, oak, redwood). All hardwood dusts have a UK Maximum Exposure Limit (MEL) of 5mg/m³. This is totally inadequate as the mucociliary escalator, the throat's natural defence, is severely impaired at 2mg/m³. Dust levels must therefore be kept as low as possible.

Inhaled soft wood dust, although not recognised as having the same potential hazard as hardwood, should be treated with caution. Respirable dust of any kind can irritate the respiratory system or interfere with mucociliary action.

A number of woods are irritants of the skin (Iroko, Keruing, Afromosia), the respiratory tract (Beech, Iroko, Maple) or the eyes (Yew, Teak, Satinwood). Some, such as Western Red Cedar, Iroko and Mahogany, cause allergic asthma. The HSE lists "hardwood" as a respiratory sensitiser.

Some woods are poisonous, such as Yew and Oleander which can cause nausea and malaise and affect the heart.

Large quantities of airborne wood dust in an enclosed space can cause an explosion. Some wood dusts will spontaneously combust on contact with certain oils or chemicals.

Pesticides

Timber may be sprayed with a pesticide when it is logged to prevent mould growth, or at any point on its journey from the forest to the workplace or home. Some boards may contain wood treated with pesticides bit it will be difficult to check this.

Mould

Moulds such as neurospora which grow on wood and board products can irritate the respiratory system and cause asthma.

VCM

When machined, PVC veneers can give off fumes of vinyl chloride monomer (VCM), a very potent cancer agent.

Combined effects

The combined effects of wood dust, formaldehyde or other substances, and any other hazards are not known. Effects of combined exposure will probably be greater than the sum of the parts, especially if dust has disabled the body's defence mechanisms.

Control of hazards

Hazards must be identified ('risk assessment') and eliminated or reduced before work starts, as demanded by COSHH (Control of Substances Hazardous to Health Regulations) and other legislation.

First ask if a safer material can be used. For instance, in erecting a wall would it be better to use blockwork or bricks with a plaster finish rather than board products, or where a floor is to be laid would it be better to use traditional wooden floor boards rather than a board product? Substitution should only be made if the new method presents either equal or less of a hazard than the original proposal.

If a board has to be used then low emission standard boards will reduce the formaldehyde hazard.

The work system must control dust and fumes from wood and glues, with dust well below the UK 5mg^-3 maximum.

In a factory or joinery shop, there should be a permanent mechanical ventilation system. Housekeeping methods must keep workshops free from dust and dust must be disposed of safely.

On a construction site or temporary workplace, cutting in the open air will reduce dust problems but not solve them. A portable dust extraction unit with a flexible hose should be fixed to the power tool. The extractor must meet British Standard BS 5415, which means it filters out 99.99% of dust particles gathered. But it may not pick up all the dust and a residue may remain airborne or settle. Respiratory protection will still be necessary. Residual dust should be cleaned afterwards using the hose of the extractor like a domestic vacuum cleaner.

Safety Representatives

Trade union safety representatives (see factsheet Daily Hazard 42) have rights of consultation and access to information in risk assessments made under COSHH and to information required in the safety plan under the new Construction (Design & Management) Regulations, which applies to large construction sites

Types of Wood based Boards

Laminated boards

By alternating the wood grain direction for each layer (laminate) and using very strong glues, high board strength and increased rigidity is achieved. Laminated boards fall into three main groups.

Plywood
Thin layers of wood (veneers) stuck together. The number and thickness of veneers is variable. Blockboard
Two veneers which sandwich many strips of wood of equal thickness. Laminboard
Similar to blockboard but the strips of wood tend to be of a smaller size and a different gluing method is used.

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Particle boards

Made from different types of cellulose based material. The raw material is processed to produce particles of varying size and bonded with a resin binder. The main types are:

Wood chipboard
Chips from either soft or hardwood, or a combination of both. Different grades of chipboard are made by varying particle size, distribution and bonding agent type and quantity. Flaxboard
Made from linen particles. Has added hazard of the disease byssinosis. Bagasse Board
Made from sugar cane. Has the added hazard of the disease bagassosis. Wafer board
Made from larger wood flakes. Oriented strand board
Is a three layer wafer board, with opposing grain as in plywood. Cement bonded particleboard
Wood particles bonded together with either Portland or magnesite cement. (See factsheet Daily Hazard No. 17).

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Fibre boards

Types of fibreboard are differentiated by the size and type of wood fibres used, the method of drying, bonding agent (where used) and the method of pressing into shape.

Hardboard
Fibres suspended in water are usually bonded by resins from the wood itself in a roller press at high temperature and pressure. Manufactured resins and drying oils can be added to mix. Medium board (MBL and MBH) and Soft Board (SB)
Similar to hardboard but manufactured at varying pressures giving varying density and strength. Softboards are sometimes impregnated with bitumen as an extra bond and for limited waterproofing. Medium density fibreboard (MDF)
MDF is manufactured by a dry process at lower pressing temperatures than for hardboard which renders the natural glues/resins in wood ineffective. A manufactured bonding agent or resin is used instead. Varying density boards with different finishes are made for different end uses. MDF is made into mouldings such as skirting board, architrave etc.

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