Well, it's on just about every sub-flooring set I ever was on.......ever notice the carps are the only one wearing a mask?Medium-density fiber board (MDF) became a common woodworking material in the 1980s. But studies of its toxic properties are changing the way it is used.
WHAT IS MDF? Most MDF is made of wood fibers derived from defibrated (ground) wood chips or other cellulosic materials and urea-formaldehyde or phenol-formaldehyde resins. MDF is commonly composed of 85-100% softwood (e.g., pine), and 0-15% hardwood (e.g., beech, oak). Most MDF contains 8-18% urea formaldehyde resin, which is 2-3 times more resin than normal particle board.
As a result, MDF releases more formaldehyde than particle board or plywood because it contains more formaldehyde resins.
CALIFORNIA RULES ON MDF. On March 7, 2008, the California Air Resources Board filed a rulemaking aimed at reducing formaldehyde emissions from wood products by 60%. The order will be phased in starting in 2009 and will be fully implemented by 2012. The 2012 rules would virtually eliminate the addition of formaldehyde-containing adhesives during manufacture of composition products for finished goods.
The new rule sets emissions standards that are applicable to hardwood plywood, particle board and MDF that is sold, supplied, offered for sale, or manufactured for sale in California as ‘finished goods.” Finished goods are defined to include any new or unused product such as kitchen cabinets, shelving, countertops and ready-to-assemble furniture.
The California rule does not apply to composite wood panels or the raw materials. All indications are that production of formaldehyde-containing raw materials probably will cease because there will be no major markets for the formaldehyde resin products by 2012.
The law is aimed at protecting consumers of finished goods in their homes and businesses, not the carpenters who build the furniture, although it is the carpenter who is at greatest risk from formaldehyde exposure.
WHY REGULATE FORMALDEHYDE? In support of the new California rule, state regulated and public health groups cited studies linking formaldehyde to workplace asthma, increased cases of asthma and allergies in children exposed at home, and cancer.
In 2004, the International Agency for Research on Cancer formally linked formaldehyde to throat cancer in humans. Other agencies that consider formaldehyde a carcinogen include the Environmental Protection Agency (EPA), the Occupational Safety and Health Administration (OSHA), the National Toxicology Program, the National Institute for Occupational Safety and Health (NIOSH), the American Conference of Governmental Industrial Hygienists (ACGIH), and the various European health agencies. It is generally accepted that formaldehyde is a carcinogen.
STUDIES OF WORKERS. Dust generated by machining MDF is known to cause eye, nose, throat and skin irritation. In one 1991 Swedish study, 94% of the workers machining MDF complained of nasal irritation.1
Then in 2004, a Finnish study compared data from 3 small furniture factories that used beech hardwood MDF with data from two factories that used mainly natural wood (birch and pine).2 Eye, nose, throat, and skin symptoms were common in both exposed groups, but the MDF group had significantly more nasal and eye symptoms than the natural wood dust groups.
The authors of the Finnish study also noted that, unlike wood dust, the fine MDF dust particles are inhaled into the respiratory tract and release formaldehyde directly to the tissues there. The authors suggest that the occupational limits for both the dust and the formaldehyde gas should be tightened.
It is also notable that these studies were done in Scandinavian countries. There don’t appear to be a lot of studies here in the United States. Searching the internet for studies also is confusing. Some of the earlier studies say formaldehyde is not a problem until you look at the outdated standards they used to determine “safe” formaldehyde levels. Many papers which look like studies are actually promotional material from manufacturers.
WORKPLACE REGULATIONS. There are already OSHA permissible exposure limits (PELs) and ACGIH threshold limit values (TLVs) which limit the amount of formaldehyde which should be in the air in the workplace.
The Federal OSHA standards are the highest levels allowed in the Western World and generally considered unprotective. The other standards (see table) are all better for workers. In order to comply with any of these standards, employers must test the workplace air repeatedly to insure the levels are within the limits. This doesn’t usually happen in our business.
AGENCY- STANDARD 8 hour limit (ppm)* ceiling limit ** (ppm)*
OSHA - PEL 0.75
ACGIH - TLV 0.3
NIOSH - REL 0.016
EUROPEAN - MAK 0.3
* ppm = parts per million ** instantaneous limit not to be exceeded at any time
If employers or designers insist on using MDF, then formaldehyde-free MDF can be purchased at a somewhat higher cost (e.g., Medex and Medite II3 made with polyurea resin). Due to the fact that workers have clearly observed that all types of MDF release more and finer dusts during machining than other wood products, employers must provide an OSHA-compliant respiratory protection program with medical certification, fit-testing and training and provide local exhaust dust control.
FOOTNOTES
1. Holmström, M., et. al.: Symptoms, Airway physiology and histology of workers exposed to medium-density fiber board. Scand. J. Work Environ. Health 17:409-413 (1991)
2. Eero Priha, et. al.: Exposure to and Acute Effects of Medium-Density Fiber Board Dust. Jour. Occup. & Envir. Hygiene, 1:738-744 (2004)
3. Google “Medite Corporation.”
