Formaldehyde indoor products

Progress in quality control and in basic understanding of the physical and chemical factors affecting formaldehyde emission processes have made it possible to predict formaldehyde indoor air levels for most use conditions. Progress in manufacturing techniques and implementation of new technology have reduced formaldehyde emission so much that UF-bonded wood products can now be used in almost all applications without indoor air concentrations exceeding 0.I pp. 

During the past 15 years formaldehyde exposures and emission limits have been significantly lowered. Occuptional threshold limits are now 1.0 ppm or lower in most countries, and actual industrial exposures are almost always half of this value or less. Indoor air standards of 0.1 ppm are now contemplated in several nations, following established procedures for correlating occupational levels of toxic chemicals with ambient air levels. Furthermore, emission standards for UF-bonded wood products have been developed that allow the prediction of formaldehyde levels under various product use conditions before formaldehyde emitting products are installed. 

Indoor Air Quality Control Techniques Radon, Formaldehyde, Combustion Products, Eds., W.J. Fisk, R.K. Spencer, D.T. Grimsrud, EJ. Offerman, B. Pedersen and R. Sextro, Noyes Data Corporation, Park Ridge, NJ, USA, 1987. 

At one time urea-formaldehyde was used extensively in the manufacture of plywood but the product is today less important than heretofore. For this purpose a resin (typically U-F molar ratio 1 1.8)-hardener mixture is coated on to wood veneers which are plied together and pressed at 95-110°C under pressure at 200-800 Ibf/in (1.38-5.52 MPa). U-F resin-bonded plywood is suitable for indoor application but is generally unsuitable for outdoor work where phenol-formaldehyde, resorcinol-fonnaldehyde or melamine modified resins are more suitable. 

Occupational and environmental exposure to chemicals can take place both indoors and outdoors. Occupational exposure is caused by the chemicals that are used and produced indoors in industrial plants, whereas nonoccupa-tional (and occupational nonindustrial) indoor exposure is mainly caused by products. Toluene in printing plants and styrene in the reinforced plastic industry are typical examples of the two types of industrial occupational exposures. Products containing styrene polymers may release the styrene monomer into indoor air in the nonindustrial environment for a long time. Formaldehyde is another typical indoor pollutant. The source of formaldehyde is the resins used in the production process. During accidents, occupational and environmental exposures may occur simultaneously. Years ago, dioxin was formed as a byproduct of production of phenoxy acid herbicides. An explosion in a factory in... 

Developments in glued laminated structures and panel products such as plywood and chipboard raises the question of the durability of adhesives as well as wood. Urea-formaldehyde adhesives are most commonly used for indoor components. For exterior use, resorcinol adhesives are used for assembly work, whilst phenolic, tannin and melamine/urea adhesives are used for manufactured wood products. Urea and casein adhesives can give good outdoor service if protected with well-maintained surface finishes. Assembly failures of adhesives caused by exudates from some timber species can be avoided by freshly sanding the surfaces before glue application. 

Volatile organic chemicals are released during a number of industrial and manufacturing operations. For example, 1,3-butadiene is an important raw material in the manufacture of synthetic rubber During manufacture small amounts of the chemical escape into the air. Formaldehyde is a raw material used in the manufacture of a variety of building materials, such as phenol-formaldehyde and melamine resins. Many household products, such as cleaning products, varnishes, waxes, paints, and organic solvents, contain VOCs, which vaporize and escape easily into the atmosphere when they are used. For this reason, VOCs often build up indoors. 

HVAC Materials Ventilation duct liners also react with ozone forming formaldehyde, acetone and C5—Ci0 aldehydes. Morrison et al. (1998) subjected new and used duct liners, air filters, sealants, sheet metal and other HVAC materials to ozone in small chambers. They observed secondary emissions of C5—Ci0 aldehydes from a new duct liner, a neoprene gasket and duct sealants. They predicted that secondary emissions from these materials could increase indoor aldehyde concentrations to levels comparable with odor thresholds. As will be discussed later, soiled HVAC materials also generate secondary products. 

In ambient air, the primary removal mechanism for acrolein is predicted to be reaction with photochemically generated hydroxyl radicals (half-life 15-20 hours). Products of this reaction include carbon monoxide, formaldehyde, and glycolaldehyde. In the presence of nitrogen oxides, peroxynitrate and nitric acid are also formed. Small amounts of acrolein may also be removed from the atmosphere in precipitation. Insufficient data are available to predict the fate of acrolein in indoor air. In water, small amounts of acrolein may be removed by volatilization (half-life 23 hours from a model river 1 m deep), aerobic biodegradation, or reversible hydration to 0-hydroxypropionaldehyde, which subsequently biodegrades. Half-lives less than 1-3 days for small amounts of acrolein in surface water have been observed. When highly concentrated amounts of acrolein are released or spilled into water, this compound may polymerize by oxidation or hydration processes. In soil, acrolein is expected to be subject to the same removal processes as in water. 

Formaldehyde is an important industrial chemical for the production of synthetic resins. These resins are applied primarily as adhesives in the production of a large number of consumer products and construction materials that end up in homes. Other sources of indoor formaldehyde include urea-formaldehyde foam insulation, textile additives, as well as combustion and tobacco smoke. Formaldehyde is one of the many VOCs present indoors and it is considered the most abundant among them. It has important toxic effects in the 0.1-5 ppm concentration range. 

Some VOCs can be malodorous pollutants, sensory irritants, or hazardous air pollutants. Hazardous VOC air pollutants include acetaldehyde, benzene, carbon tetrachloride, chloroform, ethylbenzene, formaldehyde, hexane, methylene chloride, naphthalene, paradichlorobenzene, pesticides (biocides), styrene, tetrachloroethylene, toluene, trichloroethylene, and xylenes. They are found in essentially all indoor locations, released by off gassing from numerous sources, such as construction and decorating materials, consumer products, paints, paint removers, furnishings, carpets, and from combustion of wood, kerosene, and tobacco. While more than 500 VOCs have... 

Significant quantities for formaldehyde are consumed in the production of other resins or polymers such as polyacetyls, melamine resins, and alkyl resins. Formaldehyde is also used in rubber/latex manufacture, textile treatment other than permanent-press fabrics, dye manufacture and use, photoprocessing chemicals, laboratory fixatives, embalming fluids, disinfectants, and preservatives. Formaldehyde can also be emitted by combustion appliances, wood fires, tobacco smoke, and in indoor chemistry. 

Environmental scientists have generally defined exposure and health effects on a pollutant-by-pollutant basis. In indoor environments these include multiple air pollutants (i.e., 20-50 different VOCs, including formaldehyde and other aldehydes), microbial products (including spores, cell fragments, viable organisms, and secretion products), and reactive agents such as ozone, fibers, and others. The American Thoracic Society defined six important categories listed in Table 4. 

These compounds may combine with other indoor environmental chemicals to produce additive and synergistic effects. For example, the combination of very low levels of formaldehyde (e.g., from tobacco) and terpenes (e.g., from cleaning products) produce dyspnea and other respiratory problems not observed from such levels of formaldehyde and terpenes alone. I19l... 

There are numerous sources of formaldehyde in indoor air. It is widely used as a preservative in products that are subject to attack by microorganisms. These include many household products, among which are papers, cleaning products, furnishings, insulations, and cosmetics. 31 Table 12.6 lists indoor use products known to contain formaldehyde. 

Table 12.6 Indoor Use Products that May Contain Formaldehyde...

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