Formaldehyde potential sources

The most frequent causes of allergic contact dermatitis in the United States include plants (poison ivy, poison oak, and poison sumac), metallic salts, organic dyes, plastic resins, rubber additives, and germicides.74 The most common skin patch test allergens found to be positive in patients along with potential sources of exposure are shown in Table 32.1.75 In patients with occupational contact dermatitis who were skin patch tested, the common allergens included carba mix, thiuram mix, formaldehyde, epoxy resin, and nickel.76... 

Methanol, also known as wood alcohol, is another widely discussed potential source (or carrier) of hydrogen.31 Chemically, methanol, ch oh, is a clear liquid, the simplest of the alcohols, with one carbon atom per molecule. Methanol is extensively used today— U.S. demand in 2002 exceeded 2 billion gallons. The largest U.S. methanol markets are for producing the gasoline additive mtbe (methyl tertiary butyl ether) as well as formaldehyde and acetic acid. 

Both particleboard and MDF core are characteristically 3-ply and have two potential sources of formaldehyde the adhesive used to adhere the hardwood face and back to the core, and the adhesive binder used in the manufacture of the particleboard or MDF. Hardwood plywood manufacturers are typically not vertically integrated and do not produce composition board cores, thus are dependent on other companies or plants for particleboard and MDF. 

The single largest end use for hardwood plywood is interior wall panels, generally 3-ply and 1/4 and thinner, and frequently machined with decorative v-grooves. Furniture, cabinets, door skins and a number of specialties complete an array of end use products. Many of the non wall panel products can be characterized as being industrial panels and are of 5 or more ply veneer core, 3-ply particleboard core, or 3-ply medium density fiberboard (MDF) core construction. Broad end use patterns indicate that interior wall panels represent approximately 55% of total hardwood plywood consumption. Furniture, cabinets, and fixtures represent about 30%, and door skins and specialty products about 15% (2), Potential sources of formaldehyde in two of the more typical hardwood plywood constructions are displayed in Figure 1. 

Figure 1. Potential sources of formaldehyde in two typical hardwood plywood constructions.

Although it might be thought that its CIS side chain would make cardanol an ideal candidate for surface active agents comparatively few developments have materialised. The use of CNSL as a potential source of surfactants and additives has been briefly reviewed (ref. 280). The Mannich reaction of cardanol with dialkylamines and formaldehyde (ref. 281) and the formation of cationics such as 3-pentadecyl-6-dimethylaminomethyl methosulphate has been described (ref. 2). 

Potential sources of formaldehyde in biological material are quite numerous. Formaldehyde can be derived in the catabolism of the amino acids, serine, glycine, histidine, tryptophan, and methionine, dimethylglycine and sarcosine, the purines, and ( yoxylic and glycolic acids (see 44)-... 

Formaldehyde (HCHO) is a colorless gas with a pungent odor. Formaldehyde has found wide industrial usage as a fungicide and germicide, and in disinfectants and embalming fluids. The serious sources of indoor airborne formaldehyde are furnimre, floor underlayment insulation, and environmental tobacco smoke. Urea formaldehyde (UF) is mixed with adhesives to bond veneers, particles, and fibers. It has been identified as a potential hazardous source. 

Heaters that are not vented to the exterior have the potential to act as indoor pollutant sources, especially gas heaters. While emissions of carbon monoxide and nitrogen dioxide have received investigation for more than a decade, it has been found that low-NOx unflued gas heaters can act as sources of formaldehyde to indoor air (Brown, Mahoney and Cheng, 2004). Table 16.10 summarizes volatile organic emissions from an unflued gas heater (A) where it was apparent... 

Conventional uses of methanol account for 90% of present consumption and include formaldehyde, dimethyl terephthalate, methyl methacrylate, methyl halides, methylamines and various solvent and other applications. Newer uses for methanol that have revitalized its growth and outlook include a new technology for acetic acid, single cell protein, methyl tertiary butyl ether-(MTBE), and water denitrification. Potential uses for methanol include its use as a carrier for coal in pipelines, as a source of hydrogen or synthesis gas used in direct reduction of iron ore, as a direct additive to or a feedstock for gasoline, peak power shaving and other fuel related possibilities. Table II lists the world methanol demand by end use in 1979. 

Electroless plating — An autocatalytic process of metal deposition on a substrate by reduction of metal ions from solution without using an external source of electrons. It is promoted by specific reductants, namely formaldehyde, sodium hypophosphide, sodium boro-hydride, dialkylamine borane, and hydrazine. Electroless deposition has been used to produce different metal (e.g., nickel, cobalt, copper, gold, platinum, palladium, silver) and alloy coatings. It can be applied to any type of substrate including non-conductors. Some substrates are intrinsic catalytic for the electroless deposition other can be catalyzed usually by sensibilization followed by Pd nucleation also, in some non-catalytic metallic substrates the electroless process can be induced by an initial application of an appropriate potential pulse. In practical terms, the evaluation of the catalytic activity of a substrate for the electroless deposition of a given metal is... 

The formaldehyde in some of these reactions is not only the source of the carbonyl ligands, but is also a potential alternative to the alcohol solvent as source of the hydride ligands. A similar ambiguity exists in the many hydride preparations in which H,0 and [OH] are present as well as ROH and [RO] , e.g., in ... 

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