Formaldehyde individual compounds

The California Air Resources Board has prepared risk assessments for a number of toxic airborne compounds and mixtures, designated as toxic air contaminants, TACs (Table 16.15). For example, risk assessments for individual compounds such as benzene, benzo[a]pyrene (see Chapter 10), formaldehyde, and vinyl chloride have been carried out, in addition to complex mixtures such as diesel exhaust (California Air Resources Board, 1997a) and environmental tobacco smoke (California Environmental Protection Agency, 1997). These risk assessment documents form the basis for controls imposed as part of the risk management process (e.g., see Seiber, 1996). 

Jobs has carried out an extensive series of liquid thermal conductivity measurements over a wide range of temperature on a variety ot compounds. Data on butyraldehyde have been cororlaled with temperature Data ut individual temperature point have been compiled for acetaldehyde, pm-pionaldehyde. and hutyru)deh df > The Jain for formaldehyde were estimated by the method of Robbins and Kmgtea... 

In carbohydrate chemistry, condensatiMi with carbonyl compounds such as acetone, acetaldehyde, formaldehyde and benzaldehyde is of great importance for the protection of pairs of hydroxyl groups. Trityla-tion may also be used in these instances for the protection of individual primary hydroxyl groups before carrying out the condensation with carbonyl compounds. After the condensation, the individual hydroxyl groups may be liberated by suitable detritylation methods. As yet, these possibilities have been explored very little. Wolfrom and coworkers described the condensation of 1,6-ditrityldulcitol with benzaldehyde to l,6-ditrityl-2,3,4,5-dibenzylidenedulcitol. Acetals other than those obtained by direct condensation are thus available. 

There is evidence of a cause-effect relationship between exposure to indoor (chemical vapours, gases [42], formaldehyde and volatile organic compounds) and outdoor pollution and induction of respiratory symptoms in individuals with established disease [43-45], However, the possible role of pollutants in the development of asthma and atopic airway disease seems less important and needs further elucidation. 

The possibility cannot be excluded that specific VOCs appear indoors which may turn out in the future to he much more potent in causing effects on humans than the average VOCs. In this case, these (e.g. formaldehyde) should be evaluated individually, and a list of such compounds should be established. A draft list of special compounds for which low thresholds for effects or high detection limits cause the probability of sensory effects to be grossly underestimated if this TVOC-concept is used has not yet been officially established. This list should also include compounds which are likely to cause other types of health effects than irritation and which, therefore, must be considered in a total evaluation of the indoor air quality. Potential candidates for the list are mentioned above. 

Because of the lack of structure in the absorption spectra of many simple carbonyl compounds, excitation of individual vibronic features is rarely possible. However, in simple aldehydes such as glyoxal and methylglyoxal (pyruvaldehyde)96 and propynal, 6 as indeed for formaldehyde (discussed above), such studies are possible and have recently been reported. 

Formaldehyde (for-MAL-duh-hide) is a colorless, flammable gas with a strong, pungent odor that tends to polymerize readily. Polymerization occurs when individual molecules of formaldehyde combine with each other to make very large molecules called polymers. Over 4 billion kilograms (10 billion pounds) of formaldehyde were produced in the United States in 2004, the vast majority of which was used in the production of plastics and other polymers. To make handling and shipping easier and safer, the compound is usually provided as a 37 percent solution of formaldehyde in water to which has been added an additional 15 percent of methanol (methyl alcohol) to prevent polymerization. 

Urea-formaldehyde resins and similar aminoplast precondensates form the greatest proportion of all the resins used as additives. Mono-methylated and dimethylated ureas are used, as are the analogous condensation products of formaldehyde with melamine. The monomeric compounds penetrate into the intermicellar space in the cellulose in aqueous solution, and there harden with heat to form insoluble resins (cf. also Section 28.2). Since the formation of mono- and dimethylated urea is reversible, CH2O occurs in equilibrium. Formaldehyde can form methylene cross-link bridges between the individual chains. In addition, longer cross-linking... 

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