Formaldehyde specific

Several studies have examined serum for formaldehyde-specific IgE antibodies in groups of... 

Formaldehyde-specific IgE antibodies could be detected in only 1/86 serum samples from four groups of formaldehyde-exposed subjects (Kramps et al. 1989). The groups included 28 subjects living or working in places with formaldehyde-containing construction materials (e.g., chipboard) and estimated formaldehyde concentrations ranging from 0.08 to 0.37 ppm, 18 occupationally exposed subjects from an anatomy laboratory and in other unspecified industries where air concentrations were not measured,... 

Formaldehyde-specific IgE was not detected in a group of 45 medical students, before or after the students attended a 4-week anatomy dissecting course (Wantke et al. 1996b). Estimates of laboratory air concentrations of formaldehyde ranged from 0.059 to 0.219 ppm (mean 0.124 0.05 ppm). Surveys revealed frequencies of irritation symptoms consistent with other studies (e.g., itching of the skin in 33/45 students, headache in 15/45, and burning eyes in 13/45). 

Studies of laboratory animals, as well as studies of adult humans under acute controlled exposure or occupational exposure conditions, indicate that the irritant effects of formaldehyde are restricted to tissues at portals-of-entry due to the water-solubility and reactivity of formaldehyde and the ability of cells to rapidly metabolize (and detoxify) formaldehyde. Studies designed to compare formaldehyde-specific metabolic capacities and efficiencies in portal-of-entry tissues (e.g., nasal mucosa, gastrointestinal mucosa) Ifom adult and immature animals of varying ages may be useful in determining a possible mechanistic basis for possible age-related differences in susceptibility to formaldehyde. 

Effect As discussed in the previous section, DNA-protein cross links and anti-formaldehyde-human serum albumin IgG antibodies are potential biomarkers of effect and exposure. Whereas detection of these biomarkers can represent biological responses to repeated exposure to formaldehyde (the first is not specific to formaldehyde, but the second is), it is uncertain to what degree their detection indicates that adverse health effects will occur. Further research on relationships between formaldehyde-induced upper respiratory tract tissue damage and/or dysfunction and (1) DNA-protein cross links in either white blood cells or nasal biopsy tissue or (2) levels of formaldehyde-specific IgG antibodies may help in determining if improved detection methods are needed. 

Formaldehyde release rates were measured using multiple consumer products in a dynamic chamber. Particle board and plywood had high formaldehyde specific release rate coefficients. Combined plywood and particle board had a release rate 68% of the sum of the two products and 91% of the particle board release (Table V). When particle board was combined with insulation, the combined release rate was 71% of the sum of the separate release rates and 73% of the particle board release. Particle board and carpet combinations gave similar results. 

Formaldehyde, specifically formalin, is perhaps the single-most effective preservative for shampoos and conditioners however, because of its sensitization reputation, which actually occurs well above levels used in consumer products, it is not used in most countries. Sensitization by formaldehyde is not a problem if used at 0.1% or lower concentration in personal care products, and in many cases it is used at 0.2% in household products. Most companies avoid the use of formaldehyde in baby products. 

Methenamine is placed in special tablets that do not dissolve as they travel through the acidic environment of the stomach but do dissolve once they reach the basic environment of the intestinal tract. Methenamine is thereby released in the intestinal tract, where it is stable under basic conditions. Once it reaches the acidic environment of the urinary tract, methenamine is hydrolyzed, releasing formaldehyde, as shown above. In this way, methenamine is used as a prodrug that enables delivery of formaldehyde specifically to the urinary tract. This method prevents the systemic release of formaldehyde in other organs of the body where it would be toxic. 

Specifications and Analytical Methods. The commercial material is specified as 97% minimum purity, determined by gas chromatography or acetylation. Moisture is specified at 0.05% maximum (Kad-Fischer titration). Formaldehyde content is determined by bisulfite titration. 

Specifications and Analytical Methods. The commercial aqueous solution is specified as 34% minimum butynediol, as determined by bromination or refractive index. Propargyl alcohol is limited to 0.2% and formaldehyde to 0.7%. 

Interest ia the toxicity of aldehydes has focused primarily on specific compounds, particularly formaldehyde, acetaldehyde, and acroleia (13). Litde evidence exists to suggest that occupational levels of exposure to aldehydes would result ia mutations, although some aldehydes are clearly mutagenic ia some test systems. There are, however, acute effects of aldehydes. 

Formaldehyde is sold in aqueous solutions with concentrations ranging from 25 to 56 wt % HCHO. Product specifications for typical grades (18,117—119)... 

Procedures for determining the quaUty of formaldehyde solutions ate outlined by ASTM (120). Analytical methods relevant to Table 5 foUow formaldehyde by the sodium sulfite method (D2194) methanol by specific gravity (D2380) acidity as formic acid by titration with sodium hydroxide (D2379) iron by colorimetry (D2087) and color (APHA) by comparison to platinum—cobalt color standards (D1209). 

Formaldehyde—Alcohol Solutions. These solutions are blends of concentrated aqueous formaldehyde, the alcohol, and the hemiacetal. Methanol decreases the average molecular weight of formaldehyde oligomers by formation of lower molecular weight hemiacetals. These solutions are used to produce urea and melamine resins the alcohol can act as the resin solvent and as a reactant. The low water content can improve reactivity and reduce waste disposal and losses. Typical specifications for commercially available products are shown in Table 7 (117). 

Table 7. Specifications and Physical Properties of Formaldehyde—Alcohol Solutions...

Urea—Formaldehyde and Urea-Based. In the 1970s and early 1980s, urea materials were in general use particularly for direct field retrofitting of cavity wall constmction of wood frame and masonry. However, because of formaldehyde odor and excess shrinkage under specific conditions, this ceUular plastic has limited use as an insulation. 

Nippon Shokubai and U.K. Seung are producing a fluorescent polymer claimed to be made from a co-condensation of ben2oguanamine and formaldehyde. Fine highly thermoset particles are manufactured in solution and later dried. It is useful in a wide range of appHcations, specifically plastics, and markets where bleed is a problem. 

Resoles. Like the novolak processes, a typical resole process consists of reaction, dehydration, and finishing. Phenol and formaldehyde solution are added all at once to the reactor at a molar ratio of formaldehyde to phenol of 1.2—3.0 1. Catalyst is added and the pH is checked and adjusted if necessary. The catalyst concentration can range from 1—5% for NaOH, 3—6% for Ba(OH)2, and 6—12% for hexa. A reaction temperature of 80—95°C is used with vacuum-reflux control. The high concentration of water and lower enthalpy compared to novolaks allows better exotherm control. In the reaction phase, the temperature is held at 80—90°C and vacuum-refluxing lasts from 1—3 h as determined in the development phase. SoHd resins and certain hquid resins are dehydrated as quickly as possible to prevent overreacting or gelation. The end point is found by manual determination of a specific hot-plate gel time, which decreases as the polymerization advances. Automation includes on-line viscosity measurement, gc, and gpc. 

Like methylolureas, cycHc ureas are based on reactions between urea and formaldehyde however, the amino resin is cycHc rather than linear. Many cychc urea resins have been used in textile-finishing processes, particularly to achieve wrinkle resistance and shrinkage control, but the ones described below are the most commercially important. They ate all in use today to greater or lesser extents, depending on specific end requirements (see also Textiles, finishing). 

The recovery of fiber from broke (off-specification paper or trim produced in the paper mill) is compHcated by high levels of urea—formaldehyde and melamine—formaldehyde wet-strength resin. The urea resins present a lesser problem than the melamine resins because they cure slower and are not as resistant to hydrolysis. Broke from either resin treatment may be reclaimed by hot acidic repulping. Even the melamine resin is hydrolyzed rapidly under acidic conditions at high temperature. The cellulose is far more resistant and is not harmed if the acid is neutralized as soon as repulping is complete. 

The level of technical service support provided for a given product generally tracks in large part where the suppHer considers thek product to be located within the spectmm of commodity to specialty chemicals. Technical service support levels for pure chemicals usually provided in large quantities for specific synthetic or processing needs, eg, ammonia (qv), sulfuric acid (see SuLFURic ACID AND SULFURTRIOXIDe), formaldehyde (qv), oxygen (qv), and so forth, are considerably less than for more complex materials or blends of materials provided for multistep downstream processes. Examples of the latter are many polymers, colorants, flocculants, impact modifiers, associative thickeners, etc. For the former materials, providing specifications of purity and physical properties often comprises the full extent of technical service requked or expected by customers. These materials are termed undifferentiated chemicals (9),... 

Toxic chemicals can enter the body in various ways, in particular by swallowing, inhalation and skin absorption. Skin absorption may lead to dermatitis and this can be a most annoying complaint. Whereas some chemicals may have an almost universal effect on human beings, others may attack only a few persons. A person who has worked with a given chemical for some years may suddenly become sensitised to it and from then on be unable to withstand the slightest trace of that material in the atmosphere. He may as a result also be sensitised not only to the specific chemical that caused the initial trouble but to a host of related products. Unfortunately a number of chemicals used in the plastics industry have a tendency to be dermatitic, including certain halogenated aromatic materials, formaldehyde and aliphatic amines. 

---