Toxicity of formaldehyde

The consumption of urea for urea—formaldehyde resins has decreased in recent years because of the new findings about the toxicity of formaldehyde slowly released by the resin. 

Phenol-formaldehyde resins using prepolymers such as novolaks and resols are widely used in industrial fields. These resins show excellent toughness and thermal-resistant properties, but the general concern over the toxicity of formaldehyde has resulted in limitations on their preparation and use. Therefore, an alternative process for the synthesis of phenolic polymers avoiding the use of formaldehyde is strongly desired. 

The hnding of very substantial amounts of incomplete oxidation products for methanol and formaldehyde oxidation can have considerable consequences for technical applications, such as in DMFCs. In that case, the release of formaldehyde at the fuel cell exhaust has to be avoided not only from efficiency and energetic reasons, but in particular because of the toxicity of formaldehyde. While in standard DMFC applications the catalyst loading is sufficiently high that this is not a problem, i.e., only CO2 is detected [Arico et al., 1998], the trend to reducing the catalyst loading or applications in micro fuel cells may lead to situations where the formation of incomplete oxidation products could indeed become problematic (see also Wasmus et al. [1995]). For such purposes, one could dehne a maximum space velocity above which formation of incomplete oxidation products may become critical. 

The toxicity of formaldehyde during anaerobic treatment has been reported by several authors. 1 2 3 4 5 -8 Its toxicity depends of several different parameters ... 

Skog, E. A toxicological investigation of lower aliphatic aldehydes. I. Toxicity of formaldehyde, acetaldehyde, propionaldehyde and butyraldehyde as well as of acrolein and crotonaldehyde. Acta Pharmacol, 6 299-318, 1950. 

Restani P, Galli GL Oral toxicity of formaldehyde and its derivatives. Crit Rev ToW 21 315-328, 1991... 

Debate is continuing on the safety and toxicity of formaldehyde and its products, especially urea-formaldehyde foam used as insulation in construction and phenol-formaldehyde as a plywood adhesive. Presently the TLV-STEL of formaldehyde is 0.3 ppm. Formaldehyde is on the Reasonably Anticipated to Be Human Carcinogens list. 

Yu, P.H. 1998. Deamination of methylamine and angiopathy toxicity of formaldehyde, oxidative stress and relevance to protein glycoxidation in diabetes. J Neural Transm Suppl 52 201-216. 

Nilsson, J.A., Zheng, X., Sundqvist, K., Liu, Y, Atzori, L., Elfwing, A., Arvidson, K., and Grafstrom, R.C. 1998. Toxicity of formaldehyde to human oral fibroblasts and epithelial cells Influences of culture conditions and role of thiol stams. Journal of Dental Research, 77 1896-1903. 

The minimum amount of formaldehyde that can be detected by odor varies considerably between individuals and ranges from 0.1 to 1.0 ppm (0.12-1.2 mg/m ), close to the concentration at which minimal irritant effects are felt in the eyes and in the pulmonary airways (3). Thus, the fundamental toxicity of formaldehyde lies in primary irritation to the eyes, nose, and throat when the subject is exposed to concentrations in the range of 1-5 ppm. Concentrations above 2-5 ppm cause irritation of the pharynx, lungs, and eyes, and some erythema of vaporized areas of the skin, such as the face and neck. Acute exposure to concentrations of formaldehyde of the order of three times the maximum threshold of detection of the... 

At high exposure levels the carbonyl group of formaldehyde can react with nucleophilic sites on amino acids and DNA. At the site of contact, the primary metabolic products will contribute to the toxicity of formaldehyde. The formation of formic acid generally will cause an acidosis, corrosion of the... 

The toxicity of formaldehyde is related to its metabolic products and, as a result, individual variability in metabolism will determine toxic outcomes. Human ingestion of 118 ml of formaldehyde was fatal in some cases but not others. Systemic acidosis may appear upon ingestion along with corrosion and hemorrhaging of the digestive tract. Allergic sensitization may occur after exposure. This may lead to contact dermatitis after subsequent skin exposure, as well as asthmatic attack upon inhalation exposure. Inhalation may also result in irritation of the respiratory tract and pulmonary edema. 

The toxicity of formaldehyde is route-dependent. Irritation at the point of contact is seen by inhalation, oral, and dermal routes. High doses are cytotoxic and result in degeneration and necrosis of mucosal and epithelial cell layers. These observations are consistent with the hypothesis that toxic effects are mediated by formaldehyde itself and not by metabolites. No specific target molecule has been identified, although DNA-protein cross links have been identified (Casanova and Heck 1987). As discussed in... 

Cassee FR, Stenhuis WH, Groten JP, et al. 1996c. Toxicity of formaldehyde and acrolein mixtures in vitro studies using nasal epithelial cells. Exp Toxicol Pathol 48 481-483. 

Maronpot RR, Miller RA, Clarke WJ, et al. 1986. Toxicity of formaldehyde vapor in B6C3F1 mice exposed for 13 weeks. Toxicology 41 253-266. 

Ranly DM. 1985. Assessment of the systemic distribution and toxicity of formaldehyde following pulpotomy treatment part one. J Dent Child 52 431-434. 

Tsuchiya K, Hayashi Y, Onodera M, et al. 1975. Toxicity of formaldehyde in experimental animals -concentrations of the chemical in the elution from dishes of formaldehyde resin in some vegetables. 

In the future aminos are likely to grow slowly for some time. Since the overall volume is so strongly tied to the huge quantities of urea-formaldehyde used in wood products, the course of this business is crucial. As noted, toxicity of formaldehyde is a concern, and the ultimate resolution of this issue is uncertain. However, the economy of urea-formaldehyde for this application is proven, and it appears probable that Improved technology will sustain the use of these resins in this market. We may see modified resins but their elimination is unlikely. 

Subacute oral toxicity of formaldehyde and acetaldehyde in rats has been reported by Til et al. (1988). In a drinking water study. 

Upreti et al. (1987) studied the mechanism of toxicity of formaldehyde in male rats by intraperitoneal injection of " C-labeled HCHO. In 72 hours 41% of the dose was eliminated through expired air and another 15% in urine. A significant level of radioactivity was detected bound to subcellular microsomal fractions, deoxyribonucleic acid (DNA), ribonucleic acid (RNA), protein, lipid fractions of liver, and spleen tissues. The study indicates that formaldehyde undergoes rapid absorption and distribution in the body. 

For the last decades, enzymatic synthesis of phenolic polymers has been extensively investigated [1-10]. In living cells, various oxidoreductases play an important role in maintaining the metabolism of living systems. So far, several oxidoreductases—peroxidase, laccase, bilirubin oxidase etc.—have been reported to catalyze an oxidative polymerization of phenol derivatives, and among them, peroxidase is most often used. The enzymatically synthesized phenolic polymers are expected to become an alternative to conventional phenolic resins, which have limitations of their preparation and use due to concerns over the toxicity of formaldehyde. 

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