Phenol-formaldehyde resins are polymers of a phenol, or a mixture of phenols, and formaldehyde. They are particularly heat resistant, good electrical insulators and have adhesive properties. Para-tertiary-butylphenol-formaldehyde resin is the most frequently used resin, especially as adhesives. Other areas of use include thermosettings, laminates and impregnations, binders, surface coatings, and abrasive paper. Phenol-formaldehyde resins occur as resoles, resins and resites depending of the degree of cross-linking. The resins contain several impurities (i.e. reaction intermediates, raw materials and degradation products). In general they are insoluble in water and their solubility in organic solvents varies. Degradation occurs gradually from 150 degrees C. No information on the toxicokinetics of phenol-formaldehyde resins were available. The resins appear to have a low acute oral or dermal toxicity in experimental animals. The oral LD50 in rats has been reported to be 2 900 mg/kg or higher and the dermal LD50 in rabbits is 16 ml/kg. No LC50 -value following inhalation exposure was found. However, deaths have been noted in rats inhaling vapours of a phenol-formaldehyde resin. Studies in experimental animals and observations in humans have clearly shown that phenol-formaldehyde resins are irritating to eyes, skin and mucosal membranes. No studies were available regarding repeated or prolonged exposure to phenolformaldehyde resins. In humans, cases claiming neurotoxic effects have been reported. However, detailed neuropsychologic testing failed to reveal any definite evidence of organic brain damage. Genotoxic effects are equivocal, since in two studies to detect bacterial mutagenicity both negative and positive results were found. Interestingly, persons occupationally exposed to a phenol-formaldehyde resin revealed an increase in chromosomal aberrations. No carcinogenicity studies were located in the literature. Concerning reproductive effects and teratogenicity, limited data are available. Damage to rat spermatocytes following inhalation exposure to a phenolformaldehyde resin has been reported. Furthermore, teratogenic effects due to inhalation exposure of mice and humans to a phenol-formaldehyde resin containing relatively large amounts of ethanol have been suggested. Several sensitizing agents have been detected in phenol-formaldehyde resins using the Guinea Pig Maximization Test. Both epidemiological studies and case reports clearly have shown that phenol-formaldehyde resins cause contact dermatitis in humans. Up to 1 - 3 % of a population of people with skin diseases has been shown to give positive reactions to phenol-formaldehyde resins. From the available toxicological data the critical effects related to phenolformaldehyde exposure are its allergic effects and its ability to cause irritation of the skin, eye and mucosal membranes.
ANIMAL; acute toxicity; irritancy; hypersensitivity; genetic toxicity; reproductive and developmental tests; teratogens; reproductive effect; eye; skin; mucous membrane; HUMAN; epidemiological study; case report; occupational exposure; acute effect; chronic effect; genetic effect; nervous system; respiratory system; dust; rubber industry