Formaldehyde carcinogenicity

Conolly RB, Andjelkovich DA, Casanova M, et al. 1995. Multidisciplinary, iterative examination of the mechanism of formaldehyde carcinogenicity The basis for better risk assessment. CUT Act 15 1-10. 

In combination with acids, toxic chloride gas arises in combination with formaldehyde, carcinogenic reaction-products will be formed. Cutaneous intolerance to hypochlorite may become manifest through immediate-type and delayed-type responses, and could lead to systemic reactions in patients previously sensitized by cutaneous contact (Hostynek 1989). 

Outside of carbon monoxide for which the toxicity is already well-known, five types of organic chemical compounds capable of being emitted by vehicles will be the focus of our particular attention these are benzene, 1-3 butadiene, formaldehyde, acetaldehyde and polynuclear aromatic hydrocarbons, PNA, taken as a whole. Among the latter, two, like benzo [a] pyrene, are viewed as carcinogens. Benzene is considered here not as a motor fuel component emitted by evaporation, but because of its presence in exhaust gas (see Figure 5.25). 

Under neutral or slightly alkaline conditions, only the unstable hemiformal (CH O—CH2OH, methoxymethan0I) is produced. Alpha-chloromethyl ether is synthesized from aqueous formaldehyde, methanol, and hydrogen chloride (54). However, under anhydrous conditions, a carcinogenic by-product, bis(chloromethyl)ether is also formed (55). 

Formaldehyde is classified as a probable human carcinogen by the International Agency for Research on Cancer (lARC) and as a suspected human carcinogen by the American Conference of Governmental Industrial Hygienists (ACGIH). This is based on limited human evidence and on sufficient evidence in experimental animals (136). Lifetime inhalation studies with rodents have shown nasal cancer at formaldehyde concentrations that overwhelmed cellular defense mechanisms, ie, 6 to 15 ppm. No nasal cancer was seen at 2 ppm or lower levels (137). 

P-Hydroxy acids lose water, especially in the presence of an acid catalyst, to give a,P-unsaturated acids, and frequendy P,y-unsaturated acids. P-Hydroxy acids do not form lactones readily because of the difficulty of four-membered ring formation. The simplest P-lactone, P-propiolactone, can be made from ketene and formaldehyde in the presence of methyl borate but not from P-hydroxypropionic acid. P-Propiolactone [57-57-8] is a usehil intermediate for organic synthesis but caution should be exercised when handling this lactone because it is a known carcinogen. 

Ghloromethylation. The reactive intermediate, 1-chloromethylnaphthalene [86-52-2] has been produced by the reaction of naphthalene in glacial acetic acid and phosphoric acid with formaldehyde and hydrochloric acid. Heating of these ingredients at 80—85°C at 101.3 kPa (1 atm) with stirring for ca 6 h is required. The potential ha2ard of such chloromethylation reactions, which results from the possible production of small amounts of the powerhil carcinogen methyl chloromethyl ether [107-30-2J, has been reported (21). 

Formaldehyde has been rated as a possible carcinogen by the United States Occupational Safety and Health Act (OSHA) rules and should be handled with due caution. It is also a strong lacrymator and choking respiratory irritant. It irritates the skin, eyes, and mucous membranes [76]. Since it is used for tanning leather, it is obvious that fonnaldehyde has a high potential for reactions with proteins. Formaldehyde gas is flammable and most formalin solutions contain significant amounts of methanol, which is also volatile, toxic, and flammable. 

Formaldehyde (bp = — 21°C) is ordinarily found in the laboratory in the form of a concentrated water solution (37% HCHO) known as formalin. At one time it was widely used as a preservative for biological specimens. That application has declined now that formaldehyde has been shown to be carcinogenic. Industrially, it is still used as a component of adhesives used in making plywood and fiberboard. 

The major disadvantage associated with urea-formaldehyde adhesives as compared with the other thermosetting wood adhesives, such as phenol-formaldehyde and polymeric diisocyanates, is their lack of resistance to moist conditions, especially in combination with heat. These conditions lead to a reversal of the bond-forming reactions and the release of formaldehyde, so these resins are usually used for the manufacture of products intended for interior use only. However, even when used for interior purposes, the slow release of formaldehyde (a suspected carcinogen) from products bonded with urea-formaldehyde adhesives is observed. 

Carcinogens, 21 837. See afeo Cancer agency lists of, 23 113-114 Category I, 10 580 DEHP as, 25 674-675 formaldehyde, 12 121 nonlinear and threshold models for, 25 244... 

One of the considerations regarding the use of methanol as a fuel is that it emits higher amounts of formaldehyde, which is a contributor to ozone formation and a suspected carcinogen, compared to gasoline. Proponents of methanol dispute this, saying that one-third of the formaldehyde from vehicle emissions actually comes from the tailpipe, with the other two-thirds forming photochemically, once the emissions have escaped. They state that pure methanol vehicles produce only one tenth as much of the hydrocarbons that are photochemically converted to formaldehyde as do gasoline automobiles. 

Formaldehyde (also a VOC) ETS building materials and fabrics cleaning fluids and adhesives. irritation to eye. nose and respiratory system allergy, carcinogenic. 

Furthermore, when CMME is hydrolyzed, HCl and formaldehyde are produced, which may recombine to form BCME. Therefore, although findings may reflect the carcinogenicity of BCME, commercial-grade CMME also must be considered to be a carcinogen, but perhaps of a lower potency than that of BCME. 

Toxicology. Formaldehyde is an irritant of the eyes and respiratory tract it causes both primary irritation and sensitization dermatitis at high levels it is carcinogenic in experimental animals and, although results are equivocal in humans, it is considered a suspected human carcinogen. 

Formaldehyde has been shown to be carcinogenic in two strains of rats, resulting in squamous cell cancers of the nasal cavity after repeated inhalation of about 14 ppm. In one study, 51 of 117 male and 42 of 115 female Fischer 344 rats developed this tumor, but no nasal tumors were seen at 0 or 2 ppm. No other neoplasm was increased significantly. In a similar study of mice, this nasal tumor occurred in two male mice at 14.3 ppm. None of the excesses was statistically significant except for the high-exposure rats. °... 

Kers W et al Carcinogenicity of formaldehyde in rats and mice after long-term inhalation exposme. Cancer Res 43 4382-4392, 1983... 

Sellakumar AR, Snyder CA, Solomon JJ, et ah Carcinogenicity of formaldehyde and hydrogen chloride in rats. Toxicol Appl Pharmacol 81A01- 06, 1985... 

Benzene is a clear, colorless, flammable liquid with a pleasant characteristic odor, bp 80.1°C, flash point -11.1°C, and ignition temperature 538°C. Benzene has been found to be very toxic and is on the list of Known to Be Human Carcinogens published every two years by the Department of Health and Human Services under the National Toxicology Program (NTP). There are four top 50 chemicals on this worst carcinogen list benzene 1,3-butadiene ethylene oxide and vinyl chloride. There are also four chemicals in the top 50 on the Reasonably Anticipated to Be Human Carcinogens list acrylonitrile, ethylene dichloride, formaldehyde, and propylene oxide. 

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. 

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