Carcinogens formaldehyde

Mutagenicity and carcinogenicity Formaldehyde is mutagenic in vitro and although there is conflicting evidence about its carcinogenicity, this should be taken seriously. 

It might then be oxidized enzymatically with hydrogen peroxide to produce a polymer, as described in Chap. 9. A final cure with diisocyanates or bisoxazolines would yield the equivalent of a phenol-formaldehyde resin without use of the carcinogenic formaldehyde. Terephthalic acid for polyethylene terephthalate) might be made by the oxidation of p-cymene, although two carbon atoms would be... 

These resins are used in counter tops and plastic dinner-ware. It should be possible to replace the carcinogenic formaldehyde with various cross-linking agents, such as glyoxal, bisanhydrides, bisepoxides, bisoxazolines, diisocyanates, and the like. 

Aldehydes are highly toxic compounds that are known to be human carcinogens. Formaldehyde is toxic through inhalation and is a strong irritant. The TLV is 1 ppm in air. Acetaldehyde is toxic, with narcotic effects. The TLV is 100 ppm in air, and the IDLH is 10,000 ppm. Propionaldehyde is an irritant. The toxicity hazards of the aldehydes also vary from one compound to another. Care should be taken to determine the exact hazards of any given compound. 

Solutions of formaldehyde, 30 to 50%, such as those used in preservatives, are listed as miscellaneous hazardous materials. These solutions are nonflammable, and the toxicity is below the requirements for a poison liquid. However, the material may still be carcinogenic. Formaldehyde solutions usually contain up to 15% methanol to retard polymerization. The four-digit UN identification number for nonflammable solutions is 2209. 

What are the advantages and disadvantages of switching to methanol-powered vehicles Methanol burns more cleanly than gasoline, and levels of troublesome pollutants such as carbon monoxide, unreacted hydrocarbons, nitrogen oxides, and ozone are reduced (Chapter 4). However, there is concern about the higher exhaust emissions of carcinogenic formaldehyde from methanol-powered vehicles. Since the number of methanol-powered vehicles is limited, it is still difficult to assess the extent to which these formaldehyde emissions will contribute to the total aldehyde levels from other sources. 

Formaldehyde (HGHO), the simplest aldehyde, is obtained by oxidation of methanol. It is a gas at room temperature but is often used as a 40% aqueous solution called formalin. Although formaldehyde is an important starting material for polymers, it presents a number of health hazards because of its toxicity and carcinogenicity. Formaldehyde is also an air pollutant, being produced in trace amounts in the incomplete combustion of fossil fuels. One of the concerns about methanol as a fuel (Section 12.5) is the potential for increased levels of formaldehyde in urban areas because of the production of formaldehyde from incomplete combustion of methanol. 

Carcinogenicity Formaldehyde has the potential to cause cancer in humans. Repeated and prolonged exposure increases the risk. Various animal experiments have conclusively shown formaldehyde to be a carcinogen in rats. In humans, formaldehyde exposure has been associated with cancers of the lung, nasopharynx and oropharynx, and nasal passages. 

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. 

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