Formaldehyde vapor

Another modification of this process was reported in 1988 (84). In this process, a precondensate of THPC and urea, plus excess urea, are neutralized to a pH of about 5.7, and the buffer salt is added. The fabric is then given a standard pad-dry-cure process followed by oxidation and laundering. The principal advantage of this modification is a reduction in both formaldehyde vapors and phosphine-like odors released during processing (84). 

Adequate ventilation is necessary for aH process lines to ensure worker safety. Electroless copper baths must have good ventilation to remove toxic formaldehyde vapors and caustic mist generated by the hydrogen evolution reactions and air sparging. Electroless nickels need adequate ventilation to remove nickel and ammonia vapors. Some states and municipalities requite the removal of ammonia from wastewaters. A discussion of printed circuit board environmental issues and some sludge reduction techniques is avaHable (25). 

If the compound causing the odor is known and can be chemically analyzed, it may be possible to get valid quantitative data by direct gas sampling. An example would be a plant producing formaldehyde. If the effluent were sampled for formaldehyde vapor, this could be related, through proper dispersion formulas, to indicate whether the odor would cause any problems in residential neighborhoods adjacent to the plant. 

Ocular Effects. A case-control study of office workers was conducted by Baj et al. (1994) to evaluate the risks of chronic exposures to inhaled formaldehyde, phenol and isomers of organic chlorohydrocarbons from Ksylamit which is a widely used liquid wood preservative reported to consist of a mixture of chlorinated benzenes, pentachlorophenol, alpha-chloronaphthalene, chloroparafifin, and kerosene . Twenty-two workers (18 women and 4 men) exposed for at least 6 months were the cases, and 29 non-exposed, non-smoking volunteers matched for age, sex, and place of residence were the controls. The authors indicate that all of the exposed workers developed chronic complaints, among them burning eyes, but that no remarkable increase in morbidity was found during the 6 months of exposure to Ksylamit , nor during the 3-year follow-up study (details of which were not provided). The authors attribute these symptoms to the irritant effect of the inhaled Ksylamit probably (based on the references provided) due to the formaldehyde vapor they assert emanates from the woodpreserving liquid. 

The experimental system is shown in Figure 4.9. The tested samples are placed in an airtight chamber whose volume is 301. By using a water bath, the chamber and air temperature can be maintained at the desired temperature. Tests were conducted at four air temperatures 18 0.5 °C, 30 0.8 °C, 40 0.8 °C and 50 0.6 °C, with air humidity uncontrolled but in the range 60 8%. After the system reaches thermal equilibrium, a dose of saturated formaldehyde vapor is injected into the chamber and thereafter the instantaneous concentrations of formaldehyde in the chamber are continuously recorded by an INNOVA-1312 until the equilibrium concentration C(y is reached at the equilibrium time, There are several reasons for applying a real-time photo-acoustic monitor to measure the instantaneous chamber compound concentrations for this research. First, its sampling volume is small and the air can be returned into the chamber... 

Exposure to inhaled formaldehyde via the respiratory tract is usually to molecular formaldehyde vapor, whereas exposure by other routes is usually to formalin. Exposure to formaldehyde vapor can occur in industrial settings. In recent years, a great deal of concern has arisen over the potential for exposure in buildings to formaldehyde vapor evolved from insulating foams that were not properly formulated and cured or when these foams bum. Hypersensitivity can result from prolonged, continuous exposure to formaldehyde. Furthermore, animal experiments have shown formaldehyde to be a lung carcinogen. 

Figure 26. Increased shrinkage at 200°C with exposure to formaldehyde vapor in newborn rat stratum corneum (load 2.8 gm. He atm) (11)...

Figure 41, Influence of formaldehyde vapor exposure (crosslinking) on formic acid swelling of newborn rat corneum (sample thickness 12 fi). In decending order the curves represent formaldehyde exposure times of A, control B, 0.5 hrs C, 1 hr and D, 2 hrs. Data from Ref. 18.

Let us now examine the formation of aich microstructures. Lowe and co-workers ) consider that the formation of microcells is caused by a rupture of macrocell walls by formaldehyde vapors. Indeed, oligomer polycondensation of 2-methylolphenol in the presence of acidic catalyst may partially proceed via 2-hydroxydibenzyl ethers ... 

Free formaldehyde is used in cosmetics, especially in hair shampoos, and in many disinfectants and antiseptics. The solid paraformaldehyde is used as a source of formaldehyde vapor for the disinfection of rooms. Noxythiolin, polynoxyUn, hexamidine, and taurolidine act by slow release of formaldehyde. Formaldehyde solution contains 34—38% of formaldehyde methanol as a stabilizing agent to delay polymerization of the formaldehyde. Formaldehyde gel contains 0.75% of formaldehyde and is used to treat warts. 

Formaldehyde vapors used in controlled-exposure inhalation studies can be generated by heating commercial formalin, aqueous solutions containing 30-50% formaldehyde by weight plus methanol or other substances to inhibit intrinsic polymerization, or by heating solid paraformaldehyde, a formaldehyde polymer. Unless noted otherwise, inhalation studies used in the preparation of this profile provided clear evidence that formaldehyde was the only added gas in the experimental atmosphere. 

Repeated exposure to formaldehyde vapors at 40 ppm, 6 hours/day, 5 days/week for up to 13 weeks produced 80% mortality in B6C3F1 mice, whereas mice exposed with the same protocol to 20 ppm showed no mortalities within the exposure period (Maronpot et al. 1986). Deaths occurred predominately in the fifth and sixth week of exposure and were associated with ataxia, severe body weight depression, and inflammation and metaplasia in the nasal cavity, larynx, trachea, and lungs. Deaths were attributed to occlusive tracheal lesions and/or prominent seropurulent rhinitis (Maronpot et al. 1986). 

Formaldehyde vapors are readily absorbed from the respiratory tract. Due to rapid metabolism to formate, little, if any, intact formaldehyde can be found in the blood of humans or animals exposed to formaldehyde. Fonnaldehyde is also readily absorbed from the gastrointestinal tract and meets with the same metabolic fate as formaldehyde after inhalation exposure. The studies available in the open literature suggest that very little formaldehyde is absorbed via the dermal route. In all cases, absorption appears to be limited to cell layers immediately adjacent to the point of contact. Entry of formaldehyde into the blood (i.e., systemic absorption) occurs to a very limited extent, if at all. 

Einbrodt et al. (1976) exposed students to 0.26-0.92 ppm formaldehyde vapors for 3 hours, with urine samples collected immediately after exposure and 21 hours after exposure. Urine formaldehyde and urine formic acid (formate) concentrations were found to be higher immediately after exposure compared to 21 hours later however, no baseline sample was obtained prior to exposure. If historic formaldehyde and formic acid baseline levels were assumed, then a closer examination of these data indicates that more formaldehyde (and metabolite) was excreted in the urine than could have possibly been absorbed by inhalation, indicating another route of exposure (perhaps dermal), or co-exposure to another chemical that also has formate as a metabolite (e.g., methanol), or higher personal exposures than were actually measured. There was also no indication that the urine formate levels were adjusted to compensate for urine specific gravity using urine creatinine levels, which may have markedly influenced the test results. 

Barzana E, Klibanov AM, Karel M. 1989. A colorimetric method for the enzymatic analysis of gases The determination of ethanol and formaldehyde vapors using solid alcohol oxidase. Anal Biochem 182 109-115. 

Brown KG. 1985. Risk assessment of laboratory rats and mice chronically exposed to formaldehyde vapors. Risk Anal 5 171-180. 

Dinsdale D, Riley RA, Verschoyle RD. 1993. Pulmonary cytochrome P450 in rats exposed to formaldehyde vapor. Environ Res 62 19-27. 

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