Uptake Of Formaldehyde Research Articles

Uptake of formaldehyde by MDF wood-fibres

A quantitative estimation of the phenomenon of formaldehyde vapour adsorption-desorption by MDF wood fibres is attempted. Wood fibres can act as formaldehyde reservoir, when exposed to hot vapours of it. The amount of formaldehyde adsorbed by wood fibres has been found to increase proportionally with the amount of formaldehyde being introduced. It seems that wood fibres are loosing the ability to trap formaldehyde soon after hot pressing.

Comparison of Inhaled Formaldehyde Dosimetry Predictions with DNA–Protein Cross-Link Measurements in the Rat Nasal Passages

Kimbell and coworkers (Toxicol. Appl. Pharmacol.121,253–263, 1993) developed a computational fluid dynamics (CFD) model of a F344 rat nasal passage to quantify local wall mass flux (uptake rate) of inhaled chemical. To simulate formaldehyde uptake, Kimbellet al.assumed that mass transfer of formaldehyde from the air into the nasal lining was fast and complete. This was approximated in the CFD model by setting the formaldehyde concentration at the airway walls to zero. Experimental confirmation of formaldehyde mass-flux predictions is desirable if the CFD model is to be used for predicting formaldehyde dosimetry. The purpose of this study was to see if the CFD model predictions of formaldehyde mass flux are consistent with laboratory data on formaldehyde dosimetry. In this study, a mathematical model of the nasal lining was modified to link CFD dosimetry predictions for inhaled formaldehyde with measured tissue disposition of inhaled gas. This model treats the nasal lining as a single, well-stirred compartment, accounts for formaldehyde reaction via saturable and first-order pathways, and allows comparison of model-predicted DNA–protein cross-links (DPX) with regional DPX measured in formaldehyde-exposed rats. Effective Michaelis–Menten kinetic parameters (Vmax= 3040 μm/min andKm= 59 μm) and a pseudo-first-order rate constant for elimination of formaldehyde by nonsaturable pathways (kf= 6 min−1) were estimated (fit) using an average mass flux derived from experimentally measured uptake of formaldehyde. DPX predictions obtained using the estimated kinetic parameters and linking the CFD model to the nasal-lining model compared well with experimentally measured DPX. The close correlation between predicted and measured DPX in the rat nasal passage supports the CFD model predictions of formaldehyde mass flux at the level of resolution provided by the experimental data.

Uptake of Gas-Phase Formaldehyde by Aqueous Acid Surfaces

The uptake of gas-phase formaldehyde, CH2O, by aqueous sulfuric and nitric acid droplets has been measured as a function of temperature, acid concentration, and gas−droplet contact time. The results are interpreted in terms of the mass accommodation coefficient for formaldehyde on aqueous surfaces, the Henry's law constant for formaldehyde in aqueous acid solutions, and the liquid-phase formation kinetics of methylenediol, CH2(OH)2, and protonated formaldehyde, CH3O+. Time-dependent uptake studies under mildly acid solutions where CH2(OH)2 and CH3O+ formation is slow reveal the existence of a chemisorbed surface complex for CH2O at the gas−liquid interface. Uptake studies on nitric acid and mixed sulfuric acid/nitric acid solutions show slightly enhanced uptake relative to sulfuric acid only solutions. This observation has been attributed to variation of formaldehyde solubility (expressed as Setchenow coefficients) and CH3O+ equilibrium constant in nitric and sulfuric acid solutions. The implications of t...

Uptake of formaldehyde by sulfuric acid solutions: Impact on stratospheric ozone

Chemical reactions on sulfuric acid aerosols have recently been shown to play an important role in stratospheric chemistry. In particular, these reactions push odd‐nitrogen compounds into HNO3 and thereby enhance the chlorine‐catalyzed destruction of ozone. It has been suggested that our current set of heterogeneous reactions may be incomplete. Indeed we show that formaldehyde, CH2O, is rapidly and irreversibly taken up by stirred sulfuric acid solutions (60 to 75 wt % H2SO4 at −40° to −65°C) with uptake coefficients as large as γ = 0.08. If similar uptake occurs under stratospheric pressures of CH2O (that is, 1000 times lower than used in the present study), then the removal of CH2O from the gas phase can take away a significant source of odd hydrogen in the mid‐ and high‐latitude lower stratosphere. We show here that with the inclusion of this reaction, concentrations of OH and HO2 are reduced by as much as 4% under background levels of aerosols and more than 15% under elevated (volcanic) conditions. Further, the accumulation of CH2O in stratospheric aerosols over a season may alter the composition and reactivity of these sulfuric acid‐water mixtures.

Uptake of gas-phase aldehydes by water surfaces

The uptake of gas-phase formaldehyde and acetaldehyde by water droplets was measured along with mass accomodation coefficients. Formaldehyde uptake is predictable, but that of acetaldehyde as short gas-droplet contact times is greater than predicted due to a chemisorbed surface complex at the gas-water interface that may explain the high measured concentration of acetaldehyde in clouds relative to formaldehyde. The small uptake coefficients suggest that this may be the limiting factor in aldehyde uptake into clouds. 36 refs., 10 figs., 3 tabs.

Dentine hypersensitivity. I. Effects produced by the uptake in vitro of metal ions, fluoride and formaldehyde onto dentine.

Dentine has been shown to possess affinity for a large number of varied compounds, many of which have been shown effective in clinical trials, for the treatment of dentine hypersensitivity. The mode of action of these compounds is unclear. The aim of this study was to investigate the uptake of metal ions, fluoride and formaldehyde in solution onto dentine in vitro and determine whether therapeutic effects could be mediated through occlusion of dentinal tubules. Etched dentine sections were exposed for 1 h to 1000 ppm solutions of fluoride and metal salts. Levels of fluoride and respective metals could be extracted and measured from the specimens. Saliva pretreatment had a variable but small effect on uptake of each ion, but post treatment washings reduced all levels of retained fluoride and metals. X-ray microanalysis indicated surface or immediate subsurface deposits of metals. However, surface changes were only consistently produced by zinc and more particularly tin salts. Both zinc and tin salts produced covering or obturation of tubules. The surface effects of zinc could largely be reversed by washing, but not those of tin. Formaldehyde alone or in the presence of saliva produced no effects. A 4-week study involving twice daily exposure of specimens to saliva and fluoride, metals or formaldehyde yielded essentially the same results. It is unlikely that, except for tin, the compounds tested achieve their apparent clinical effects mediated by direct occlusion of dentinal tubules.

Effect of acetaldehyde and cyanamide on the metabolism of formaldehyde by hepatocytes, mitochondria, and soluble supernatant from rat liver

Formaldehyde can be metabolized primarily by two different pathways, one involving oxidation by the low- K m mitochondrial aldehyde dehydrogenase, the other involving a specific, glutathione-dependent, formaldehyde dehydrogenase. To estimate the roles played by each enzyme in formaldehyde metabolism by rat hepatocytes, experiments with acetaldehyde and cyanamide, a potent inhibitor of the low- K m aldehyde dehydrogenase were carried out. The glutathione-dependent oxidation of formaldehyde by 100,000 g rat liver supernatant fractions was not affected by either acetaldehyde or by cyanamide. By contrast, the uptake of formaldehyde by intact mitochondria was inhibited 75 to 90% by cyanamide. Acetaldehyde inhibited the uptake of formaldehyde by mitochondria in a competitive fashion. Formaldehyde was a weak inhibitor of the oxidation of acetaldehyde by mitochondria, suggesting that, relative to formaldehyde, acetaldehyde was a preferred substrate. In isolated hepatocytes, cyanamide, which inhibited the oxidation of acetaldehyde by 75 to 90%, produced only 30 to 50% inhibition of formaldehyde uptake by cells as well as of the production of 14CO 2 and of formate from [ 14C]formaldehyde. The extent of inhibition by cyanamide was the same as that produced by acetaldehyde (30–40%). In the presence of cyanamide, acetaldehyde was no longer inhibitory, suggesting that acetaldehyde and cyanamide may act at the same site(s) and inhibit the same formaldehyde-oxidizing enzyme system. These results suggest that, in rat hepatocytes, formaldehyde is oxidized by cyanamide- and acetaldehydesensitive (low- K m aldehyde dehydrogenase) and insensitive (formaldehyde dehydrogenase) reactions, and that both enzymes appear to contribute about equally toward the overall metabolism of formaldehyde.

Reaction of Formaldehyde and Dimethylol Urea with Unmodified and Modified Cellulose

In order to understand the role of neutral salts in the crosslinking reaction, cellulose was deliberately oxidized with nitrogen dioxide, and the effect of oxidation on the uptake of formaldehyde and dimethylol urea by the oxycellulose both in the presence and absence of added salt was studied. The large increase in the add-on of crosslinking molecules by oxycellulose in the presence of added salt is interpreted in terms of electrostatic interactions between crosslinking molecules and cellulose, which behaves as solid polyelectrolyte under certain conditions.

Retention of inhaled formaldehyde, propionaldehyde, and acrolein in the dog.

Aldehydes in the vapor phase of cigarette smoke are of considerable interest in terms of tissue irritation, ciliatoxicity, and other effects. This study deals with the handling by the canine respiratory tract of formaldehyde, acrolein, and propionaldehyde, which are present in the gas phase in relatively high concentrations. Specific aims included measurement of retention of each compound by the entire respiratory tract and by upper and lower portions under varying conditions of ventilatory rate, tidal volume, and concentration inhaled. Uptake of formaldehyde was always close to 100% regardless of any other factor. The total-tract retention of propionaldehyde and acrolein was much lower and of similar magnitude. In terms of regional uptake, retention of propionaldehyde was greater than that of acrolein in the lower tract and less than that of acrolein in the upper tract.

Absorption of Formaldehyde by Wool

A radiochemical method has been used to follow the course of reaction of formaldehyde with wool. The amount of formaldehyde absorbed from aqueous solutions was dependent on the conditions of treatment. It was found that the pH of the solution, the concentration of formaldehyde in the solution, and the treatment time and temperature markedly affect the extent of the wool-formaldehyde reaction. The presence of salt in the solution has some modifying effect on the uptake of formaldehyde by wool, and there are some apparent differences in the effects of different salts. The amount of formaldehyde bound by the wool was affected by the rinsing conditi ons to which the formalized material was subjected, indicating that not all of the absorbed formaldehyde was present in the form of stable products; this was confirmed by the gradual loss of formaldehyde from formalized wool on exposure to the atmosphere.

Some observations concerning the chemical reactions occurring between formaldehyde and peptone.

Abstract The uptake of formaldehyde by peptone has been studied. Relatively stable powders (formol-peptones) can be prepared by exposing peptone powder to the vapour phase over formalin for four days and drying the product in vacuo. Different batches of such powders, obtained from the same sample of peptone are of similar composition but formolpeptones obtained from different makes of peptone may differ considerably in composition. The state of binding between the formaldehyde and the peptone in powder and in solution has been investigated by means of the chromotropic acid and Vorländer's reactions. The firmness with which formaldehyde is bound to peptone in solution depends not only on the quantities of formaldehyde and peptone present but also on the previous relationship of the two substances. The reactions between formaldehyde and peptone have been found to be complex. Equilibrium is not readily attained either in solution or when peptone powder is exposed to formalin vapour.