Formaldehyde Uptake Research Articles

Uptake and reactivity of formaldehyde on lime-cement-plaster under typical indoor air conditions

Uptake and reactivity of formaldehyde on lime-cement-plaster under typical indoor air conditions

Alginate@Fe3O4@Bentonite nanocomposite for formaldehyde removal from synthetic and real effluent: optimization by central composite design.

In this study, Alginate@ Fe3O4/Bentonite nanocomposite was utilized to eliminate formaldehyde from wastewater. Structural features of bentonite, bentonite@Fe3O4, and Alginate@Fe3O4@Bentonite were determined using FT-IR, PXRD, Mapping, EDX, TEM, SEM, VSM, and BET analyses. The central composite design method was employed to find the optimal conditions for formaldehyde removal using Alg@Fe3O4@Bent nanocomposite. The maximum formaldehyde uptake efficiency (94.56%) was obtained at formaldehyde concentration of 10.69ppm, the nanocomposite dose of 1.28g/L, and pH of 9.96 after 16.53min. Also, Alginate@Fe3O4@Bentonite composite was used to eliminate formaldehyde from Razi petrochemical wastewater and was able to eliminate 91.24% of formaldehyde, 70% of COD, and 68.9% of BOD5. The isotherm and kinetic investigations demonstrated that the formaldehyde uptake process by the foresaid adsorbent follows the Langmuir isotherm and quasi-first-order kinetic models, respectively. Also, the maximum uptake capacity was obtained at 50.25mg/g. Moreover, the formaldehyde uptake process by the aforementioned nanocomposite was exothermic and spontaneous. Furthermore, the formaldehyde adsorption efficiency decreased slightly after six reuse cycles (less than 10%), indicating that Alginate@Fe3O4@Bentonite nanocomposite has remarkable recyclability. Besides, the influence of interfering ions like nitrate, carbonate, chloride, phosphate, and sulfate was studied on the formaldehyde removal efficiency and the results displayed that all ions except nitrate ion have low interaction with formaldehyde (less than 3% reduction in removal efficiency).

Validation of two contrasting capturing mechanisms for gaseous formaldehyde between two different types of strong metal-organic framework adsorbents

In this research, the adsorption behavior of formaldehyde (FA) onto two types of metal-organic frameworks (MOFs: MOF-199 [M199] and UiO-66-NH2 [U6N]) is investigated against changes in the key process variables (e.g., FA partial pressure (0.5-10Pa), temperature (30-120 °C), and relative humidity (RH: 0%, 50%, and 100%)). The results revealed that the FA adsorption behavior onto both MOFs is exothermic in nature. Besides, their relative dominance for FA uptake varies interactively with the changes in RH and FA partial pressure levels. As the FA levels increase in dry conditions, their breakthrough volumes (BTV (100% BT)) exhibit contrasting trends: The values of U6N decreased noticeably from 5232 and 3792L·atm·g-1, while those of M199 increased from 4152 to 5772L·atm·g-1. The superiority of U6N over M199 in the lower FA level (at<5Pa) is supported by the Lewis acid-base interactions with amine groups (U6N) in line with kinetic/isotherm studies. Such superiority is also persistent at higher (10Pa) FA level under all humid conditions in line with its higher moisture stability. However, in dry conditions, the reversal of relative dominance in which M199 exhibits enhanced efficacy for 10 Pa FA uptake (relative to U6N) should reflect its breathing effects with the potent role of pore-diffusion mechanism. This study offers valuable insights into the construction of tunable adsorbents with enhanced adsorptivity toward key targets.

Development and Optimization of an Airborne Formaldehyde Microfluidic Analytical Device Based on Passive Uptake through a Microporous Tube.

This paper describes a compact microfluidic analytical device developed for the detection of low airborne formaldehyde concentrations. This microdevice was based on a three-step analysis, i.e., the passive gaseous formaldehyde uptake using a microporous membrane into an acetylacetone solution, the derivatization with acetylacetone to form 3,5-diacetyl-1,4-dihydrolutidine, and the quantification of the latter using fluorescence detection. For a rapid and easier implementation, a cylindrical geometry of the microporous element was considered to perform laboratory-controlled experiments with known formaldehyde concentrations and to establish the proof of concept. This work reports the evaluation of the uptake performance according to the microporous tube length, the liquid flow rate inside the tube, the gas flow rate outside the tube, and the gaseous formaldehyde concentration. A 10.0 cm microporous tube combined with a gas flow rate of 250 NmL/min (normal milliliters per minute) and a liquid flow rate of 17 µL/min were found to be the optimized conditions. In these experimental conditions, the fluorescence signal increased linearly with the gaseous formaldehyde concentration in the range 0–118 µg/m3, with the detection limit being estimated as 0.13 µg/m3 when considering a signal-to-noise ratio of 3.

Effect of Process Variables on the Solvolysis Depolymerization of Pine Kraft Lignin

Lignin modification opens the possibility of using it in polyol bio-based polymers, such as phenol–formaldehyde resins, polyurethanes, composites, and binders. Pine kraft lignin Indulin AT was partially depolymerized and the resulting products analyzed to determine their degree of valorization. Depolymerized lignin products were analyzed by GPC-SEC (molar mass), ∆ε-IDUS (phenolic hydroxyls), HACL (formaldehyde uptake), 13C-NMR (hydroxyl and methoxyl groups), and 1H-DOSY (molar mass distribution). The dominant parameter in lignin depolymerization by solvolysis was reaction temperature. According to the results, a higher reaction temperature decreases the average molar masses and PDI of lignin as well as the primary and secondary aliphatic hydroxyls, while simultaneously increasing the phenolic hydroxyls and formaldehyde uptake of lignin. Other variables (time, formic acid wt %, ethanol wt %, lignin load) had lesser effects. Partial depolymerization by solvolysis in mild conditions without catalyst is a viable valorization route for lignin, by which lignin properties can be significantly improved.

Facile stabilization of a cyclodextrin metal-organic framework under humid environment via hydrogen sulfide treatment.

Increasing resistance to humid environments is a major challenge for the application of γ-CD-K-MOF (a green MOF) in real-world utilisation. γ-CD-K-MOF–H2S with enhanced moisture tolerance was obtained by simply treating MOF with H2S gas. XPS, Raman and TGA characterizations indicated that the H2S molecules coordinated with the metal centers in the framework. H2S acting as a newly available water adsorption potential well near the potassium centers protects the metal–ligand coordination bond from attack by water molecules and thus improves the moisture stability of MOF. After 7 days exposure in 60% relative humidity, γ-CD-K-MOF–H2S retained its crystal structure and morphology, while γ-CD-K-MOF had nearly collapsed. In addition, the formaldehyde uptake tests indicated that γ-CD-K-MOF retain their permanent porosity after interaction with H2S. This simple and facile one-step strategy would open a new avenue for preparation of moisture stable MOFs for practical applications.

Foliage houseplant responses to low formaldehyde levels

Abstract House plants are reported to ‘clean’ formaldehyde from indoor environments and thus reduce its deleterious health effects. We measured formaldehyde removal rates at concentrations similar to those caused by new furniture or office photocopiers. We also measured CO2 and humidity changes, counted the stomata density and monitored leaf color and shape changes. Controls were an artificial polyester “fern” and methanol as the VOC. All plants reduced formaldehyde from 0.75 ppm to below 0.2 ppm in six hours.. The plants fall into two major groups with different responses: one group showed high removal rates: Boston fern (0.85 m h−1), golden pothos (0.41 m h−1), Spanish moss (0.44 m h−1) and spider plant (0.40 m h−1) - faster than the artificial fern (0.09 m h−1). They also show no change in color and appear to completely assimilate formaldehyde. Another group absorbed formaldehyde at a significantly lower rate (dumb cane: 0.07 m h−1; aloe vera: 0.17 m h−1; and Chinese evergreen: 0.09 m h−1) and had a generally different overall behavior from the ‘fast’ group - different CO2, humidity and variance changes - suggesting a different formaldehyde absorption mechanism. An ‘intermediate case’, snake plant (0.29 m h−1), has a slower rate than the fast group but also exhibited other changes, suggesting some combination of both mechanisms. Overall good correlations between formaldehyde uptake rates and stomata counts, total leaf area and water evapotranspiration rates were shown by all these plants.

Over-expression of the Arabidopsis formate dehydrogenase in chloroplasts enhances formaldehyde uptake and metabolism in transgenic tobacco leaves.

Over-expression of AtFDH controlled by the promoter of Rubisco small subunit in chloroplasts increases formaldehyde uptake and metabolism in tobacco leaves. Our previous study showed that formaldehyde (HCHO) uptake and resistance in tobacco are weaker than in Arabidopsis. Formate dehydrogenase in Arabidopsis (AtFDH) is a key enzyme in HCHO metabolism by oxidation of HCOOH to CO2, which enters the Calvin cycle to be assimilated into glucose. HCHO metabolic mechanism in tobacco differs from that in Arabidopsis. In this study, AtFDH was over-expressed in the chloroplasts of transgenic tobacco using a light inducible promoter. 13C-NMR analysis showed that the carbon flux from H13CHO metabolism was not introduced into the Calvin cycle to produce glucose in transgenic tobacco leaves. However, the over-expression of AtFDH significantly enhanced the HCHO metabolism in transgenic leaves. Consequently, the productions of [4-13C]Asn, [3-13C]Gln, [U-13C]oxalate, and H13COOH were notably greater in transgenic leaves than in non-transformed leaves after treatment with H13CHO. The increased stomatal conductance and aperture in transgenic leaves might be ascribed to the increased yield of oxalate in the guard cells with over-expressed AtFDH in chloroplasts. Accordingly, the transgenic plants exhibited a stronger capacity to absorb gaseous HCHO. Furthermore, the higher proline content in transgenic leaves compared with non-transformed leaves under HCHO stress might be attributable to the excess formate accumulation and Gln production. Consequently, the HCHO-induced oxidative stress was reduced in transgenic leaves.

Development of microfluidic analytical method for on-line gaseous Formaldehyde detection

Abstract This paper reports on the development of a novel colorimetric analytical method based on microfluidic technologies for the detection of low airborne Formaldehyde concentrations, representative of those found in indoor air, i.e. 10–100 μg m−3. The new analytical technique operates according to 4 distinct steps: 1) gas sampling, 2) gaseous Formaldehyde uptake into the aqueous solution using an annular gas/liquid flow at room temperature, 3) derivatization reaction with acetylacetone solution at 65 °C producing 3,5-Diacetyl-1,4-dihydrolutidine (DDL) and 4) colorimetric DDL detection with a liquid-core-waveguide. Laboratory experiments were performed to determine the experimental conditions permitting to obtain a stable annular flow, i.e. a liquid flow rate above 5 μL min−1 and gas to liquid flow rate ratios greater than 1000. Effects of liquid-core-waveguide of internal diameter and length were also investigated. Using liquid and gas flow rates of 35 μL min−1 and 35 mL min−1 respectively, the resulting uptake yield of gaseous Formaldehyde in aqueous solution was around 90% and the detection limit of gaseous Formaldehyde was 0.7 μg m−3, which is consistent with the guideline values for indoor air. In addition, the low reagent consumption increases significantly the device autonomy up to 20 days with 1L of acetylacetone solution.

A novel formaldehyde metabolic pathway plays an important role during formaldehyde metabolism and detoxification in tobacco leaves under liquid formaldehyde stress

Tobacco and Arabidopsis are two model plants often used in botany research. Our previous study indicated that the formaldehyde (HCHO) uptake and assimilation capacities of tobacco leaves were weaker than those of Arabidopsis leaves. After treatment with a 2, 4 or 6mM HCHO solution for 24h, detached tobacco leaves absorbed approximately 40% of the HCHO from the treatment solution. (13)C-NMR analysis detected a novel HCHO metabolic pathway in 2mM H(13)CHO-treated tobacco leaves. [4-(13)C]Asn, [3-(13)C]Gln and [U-(13)C]oxalic acid (OA) were produced from this pathway after H(13)COOH generation during H(13)CHO metabolism in tobacco leaves. Pretreatments of cyclosporin A (CSA) and dark almost completely inhibited the generation of [4-(13)C]Asn, [3-(13)C]Gln and [U-(13)C]OA from this pathway but did not suppressed the production of H(13)COOH in 2mM H(13)CHO-treated tobacco leaves. The evidence suggests that this novel pathway has an important role during the metabolic detoxification of HCHO in tobacco leaves. The analysis of the chlorophyll and Rubisco contents indicated that CSA and dark pretreatments did not severely affect the survival of leaf cells but significantly inhibited the HCHO uptake by tobacco leaves. Based on the effects of CSA and dark pretreatments on HCHO uptake and metabolism, it is estimated that the contribution of this novel metabolic pathway to HCHO uptake is approximately 60%. The data obtained from the (13)C-NMR analysis revealed the mechanism underlying the weaker HCHO uptake and assimilation of tobacco leaves compared to Arabidopsis leaves.

Catalytic oxidation of formaldehyde by ruthenium multisubstituted tungstosilicic polyoxometalate supported on cellulose/silica hybrid

Abstract Cellulose/silica hybrid material produced by a sol–gel method from cellulosic fibres and silica precursors (tetraethoxysilane and 3-aminopropyltriethoxysilane) was functionalized with α-[SiW 9 O 37 Ru III 3 (H 2 O) x Cl 3− x ] (10 −x )− (Ru-POM), and thoroughly characterised by 13 C and 29 Si solid state NMR, FTIR spectroscopy, UV–vis reflectance spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy (SEM), and chemical analysis. The supported Ru-POM exhibited catalytic activity for the gas phase heterogeneous aerobic oxidation of formaldehyde ( ca. 830 ppm in polluted air) at room temperature, in a packed-bed reactor operating at a linear velocity ca. 0.33 m/s and ca. 0.5 s residence time. Maximum formaldehyde uptake was 1.10 g/min per kg of hybrid material doped with Ru-POM ( ca. 1.4% w/w). More than 400 turnovers were achieved without significant loss of catalytic activity and the only detected oxidation products of formaldehyde were carbon dioxide and water. A plausible mechanism for the catalytic oxidation of formaldehyde by supported Ru-POM has been proposed and includes formaldehyde oxidation in oxygenated ruthenium complex.

Foliar trichome-aided formaldehyde uptake in the epiphytic Tillandsia velutina and its response to formaldehyde pollution

Epiphytic Tillandsia (Bromeliaceae) species have been found to be efficient biomonitors of atmospheric heavy metals and persistent organic pollutants, but have not been used to monitor or remove the primary indoor atmospheric pollutant formaldehyde (FA). The absorptive capacity of Tillandsia trichomes is well-established, but potential secondary effects of foliar trichomes on gas exchange remain unclear. Our study investigated whether Tillandsia species can absorb FA efficiently and if the leaf trichomes function to improve FA uptake, using Tillandsia velutina. Plants with intact trichomes, decreased FA concentration by 48.42% in 12 h from 1060 μg m(-3) to 546.67 μg m(-3), while FA concentration decreased only by 22.51% in the plants without trichomes. Moreover, the more trichomes removed from the leaves, the lower the capability of FA uptake per unit leaf area, which suggested that T. velutina was capable of absorbing a large amount of FA via the leaves and specialized trichomes facilitated the whole leaf tissue FA absorption. In addition, all plants exposed to FA were chloric, had a reduction in measured leaf chlorophyll, and an increment in permeability of plasma membranes. However, plants in which trichomes had been removed declined or increased more quickly than plants with intact trichomes, indicating Tillandsia leaf trichomes also give the leaves some protection against this toxin.

Adsorption and photocatalytic oxidation of formaldehyde on a clay-TiO2 composite

We investigated the adsorption capacity and photocatalytic removal efficiency of formaldehyde using a hectorite-TiO(2) composite in a bench flow reactor. The same experimental conditions were applied to pure TiO(2) (Degussa P25) as a reference. The catalysts were irradiated with either a UVA lamp (365 nm) or with one of two UVC lamps of 254 nm and 254+185 nm, respectively. Formaldehyde was introduced upstream at concentrations of 100-500 ppb, with relative humidity (RH) in the range 0-66% and residence times between 50 and 500 ms. Under dry air and without illumination, saturation of catalyst surfaces was achieved after ≈ 200 min for P25 and ≈ 1000 min for hectorite-TiO(2). The formaldehyde uptake capacity by hectorite-TiO(2) was 4.1 times higher than that of P25, almost twice the BET surface area ratio. In the presence of humidity, the difference in uptake efficiency between both materials disappeared, and saturation was achieved faster (after ≈ 200 min at 10% RH and ≈ 60 min at 65% RH). Under irradiation with each of the three UV sources, removal efficiencies were proportional to the Ti content and increased with contact time. The removal efficiency decreased at high RH. A more complete elimination of formaldehyde was observed with the 254+185 nm UV source.

Characterization and adsorption properties of polymer-based microporous carbons with different surface chemistry

Polymers are promising activated carbon precursors due to their high percentage of carbon and also due to their abundance in a relatively pure state from waste recovery. Microporous activated carbons were prepared from poly(ethyleneterephthalate) (APETW, APETOX) and polyacrylonitrile (APAN). Their surface behaviour was characterized under dry and wet conditions by X-ray photoelectron spectroscopy (XPS), pH, pHPZC and Boehm titration. The oxygen content of the nitrogen-free APETW and APETOX (SBET = 1440 and 1509 m2/g) is 4.3 and 10.0 at.%, respectively. APAN (356 m2/g) contains 5.4 at.% oxygen and 5.3 at.% nitrogen. The ratios of the surface density of the titrated groups are approximately 20:28:65 in APETW, APETOX and APAN, respectively. The last has the most basic character. The larger oxygen content of APETOX yields greater affinity towards water, as does the presence of nitrogen functionalities in APAN. The higher the concentration of the functional groups, the higher is the water uptake at low relative humidity. The greatest formaldehyde uptake per unit surface area was found in APAN, which is decorated with both nitrogen and oxygen functional surface groups. Due to the competitive adsorption of formaldehyde and water, increasing oxygen concentration in the APETW sample changed the kinetics of sorption but did not affect the formaldehyde uptake at saturation.

A Distributed-Parameter Model for Formaldehyde Uptake and Disposition in the Rat Nasal Lining

DNA–protein cross-links (DPX) serve as a dosimeter for inhaled formaldehyde and are associated with tumor induction in rat nasal passages after chronic exposure to 6 ppm and above. To determine the role of epithelium-specific morphometry in formaldehyde-induced patterns of injury, we developed a mathematical model that links airflow-driven formaldehyde uptake with DPX formation in regions of the rat nose with high and low tumor incidence. A three-dimensional, anatomically accurate computational fluid dynamics model of rat nasal airflow and inhaled gas uptake was integrated with a physiologically based mathematical model incorporating tissue thickness, formaldehyde diffusion, its removal by enzymatic and nonenzymatic processes, and DNA distribution in the nasal mucosa to predict DPX formation. The model implicitly incorporates the reversible conversion of formaldehyde to methylene glycol. Where possible, parameter values were taken from the literature or estimated using published correlations. The Michaelis–Menten kinetic constants Vmax and Km, as well as a first-order constant for formaldehyde removal, were left as fitted parameters. The resultant model fit to the experimentally measured DPX in the high- and low-tumor-incidence regions of the rat nasal passages was very good. Sensitivity analysis indicates that among the fitted parameters, model fits are most sensitive to Vmax and that predictions were sensitive to changes in tissue thickness when all other parameters are held constant. The model structure facilitates extrapolation to primates and humans and application to other soluble, reactive gases.

Determination of Polyphenolic Content of Bark Extracts for Wood Adhesives

Summary The phenolic content of condensed tannins varies considerably, depending on the method of determination. Even though the Stiasny precipitation number has been commonly used to estimate the amount of reactive tannin towards formaldehyde, particularly in adhesive applications, this estimation alone is not sufficient. In this study two methods of determining the amount of reactive tannin towards formaldehyde were examined. These were (1) the reactivity towards formaldehyde or the Stiasny precipitation number, and (2) the formaldehyde uptake. Five different types of tannin were examined from Rhizophora mucronata, P. radiata, mimosa, quebracho and chestnut. The study indicates that the phenolic content in tannin can be better estimated by determining both the Stiasny number and the amount of formaldehyde uptake. High correlation (r2 = 0.905) was detected between the two methods. The study also revealed that hot water extracts of R. mucronata contain relatively small amounts of reactive polyphenols and are less reactive than sulfite extracts. The consumption of formaldehyde by this type of tannin was only 0.294 molecules per flavanoid unit. Similar to R. mucronata, the sulfite extracts of P. radiata contain relatively high amounts of reactive polyphenols and reacted with substantially higher amounts of formaldehyde per flavanoid unit, comparable to mimosa and quebracho tannins. Nonetheless, the reactivity towards formaldehyde (gel time) of the latter tannins is muchlower, despite their higher polyphenolic content. Of the two methods used to estimate the polyphenolic content of bark extracts, the Stiasny number had a relatively higher correlation (r2 = 0.518) with gel time than formaldehyde uptake (r2 = 0.345) did. The behaviour of these tannins in relation to their reactivity and chemical structures is discussed.

Use of computational fluid dynamics models for dosimetry of inhaled gases in the nasal passages.

Computational fluid dynamics (CFD) models of the nasal passages of a rat, monkey, and human are being used (1) to determine important factors affecting nasal uptake, (2) to make interspecies dosimetric comparisons, (3) to provide detailed anatomical information for the rat, monkey, and human nasal passages, and (4) to provide estimates of regional air-phase mass transport coefficients (a measure of the resistance to gas transport from inhaled air to airway walls) in the nasal passages of all three species. For many inhaled materials, lesion location in the nose follows patterns that are both site and species specific. For reactive, water-soluble (Category 1) gases, regional uptake can be a major factor in determining lesion location. Since direct measurement of airflow and uptake is experimentally difficult, CFD models are used here to predict uptake patterns quantitatively in three-dimensional reconstructions of the F344 rat, rhesus monkey, and human nasal passages. In formaldehyde uptake simulations, absorption processes were assumed to be as rapid as possible, and regional flux (transport rate) of inhaled formaldehyde to airway walls was calculated for rats, primates, and humans. For uptake of gases like vinyl acetate and acrylic acid vapors, physiologically based pharmacokinetic uptake models incorporating anatomical and physical information from the CFD models were developed to estimate nasal tissue dose in animals and humans. The use of biologically based models in risk assessment makes sources of uncertainty explicit and, in doing so, allows quantification of uncertainty through sensitivity analyses. Limited resources can then be focused on reduction of important sources of uncertainty to make risk estimates more accurate.

USE OF COMPUTATIONAL FLUID DYNAMICS MODELS FOR DOSIMETRY OF INHALED GASES IN THE NASAL PASSAGES

Computational fluid dynamics (CFD) models of the nasal passages of a rat, monkey, and human are being used (1) to determine important factors affecting nasal uptake, (2) to make interspecies dosimetric comparisons, (3) to provide detailed anatomical information for the rat, monkey, and human nasal passages, and (4) to provide estimates of regional air-phase mass transport coefficients (a measure of the resistance to gas transport from inhaled air to airway walls) in the nasal passages of all three species. For many inhaled materials, lesion location in the nose follows patterns that are both site and species specific. For reactive, water-soluble (Category 1) gases, regional uptake can be a major factor in determining lesion location. Since direct measurement of airflow and uptake is experimentally difficult, CFD models are used here to predict uptake patterns quantitatively in three-dimensional reconstructions of the F344 rat, rhesus monkey, and human nasal passages. In formaldehyde uptake simulations, absorption processes were assumed to be as rapid as possible, and regional flux (transport rate) of inhaled formaldehyde to airway walls was calculated for rats, primates, and humans. For uptake of gases like vinyl acetate and acrylic acid vapors, physiologically based pharmacokinetic uptake models incorporating anatomical and physical information from the CFD models were developed to estimate nasal tissue dose in animals and humans. The use of biologically based models in risk assessment makes sources of uncertainty explicit and, in doing so, allows quantification of uncertainty through sensitivity analyses. Limited resources can then be focused on reduction of important sources of uncertainty to make risk estimates more accurate.

Heterogeneous interaction of formaldehyde with cold sulfuric acid: Implications for the upper troposphere and lower stratosphere

Laboratory studies of formaldehyde uptake on thin sulfuric acid films indicate that HCHO can be taken up for long periods of time without saturation. Initial Henry's law solubility coefficients are large (H* = 106–107 M atm−1) at stratospheric temperatures. This uptake is due to rapid formation of HCHO(aq), CH2(OH)2, and possibly HOCH2OSO2(OH) in solution. Over a longer time period, steady‐state uptake continues with γ≈0.002 due to formaldehyde polymerization. Although uptake by stratospheric sulfate aerosols will not provide a significant sink for atmospheric formaldehyde, it may lead to high condensed‐phase concentrations of HCHO and polymerization in solution. Reaction of condensed HCHO with nitric acid in sulfuric acid has also been observed, converting HNO3 to odd nitrogen (NOx) and formaldehyde to formic acid. This reaction may have considerable impact on the HNO3/NOx ratio, as its rate is likely comparable to the HNO3 photolysis rate.

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, Kimbell et 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 microM/min and Km = 59 microM) 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.