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Atmospheric Environment (v.41, #15)

Editorial board (pp. i).

Chemical and physical factors that influence pollutant dynamics in indoor atmospheric environments by Charles J. Weschler; John C. Little (pp. 3109-3110).

Impact of reaction products from building materials and furnishings on indoor air quality—A review of recent advances in indoor chemistry by E. Uhde; T. Salthammer (pp. 3111-3128).

The variety of chemical substances present in modern building products, household products and furnishings provides potential for chemical reactions in the material (case 1), on the material surface (case 2) and in the gas phase (case 3). Such “indoor chemistry” is known as one of the main reasons for primary and secondary emissions. The conditions of production often cause unwanted side reactions and a number of new compounds can be found in finished products. Elevated temperatures are responsible for the degradation of cellulose, decomposition of non-heat-resistant additives and other thermally induced reactions like Diels–Alder synthesis. Heterogeneous chemistry takes place on the surface of materials. Well-known examples are the formation of aliphatic aldehydes from the oxidation of unsaturated fatty acids or the cleavage of photoinitiators under the influence of light. In case of composite flooring structures hydrolysis is one of the major pathways for the appearance of alcohols from esters. If different kinds of material are fixed together, emissions of new VOCs formed by inter-species reactions are possible. Other indoor air pollutants are formed by rearrangement of cleavage products or by metabolism. Compounds with –CC– bonds like terpenes, styrene, 4-phenylcyclohexene, etc. undergo gas phase reactions with O₃, NO _x, OH and other reactive gases. It has been shown that such products derived from indoor-related reactions may have a negative impact on indoor air quality due to their low odor threshold or health-related properties. Therefore, the understanding of primary and secondary emissions and the chemical processes behind is essential for the evaluation of indoor air quality. This publication gives an overview on the current state of research and new findings regarding primary and secondary emissions from building products and furnishings.

Keywords: Keyword index; Building products; Chemical reactions; Primary and secondary emissions; Indoor chemistry

Reactions between ozone and building products: Impact on primary and secondary emissions by M. Mélanie Nicolas; Olivier Ramalho; F. François Maupetit (pp. 3129-3138).

Reactions of ozone on common building products were studied in a dedicated emission test chamber system. Fourteen new and unused products were exposed to 100–160ppb of ozone at 23°C and 50% RH during 48h experiments. Ozone deposition velocities calculated at steady state were between 0.003cms⁻¹ (alkyd paint on polyester film) and 0.108cms⁻¹ (pine wood board). All tested product showed modified emissions when exposed to ozone and secondary emissions of several aldehydes were identified. Carpets and wall coverings emitted mainly C₅–C₁₀ n-aldehydes, typical by-products of surface reactions. Linoleum, polystyrene tiles and pine wood boards also showed increased emissions of formaldehyde, benzaldehyde and hexanal associated with reduced emissions of unsaturated compounds suggesting the occurrence of gas-phase reactions. The ozone removal on the different tested products was primarily associated with surface reactions. The relative contribution of gas-phase reactions to the total ozone removal was estimated to be between 5% and 30% for pine wood boards depending on relative humidity (RH) and on the incoming ozone concentration and 2% for polystyrene tiles. On pine wood board, decreasing ozone deposition velocities were measured with increasing ozone concentrations and with RH increasing in the range 30–50%.

Keywords: Ozone; Building products; Secondary emissions; Deposition velocity; Indoor chemistry

Generation of sub-micron particles and secondary pollutants from building materials by ozone reaction by Taisuke Aoki; S.-i. Shin-ichi Tanabe (pp. 3139-3150).

This study reports results from two different experiments examining reactions between ozone and common building materials that can lead to the formation of secondary products and particulate-phase materials. Monitored species include sub-micron particles and volatile organic compounds (VOCs). In the first set of experiments, various building materials were placed in a 20L stainless-steel chamber and exposed to ozone. The materials included expanded polystyrene, a natural rubber adhesive, cedar board, Japanese Cyprus board and silver fir board, as well as d-limonene, which is a known constituent of certain woods and cleaning products. The combination of ozone and either d-limonene, cedar board or cypress board produced sub-micron particles, with most of the increase occurring in the size range of 0.01–0.5μm diameter. This was not observed for the other materials. In the case of cedar board, the consequence of ozone exposure over an extended time interval was monitored. As the exposure time elapsed, the concentration of sub-micron particles moderately decreased. In the second set of experiments, unwaxed or waxed plastic tiles were placed in the 20L chamber and exposed to ozone. Sub-micron particles and organic compounds were measured during the course of the experiments. In the case of the waxed tile, the number of 0.01–1.0μm size particles grew about50×108particlesm-3; particle growth was significantly less for the un-waxed tile. For both the waxed and un-waxed tiles, the emission rates of heptane, nonane, nonanal, and decanal increased after ozone was added to the supply air. (However, it is not clear if some or all of this production was due to ozone reacting with the sorbent used for sampling or with compounds captured by the sorbent.) This study provides further evidence that ozone-initiated reactions with building materials can be a significant source of both sub-micron particles and secondary organic compounds in indoor environments.

Keywords: Indoor chemistry; Secondary product; Floor waxing; Limonene; Secondary organic aerosol

Ozone removal by HVAC filters by P. Zhao; J.A. Siegel; R.L. Corsi (pp. 3151-3160).

Residential and commercial HVAC filters that have been loaded with particles during operation in the field can remove ozone from intake or recirculated air. However, knowledge of the relative importance of HVAC filters as a removal mechanism for ozone in residential and commercial buildings is incomplete. We measured the ozone removal efficiencies of clean (unused) fiberglass, clean synthetic filters, and field-loaded residential and commercial filters in a controlled laboratory setting. For most filters, the ozone removal efficiency declined rapidly but converged to a non-zero (steady-state) value. This steady-state ozone removal efficiency varied from 0% to 9% for clean filters. The mean steady-state ozone removal efficiencies for loaded residential and commercial filters were 10% and 41%, respectively. Repeated exposure of filters to ozone following a 24-h period of no exposure led to a regeneration of ozone removal efficiency. Based on a theoretical scaling analysis of mechanisms that are involved in the ozone removal process, we speculate that the steady-state ozone removal efficiency is limited by reactant diffusion out of particles, and that regeneration is due to internal diffusion of reactive species to sites available to ozone for reaction. Finally, by applying our results to a screening model for typical residential and commercial buildings, HVAC filters were estimated to contribute 22% and 95%, respectively, of total ozone removal in HVAC systems.

Keywords: Indoor air quality; Diffusion; Reactions; Particles; Regeneration

Personal reactive clouds: Introducing the concept of near-head chemistry by R.L. Corsi; J. Siegel; A. Karamalegos; H. Simon; G.C. Morrison (pp. 3161-3165).

The “personal cloud” effect and its impact on human exposure to airborne pollutants are well documented. A great deal is also known regarding indoor air chemistry, particularly as related to ozone reactions with mono-terpenes. In this paper we hypothesize the presence of personal reactive clouds that result from ozone reactions with terpenes and terpenoids emitted from personal care products. A proof of concept assessment was completed based on reaction rates between ozone and five reactive organic compounds that are found in personal care products. Screening experiments were also completed with three perfumes and two hairsprays to determine the extent of secondary organic aerosol formation in the breathing zone of a subject who had applied these products. The results of screening calculations and preliminary experiments confirm that chemistry occurs in the near-head region of individuals who apply scented personal care products to their hair or facial skin. Additional research is needed to characterize reaction products and health consequences associated with near-head chemistry and associated personal reactive clouds.

Keywords: Ozone; Terpenes; Breathing zone; Reaction products; Ultra fine particles

Ozone reactions with indoor materials during building disinfection by D. Poppendieck; H. Hubbard; M. Ward; C. Weschler; R.L. Corsi (pp. 3166-3176).

There is scant information related to heterogeneous indoor chemistry at ozone concentrations necessary for the effective disinfection of buildings, i.e., hundreds to thousands of ppm. In the present study, 24 materials were exposed for 16h to ozone concentrations of 1000–1200ppm in the inlet streams of test chambers. Initial ozone deposition velocities were similar to those reported in the published literature for much lower ozone concentrations, but decayed rapidly as reaction sites on material surfaces were consumed. For every material, deposition velocities converged to a relatively constant, and typically low, value after approximately 11h. The four materials with the highest sustained deposition velocities were ceiling tile, office partition, medium density fiberboard and gypsum wallboard backing. Analysis of ozone reaction probabilities indicated that throughout each experiment, and particularly after several hours of disinfection, surface reaction resistance dominated the overall resistance to ozone deposition for nearly all materials. Total building disinfection by-products (all carbonyls) were quantified per unit area of each material for the experimental period. Paper, office partition, and medium density fiberboard each released greater than 38mgm⁻² of by-products.

Keywords: Heterogeneous chemistry; Reaction probability; Deposition velocity; By-products

Evidence of acid–base interactions between amines and model indoor surfaces by ATR-FTIR spectroscopy by Hugo Destaillats; Brett C. Singer; Lara A. Gundel (pp. 3177-3181).

Molecular associations of pyridine with cellulose and gypsum, surrogates for common indoor surface materials, were studied using an attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectrophotometric method. The purpose of this study was to gain insight into the molecular interactions of amines with well-characterized materials that affect their partitioning between indoor air and surfaces. The experimental results suggest the presence of at least two sorptive states for volatile and semivolatile amines, attributed to the chemisorbed species and to a more labile surface state (i.e., physisorbed pyridine). Both exhibited spectroscopic signatures corresponding to aromatic C–H stretching modes (2950–3100cm⁻¹) in the studied spectral region. Chemisorbed pyridine could be identified by the presence of additional IR signals in the N–H and O–H stretching region of the spectrum (2900–3600cm⁻¹). During desorption under a stream of N₂, surface enrichment in the chemisorbed species was evidenced by a slower reduction of the absorbance of the broad band at 2900–3600cm⁻¹ in relation to the total pyridine absorbance change. This spectroscopic evidence for acid–base interactions between amines and surfaces is consistent with the desorption behavior observed in previous work for nicotine from model surfaces.

Keywords: Acid–base; Nicotine; Pyridine; Sorption; Gypsum; Cellulose; Surface materials

Decomposition of indoor ammonia with TiO₂-loaded cotton woven fabrics prepared by different textile finishing methods by Yongchun Dong; Zhipeng Bai; Ruihua Liu; Tan Zhu (pp. 3182-3192).

Addition of urea-based antifreeze admixtures during cement mixing in construction of buildings has led to increasing indoor air pollution due to continuous transformation and emission of urea to gaseous ammonia in indoor concrete wall. In order to control ammonia pollution from indoor concrete wall, the aqueous dispersion was firstly prepared with nano-scale TiO₂ photocatalysts and dispersing agent, and then mixed with some textile additives to establish a treating bath or coating paste. Cotton woven fabrics were used as the support materials owing to their large surface area and large number of hydrophilic groups on their cellulose molecules and finished using padding and coating methods, respectively. Two TiO₂-loaded fabrics were obtained and characterized by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). Moreover, a specifically designed ammonia photocatalytic system consisting of a small environmental chamber and a reactor was used for assessing the performance of these TiO₂-loaded fabrics as the wall cloth or curtains used in house rooms in the future and some factors affecting ammonia decomposition are discussed. Furthermore, a design equation of surface catalytic kinetics was developed for describing the decomposition of ammonia in air stream. The results indicated that increasing dosage of the TiO₂ aqueous dispersion in treating bath or coating paste improved the ammonia decomposition. And ammonia was effectively removed at low ammonia concentration or gas flow rate. When relative humidity level was 45%, ammonia decomposition was remarkably enhanced. It is the fact that ammonia could be significantly decomposed in the presence of the TiO₂-padded cotton fabric. Whereas, the TiO₂-coated cotton fabric had the reduced photocatalytic decomposition of ammonia and high adsorption to ammonia owing to their acrylic binder layer. Finally, the reaction rate constant k and the adsorption equilibrium constant K values were determined through a curve-fitting method and the TiO₂-padded cotton fabric had the higher k value and lower K value than the TiO₂-coated cotton fabric.

Keywords: Ammonia decomposition; Photocatalyst; Cotton fabric; Padding; Coating

Formaldehyde emission—Comparison of different standard methods by Maria Risholm-Sundman; Annelise Larsen; Ewa Vestin; Anders Weibull (pp. 3193-3202).

The emission of formaldehyde is an important factor in the evaluation of the environmental and health effects of wood-based board materials. This article gives a comparison between commonly used European test methods: chamber method [EN 717-1, 2004. Wood-based panels—determination of formaldehyde release—Part 1: formaldehyde emission by the chamber method. European Standard, October 2004], gas analysis method [EN 717-2, 1994. Wood-based panels—determination of formaldehyde release—Part 2: formaldehyde release by the gas analysis method, European Standard, November 1994], flask method [EN 717-3, 1996. Wood-based panels—determination of formaldehyde release—Part 3: formaldehyde release by the flask method, European Standard, March 1996], perforator method [EN 120, 1993. Wood based panels—determination of formaldehyde content—extraction method called perforator method, European Standard, September 1993], Japanese test methods: desiccator methods [JIS A 1460, 2001. Building boards. Determination of formaldehyde emission—desiccator method, Japanese Industrial Standard, March 2001 and JAS MAFF 233, 2001] and small chamber method [JIS A 1901, 2003. Determination of the emission of volatile organic compounds and aldehydes for building products—small chamber method, Japanese Industrial Standard, January 2003], for solid wood, particleboard, plywood and medium density fiberboard.The variations between the results from different methods can partly be explained by differences in test conditions. Factors like edge sealing, conditioning of the sample before the test and test temperature have a large effect on the final emission result. The Japanese limit for F**** of 0.3mgl⁻¹ (in desiccator) for particleboards was found to be equivalent to 0.04mgm⁻³ in the European chamber test and 2.8mg per 100g in the perforator test. The variations in inter-laboratory tests are much larger than in intra-laboratory tests; the coefficient of variation is 16% and 6.0% for the chamber method, 25% and 3.5% for the gas analysis method and 15% and 5.2% for the desiccator method.

Keywords: Emission testing; Formaldehyde; Chamber; Building materials; Wood; Particleboard; Wood-based boards

Influence of temperature on formaldehyde emission parameters of dry building materials by Yinping Zhang; Xiaoxi Luo; Xinke Wang; Ke Qian; Rongyi Zhao (pp. 3203-3216).

The diffusion coefficient, D, partition coefficient, K, and the initial volatile organic compounds (VOCs) in dry building materials, are the three key parameters used to predict the VOC emissions. D and K may be strongly affected by temperature. We have developed a new and simple method, the C-history method, to measure the diffusion coefficient, D and the partition coefficient, K of formaldehyde in dry building materials at temperatures of 18, 30, 40 and 50°C. The measured variations of the diffusion coefficients and the partition coefficients with temperature for particle board, vinyl floor, medium- and high-density board are presented. A formula relating the partition coefficient and related factors is obtained through analysis. This formula can predict the partition coefficient in principle and provide an insight for fitting experimental data, and it agrees well with the experimental results.

Keywords: Volatile organic compounds; Indoor air quality; Diffusion coefficient; Partition coefficient

The influence of humidity on the emission of di-(2-ethylhexyl) phthalate (DEHP) from vinyl flooring in the emission cell “FLEC” by P.A. Per Axel Clausen; Ying Xu; Kofoed-Sorensen Vivi Kofoed-Sørensen; John C. Little; Peder Wolkoff (pp. 3217-3224).

Asthma in children appears to be associated with both phthalate esters and dampness in buildings. An important question is whether the concentrations of phthalate esters correlate with dampness (expressed as relative humidity—RH) in indoor air. The objective was to study the influence of RH on the specific emission rate (SER) of di-(2-ethylhexyl)phthalate (DEHP) from one type of vinyl flooring in the well characterized Field and Laboratory Emission Cell (FLEC). The vinyl flooring with ca. 17% (w/w) DEHP as plasticizer was tested in 6 FLECs at 22°C. The RH in the 6 FLECs was 10%, 30%, 50% (in triplicate) and 70%. The RH was changed after 248d in 2 of the 50%-FLECs to 10% and 70%, and to 50% in the 10%-and 70%-FLECs. The data show that the SER of DEHP from vinyl flooring in FLECs during a 1yr period is independent of the RH. A new physically based emission model for semivolatile organic compounds was found to be consistent with the experimental data and independent of the RH. The model helps to explain the RH results, because it appears that RH does not significantly influence any of the identified controlling mechanisms.

Keywords: Vinyl flooring; Emission; DEHP; Humidity; Plasticizer

Texanol^® ester alcohol emissions from latex paints: Temporal variations and multi-component recoveries by C.-C. C.-C. Lin; R.L. Corsi (pp. 3225-3234).

This paper focuses on emissions of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (TMPD-MIB) from two latex paints applied to three substrates (aluminum, gypsum board, and concrete). The first 48h of each experiment involved small chamber testing. Specimens were then maintained in an office environment with intermittent rotation into chambers. Emission rates were observed for periods as long as 15 months, but were relatively low after 150h. Airborne recoveries of TMPD-MIB were a strong function of the type of paint and substrate. Recoveries in air of approximately 50% (semi-gloss paint) to 90% (flat paint) were observed after 15 months for regular applications to gypsum board, but were less than 25% after 8–15 months for applications to concrete. TMPD-MIB was recovered in the dried paint film and substrate (in the case of gypsum board) with 96±6% mass closure.

Keywords: Gypsum board; Concrete; Mass recovery; Mass closure; Chamber experiments

Measuring emissions of organophosphate flame retardants using a passive flux sampler by Y. Ni; K. Kumagai; Y. Yanagisawa (pp. 3235-3240).

Flame retardants are used in polymers to reduce the flammability of building materials, electric appliances, fabric and papers. In recent years, organophosphate flame retardants have been used as substitutes for polybrominated flame retardants (BFRs). In Japan, the amount of organophosphate flame retardants used in 2001 was about five times more than in 2000. Recently, several studies have shown the health concerns for some organophosphate flame retardants. Little research has been performed on the emission of organophosphate flame retardants, especially the relationship between content and emissions. In this study, a new type of passive sampler was developed to measure emissions of organophosphate flame retardants from plastic materials. With this sampler, emissions from polyvinyl chloride wallpaper samples with different content of tris(2-chloroisopropyl)phosphate (TCPP) at different temperatures were examined. The observed maximum emissions of TCPP from 1, 3, 5, 10 and 20 w/w% content wallpaper materials were 262.3, 452.6, 644.8, 1119.1 and 2166.8μgm⁻²h⁻¹, respectively. Emissions from 5% TCPP content materials at 40 and 60°C were 1135.7 and 2841.2μgm⁻²h⁻¹, respectively. A significantly positive correlation between the flux of TCPP and the TCPP content of the wallpaper samples was observed. A linear relationship was found between the inverse of temperature and the logarithm of TCPP emission. The results imply that the use of materials with a high organophosphate flame retardant content can lead to high emission rates in high-temperature indoor environments.

Keywords: Organophosphate flame retardants; Passive flux sampler; Wallpaper; TCPP

Transport of polar and non-polar volatile compounds in polystyrene foam and oriented strand board by Huali Yuan; John C. Little; Alfred T. Hodgson (pp. 3241-3250).

Transport of hexanal and styrene in polystyrene foam (PSF) and oriented strand board (OSB) was characterized. A microbalance was used to measure sorption/desorption kinetics and equilibrium data. While styrene transport in PSF can be described by Fickian diffusion with a symmetrical and reversible sorption/desorption process, hexanal transport in both PSF and OSB exhibited significant hysteresis, with desorption being much slower than sorption. A porous media diffusion model that assumes instantaneous local equilibrium governed by a nonlinear Freundlich isotherm was found to explain the hysteresis in hexanal transport. A new nonlinear sorption and porous diffusion emissions model was, therefore, developed and partially validated using independent chamber data. The results were also compared to the more conventional linear Fickian-diffusion emissions model. While the linear emissions model predicts styrene emissions from PSF with reasonable accuracy, it substantially underestimates the rate of hexanal emissions from OSB. Although further research and more rigorous validation is needed, the new nonlinear emissions model holds promise for predicting emissions of polar VOCs such as hexanal from porous building materials.

Keywords: Emissions; Model; Diffusion; Sorption; Desorption; Hysteresis; Styrene; Hexanal

Sorption of organic gases in residential rooms by Brett C. Singer; Alfred T. Hodgson; Toshifumi Hotchi; Katherine Y. Ming; Richard G. Sextro; Emily E. Wood; Nancy J. Brown (pp. 3251-3265).

Experiments were conducted to characterize organic gas sorption in residential rooms studied “as-is” with furnishings and material surfaces unaltered and in a furnished chamber designed to simulate a residential room. Results are presented for 10 rooms (five bedrooms, two bathrooms, a home office, and two multi-function spaces) and the chamber. Exposed materials were characterized and areas quantified. A mixture of volatile organic compounds (VOCs) was rapidly volatilized within each room as it was closed and sealed for a 5-h Adsorb phase; this was followed by 30-min Flush and 2-h closed-room Desorb phases. Included were alkane, aromatic, and oxygenated VOCs representing a range of ambient and indoor air pollutants. Three organophosphorus compounds served as surrogates for Sarin-like nerve agents. Measured gas-phase concentrations were fit to three variations of a mathematical model that considers sorption occurring at a surface sink and potentially a second, embedded sink. The 3-parameter sink–diffusion model provided acceptable fits for most compounds and the 4-parameter two-sink model provided acceptable fits for the others. Initial adsorption rates and sorptive partitioning increased with decreasing vapor pressure for the alkanes, aromatics and oxygenated VOCs. Best-fit sorption parameters obtained from experimental data from the chamber produced best-fit sorption parameters similar to those obtained from the residential rooms.

Keywords: Adsorption; Hazardous air pollutants; Nerve agents; Sink effect; Volatile organic compounds

Occurrence of organic and inorganic biocides in the museum environment by A. Schieweck; W. Delius; N. Siwinski; W. Vogtenrath; C. Genning; T. Salthammer (pp. 3266-3275).

In the museum environment organic and inorganic chemicals can be found, which originate from both outside and inside the building. Many of the contaminants may cause adverse effects on works of art and human health, but in the past, pollution research in museums has focused on the protection of artifacts, while the risk assessment for humans has been neglected. Especially, the application of biocides leads to a conflict of interest: on the one hand cultural assets have to be protected against microorganisms, insects and rodents while on the other hand it is essential to provide healthy conditions for museum staff and visitors. It has recently been shown that the release of organic indoor pollutants from building products is one of the main reasons for deterioration of artifacts. In this work, we present the results of screening measurements on biocides in different locations of German museums. The major components that could be identified were DDT, PCP, lindane, methoxychlor, naphthalene, chlorinated naphthalenes, 1,4-dichlorobenzene, PCBs and arsenic. It is demonstrated that the application of chlorinated organic compounds and arsenic for preventive conservation is one of the prime reasons for indoor pollution in museums and provides a potential for exposure. However, the concentrations in air, dust and material are widely different and a health risk for humans has to be evaluated case by case.

Keywords: Museums; Biocides; Pesticides; Exposure; Guideline values

Gas-phase exposure history derived from material-phase concentration profiles by G.C. Morrison; J.C. Little; Y. Xu; M. Rao; D. Enke (pp. 3276-3286).

Non-reactive gas-phase pollutants such as benzene diffuse into indoor furnishings and leave behind a unique material-phase concentration profile that serves as a record of the past gas-phase indoor concentrations. The inverse problem to be solved is the diffusion equation in a slab such as vinyl flooring. Using knowledge of the present material-phase concentration profile in the slab, we seek to determine the historical material-phase concentration at the surface exposed to indoor air, and hence the historical gas-phase concentration, which can be used directly to determine exposure. The problem as posed has a unique solution that may be solved using a variety of approaches. We use a trained artificial neural network (ANN) to derive solutions for hypothetical exposure scenarios. The ANN results show that it is possible to estimate the intensity and timing of past exposures from the material-phase concentration profile in a building material. The overall method is limited by (1) the resolution of techniques for measuring spatial material-phase concentration profiles, (2) how far back in time we seek to determine exposure and (3) the representational power of the ANN solution. For example, we estimate that this technique can estimate exposure to phenol up to 0.5 y in the past from analyses of vinyl flooring.

Keywords: Inverse diffusion; Exposure; Exposure history; Artificial neural network; Indoor air pollution

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Atmospheric Environment (v.41, #15)