Exposure to second-hand smoke air pollution assessed from bar patrons' urinary cotinine.

We used physical and pharmacokinetic modeling to estimate personal exposures to respirable particle (RSP) and carcinogenic particulate polycyclic aromatic hydrocarbon (PPAH) air pollution from second-hand smoke (SHS) from the increase in urinary cotinine of eight patrons of three bars in Bismarck, North Dakota. We compared SHS-RSP levels to the U.S. Air Quality Index (AQI), used to forecast outdoor air pollution conditions. We measured smoker density and air exchange rates to generalize our results. Urinary cotinine increased by an average of 4.28 ng/ml to 6.88 ng/ml to 9.55 ng/ml above preexposure background from 6-hr exposures in the three bars. Corresponding estimated SHS-RSP levels were, respectively, 246 microg/m3, 396 microg/m3, and 549 microg/m3, comparable to those measured in 6 Wilmington, Delaware, bars and in 14 western New York bars. Estimated personal SHS-RSP air pollution exposures for the eight subjects, when converted to the 24-hr averaging time of the AQI, were "code red" (unhealthy). Measured outdoor air quality RSP levels for the same period were 1%-3% of the indoor RSP levels in the three bars, and were AQI "code green" (healthy). Estimated SHS-PPAH levels were comparable to peak 3-hr PPAH levels reported at a highway tollbooth. Bismarck cotinine-estimated SHS-RSP varied with smoker density, as did measured SHS-RSP levels in smoking bars in Delaware and New York. Our results show that smoking in bars produces levels of personal air pollution for bar patrons that merit air pollution alerts when sustained in the outdoor air.     

Indoor air is a significant source of tri-decabrominated diphenyl ethers to outdoor air via ventilation systems

Ventilation of indoor air has been hypothesized to be a source of PBDEs to outdoors. To study this, tri-decabrominated diphenyl ethers were analyzed in outgoing air samples collected inside ventilation systems just before exiting 33 buildings and compared to indoor air samples from microenvironments in each building collected simultaneously. Median ∑(10)PBDE (BDE- 28, -47, -99, -153, -183, -197, -206, -207, -208, -209) concentrations in air from apartment, office and day care center buildings were 93, 3700, and 660 pg/m(3) for outgoing air, and 92, 4700, and 1200 pg/m(3) for indoor air, respectively. BDE-209 was the major congener found. No statistically significant differences were seen for individual PBDE concentrations in matched indoor and outgoing air samples, indicating that outgoing air PBDE concentrations are equivalent to indoor air concentrations. PBDE concentrations in indoor and outgoing air were higher than published outdoor air values suggesting ventilation as a conduit of PBDEs, including BDE-209, from indoors to outdoors. BDE-209 and sum of BDE-28, -47, -99, and -153 emissions from indoor air to outdoors were roughly estimated to represent close to 90% of total emissions to outdoor air for Sweden, indicating that contaminated indoor air is an important source of PBDE contamination to outdoor air.     

Perfluorinated sulfonamides in indoor and outdoor air and indoor dust: occurrence, partitioning, and human exposure

Perfluorinated alkyl sulfonamides (PFASs) which are used in a variety of consumer products for surface protection were investigated through a comprehensive survey of indoor air, house dust, and outdoor air in the city of Ottawa, Canada. This study revealed new information regarding the occurrence and indoor air source strength of several PFASs including N-methylperfluorooctane sulfonamidoethanol (MeFOSE), N-ethylperfluorooctane sulfonamidoethanol (EtFOSE), N-ethylperfluorooctane sulfonamide (EtFOSA), and N-methylperfluorooctane sulfonamidethylacrylate (MeFOSEA). Passive air samplers consisting of polyurethane foam disks were calibrated and used to conduct the indoor and outdoor survey. Indoor air concentrations for MeFOSE and EtFOSE (1490 and 740 pg m(-3), respectively) were about 10-20 times greater than outdoor concentrations, establishing indoor air as an important source to the outside environment. EtFOSA and MeFOSEA concentrations were lower in indoor air (40 and 29 pg m(-3) respectively) and below detection in outdoor air samples. For indoor dust, highest concentrations were recorded for MeFOSE and EtFOSE with geometric mean concentrations of 110 and 120 ng g(-1), while concentrations for EtFOSA and MeFOSEA were below detection and 7.9 ng g(-1) respectively. MeFOSE and EtFOSE concentrations in house dust followed levels in indoor air. However, resolution of the coupled air and dust data (for the same homes) was not successful using existing KoA-based models for surface-air exchange. The partitioning to house dust was greatly underpredicted. The difficulties with existing models may be due to the high activity coefficient of PFASs in octanol and/or a situation where the dust is greatly oversaturated with respect to the air due to components of the dust being contaminated with PFASs. A human exposure assessment based on median air and dust concentrations revealed that human exposure through inhalation (100% absorption assumed) and dust ingestion were approximately 40 and approximately 20 ng d(-1), respectively. However, for children the dust ingestion pathway was dominant and accounted for approximately 44 ng d(-1).     

Modeling the influence of intermittent rain events on long-term fate and transport of organic air pollutants

The deposition of particles and substances in air is under strong influence of the precipitation patterns of the atmosphere. Most multimedia models, like type III Mackay models, treat rain as a continuous phenomenon. This may cause severe overestimation of the substance removal from the atmosphere through wet deposition and an underestimation of travel distances, leading to the following questions: How strong is the influence of the intermittent character of rain on concentrations, residence times, deposited fractions, and characteristic transport distances of different substances in air? Is there an expression that can provide an accurate approximation to be used in steady-state multimedia models? Assuming a periodically intermittent rain, the mass of an emitted substance that is present in the air compartment is calculated as a function of the deposition rate constants during dry and wet periods and the durations of these periods. In this paper, results for 300 different organic chemicals are presented and illustrated in more detail for four typical substances, showing the following: (i) Deposition velocities can be up to 4 orders of magnitude higher during rain events than during dry periods, especially for persistent substances with low Henry constant. (ii) For substances with a short reaction time (residence time as determined by atmospheric degradation alone) (e.g., propoxur), the assumption of continuous rain may lead to an underestimation of the atmospheric residence time and travel distance by up to 3 orders of magnitude. For this group of substances, the residence time during dry period provides a good estimate of the overall atmospheric residence time. (iii) For substances with reaction times close to the duration of the dry period, the behavior is driven by the length of the time interval between two rain events, as for example, for methomyl. (iv) For very persistent substances such as pentachloronitrobenzene or carbon tetrachloride, the continuous rain approximation provides a good estimate. On the basis of these findings, an accurate but simple approximation is provided by eq 17 for the incorporation of intermittent rain behavior in steady-state multimedia models.     

Redistribution of traffic related air pollution associated with a new road tunnel

The aim of this study was to assess the effect of a new road tunnel on the concentration and distribution of traffic-related air pollution (TRAP), specifically nitrogen dioxide (NO(2)) and particulate matter (PM), and to determine its relationship to change in traffic flow. We used continuously recorded data from four monitoring stations at nonroadside locations within the study area and three regional monitors outside the area. The four monitors in the study area were in background locations where smaller pollutant changes were expected compared with changes near the bypassed main road. We also deployed passive samplers to assess finer spatial variability in NO(2) including application of a land use regression model (LUR). The study was conducted from 2006 to 2008. Analysis of the continuously recorded data showed that the tunnel intervention did not lead to consistent reductions in NO(2) or PM over the wider study area. However, there were significant decreases in NO(2), NO(x), and PM(10) in the eastern section of the study area. Analysis of passive sampler data indicated that the greatest reductions in NO(2) concentrations occurred within 100 m of the bypassed main road. The LUR model also demonstrated that changes in NO(2) were most marked adjacent to the bypassed main road. These findings support the use of methods that highlight fine spatial variability in TRAP and demonstrate the utility of traffic interventions in reducing air pollution exposures for populations living close to main roads.     

Probabilistic approach to estimating indoor air concentrations of chlorinated volatile organic compounds from contaminated groundwater: a case study in San Antonio, Texas

This paper describes a probabilistic model, based on the Johnson-Ettinger algorithm, developed to characterize the current and historic exposure to tricholorethylene (TCE) and tetrachlorethylene (PCE) in indoor air from plumes of groundwater contamination emanating from the former Kelly Air Force Base in San Antonio, Texas. We estimate indoor air concentration, house by house, in 30?101 homes and compare the estimated concentrations with measured values in a small subset of homes. We also compare two versions of the Johnson-Ettinger model: one used by the Environmental Protection Agency (EPA) and another based on an alternative parametrization. The modeled mean predicted PCE concentration historically exceeded PCE screening levels (0.41 ug/m(3)) in 5.5% of houses, and the 95th percentile of the predicted concentration exceeded screening levels in 85.3% of houses. For TCE, the mean concentration exceeded the screening level (0.25 ug/m(3)) in 49% of homes, and the 95th percentile of the predicted concentration exceeded the screening level in 99% of homes. The EPA model predicts slightly lower indoor concentrations than the alternative parametrization. Comparison with measured samples suggests both models, with the inputs selected, underestimate indoor concentrations and that the 95th percentiles of the predicted concentrations are closer to measured concentrations than predicted mean values.     

Rapidly equilibrating micrometer film sampler for priority pollutants in air

Modified polymer-coated glass samplers (POGs), termed EVA samplers, consist of micrometer-thin layers of ethylene vinyl acetate (EVA) coated onto a glass fiber filter or aluminum foil substrate. These samplers were designed to equilibrate rapidly with priority pollutants in air, making them ideal for short-term spatial studies in ambient or indoor air. The EVA sampler was calibrated by measuring the uptake of polychlorinated biphenyls (PCBs) over 8 weeks in an indoor environment, and four different film thicknesses were monitored that ranged from 0.1 to 30 μm. The results were used to calculate the average mass transfer coefficient (50.5 m/day) and generate contour maps that provide guidance in choosing an appropriate EVA sampler for a particular study based on film thickness, deployment time, and the log K(OA) of the anlayte. A range of air pollutant classes was also added to the EVA sampler prior to deployment to assess depuration rates. These included polychlorinated biphenyls (PCBs), current-use pesticides (CUPs), perfluorinated compounds (PFCs), and polybrominated diphenyl ethers (PBDEs). On the basis of the depuration profiles, the EVA sampler was a suitable equilibrium sampler for several CUPs and PCBs; however, for the high molecular weight PCBs and PBDEs, the EVA sampler operates as a linear uptake sampler. Samplers were also evaluated for their use as a rapid screening tool for assessing concentrations of siloxanes in indoor air. The EVA sampler was used to estimate air concentrations for D4 and D5 in laboratory air to be 118 and 89 ng/m(3), respectively. Analyses were performed directly using thermal desorption gas chromatography/mass spectrometry (TDS-GC-MS). EVA samplers show promise due to their relatively low cost and ease of deployment and applicability to a wide range of priority chemicals. The ability to alter the film thickness, and hence the sorption capacity and performance of the EVA sampler, allows for a versatile sampler that can be used under varying sampling conditions and deployment times.     

Selected volatile organic compounds in residential air in the city of Ottawa, Canada

Airborne levels of selected volatile organic chemicals (VOCs) that are priorities for exposure assessment under the Canadian Environmental Protection Act (CEPA) 1999 were measured in both indoor air and outdoor air of 75 residential houses, in the city of Ottawa, Canada, during the winter of 2002/2003. The houses were randomly selected using Ottawa 2001 population census data. VOCs were collected on adsorbent tubes and measured by thermal desorption GC/MS. Among 37 chemicals monitored, 17 were detected with a frequency greater than 80% in indoor air; 9 were between 30% and 80%; 7 were between 1% and 30%; and 4 were not detected. Concentrations of VOCs in both indoor and outdoor air are presented. Virtually all of the target VOCs were detected more frequently and were present at significantly higher levels, in indoor air than in outdoor air. As an indication of the contribution of indoor levels of these chemicals, ratios of the concentration found in indoor air to outdoor air (I/O) and the indoor source strength expressed in estimated emission rate per house are also presented. Compared with earlier published studies including a 1991/1992 Canadian national survey of VOCs in residential air, levels of target analytes in indoor air in this study were lower for a number of chemicals, indicating a possible trend toward decreased inhalation exposure to these chemicals in residential environments. This study has yielded up-to-date information on levels of a variety of priority airborne chemicals in residential air, which is being used to estimate current exposure to these substances as input to health risk assessments and risk management actions under CEPA 1999.     

Single-layer model to predict the source/sink behavior of diffusion-controlled building materials

Building materials may act as both sources of and sinks forvolatile organic compounds (VOCs) in indoor air. A strategy to characterize the rate of absorption and desorption of VOCs by diffusion-controlled building materials is validated. A previously developed model that predicts mass transfer between a flat slab of material and the well-mixed air within a chamber or room is extended. The generalized model allows a nonuniform initial material-phase concentration and a transient influent gas-phase concentration to be simultaneously considered. An analytical solution to the more general model is developed. Experimental data are obtained by placing samples of vinyl flooring inside a small stainless steel chamber and exposing them to absorption/desorption cycles of n-dodecane and phenol. Measured values for the material-air partition coefficient and the material-phase diffusion coefficient were obtained previously in a series of completely independent experiments. The a priori model predictions are in close agreement with the observed experimental data.     

Evaluating differences between measured personal exposures to volatile organic compounds and concentrations in outdoor and indoor air

Accurate estimation of human exposures to volatile organic compounds (VOCs) is a key element of strategies designed to protect public health from the adverse effects of hazardous air pollutants. The focus here is on examining the capability of three different exposure metrics (outdoor community concentrations, indoor residential concentrations, and a simple time-weighted model) to estimate observed personal exposures to 14 VOCs. The analysis is based on 2-day average concentrations of individual VOCs measured concurrently in outdoor (O) air in three urban neighborhoods, indoor (I) air in participant's residences, and personal (P) air near the breathing zone of 71 healthy, nonsmoking adults. A median of four matched P-I-O samples was collected for each study participant in Minneapolis/St. Paul over three seasons (spring, summer, and fall) in 1999 using charcoal-based passive air samplers (3M model 3500 organic vapor monitors). Results show a clear pattern for the 14 VOCs, with P > I > O concentrations. Intra-individual variability typically spanned at least an order of magnitude, and inter-individual variability spanned 2 or more orders of magnitude for each of the 14 VOCs. Although both O and I concentrations generally underestimated personal exposures, I concentrations provided a substantially better estimate of measured P concentrations. Mean squared error (MSE) as well as correlation measures were used to assess estimator performance at the subject-specific level, and hierarchical, mixed effects models were used to estimate the bias and variance components of MSE by tertile of personal exposure. Bias and variance both tended to increase in the upper third of the P exposure distribution for O versus P and I versus P. A simple time-weighted model incorporating measured concentrations in both outdoor community air and indoor residential air provided no improvement over I concentration alone for the estimation of P exposure.     

Daily and peak 1 h indoor air pollution and driving factors in a rural Chinese village

We investigate wintertime indoor air quality and personal exposures to carbon monoxide (CO) in a rural village in Jilin province, where relatively homogeneous climatic and sociocultural factors facilitate investigation of household structural, fuel-related, and behavioral determinants of air pollution as well as relationships between different measures of air quality. Our time-resolved wintertime measurements of carbon monoxide and respirable particles (RSP) enable exploration of peak pollution periods in a village in Jilin Province, China, characterized by household use of both coal and biomass, as well as several "improved" (gas or electric) fuels. Our data indicate a 6-fold increase in peak 1 h PM (1.9 mg/m3) concentrations relative to 24 h mean PM (0.31 mg/m3). Peak 1 h CO concentrations (20.5 ppm) routinely approached and often (27%) exceeded the World Health Organization's 1 h guideline of 26 ppm, although the vast majority (95%) of kitchens were within China's residential indoor air quality guideline for CO on a 24 h basis. Choice of heating fuel and household smoking status were significant predictors of indoor air quality. Whether solid or "improved" (gas or electric) fuel was used for cooking had an even stronger effect, but in the opposite direction from expected, on both peak and daily average measures of air pollution. Peak pollution period concentrations of CO and PM were strongly correlated to daily concentrations of CO and RSP, respectively. Our results suggestthat due to the primary role of heating as a determinant of wintertime indoor air quality in northern Chinese villages, health-oriented interventions limited to provision of improved cooking fuel are insufficient. Our results illustrate that peak pollution periods may routinely exceed exposure regulations and evacuation limits, although this and previous studies document typical 24 h CO concentrations in rural Chinese kitchens to be within guidelines. Within a given village and for a given pollutant, daily pollutant concentrations may be strong predictors of peak pollution period concentrations.     

Use of time- and chemically resolved particulate data to characterize the infiltration of outdoor PM2.5 into a residence in the San Joaquin Valley

Recent studies associate particulate air pollution with adverse health effects. The indoor exposure to particles of outdoor origin is not well-characterized, particularly for individual chemical species. In response to this, a field study in an unoccupied, single-story residence in Clovis, CA, was conducted. Real-time particle monitors were used both outdoors and indoors to quantity PM2.5 nitrate, sulfate, and carbon. The aggregate of the highly time-resolved sulfate data, as well as averages of these data, was fit using a time-averaged form of the infiltration equation, resulting in reasonable values for the penetration coefficient and deposition loss rate. In contrast, individual values of the indoor/outdoor ratio can vary significantly from that predicted by the model for time scales ranging from a few minutes to several hours. Measured indoor ammonium nitrate levels were typically significantly lower than expected solely on the basis of penetration and deposition losses. The additional reduction is due to the transformation of ammonium nitrate into ammonia and nitric acid gases indoors, which are subsequently lost by deposition and sorption to indoor surfaces. This result illustrates that exposure assessments based on total outdoor particle mass can obscure the actual causal relationships for indoor exposures to particles of outdoor origin.     

Effect of vapor source-building separation and building construction on soil vapor intrusion as studied with a three-dimensional numerical model

A three-dimensional numerical model of the soil vapor-to-indoor air pathway is developed and used as a tool to anticipate not-yet-measured relationships between the vapor attenuation coefficient, alpha (indoor air concentration/source vapor concentration), and vapor source-building lateral separation, vapor source depth, and building construction characteristics (depth of building foundation) for nondegrading chemicals. The numerical model allows for diffusive and advective transport, multicomponent systems and reactions, spatially distributed foundation cracks, and transient indoor and ambient pressure fluctuations. Simulations involving different lateral separations between the vapor source and building show decreasing alpha values with increasing lateral separation. For example, alpha is 2 orders of magnitude less when a 30 m x 30 m source located 8 m below ground surface is displaced from the edge of the building by 20 m. The decrease in alpha with increasing lateral separation is greater for shallower source depths. For example, alpha is approximately 5 orders of magnitude less when a 30 m x 30 m source located 3 m below ground surface is displaced from the edge of the building by 20 m. To help visualize the effects of changing vapor source-building separations, normalized vapor concentration contour plots for both horizontal and vertical cross sections are presented for a sequence of lateral separations ranging from the case in which the 30 m x 30 m source and 10 m x 10 m building footprint centers are collocated to shifting of the source positioning by 50 m. Simulations involving basement and slab-on-grade constructions produce similar trends. In addition, when buildings are overpressurized to create outflow to soil gas on the order of 1-3 L/min, emissions to indoor air are reduced by over 5 orders of magnitude relative to intrusion rates at zero building underpressurization. The results are specific to simulations involving homogeneous soil properties, nondegrading chemicals, steady source concentrations and building underpressurizations, and the geometries studied in this work.     

Use of real-time light scattering data to estimate the contribution of infiltrated and indoor-generated particles to indoor air

The contribution of outdoor particulate matter (PM) to residential indoor concentrations is currently not well understood. Most importantly, separating indoor PM into indoor- and outdoor-generated components will greatly enhance our knowledge of the outdoor contribution to total indoor and personal PM exposures. This paper examines continuous light scattering data at 44 residences in Seattle, WA. A newly adapted recursive model was used to model outdoor-originated PM entering indoor environments. After censoring the indoor time-series to remove the influence of indoor sources, nonlinear regression was used to estimate particle penetration (P, 0.94 +/- 0.10), air exchange rate (a, 0.54 +/- 0.60 h(-1)), particle decay rate (k, 0.20 +/- 0.16 h(-1)), and particle infiltration (F(inf), 0.65 +/- 0.21) for each of the 44 residences. All of these parameters showed seasonal differences. The F(inf) estimates agree well with those estimated from the sulfur-tracer method (R2 = 0.78). The F(inf) estimates also showed robust and expected behavior when compared against known influencing factors. Among our study residences, outdoor-generated particles accounted for an average of 79 +/- 17% of the indoor PM concentration, with a range of 40-100% at individual residences. Although estimates of P, a, and k were dependent on the modeling technique and constraints, we showed that a recursive mass balance model combined with our censoring algorithms can be used to attribute indoor PM into its outdoor and indoor components and to estimate an average P, a, k, and F(inf), for each residence.     

Spatial distribution of polybrominated diphenyl ethers in southern Ontario as measured in indoor and outdoor window organic films

Organic films were collected from indoor and outdoor window surfaces, along an urban-rural transect extending northward from Toronto, Ontario, Canada, and analyzed for 41 polybrominated diphenyl ether congeners (PBDE). For exterior films, urban sigmaPBDE concentrations were approximately 10x greater than rural concentrations, indicating an urban-rural gradient and greater PBDE sources in urban areas. Urban films ranged from 2.5 to 14.5 ng/m2 (mean = 9.0 ng/ m2), excluding the regional "hotspot" Electronics Recycling Facility, compared to 1.1 and 0.56 ng/m2 at the Suburban and Rural sites. Interior urban films (mean = 34.4 ng/m2) were 3 times greater than rural films (10.3 ng/m2) and were representative of variations in building characteristics. Indoor films were 1.5-20 times greater than outdoor films, consistent with indoor sources of PBDEs and enhanced degradation in outdoor films. Congener profiles were dominated by BDE-209 (51.1%), consistent with deca-BDE as the main source mixture, followed by congeners from the penta-BDE mixture (BDE-99:13.6% and -47:9.4%) and some octa-BDE (BDE-183:1.5%). Congener patterns suggest a degradative loss of lower brominated compounds in outdoor films versus indoor films. Gas-phase air concentrations were back-calculated from film concentrations using the film-air partition coefficient (K(FA)). Mean calculated air concentrations were 4.8 pg/m3 for outdoor and 42.1 pg/m3 for indoor urban sites, indicating that urban indoor air is a source of PBDEs to urban outdoor air and the outdoor regional environment.     

Polyfluorinated compounds in residential and nonresidential indoor air

Indoor air concentrations of fifteen volatile per- and polyfluorinated compounds (PFCs) (five fluorotelomer alcohols (FTOHs), three fluorotelomer acrylates (FTAs), three perfluorinated sulfonamido ethanols (FASEs), and three perfluorinated sulfonamides (FASAs)) were determined in residential and nonresidential indoor air environments. Air samples were taken with passive samplers, consisting of XAD-4 impregnated polyurethane foam (PUF) disks in steel housings. Impregnated PUF disks were extracted by fluidized bed extraction (FBE) using methyl-tert-butyl ether/acetone (1:1) and analyzed by gas chromatography-mass spectrometry. Total PFC indoor air concentrations ranged from 8.2 to 458 ng m(-3). Individual PFC concentrations were between 42 pg m(-3) (6:2 FTA) and 209 ng m(-3) (8:2 FTOH). Concentrations of total FTOHs, FTAs, and FASAs + FASEs ranged from 0.2 to 152 ng m(-3) (FTAs), from 3.3 to 307 ng m(-3) (FTOHs), and from 4.4 to 148 ng m(-3) (FASAs + FASEs). Most elevated individual, group, and total PFC concentrations were detected in two stores selling outdoor equipment, one furniture shop, and one carpet shop. Indoor air concentrations were several orders of magnitude higher than published outdoor air concentrations indicating indoor air environments as sources for PFCs to the atmosphere. Concentrations were used to estimate human exposure to investigated PFCs.     

Predicting residential air exchange rates from questionnaires and meteorology: model evaluation in central North Carolina

A critical aspect of air pollution exposure models is the estimation of the air exchange rate (AER) of individual homes, where people spend most of their time. The AER, which is the airflow into and out of a building, is a primary mechanism for entry of outdoor air pollutants and removal of indoor source emissions. The mechanistic Lawrence Berkeley Laboratory (LBL) AER model was linked to a leakage area model to predict AER from questionnaires and meteorology. The LBL model was also extended to include natural ventilation (LBLX). Using literature-reported parameter values, AER predictions from LBL and LBLX models were compared to data from 642 daily AER measurements across 31 detached homes in central North Carolina, with corresponding questionnaires and meteorological observations. Data was collected on seven consecutive days during each of four consecutive seasons. For the individual model-predicted and measured AER, the median absolute difference was 43% (0.17 h(-1)) and 40% (0.17 h(-1)) for the LBL and LBLX models, respectively. Additionally, a literature-reported empirical scale factor (SF) AER model was evaluated, which showed a median absolute difference of 50% (0.25 h(-1)). The capability of the LBL, LBLX, and SF models could help reduce the AER uncertainty in air pollution exposure models used to develop exposure metrics for health studies.     

Heat and mass transfer coefficients at the surface of elliptical cylinders placed in a turbulent air flow

Heat and mass transfer coefficients were measured at the surface of elliptical cylinders of three different lengths (0·10 m, 0·15 m and 0·20 m) and five ratios of major to minor axis placed in a cross flow of air. The flow was characteristic of food pilot plants, i.e. an air velocity ranging from 0·5m s⁻¹ to 2·0 m s⁻¹ and a turbulence intensity, Tu, of about 12%. In agreement with theory, the transfer coefficients measured at this turbulence intensity were higher than those usually indicated in chemical engineering literature, which are based on experiments in ‘aeronautic’ wind tunnels where the turbulence intensity is close to 0%. The air flow properties (air velocity and turbulence intensity) have a greater effect than body shape characteristics (length and ratio). Velocity and turbulence intensity measurements in a chilling room and a dryer showed that the flow is intermittent and highly turbulent (Tu from 17 to 60%). Thus, the turbulence has to be taken into account in food engineering studies.     

Evaluation of the intrinsic photocatalytic oxidation kinetics of indoor air pollutants

This paper presents a methodology for the evaluation of the intrinsic photocatalytic oxidation (PCO) kinetics of indoor air pollutants. It combines computational fluid dynamics (CFD) modeling of the fluid flow in the reactor with radiation field modeling and photocatalytic reaction kinetics to yield a rigorous model of a flat-plate, single-pass, flow-through photocatalytic reactor for indoor air purification. This method was applied to model the PCO of trichloroethylene (TCE) in humidified air and to derive kinetic parameters directly from kinetic data in an integral flow reactor. Steady-state PCO experiments of TCE over irradiated TiO2 (Degussa P25) thin films immobilized on glass supports were carried out at different radiation intensities, flow rates, and inlet substrate concentrations. The oxidation rate of TCE was found to be first-order on the incident photon flux and to follow a Langmuir-Hinshelwood type reaction kinetics rate law. Mass transfer resistances were observed at Reynolds numbers less than 46. Apparent quantum yields were found to be up to 0.97 mol Einstein(-1). A comparison of the model prediction with the experimental results in an integral reactor yielded pollutant-specific kinetic rate parameters which were independent of reactor geometry, radiation field, and fluid-dynamics. The kinetic parameters would,therefore, be more universally applicable to the design and scale-up of photocatalytic reactors for indoor air purification.     

Personal exposure to polybrominated diphenyl ethers (PBDEs) in residential indoor air

We used personal air samplers to measure indoor air exposure to polybrominated diphenyl ethers (PBDEs) for 20 residents of the Greater Boston Area (Massachusetts). Area air measures were simultaneously collected from two rooms in each participant's home. Total personal air concentrations (particulate + vapor) were 469 pg/m3 for non-209 BDEs and 174 pg/m3 for BDE 209, significantly higher than bedroom and main living room concentrations (p = 0.01). The ratio of personal air to room air increased from 1 for vapor-phase congeners to 4 for fully particulate-bound congeners, indicating a personal cloud effect. Bedroom and main living area air samples were moderately correlated for non-209 BDEs (r = 0.45, p = 0.045) and BDE 209 (r = 0.58, p = 0.008). Use of personal air concentrations increased estimates of inhalation exposure over those previously reported. Inhalation may account for up to 22% of the total BDE 209 exposure in U.S. adults.