Organic air pollutants inside and outside residences in Shimizu, Japan: levels, sources and risks

Concentrations of 38 organic air pollutants including aromatic hydrocarbons (AHCs), carbonyl compounds (CCs), volatile organic halogenated compounds (VOHCs), and organophosphorus compounds (OPCs) were measured in indoor and outdoor air in an industrial city, Shimizu, Shizuoka Prefecture, Japan. Levels of pollutants tended to be higher indoors than outdoors in both summer and winter except for benzene, carbon tetrachloride, trichloroethylene, tetrachloroethylene, and dichlorvos (DDVP). This trend was especially pronounced for CCs such as formaldehyde and acetaldehyde. For the organic air pollutants, the concentrations of AHCs and VOHCs substantially increased in winter, but not those of CCs and OPCs; the trends were similar for both indoors and outdoors. We investigated possible indoor sources of pollutants statistically. Multiple regression analysis of corresponding indoor and outdoor concentrations and the responses to our questionnaire showed that indoor concentrations of certain AHCs were significantly affected by their outdoor concentrations and cigarette smoking. For formaldehyde, indoor concentrations were significantly affected by house age and the presence of carpet or pets. For p-dichlorobenzene (pDCB), the concentrations in bedroom trended to be higher than those in other indoors and outdoors, suggested that mothballs for clothes present in bedrooms are the principal indoor source of pDCB. We compared indoor and outdoor pollutant concentrations to acceptable risk limits for 11 organic air pollutants. In indoors without smoking samples, the geometric mean concentrations of benzene, formaldehyde, acetaldehyde, carbon tetrachloride, pDCB, and DDVP exceeded the equivalent concentration representing the upper bound of one-in-one-hundred-thousand (1x10(-5)) excess risk over a lifetime of exposure.     

Ultrafine particle emissions from essential‐oil‐based mosquito repellent products

Ultrafine particle (UFP) emissions from three essential‐oil‐based mosquito repellent products (lemon eucalyptus (LE), natural insects (NI), and bite shield (BS)) were tested in a 386 l chamber at a high air exchange rate of 24/h with filtered laboratory air. Total particle number concentration and size distribution were monitored by a condensation particle counter and a scanning mobility particle sizer, respectively. UFPs were emitted from all three products under indoor relevant ozone concentrations (~ 17 ppb). LE showed a nucleation burst followed by a relatively stable and continuous emission while the other two products (NI and BS) showed episodic emissions. The estimated maximum particle emission rate varied from 5.4 × 10⁹ to 1.2 × 10¹² particles/min and was directly related to the dose of mosquito repellent used. These rates are comparable to those due to other indoor activities such as cooking and printing. The emission duration for LE lasted for 8–78 min depending on the dose applied while the emission duration for NI and BS lasted for 2–3 h.     

Modelling of Emission and Re-emission of Volatile Organic Compounds from Building Materials with Indoor Air Applications

Polymer materials and their additives are today ever present in our daily surroundings. These materials have been found to emit a number of different volatile organic compounds (VOCs) into the ambient air, thus affecting the quality of the indoor air VOCs with detectable concentrations are exchanged between the different materials and indoor air. Materials present in the system act as sorbents as well as sources of emission, depending on the concentration of the VOCs in the air at a specific time. This work demonstrates a method of studying the phenomena of absorption/re-emission. A hypothetical room that resembles a furnished office has been studied. A PVC flooring material was used as a primary emission source in a system where materials such as wood, paint, cloth, chipboard, and cellulose were present. Mass transfer in the solid materials was assumed to be by diffusion. The results show that the mechanism of absorption/re-emission of volatiles may extend the time of residence in an indoor system considerably. A person working in this environment could risk longer exposure to toxic volatiles than if there were no absorption/re-emission effects.     

Comparison of three small chamber test methods for the measurement of VOC emission rates from paint

The aim of this study was to demonstrate a correlation between the measurement of emission rates of volatile organic compounds (VOCs) in three different climate chambers. In order to achieve this aim, the early state of the emission process in the three chambers was investigated and the effects of some important factors on the emission rates from paint were determined. The paper presents results of measurements in three different climate chambers. For the study, a 1-m3 chamber, a field and laboratory emission cell (FLEC), and a chamber for laboratory investigation of materials pollution and air quality (CLIMPAQ) were used. The airflow and surface area were selected so that the area-specific ventilation rates were identical in the three chambers. Temperature and relative humidity were identical during all the measurements. The paint examined was a solvent-based alkyd paint intended for indoor, which use contained between 30 and 60% of white spirit in wet condition. The paint was applied to electropolished and cleaned stainless steel plates. After application, the test material was stored for 14 days for drying in a well-ventilated conditioning room before the measurements were made. After 2 weeks storage, the most pronounced emissions were pentanal, hexanal, octanal, and decanol. The period before the emission rate stabilized differed for the three chambers studied. However, all chambers gave similar emission rates within the overall uncertainty used in these experiments.     

Size-resolved emission rates of airborne bacteria and fungi in an occupied classroom

The role of human occupancy as a source of indoor biological aerosols is poorly understood. Size-resolved concentrations of total and biological particles in indoor air were quantified in a classroom under occupied and vacant conditions. Per-occupant emission rates were estimated through a mass-balance modeling approach, and the microbial diversity of indoor and outdoor air during occupancy was determined via rDNA gene sequence analysis. Significant increases of total particle mass and bacterial genome concentrations were observed during the occupied period compared to the vacant case. These increases varied in magnitude with the particle size and ranged from 3 to 68 times for total mass, 12-2700 times for bacterial genomes, and 1.5-5.2 times for fungal genomes. Emission rates per person-hour because of occupancy were 31 mg, 37 × 10(6) genome copies, and 7.3 × 10(6) genome copies for total particle mass, bacteria, and fungi, respectively. Of the bacterial emissions, ～18% are from taxa that are closely associated with the human skin microbiome. This analysis provides size-resolved, per person-hour emission rates for these biological particles and illustrates the extent to which being in an occupied room results in exposure to bacteria that are associated with previous or current human occupants. PRACTICAL IMPLICATIONS: Presented here are the first size-resolved, per person emission rate estimates of bacterial and fungal genomes for a common occupied indoor space. The marked differences observed between total particle and bacterial size distributions suggest that size-dependent aerosol models that use total particles as a surrogate for microbial particles incorrectly assess the fate of and human exposure to airborne bacteria. The strong signal of human microbiota in airborne particulate matter in an occupied setting demonstrates that the aerosol route can be a source of exposure to microorganisms emitted from the skin, hair, nostrils, and mouths of other occupants.     

On-site passive flux sampler measurement of emission rates of carbonyls and VOCs from multiple indoor sources

In indoor environments with high levels of air pollution, it is desirable to remove major sources of emissions to improve air quality. In order to identify the emission sources that contribute most to the concentrations of indoor air pollutants, we used passive flux samplers (PFSs) to measure emission rates of carbonyl compounds and volatile organic compounds (VOCs) from many of the building materials and furnishings present in a room in a reinforced concrete building in Tokyo, Japan. The emission flux of formaldehyde from a desk was high (125 μg/m²/h), whereas fluxes from a door and flooring were low (21.5 and 16.5 μg/m²/h, respectively). The emission fluxes of toluene from the ceiling and the carpet were high (80.0 and 72.3 μg/m²/h, respectively), whereas that from the flooring was low (9.09 μg/m²/h). The indoor and outdoor concentrations of formaldehyde were 61.5 and 8.64 μg/m³, respectively, and those of toluene were 43.2 and 17.5 μg/m³, respectively. The air exchange rate of the room as measured by the perfluorocarbon tracer (PFT) method was 1.84/h. Taking into consideration the area of the emission sources, the carpet, ceiling, and walls were identified as the principal emission sources, contributing 24%, 20%, and 22% of the formaldehyde, respectively, and 22%, 27%, and 14% of the toluene, respectively, assuming that the emission rate from every major emission sources could be measured. In contrast, the door, the flooring, and the desk contributed little to the indoor levels of formaldehyde (1.0%, 0.54%, and 4.1%, respectively) and toluene (2.2%, 0.31%, and 0.85%, respectively).     

Material emission rates: Literature review,and the impact of indoor air temperature and relative humidity

An extensive literature review of research on the impact of indoor air conditions; temperature, relative humidity and surface air velocity on materials emission rates is presented. This paper also presents the results of an experimental work to study the impact of room air temperature and relative humidity on materials emission rates. The results indicate that both the temperature and relative humidity have a significant effect on the emissions from paint and varnish. In the case of varnish, the results were consistent with earlier results. However, the paint results show inconsistent emission behaviour. Further, for both materials, the individual compounds did not necessarily follow the same trend established for the TVOC.     

Ozone in indoor environments: concentration and chemistry

The concentration of indoor ozone depends on a number of factors, including the outdoor ozone concentration, air exchange rates, indoor emission rates, surface removal rates, and reactions between ozone and other chemicals in the air. Outdoor ozone concentrations often display strong diurnal variations, and this adds a dynamic excitation to the transport and chemical mechanisms at play. Hence, indoor ozone concentrations can vary significantly from hour-to-hour, day-to-day, and season-to-season, as well as from room-to-room and structure-to-structure. Under normal conditions, the half-life of ozone indoors is between 7 and 10 min and is determined primarily by surface removal and air exchange. Although reactions between ozone and most other indoor pollutants are thermodynamically favorable, in the majority of cases they are quite slow. Rate constants for reactions of ozone with the more commonly identified indoor pollutants are summarized in this article. They show that only a small fraction of the reactions occur at a rate fast enough to compete with air exchange, assuming typical indoor ozone concentrations. In the case of organic compounds, the "fast" reactions involve compounds with unsaturated carbon-carbon bonds. Although such compounds typically comprise less than 10% of indoor pollutants, their reactions with ozone have the potential to be quite significant as sources of indoor free radicals and multifunctional (-C=O, -COOH, -OH) stable compounds that are often quite odorous. The stable compounds are present as both gas phase and condensed phase species, with the latter contributing to the overall concentration of indoor submicron particles. Indeed, ozone/alkene reactions provide a link between outdoor ozone, outdoor particles and indoor particles. Indoor ozone and the products derived from reactions initiated by indoor ozone are potentially damaging to both human health and materials; more detailed explication of these impacts is an area of active investigation.     

Preventing the entry of outdoor particles with the indoor positive pressure control method: Analysis of influencing factors and cost

Maintaining positive pressure indoors with a mechanical ventilation system is a popular control method for preventing the entry of outdoor airborne particles. This paper analyzes the factors which affect the satisfied superfluous airflow rates of positive pressure control. Through modeling a large amount of cases with a validated model, the factors, e.g. temperature difference, outdoor wind velocity, effective air leakage gaps in the envelopes, the area of the air leakage and the room, were analyzed. Based on the theoretical model, a correlating equation to calculate the satisfied superfluous airflow rate was established by multiple full quadratic regressions. The correlating equation is simple for engineers or designers to use to determine the satisfied superfluous airflow rate. This paper also aims to find which method, pressure control or indoor air cleaning, costs less to prevent the same amount of outdoor-originated particles from entering indoor environments. Generally speaking, indoor air cleaning control method requires less supply airflow rate than positive pressure control method for reducing the concentration of indoor particles with outdoor origin. An exception for this is a situation with a very low indoor/outdoor particle concentration (I/O ratio) requirement.     

Contaminant levels,source strengths,and ventilation rates in California retail stores

This field study measured ventilation rates and indoor air quality in 21 visits to retail stores in California. Three types of stores, such as grocery, furniture/hardware stores, and apparel, were sampled. Ventilation rates measured using a tracer gas decay method exceeded the minimum requirement of California's Title 24 Standard in all but one store. Concentrations of volatile organic compounds (VOCs), ozone, and carbon dioxide measured indoors and outdoors were analyzed. Even though there was adequate ventilation according to standard, concentrations of formaldehyde and acetaldehyde exceeded the most stringent chronic health guidelines in many of the sampled stores. The whole‐building emission rates of VOCs were estimated from the measured ventilation rates and the concentrations measured indoor and outdoor. Estimated formaldehyde emission rates suggest that retail stores would need to ventilate at levels far exceeding the current Title 24 requirement to lower indoor concentrations below California's stringent formaldehyde reference level. Given the high costs of providing ventilation, effective source control is an attractive alternative.     

多孔材料污染物散发外部影响因素作用分析

基于所建的污染物散发模型,分析了室内温度、传质系数、换气次数对多孔材料污染物散发的影响。结果显示,室内温度对材料内污染物散发的影响非常明显,温度越高,污染物散发时间越短;提高传质系数不能显著加速污染物散发,而降低该值却可以抑制污染物的释放;换气次数对污染物散发影响很小,但可以通过改变换气次数来控制室内污染物浓度。     

Gas-Phase Mass Transfer Model for Predicting Volatile Organic Compound (VOC) Emission Rates from Indoor Pollutant Sources

Abstract Analysis of the impact of sources on indoor pollutant concentrations and occupant exposure to indoor pollutants requires knowledge of the emission rates from the sources. Emission rates are often determined by chamber testing and the data from the chamber test are fitted to an empirical model. While the empirical models are useful, they do not provide information necessary to scale the chamber data to buildings nor do they provide information necessary to understand the processes controlling emissions. A mass transfer model for gas-phase-limited mass transfer is developed and described in this paper. Examples of sources with gas-phase-limited emissions are moth cakes, floor wax, stain, and varnish. The mass transfer model expresses the emission rate in terms of a mass transfer coefficient and a driving force. The mass transfer coefficient can be predicted from correlations of the Nusselt number and the Reynolds number. The experiments and data analysis used to develop the correlation are described in the paper. Experiments to verify the assumptions used to describe the driving force are also described. Suggestions for using data from existing empirical emission models to determine parameters for the mass transfer model are provided. The mass transfer model provides a significantly better fit to data from an indoor air quality test house than does the empirical first order decay model.     

Real‐world volatile organic compound emission rates from seated adults and children for use in indoor air studies

Human beings emit many volatile organic compounds (VOCs) of both endogenous (internally produced) and exogenous (external source) origin. Here we present real‐world emission rates of volatile organic compounds from cinema audiences (50‐230 people) as a function of time in multiple screenings of three films. The cinema location and film selection allowed high‐frequency measurement of human‐emitted VOCs within a room flushed at a known rate so that emissions rates could be calculated for both adults and children. Gas‐phase emission rates are analyzed as a function of time of day, variability during the film, and age of viewer. The average emission rates of CO₂, acetone, and isoprene were lower (by a factor of ~1.2‐1.4) for children under twelve compared to adults while for acetaldehyde emission rates were equivalent. Molecules influenced by exogenous sources such as decamethylcyclopentasiloxanes and methanol tended to decrease over the course of day and then rise for late evening screenings. These results represent average emission rates of people under real‐world conditions and can be used in indoor air quality assessments and building design. Averaging over a large number of people generates emission rates that are less susceptible to individual behaviors.     

Ventilation rates in the bedrooms of 500 Danish children

The ongoing “Indoor Environment and Children’s Health” (IECH) study investigates the environmental risk factors in homes and their association with asthma and allergy among children aged 1–5 years. As part of the study, the homes of 500 children between 3 and 5 years of age were inspected. The selected children included 200 symptomatic children (cases) and 300 randomly selected children (bases). As part of the inspection, the concentration of carbon dioxide in the bedrooms of the children was continuously measured over an average of 2.5 days. The ventilation rates in the rooms during the nights when the children were sleeping in the room were calculated using a single-zone mass balance for the occupant-generated CO₂. The calculated air change rates were log-normally distributed (R² > 0.98). The geometric mean of the air change rates in both the case and the base group was 0.46 air changes per hour (h⁻¹; geom. SD = 2.08 and 2.13, respectively). Approximately 57% of both cases and bases slept at a lower ventilation rate than the minimum required ventilation rate of 0.5 h⁻¹ in new Danish dwellings. Only 32% of the bedrooms had an average CO₂ concentration below 1000 ppm during the measured nights. Twenty-three percent of the rooms experienced at least a 20-minute period during the night when the CO₂ concentration was above 2000 ppm and 6% of the rooms experienced concentrations above 3000 ppm. The average air change rate was higher with more people sleeping in the room. The air change rate did not change with the increasing outdoor temperature over the 10-week experimental period. The calculation method provides an estimate of the total airflow into the bedroom, including airflows both from outdoors and from adjacent spaces. To study the accuracy of the calculated air change rates and their deviation from the true outside air change rates, we calculated CO₂ concentrations at different given air change rates using an indoor air quality and ventilation model (Contam). Subsequently we applied our calculation procedure to the obtained data. The air change rate calculated from the generated CO₂ concentrations was found to be between 0% and 51% lower than the total air change rate defined in the input variables for the model. It was, however, higher than the true outside air change rate. The relative error depended on the position of the room in relation to the adjacent rooms, occupancy in the adjacent room, the nominal air change rate and room-to-room airflows.     

The influence of the concealed pollution sources upon the indoor air quality in houses

This report presents the results of investigations on the indoor air quality of common Japanese detached houses. It is necessary to control the emission rates from the interior materials and the ventilation rates to keep indoor concentration of VOC enough low. And it is also necessary to consider the influence of the pollution sources in the concealed spaces for better indoor air quality in some kinds of building structures and some kinds of ventilation systems. In this study the influences of the concealed pollution sources upon the indoor concentrations of pollutants were investigated using three detached houses with four ventilation systems and the following results were obtained. When the ventilation system was changed from the air-supply type to the air-exhaust type, the indoor concentrations of formaldehyde increased. The infiltration ratios: the ratios of the infiltration rate to the indoor space toward the emission rate of a pollutant in the concealed space were measured using the tracer-gas method. The ratios from the beam spaces and the partition were about 100% in most cases. The ratios from the crawl space under the first floor and the truss space under the roof were lower than those from the beam space and partitions in most cases, because those spaces have ventilation openings. But the ratio from the crawl space reached about 100% in the house without ventilation openings at the crawl space. And even in the house with ventilation openings at crawl space, the ratio reached 50% in the house with the exhaust-ventilation system. Therefore, it became clear that the use of the medicine to prevent the deterioration of the wooden structure and the white ants in the crawl spaces must be limited. The ratio from the envelope wall was changed with the pressure difference between inside and outside. These results showed that it is necessary to prevent infiltration from the concealed spaces and to control the emission rate from the concealed pollution sources.     

Indoor air quality for chemical and ultrafine particle contaminants from printers

There are various emission sources of chemical contaminants, such as volatile organic compounds (VOCs) and ozone and particulate matter. This report is a study into the indoor air of a room containing either a laser printer/ink-jet printer, and the air contaminations were monitored for VOCs, ozone and ultrafine particle. The result confirmed an increase in the concentration of ozone and ultrafine particle numbers in the printing processes of the printer. The emission of VOCs and ozone were measured by the use of a test chamber. The chamber concentrations of styrene, xylenes and ozone were increased in printing process of the laser printer, and pentanol was detected from the ink-jet printer. The results suggest that an office or residential printer may be a source of indoor air contamination. It is necessary for emission from printers to monitor not only VOCs and particle but also ultrafine particles and other contaminants in indoor air.     

Risk of indoor airborne infection transmission estimated from carbon dioxide concentration

The Wells-Riley equation, which is used to model the risk of indoor airborne transmission of infectious diseases such as tuberculosis, is sometimes problematic because it assumes steady-state conditions and requires measurement of outdoor air supply rates, which are frequently difficult to measure and often vary with time. We derive an alternative equation that avoids these problems by determining the fraction of inhaled air that has been exhaled previously by someone in the building (rebreathed fraction) using CO2 concentration as a marker for exhaled-breath exposure. We also derive a non-steady-state version of the Wells-Riley equation which is especially useful in poorly ventilated environments when outdoor air supply rates can be assumed constant. Finally, we derive the relationship between the average number of secondary cases infected by each primary case in a building and exposure to exhaled breath and demonstrate that there is likely to be an achievable critical rebreathed fraction of indoor air below which airborne propagation of common respiratory infections and influenza will not occur.     

Particle loading rates for HVAC filters, heat exchangers, and ducts

The rate at which airborne particulate matter deposits onto heating, ventilation, and air-conditioning (HVAC) components is important from both indoor air quality (IAQ) and energy perspectives. This modeling study predicts size-resolved particle mass loading rates for residential and commercial filters, heat exchangers (i.e. coils), and supply and return ducts. A parametric analysis evaluated the impact of different outdoor particle distributions, indoor emission sources, HVAC airflows, filtration efficiencies, coils, and duct system complexities. The median predicted residential and commercial loading rates were 2.97 and 130 g/m(2) month for the filter loading rates, 0.756 and 4.35 g/m(2) month for the coil loading rates, 0.0051 and 1.00 g/month for the supply duct loading rates, and 0.262 g/month for the commercial return duct loading rates. Loading rates are more dependent on outdoor particle distributions, indoor sources, HVAC operation strategy, and filtration than other considered parameters. The results presented herein, once validated, can be used to estimate filter changing and coil cleaning schedules, energy implications of filter and coil loading, and IAQ impacts associated with deposited particles. PRACTICAL IMPLICATIONS: The results in this paper suggest important factors that lead to particle deposition on HVAC components in residential and commercial buildings. This knowledge informs the development and comparison of control strategies to limit particle deposition. The predicted mass loading rates allow for the assessment of pressure drop and indoor air quality consequences that result from particle mass loading onto HVAC system components.     

Air exchange rates and migration of VOCs in basements and residences

Basements can influence indoor air quality by affecting air exchange rates (AERs) and by the presence of emission sources of volatile organic compounds (VOCs) and other pollutants. We characterized VOC levels, AERs, and interzonal flows between basements and occupied spaces in 74 residences in Detroit, Michigan. Flows were measured using a steady‐state multitracer system, and 7‐day VOC measurements were collected using passive samplers in both living areas and basements. A walk‐through survey/inspection was conducted in each residence. AERs in residences and basements averaged 0.51 and 1.52/h, respectively, and had strong and opposite seasonal trends, for example, AERs were highest in residences during the summer, and highest in basements during the winter. Airflows from basements to occupied spaces also varied seasonally. VOC concentration distributions were right‐skewed, for example, 90th percentile benzene, toluene, naphthalene, and limonene concentrations were 4.0, 19.1, 20.3, and 51.0 μg/m³, respectively; maximum concentrations were 54, 888, 1117, and 134 μg/m³. Identified VOC sources in basements included solvents, household cleaners, air fresheners, smoking, and gasoline‐powered equipment. The number and type of potential VOC sources found in basements are significant and problematic, and may warrant advisories regarding the storage and use of potentially strong VOCs sources in basements.     

Characterizing airborne fungal and bacterial concentrations and emission rates in six occupied children's classrooms

Baseline information on size‐resolved bacterial, fungal, and particulate matter (PM) indoor air concentrations and emission rates is presented for six school classrooms sampled in four countries. Human occupancy resulted in significantly elevated airborne bacterial (81 times on average), fungal (15 times), and PM mass (nine times) concentrations as compared to vacant conditions. Occupied indoor/outdoor (I/O) ratios consistently exceeded vacant I/O ratios. Regarding size distributions, average room‐occupied bacterial, fungal, and PM geometric mean particle sizes were similar to one another while geometric means estimated for bacteria, fungi, and PM mass during vacant sampling were consistently lower than when occupied. Occupancy also resulted in elevated indoor bacterial‐to‐PM mass‐based and number‐based ratios above corresponding outdoor levels. Mean emission rates due to human occupancy were 14 million cells/person/h for bacteria, 14 million spore equivalents/person/h for fungi, and 22 mg/person/h for PM mass. Across all locations, indoor emissions contributed 83 ± 27% (bacteria), 66 ± 19% (fungi), and 83 ± 24% (PM mass) of the average indoor air concentrations during occupied times.