Automobile proximity and indoor residential concentrations of BTEX and MTBE

Attached garages have been identified as important sources of indoor residential air pollution. However, the literature lacks information on (1) how the proximity of cars to the living area affects indoor concentrations of gasoline-related compounds, such as benzene; and (2) the origin of these pollutants, i.e., vapor or tailpipe emissions. We analyzed data from the Relationships of Indoor, Outdoor, and Personal Air (RIOPA) study to evaluate indoor (C_in) and outdoor (C_out) concentrations for 114 residences with cars either in an attached garage, a detached garage or carport, or without cars. Results indicate that single-family detached homes with cars in attached garages were affected the most by parked vehicles, followed by homes with vehicles in carports. Concentrations in homes with cars in detached garages were similar to those in residences without cars. Low ventilation rates exacerbated C_in in homes with attached garages. In general, the contribution from gasoline-related sources to indoor benzene and MTBE concentrations appeared to have been dominated by car exhaust, or by a combination of tailpipe and gasoline vapor emissions. Residing in a home with an attached garage could lead to benzene exposures that are an order of magnitude higher than exposures from commuting in a car in heavy traffic, with a risk of 17 excess cancers in a population of a million. Strategies to lower exposure to gasoline-related contaminants in homes include improving construction practices to prevent the infiltration of pollutants into the living quarters or incorporating detached garages.     

Use of biomarkers in an indoor air study: lack of correlation between aromatic VOCs with respective urinary biomarkers

The benzene and toluene levels inside of eight homes with attached garages were measured during July 1998 in Fairbanks, Alaska. A thermal desorption tube method and charcoal tube method were used to collect and analyze samples (thermal desorption tube method %RDS = 1.9 for n = 6; charcoal tube method %RDS = 6.5 for n = 4). Results for both methods were compared and showed indoor benzene levels ranging between 1.2 and 72 ppbv. The charcoal tube method usually gave lower results than the thermal desorption method. Nevertheless, the difference observed in benzene levels from each method was not significant as determined by application of the Wilcoxon t-test to these data. Using the thermal desorption method, the range of toluene found in homes was 0.1-111 ppbv. A correlation between toluene and benzene levels suggested the same point source. The benzene and toluene content of the indoor air and the number of small engines stored in the attached garage was also correlated. There was no correlation found between the urinary biomarker concentrations and the level of benzene or toluene measured inside the homes in the summer.     

Effects of Modified Residential Construction on Indoor Air Quality

Indoor air quality (IAQ) was assessed in homes in an experimental community of single-family dwellings that had been built with materials chosen for low pollutant emission and other modified design features to provide enhanced residential indoor air quality. The IAQ was measured in six of these experimental homes and also in three conventionally built homes of similar size and price range. The IAQ was assessed shortly after construction before the houses were occupied and again after each of the houses had been occupied for five months. Before occupancy, there were higher levels of airborne panicles and of some volatile organic compounds in the conventional homes than in the experimental homes. During occupancy, benzene, ethylbenzene, m-and p-xylene, and o-xylene were all higher in the conventional homes, but dichloromethane, Freon 11, and trichlorethylene were higher in the experimental homes. In the conventional homes, mean levels of benzene and chloroform increased, whereas methylchlomform and toluene levels decreased from preoccupancy to occupancy. In the experimental homes, dichloromethane increased, and m-and p-xylene and o-xylene decreased from preoccupancy to occupancy. The results suggest that attached garages, geographical siting, and occupants' activities substantially influenced the IAQ in these homes. The enhanced indoor air quality homes tested in this study were judged to be at least partially effective, with the most obvious sustained IAQ benefits being related to the lack of an attached garage.     

Levels and sources of volatile organic compounds in homes of children with asthma

Many volatile organic compounds (VOCs) are classified as known or possible carcinogens, irritants, and toxicants, and VOC exposure has been associated with the onset and exacerbation of asthma. This study characterizes VOC levels in 126 homes of children with asthma in Detroit, Michigan, USA. The total target VOC concentration ranged from 14 to 2274 μg/m³ (mean = 150 μg/m³; median = 91 μg/m³); 56 VOCs were quantified; and d‐limonene, toluene, p, m‐xylene, and ethyl acetate had the highest concentrations. Based on the potential for adverse health effects, priority VOCs included naphthalene, benzene, 1,4‐dichlorobenzene, isopropylbenzene, ethylbenzene, styrene, chloroform, 1,2‐dichloroethane, tetrachloroethene, and trichloroethylene. Concentrations varied mostly due to between‐residence and seasonal variation. Identified emission sources included cigarette smoking, solvent‐related emissions, renovations, household products, and pesticides. The effect of nearby traffic on indoor VOC levels was not distinguished. While concentrations in the Detroit homes were lower than levels found in other North American studies, many homes had elevated VOC levels, including compounds that are known health hazards. Thus, the identification and control of VOC sources are important and prudent, especially for vulnerable individuals. Actions and policies to reduce VOC exposures, for example, sales restrictions, improved product labeling, and consumer education, are recommended.     

Volatile organic compounds in 169 energy-efficient dwellings in Switzerland

Exposure to elevated levels of certain volatile organic compounds (VOCs) in households has been linked to deleterious health effects. This study presents the first large-scale investigation of VOC levels in 169 energy-efficient dwellings in Switzerland. Through a combination of physical measurements and questionnaire surveys, we investigated the influence of diverse building characteristics on indoor VOCs. Among 74 detected compounds, carbonyls, alkanes, and alkenes were the most abundant. Median concentration levels of formaldehyde (14 μg/m³), TVOC (212 μg/m³), benzene (<0.1 μg/m³), and toluene (22 μg/m³) were below the upper exposure limits. Nonetheless, 90% and 50% of dwellings exceeded the chronic exposure limits for formaldehyde (9 μg/m³) and TVOC (200 μg/m³), respectively. There was a strong positive correlation among VOCs that likely originated from common sources. Dwellings built between 1950s and 1990s, and especially, those with attached garages had higher TVOC concentrations. Interior thermal retrofit of dwellings and absence of mechanical ventilation system were associated with elevated levels of formaldehyde, aromatics, and alkanes. Overall, energy-renovated homes had higher levels of certain VOCs compared with newly built homes. The results suggest that energy efficiency measures in dwellings should be accompanied by actions to mitigate VOC exposures as to avoid adverse health outcomes.     

地下车库通风量的确定与控制

不同时间出入地下车库的车辆数量不同，污染物排放量随之不同，用于稀释污染物浓度的排风量应是可变化的，就地下车库通风量的确定与控制进行了探讨。     

Numerical approach of carbon monoxide concentration dispersion in an enclosed garage

This paper draws attention to the lack of information about the carbon monoxide (CO) dispersion in enclosed garages, a typical occupational microenvironment, with high expected CO concentrations, where employees are exposed daily as well as garage users, and refers to the numerical prediction of CO concentration inside the garage. A mathematical model implemented in a general computer code that can provide detailed information on CO concentration as well as air flow field prevailing in three-dimensional enclosed spaces of any geometrical complexity is presented. This model involves the partial differential equations governing CO levels and airflow transfer in large enclosures. For the evaluation of the mathematical model, experimental CO concentrations measured inside are used as input data. This paper refers to a number of simulations where different ventilation rates were examined in order to provide adequate ventilation to dilute indoor CO sources and CO levels. Regarding the airflow patterns it was found that while the ventilation of indoor spaces improved the CO concentration decreased to half the value. The simulation results could be used as a base for ventilation design for enclosed garages, aimed at a proper ventilation system selection for a more healthy and comfortable working microenvironment.     

Indoor climate in interior Alaska: simultaneous measurement of ventilation, benzene and toluene in residential indoor air of two homes

Benzene and toluene mixing ratios were measured in the indoor air of two subarctic homes during summer and winter. Benzene in the living area of these homes ranged from 1 to 25 ppbv and toluene ranged from 1 to 104 ppbv. Source strength estimate calculations supported the hypothesis that gasoline in the home's attached garage is the primary source of these compounds in living area air. These calculations demonstrated that the home with the air-to-air heat exchangers and forced ventilation had less transport of aromatics than the unventilated home. Perturbation experiment showed that a full metal gasoline can in the garage was consistent with the importance of the garage as a source for the concentration of aromatics in the air of the living spaces in these Alaskan homes. The type of ventilation system also had an important effect on the quality of air in the living area.     

Air pollution in the microenvironment of parked new cars

Potential health effects of material emissions in new motor vehicles are of great public concern in China. To estimate the pollution levels, air samples were taken from 802 new cars parked in a well-ventilated underground parking garage in Beijing, China. These vehicles were all manufactured in and after 2003, and represented three different price ranges. For comparison, 20 older vehicles (manufactured before 2003) were also examined. Monitoring items included benzene, toluene, xylene, and formaldehyde. Preliminary results indicate that 82% of the vehicles studied had toluene levels exceeding the Chinese National Indoor Air Quality Standard. For benzene, xylene, and formaldehyde, the rates of noncompliance were 75%, 25%, and 24%, respectively. For all the pollutants, newer vehicles had higher concentrations than older ones. There seems a connection between the types of interior materials used in the passenger cabins and the concentrations of certain air pollutants.     

Indoor air quality,air exchange rates,and radioactivity in new built temporary houses following the Great East Japan Earthquake in Minamisoma,Fukushima

This study measured air exchange rates, indoor concentrations of aldehydes and volatile organic compounds (VOCs), and radioactivity levels at 19 temporary houses in different temporary housing estate constructed in Minamisoma City following the Great East Japan Earthquake. The 19 surveyed houses represented all of the companies assigned to construct temporary houses in that Minamisoma City. Data were collected shortly after construction and before occupation, from August 2011 to January 2012. Mean air exchange rates in the temporary houses were 0.28/h, with no variation according to housing types and construction date. Mean indoor concentrations of formaldehyde, acetaldehyde, toluene, ethylbenzene, m/p‐xylene, o‐xylene, styrene, p‐dichlorobenzene, tetradecane, and total VOCs (TVOCs) were 29.2, 72.7, 14.6, 6.35, 3.05, 1.81, 7.29, 14.3, 8.32, and 901 μg/m³, respectively. The levels of acetaldehyde and TVOCs exceeded the indoor guideline (48 μg/m³) and interim target (400 μg/m³) in more than half of the 31 rooms tested. In addition to guideline chemicals, terpenes (α‐pinene and d‐limonene) and acetic esters (butyl acetate and ethyl acetate) were often detected in these houses. The indoor radiation levels measured by a Geiger–Müller tube (Mean: 0.22 μSv/h) were lower than those recorded outdoors (Mean: 0.42 μSv/h), although the shielding effect of the houses was less than for other types of buildings.     

Effects of energy retrofits on Indoor Air Quality in multifamily buildings

We assessed 45 multifamily buildings (240 apartments) from Finland and 20 (96 apartments) from Lithuania, out of which 37 buildings in Finland and 15 buildings in Lithuania underwent energy retrofits. Building characteristics, retrofit activities, and energy consumption data were collected, and Indoor Air Quality (IAQ) parameters, including carbon monoxide (CO), nitrogen dioxide (NO₂), formaldehyde (CH₂O), selected volatile organic compounds (benzene, toluene, ethylbenzene, and xylenes (BTEX), radon, and microbial content in settled dust were measured before and after the retrofits. After the retrofits, heating energy consumption decreased by an average of 24% and 49% in Finnish and Lithuanian buildings, respectively. After the retrofits of Finnish buildings, there was a significant increase in BTEX concentrations (estimated mean increase of 2.5 µg/m³), whereas significant reductions were seen in fungal (0.6‐log reduction in cells/m²/d) and bacterial (0.6‐log reduction in gram‐positive and 0.9‐log reduction in gram‐negative bacterial cells/m²/d) concentrations. In Lithuanian buildings, radon concentrations were significantly increased (estimated mean increase of 13.8 Bq/m³) after the retrofits. Mechanical ventilation was associated with significantly lower CH₂O concentrations in Finnish buildings. The results and recommendations presented in this paper can inform building retrofit studies and other programs and policies aimed to improve indoor environment and health.     

Determination of exposure to benzene, toluene and xylenes in Turkish primary school children by analysis of breath and by environmental passive sampling

Benzene, toluene, m/p-xylene and o-xylene (BTX) are toxic volatile organic compounds and ubiquitous air pollutants. Smoking and consumer products are indoor sources of BTX, whereas traffic and industrial activities are primary sources contributing to outdoor levels of BTX. The aim of this study was to characterize exposure of children to BTX by personal air sampling using diffusive samplers and by analysis of end-exhaled air. For this study, 101 children of 10-11 years of age were recruited from four primary schools in Southern Turkey during the warm season (May 2008). Two schools were situated in a residential area near primary and secondary iron and steel works (Payas) and two schools were located in a non-industrialized city (Iskenderun). The children and their parents were visited at home for an interview and to identify possible sources of BTX in the residence. Median concentrations of benzene determined by diffusive samplers were higher in Payas (4.1 μg/m³) than in Iskenderun (2.7 μg/m³, p < 0.001). For toluene, no differences were observed, whereas for xylene isomers air concentrations tended to be lower for children living in Payas. The median end-exhaled air concentrations were 8.2, 29, 3.8, and 5.7 pmol/L for benzene, toluene, m/p-xylene and o-xylene, respectively (Payas), and 6.9, 25, 4.9, and 6.0 pmol/L, respectively (Iskenderun). Concentrations of toluene in end-exhaled air were 50% higher in children living with household members who smoked indoors (p < 0.05) and benzene in end-exhaled air was more than 3-fold higher for those children who were exposed to tobacco smoke inside a vehicle (p < 0.001). End-exhaled concentrations of benzene were also higher in children living in a residence with an attached garage (p < 0.05). These exposure modifying factors were not identified when using the results obtained with diffusive samplers.     

Model validation study of carbon monoxide transport due to portable electric generator operation in an attached garage

A series of tests was conducted to characterize the indoor carbon monoxide (CO) concentrations resulting from portable electric generators operating in the attached garage of a test house under various use and environmental conditions. An extensive model validation effort using the multizone airflow and indoor air quality (IAQ) model CONTAM was carried out using the data from seven tests with a generator operating in the attached garage to compare predicted CO concentrations with measured values. The agreement between the measurements and predictions of the O₂ concentrations in the garage and the average CO concentration for the house zones was excellent for the data set as a whole. The agreement was somewhat worse for the garage CO concentrations. Overall, the house zone average and garage CO concentration predictions and measurements were within about 20% and 30%, respectively, when averaged over all cases.     

The MERMAID study: indoor and outdoor average pollutant concentrations in 10 low‐energy school buildings in France

Indoor air quality was characterized in 10 recently built energy‐efficient French schools during two periods of 4.5 days. Carbon dioxide time‐resolved measurements during occupancy clearly highlight the key role of the ventilation rate (scheduled or occupancy indexed), especially in this type of building, which was tightly sealed and equipped with a dual‐flow ventilation system to provide air refreshment. Volatile organic compounds (VOCs) and inorganic gases (ozone and NO₂) were measured indoors and outdoors by passive techniques during the occupied and the unoccupied periods. Over 150 VOC species were identified. Among them, 27 species were selected for quantification, based on their occurrence. High concentrations were found for acetone, 2‐butanone, formaldehyde, toluene, and hexaldehyde. However, these concentrations are lower than those previously observed in conventional school buildings. The indoor/outdoor and unoccupied/occupied ratios are informative regarding emission sources. Except for benzene, ozone, and NO₂, all the pollutants in these buildings have an indoor source. Occupancy is associated with increased levels of acetone, 2‐butanone, pentanal, butyl acetate, and alkanes.     

Home interventions are effective at decreasing indoor nitrogen dioxide concentrations

Nitrogen dioxide (NO₂), a by‐product of combustion produced by indoor gas appliances such as cooking stoves, is associated with respiratory symptoms in those with obstructive airways disease. We conducted a three‐armed randomized trial to evaluate the efficacy of interventions aimed at reducing indoor NO₂ concentrations in homes with unvented gas stoves: (i) replacement of existing gas stove with electric stove; (ii) installation of ventilation hood over existing gas stove; and (iii) placement of air purifiers with high‐efficiency particulate air (HEPA) and carbon filters. Home inspection and NO₂ monitoring were conducted at 1 week pre‐intervention and at 1 week and 3 months post‐intervention. Stove replacement resulted in a 51% and 42% decrease in median NO₂ concentration at 3 months of follow‐up in the kitchen and bedroom, respectively (P = 0.01, P = 0.01); air purifier placement resulted in an immediate decrease in median NO₂ concentration in the kitchen (27%, P < 0.01) and bedroom (22%, P = 0.02), but at 3 months, a significant reduction was seen only in the kitchen (20%, P = 0.05). NO₂ concentrations in the kitchen and bedroom did not significantly change following ventilation hood installation. Replacing unvented gas stoves with electric stoves or placement of air purifiers with HEPA and carbon filters can decrease indoor NO₂ concentrations in urban homes.     

地下车库通风的变频控制研究

针对目前地下车库变风量系统中常用的间歇控制法和双速风机法存在的控制过于简单、不能很好地改善地下车库内的空气品质、不能最大限度地节能的问题,提出了根据车库内CO浓度的实时变化情况,采用风机变频控制地下车库通风量的方法。介绍了某地下车库通风系统的风机变频控制改造工程。结果表明,风机变频控制改造在技术上是可行的,能节约电能,且投资回收期较短。     

The IVAIRE project – a randomized controlled study of the impact of ventilation on indoor air quality and the respiratory symptoms of asthmatic children in single family homes

A randomized controlled trial was carried out to measure the impact of an intervention on ventilation, indoor air contaminants, and asthma symptoms of children. Eighty‐three asthmatic children living in low‐ventilated homes were followed over 2 years. Several environmental parameters were measured during the summer, fall, and winter. The children were randomized after Year 1 (43 Intervention; 40 Control). The intervention included the installation of either a Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV). During the fall and winter seasons, there was a significant increase in the mean ventilation rate in the homes of the intervention group. A statistically significant reduction in mean formaldehyde, airborne mold spores, toluene, styrene, limonene, and α‐pinene concentrations was observed in the intervention group. There was no significant group difference in change in the number of days with symptoms per 14 days. However, there was a significant decrease in the proportion of children who experienced any wheezing (≥1 episode) and those with ≥4 episodes in the 12‐month period in the intervention group. This study indicates that improved ventilation reduces air contaminants and may prevent wheezing. Due to lack of power, a bigger study is needed.     

Classroom ventilation and indoor air quality—results from the FRESH intervention study

Inadequate ventilation of classrooms may lead to increased concentrations of pollutants generated indoors in schools. The FRESH study, on the effects of increased classroom ventilation on indoor air quality, was performed in 18 naturally ventilated classrooms of 17 primary schools in the Netherlands during the heating seasons of 2010–2012. In 12 classrooms, ventilation was increased to targeted CO₂ concentrations of 800 or 1200 ppm, using a temporary CO₂ controlled mechanical ventilation system. Six classrooms were included as controls. In each classroom, data on endotoxin, β(1,3)‐glucans, and particles with diameters of <10 μm (PM₁₀) and <2.5 μm (PM_2.5) and nitrogen dioxide (NO₂) were collected during three consecutive weeks. Associations between the intervention and these measured indoor air pollution levels were assessed using mixed models, with random classroom effects. The intervention lowered endotoxin and β(1,3)‐glucan levels and PM₁₀ concentrations significantly. PM₁₀ for instance was reduced by 25 μg/m³ (95% confidence interval 13–38 μg/m³) from 54 μg/m³ at maximum ventilation rate. No significant differences were found between the two ventilation settings. Concentrations of PM_2.5 and NO₂ were not affected by the intervention. Our results provide evidence that increasing classroom ventilation is effective in decreasing the concentrations of some indoor‐generated pollutants.     

Environmental monitoring of benzene and toluene produced in indoor air due to combustion of solid biomass fuels

Exposure to benzene and toluene from the combustion of solid biomass fuels is one of the important causes of morbidity and mortality in developing countries. In this study, we assessed the exposure of cooks to benzene and toluene from biomass fuel combustion in 55 rural homes. The GC-MS was used for quantification while a personnel sampler was used for environmental monitoring. The benzene exposure differed significantly (p < 0.0001) across different types of indoor kitchen fuel combinations. The geometrical mean (GM) of benzene exposure for cooks during cooking hours in an indoor kitchen using mixed fuel was 75.3 microg/m3 (with partition) and 63.206 microg/m3 (without partition), while the exposure was 11.7 microg/m3 for open type. The benzene exposure was significantly higher (p < 0.05) in an indoor kitchen with respect to open type using mixed fuels. Concentration of benzene (114.1 microg/m3) for cooks in an indoor kitchen with partition using dung fuel was significantly higher in comparison to non-cooks (5.1 microg/m3) for open type. Benzene exposure was not significantly different for kitchen with ventilation (31.2 microg/m3) and without ventilation (45.0 microg/m3) using wood fuel. However, this value was significantly (p < 0.05) lower than in indoor kitchens with or without partition. An almost similar trend was observed for toluene but the difference was statistically non-significant. This study may be helpful in developing a regional exposure database and in the facilitation of health risk assessment due to volatile organic pollutants in our day-to-day environment.     

Enhancement of ventilation performance of a residential split-system air-conditioning unit

The design of ventilation performance of air-conditioning systems in large commercial and office buildings is quite established. However, it is not the same with the designs of air-conditioning systems in most residential buildings. Split system air-conditioning units are commonly employed in residential buildings in the tropics due to their convenience in terms of energy conservation, aesthetics, flexibility, acoustic performance and ease of operation. Such units are also popular among small offices, shopping complex and even as supplementary air-conditioning units beyond normal office-hours in large commercial and office buildings. This paper presents findings from a recent study of the ventilation performance and indoor air quality (IAQ) in a master bed room of a condominium unit in Singapore, employed with a split system air-conditioning unit. The attached bathroom is equipped with an exhaust fan, whose operation and its impact on the resulting ventilation characteristics was also studied. Four adults occupied the room throughout the course of the experiments. It was observed that the carbon dioxide level in the bed room can exceed 2000 ppm without the exhaust fan in about 2 h. The operation of the exhaust fan quickly lowered the level of carbon dioxide to about 1000 ppm. The findings suggest the need to design for ventilation provision in split system air-conditioning units.