Reflections on the state of research: Indoor environmental quality

ArticleinIndoor Air 21(3):219-30 · December 2010with 206 Reads
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Abstract
Abstract More than 30 years after the First International Indoor Climate Symposium, ten researchers from the USA, Slovakia, Sweden, and Denmark gathered to review the current status of indoor environmental research. We initiated our review with discussions during the 1-day meeting and followed that with parallel research and writing efforts culminating with internal review and revision cycles. In this paper, we present our choices for the most important research findings on indoor environmental quality from the past three decades followed by a discussion of the most important research questions in our field today. We then continue with a discussion on whether there are research areas for which we can ‘close the book’ and say that we already know what is needed. Finally, we discuss whether we can maintain our identity in the future or it is time to team up with new partners. In the early years of this field, the accumulated knowledge was small and it was possible for any researcher to acquire a complete understanding. To do so has become impossible today as what we know has grown to exceed the learning capacity of any person. These circumstances challenge us to work collectively to synthesize what we do know and to define clearly what remains to be learned. If we fail to do these things well, we risk repeating research without memory, an inefficiency that we cannot afford.

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    This paper reports effects of reactions between ozone and selected terpenes on the concentrations and size distributions of airborne particles in a typical indoor setting. The studies were conducted in adjacent, identical offices. In the first set of experiments, known concentrations of ozone and a selected terpene (either d-limonene, alpha-terpinene, or a terpene-based cleaner whose major constituent is alpha-pinene) were deliberately introduced into one of the offices while the other office served as a control. Subsequent particle formation and redistribution were monitored with an eight-channel optical particle counter. Particle formation was observed in each terpene system, but was greatest in the case of d-limonene. The number of particles in the 0.1-0.2 mu m diameter size range was as much as 20 times larger in the office with deliberately supplemented ozone and d-limonene than in the office serving as the control. The concentration differences in the larger size ranges developed with time, indicating the importance of coagulation and condensation processes in this indoor environment. In the second set of experiments, d-limonene was deliberately introduced into one of the offices. but ozone was not supplemented in either office; instead, the indoor ozone concentrations were those that happened to be present (primarily as a consequence of outdoor-to-indoor transport). In the office that contained supplemental d-limonene, the concentrations of the 0.1-0.2 mu m particles tracked those of indoor ozone (the limiting reagent) and were as much as 10 times greater than levels measured in the comparable office that did not contain supplemental d-limonene. The results demonstrate that ozone/terpene reactions can be a significant source of sub-micron particles in indoor settings, and further illustrate the potential for reactions among commonly occurring indoor pollutants to markedly influence indoor environments.
  • Article
    Volatile organic compounds (VOCs) have been measured in a freshly carpeted 20-m[sup 3] stainless-steel room in both the absence and presence of ozone (ozone concentrations ranging from 30 to 50 ppb, with one experiment conducted at 400 ppb). Four different types of carpeting were exposed, and in each set of experiments, the room was ventilated at 1 air exchange/h. The gas-phase concentrations of selected carpet emissions (e.g., 4-phenylcyclohexene, 4-vinylcyclohexene, and styrene) significantly decreased in the presence of ozone. Conversely, the concentrations of other compounds (e.g., formaldehyde, acetaldehyde, and aldehydes with between 5 and 10 carbons) significantly increased. Furthermore, the total concentration of VOCs increased markedly in the presence of ozone. The additional VOCs appear to have been generated by reactions between ozone and relatively nonvolatile compounds associated with the carpets. These studies suggest that VOCs measured within a building at elevated ozone levels (>30 ppb) may differ from those measured at lower ozone levels (
  • Article
    A survey of 1,462 people was carried out in Perth, West ern Australia to develop an understanding of the public perception and attitude towards the risk posed by indoor air pollutants. It was found that the public had a limited awareness of the issues involving the health risk posed by indoor air pollutants. The risk was perceived to be low, and a high proportion of the population (90.5%) indicated that they found the risk to be worse but accept able. The sample population indicated that they were not prepared to reduce the risk they perceived by spending money. Whilst the population perceived the health risk of indoor air pollutants to be low, they exhibited a high lev el of concern over the health risks of three specific indoor air pollutants, i.e. asbestos, pesticides and environmen tal tobacco smoke. The public perceived universities and research institutes to be the most credible sources of health-related information although the media was seen as the most important source of information on the health risks of indoor air pollutants.
  • Article
    The association between type of ventilation and outdoor-air flow rates and Sick Building Syndrome (SBS) and SBS symptoms was studied in a cross-sectional questionnaire and field study comprising 160 office buildings, and 260–2649 respondents with case-controls as well as prevalence comparisons. Measured ventilation rates were higher than required by most building codes and consisted of fresh-air (outdoor-air) inflow of 17±14 L/p and 2.0±1.3 air changes/h. Increased risk of SBS and elevated prevalence of general SBS symptoms were associated with low outdoor-air flow rates, presence of copying machines in office rooms, and ventilation operating hours was less than 10 h/d. There was a suspected association between SBS and air humidification, recirculation of exhaust air at high outdoor-air flow rates but not at low outdoor-air flow rates, and with natural or mechanical exhaust ventilation systems. SBS was not associated with the presence of a rotary heat exchanger or with the supply air temperature higher than the room air temperature.
  • Article
    The presence of Volatile Organic Compounds (VOC) in indoor air has in past decades often been associated with adverse health effects such as sensory irritation, odour and the more complex set of symptoms called the Sick Building Syndrome (SBS). More recently, a possible link between the increase in the prevalence of allergies throughout the industrialized areas of the world and exposure to elevated concentrations of VOCs has been suggested. In many cases, the total VOC (TVOC) is used as a measure of the concentration of air pollution and, by extension, as a measure of the health risk in non-industrial buildings. However, the TVOC concept has been questioned for a number of reasons, including the facts that it is an ambiguous concept, that individual VOCs making up the whole can be expected to give rise to different effects in people and that researchers have been using different definitions and interpretations of TVOC. This means that simple addition of the quantities of individual VOCs may not be relevant from a health point of view.
  • Article
    Ten healthy humans were exposed to combinations of volatile organic compounds (VOCs) and air temperature (0 mg/m3 and 10 mg/m3 of a mixture of 22 volatile organic compounds and 18, 22 and 26° C). Previously demonstrated effects of VOCs and thermal exposures were replicated. For the first time nasal cross-sectional areas and nasal volumes, as measured by acoustic rhinometry, were shown to decrease with decreasing temperature and increasing VOC exposure. Temperature and pollutant exposures affected air quality, the need for more ventilation, skin humidity on the forehead, sweating, acute sensory irritation and possibly watering eyes in an additive way. Interactions were found for odor intensity (p = 0.1), perceived facial skin temperature and dryness, general well-being, tear film stability, and nasal cavity dimension. The presence of interactions implies that in the future guidelines for acceptable indoor air concentrations of VOCs should depend on room air temperature.
  • Article
    A review is presented of investigations of volatile organic compound (VOC) concentrations in indoor air of buildings of different classifications (dwellings, offices, schools, hospitals) and categories (established, new and complaint buildings). Measured concentrations obtained from the published literature and from research in progress overseas were pooled so that VOC concentration profiles could be derived for each building classification/category. Mean concentrations of individual compounds in established buildings were found to be generally below 50 μg/m3, with most below 5 μg/m3. Concentrations in new buildings were much greater, often by an order of magnitude or more, and appeared to arise from construction materials and building contents. The nature of these sources and approaches to reduce indoor air concentrations by limiting source VOC emissions is discussed. Total VOC (TVOC) concentrations were substantially higher than concentrations of any individual VOCs in all situations, reflecting the large number of compounds present, but interpretation of such measurements was limited by the lack of a common definition for TVOC relevant to occupant exposure.
  • Article
    The airway irritation of (+)-α-pinene, ozone, mixtures thereof, and formaldehyde was evaluated by a mouse bioassay, in which sensory irritation, bronchoconstriction, and pulmonary irritation were measured. The effects are distinguished by analysis of the respiratory parameters. Significant sensory irritation (assessed from reduction of mean respiratory rate) was observed by dynamic exposure of the mice, over a period of 30 min, to a ca. 22 s old reaction mixture of ozone and (+)-α-pinene from a Teflon flow tube. The starting concentrations were 6 ppm and 80 ppm, respectively, which were diluted and let into the exposure chamber. About 10% ozone remained unreacted (0.4 ppm), <0.2 ppm formaldehyde, <0.4 ppm pinonaldehyde, <2 ppm formic acid, and <1 ppm acetic acid were formed. These concentrations, as well as that of the unreacted (+)-α-pinene (51 ppm), were below established no effect levels. The mean reduction of the respiratory rate (30%) was significantly different (p≪0.001) from clean air, as well as from exposure of (+)-α-pinene, ozone, and formaldehyde themselves at the concentrations measured. Addition of the effects of the measured residual reactants and products cannot explain the observed sensory irritation effect. This suggests that one or more strong airway irritants have been formed. Therefore, oxidation reactions of common naturally occurring unsaturated compounds (e.g., terpenes) may be relevant for indoor air quality.
  • Article
    Total volatile organic compounds (TVOC) are determined in intake, room-supply and room air in 86 office rooms in 29 office buildings in northern Sweden. Measurements of formaldehyde were also made in room air. Building and room characteristics were identified and symptom reports collected from 1087 office workers. Concentrations of TVOC and formaldehyde in room air were low, with mean values of 71 µg/m3 and 31 µg/m3, respectively. The TVOC concentration was generally lower in room air than in supply air or intake air. The “loss” (difference in measured values) of TVOC from supply to room air was associated with raised concentrations of formaldehyde and raised prevalences of occupant symptoms. High TVOC concentrations in room air were associated with reduced prevalences of occupant symptoms.
  • Article
    Energy conservation and inadequate building technology sometimes cause a deterioration of indoor air quality and thereby produce potential health risks. Thus, some buildings may be diagnosed as “sick buildings”; the concept is commonly associated with acute sensory effects on humans. At present, the problem is frequently observed in newly built or remodelled preschool and office buildings. The symptoms include irritation of the eyes, the nose, and the throat, a sensation of dryness in the mucuos membranes and the skin, erythema of the skin, mental fatigue, and weak but persistant odors. This paper summarizes and examines these problems in a sensory-chemical as well as a social-psychological context. It is concluded that: (1) “Sick buildings” are basically a physical environment problem. (2) Sensations predominate reactions to “sick buildings” but the perceptual mechanisms are largely unknown. (3) Since there is a complex pattern of pollutants in indoor air, one cannot expect to find simple causal relationships. (4) Most reactions are largely nonspecific and refer to the chemical and somesthetic senses. The resultant perceptions are unitary, but multisensory in origin. Sensory interactions are known to occur. (5) The “sick building” syndrome is best understood by assuming that the sensory systems perform a pattern-recognition analysis. (6) It may partly be the result of a changed sensitivity in the populations exposed and/or a summation of numerous subthreshold sensory stimuli or interaction between gases-particles.
  • Article
    This study investigated the formation of secondary pollutants resulting from household product use in the presence of ozone. Experiments were conducted in a 50-m3 chamber simulating a residential room. The chamber was operated at conditions relevant to US residences in polluted areas during warm-weather seasons: an air exchange rate of 1.0 h−1 and an inlet ozone concentration of approximately 120 ppb, when included. Three products were used in separate experiments. An orange oil-based degreaser and a pine oil-based general-purpose cleaner were used for surface cleaning applications. A plug-in scented-oil air freshener (AFR) was operated for several days. Cleaning products were applied realistically with quantities scaled to simulate residential use rates. Concentrations of organic gases and secondary organic aerosol from the terpene-containing consumer products were measured with and without ozone introduction. In the absence of reactive chemicals, the chamber ozone level was approximately 60 ppb. Ozone was substantially consumed following cleaning product use, mainly by homogeneous reaction. For the AFR, ozone consumption was weaker and heterogeneous reaction with sorbed AFR-constituent VOCs was of similar magnitude to homogeneous reaction with continuously emitted constituents. Formaldehyde generation resulted from product use with ozone present, increasing indoor levels by the order of 10 ppb. Cleaning product use in the presence of ozone generated substantial fine particle concentrations (more than 100 μg m−3) in some experiments. Ozone consumption and elevated hydroxyl radical concentrations persisted for 10–12 h following brief cleaning events, indicating that secondary pollutant production can persist for extended periods.
  • Article
    Reactive building materials offer an opportunity to provide indoor air cleaning with minimal energy use. Laboratory and test house experiments provide evidence that indoor ozone concentrations can be diminished by activated carbon (AC) and unpainted gypsum wallboard (GWB) panels. These two materials are highly reactive with ozone and produce few byproducts. When measured in a 14.2 m3 stainless-steel chamber, the mean deposition velocities to the materials were 5.3 m h-1 for AC and 2.4 m h−1 for GWB for a variety of airflow and relative humidity conditions. The ozone decay rates for both the materials were also measured in an unoccupied 34.5 m3 bedroom under various mixing conditions. In this case, ozone removal increased relative to background by 27–100% with a 4.4 m2 panel of a reactive material placed on one wall of the bedroom. The ozone decay rate for the bedroom increased over background by approximately 2–3 h−1 for GWB and 2–7 h−1 for AC. Application of a mass balance model for a typical home demonstrates that effectiveness for ozone removal depends weakly on the air exchange rate and strongly on the panel material, panel area, and mixing conditions. An ozone removal effectiveness of over 80% is possible with sufficient panel area and positioning that provides elevated air speeds near the panels.
  • Article
    A nationwide survey of 4 373 office workers at 47 office sites was conducted to assess the prevalence of the sick building syndrome and to investigate associated factors. The office buildings sampled included those ventilated by either natural, mechanical, or forced air, or by air conditioning or some form of comfort cooling, including fan-coil, induction, and constant or variable air volume systems. Results showed a higher prevalence of reports of work-related symptoms of dry eyes, dry throut, stuffy/congested nose, itchy/watery eyes, runny nose, lethargy/tiredness, and headache in air conditioned buildings than in unconditioned buildings. Symptom prevalence was higher in buildings ventilated with water-based cooling systems, e.g., fan-coil or induction systems, than in buildings with all-air systems. A significant relationship was found between the type of humidification used in air-conditioned buildings (none, evaporative/spray, or steam) and the prevalence of itchy eyes, stuffy nose, lethargy, breathing difficulty, and chest tightness. Results also suggest that the “sick building syndrome” is associated with a variety of individual characteristics (sex, age), occupational factors (job type, length of video display unit use, occupancy duration in building, job stress), architectural features (type of office, type of building ventilation system), and psychological processes (perceived environmental control, perceived ambient conditions, perceived environmental satisfaction). A path analytic model is presented that suggests that psychological processes mediate the association between individual, occupational, and environmental characteristics and reports of the “sick building syndrome”.
  • Article
    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.
  • Article
    It is generally believed that indoor air pollution, one way or another may cause indoor air complaints. However, any association between volatile organic compounds (VOCs) concentrations and increase of indoor climate complaints, like the sick-building syndrome symptoms, is not straightforward. The reported symptom rates of, in particular, eye and upper airway irritation cannot generally be explained by our present knowledge of common chemically non-reactive VOCs measured indoors. Recently, experimental evidence has shown those chemical reactions between ozone (either with or without nitrogen dioxide) and unsaturated organic compounds (e.g. from citrus and pine oils) produce strong eye and airway irritating species. These have not yet been well characterised by conventional sampling and analytical techniques. The chemical reactions can occur indoors, and there is indirect evidence that they are associated with eye and airway irritation. However, many other volatile and non-volatile organic compounds have not generally been measured which could equally well have potent biological effects and cause an increase of complaint rates, and posses a health/comfort risk. As a consequence, it is recommended to use a broader analytical window of organic compounds than the classic VOC window as defined by the World Health Organisation. It may include hitherto not yet sampled or identified intermediary species (e.g., radicals, hydroperoxides and ionic compounds like detergents) as well as species deposited onto particles. Additionally, sampling strategies including emission testing of building products should carefully be linked to the measurement of organic compounds that are expected, based on the best available toxicological knowledge, to have biological effects at indoor concentrations.
  • Article
    Volatile organic compounds (VOCs) are prevalent components of indoor air pollution. Among the approaches to remove VOCs from indoor air, photocatalytic oxidation (PCO) is regarded as a promising method. This paper is a review of the status of research on PCO purification of VOCs in indoor air. The review and discussion concentrate on the preparation and coating of various photocatalytic catalysts; different kinetic experiments and models; novel methods for measuring kinetic parameters; reaction pathways; intermediates generated by PCO; and an overview of various PCO reactors and their models described in the literature. Some recommendations are made for future work to evaluate the performance of photocatalytic catalysts, to reduce the generation of harmful intermediates and to design new PCO reactors with integrated UV source and reaction surface.
  • Article
    The quantity, identity, and distribution of biomass in indoor and outdoor aerosols are poorly described. This is not consistent with the current understanding of atmospheric chemistry or the microbiological characterization of aquatic and terrestrial environments. This knowledge gap is due to both difficulties in applying contemporary microbiological techniques to the low biomass concentrations present in aerosols, and the traditional reliance of aerosol researchers on culture-based techniques—the quantitative limitations and ecological biases of which have been well-documented and are now avoided in other environmental matrices. This article reviews the emergence of the polymerase chain reaction (PCR) as a nonculture-based method to determine the identity, distribution, and abundance of airborne microorganisms. To encourage the use of PCR-based techniques by a broad spectrum of aerosol researchers, emphasis is given to the critical, aerosol specific method issues of sample processing, DNA extraction, and PCR inhibition removal. These methods are synthesized into a generalized procedure for the PCR-based study of microbial aerosols—equally applicable to both indoor and outdoor aerosol environments.
  • Article
    Some of the significant adverse impacts of used filters on indoor air quality of buildings and potential solutions are discussed. The presence of used filters in building results in occupants suffering from Sick Building Syndrome (SBS) symptoms. Used filters have an adverse impact on indoor air quality spreading different kinds of diseases among building occupants, including asthma and other allergic diseases. These filters are unable to prevent particulate and gaseous pollutants from entering the buildings through the ventilation system. The airflow through through these filters need to started earlier to control pollutants before buildings are occupied and improve indoor air quality. The development of low-polluting filtration techniques with higher efficiencies and lower pressure drops is another solution to prevent adverse impact of used filters in buildings.
  • Article
    A variety of organic compounds have been identified in size-fractionated indoor aerosol samples. These include aliphatic alcohols and phosphate esters not previously identified in ambient aerosols, as well as phthalate ester plasticizers whose numbers and relative abundances appear greater than those of outdoor samples. Several of the identified organics are evidence that relatively stable chemicals used within a building are likely to accumulate in the aerosol circulating throughout that building.
  • Article
    A general mathematical model is presented for predicting the concentrations of chemically reactive compounds in indoor air. The model accounts for the effects of ventilation, filtration, heterogeneous removal, direct emission, and photolytic and thermal chemical reactions. The model is applied to the induction of photochemically reactive pollutants into a museum gallery, and the predicted NO, NO_x-NO, and O_3 concentrations are compared to measured data. The model predicts substantial production of several species due to chemical reaction, including HNO_2, HNO_3, NO_3, and N_2O_5. Circumstances in which homogeneous chemistry may assume particular importance are identified and include buildings with glass walls, indoor combustion sources, and direct emission of olefins.
  • Article
    Indoor air pollution emerges as an important risk factor for acute respiratory infections (ARI) in developing countries. In many developing countries in addition to an increasing amount of tobacco smoke many homes contain high levels of smoke from the combustion of biofuels such as wood crop residues and animal dung for cooking or heating. In about half the worlds households such fuels are used for cooking daily usually without a flue or chimney and with poor ventilation. Results of investigations in 6 developing nations have shown the range of indoor pollution in such circumstances. The best single indicator for comparison of toxic noncarcinogenic effects is most likely respirable particulates similar to tar reported for cigarette emissions. Results of studies in animals suggest any difference in respiratory-system toxicity according to mass is not likely to be large. On the basis of the small amount of evidence available peak and daily exposures to indoor particulate levels in villages in developing countries seem to be about 20 times greater than in developed nations. The results of a semi-quantitative epidemiological study conducted in Nepal showed a direct relation between reported hours/day spent near the stove by infants and children aged under 2 years and episodes of life threatening acute respiratory infections. If one discounts the many possible confounding factors extrapolation shows that by moving all children into the lowest smoke exposure groups as much as 25% of moderate and severe infections would be eliminated. Extrapolation from studies of both ARI and environmental tobacco smoke also indicates indirectly the potential effect of indoor smoke from biofuels. Some environmental tobacco smoke studies have reported a dose-response relation between the number of cigarettes smoked in the home and respiratory symptoms in children. In sum biofuel smoke is likely to be a factor in ARI but its importance in relation to other risk factors is difficult to establish. It may be that prevention of acute respiratory infections could be best realized by initially addressing other risk factors or by addressing smoke solely in the context of broad based programs for several risk factors.
  • Article
    The uptake rates of low-molecular weight aldehydes and ketones by peace lily (Spathiphyllum clevelandii) and golden pothos (Epipremnum aureum) leaves at typical indoor ambient concentrations (10(1)-10(2) ppbv) were determined. The C3-C6 aldehydes and C4-C6 ketones were taken up by the plant leaves, but the C3 ketone acetone was not. The uptake rate normalized to the ambient concentration C(a) ranged from 7 to 19 mmol m(-2) s(-1) and from 2 to 7 mmol m(-2) s(-1) for the aldehydes and ketones, respectively. Longer-term fumigation results revealed that the total uptake amounts were 30-100 times as much as the amounts dissolved in the leaf, suggesting that volatile organic carbons are metabolized in the leaf and/or translocated through the petiole. The ratio of the intercellular concentration to the external (ambient) concentration (C(i)/C(a)) was significantly lower for most aldehydes than for most ketones. In particular, a linear unsaturated aldehyde, crotonaldehyde, had a C(i)/C(a) ratio of approximately 0, probably because of its highest solubility in water.
  • Article
    Indoor and outdoor airborne particle mass, protein, endotoxin and (1 --> 3)-beta-D-glucan in three size fractions (PM2.5, PM10, and TSP) were measured in ten single-family homes, along with quantifying household activities in the sampling room. Correlations between human activity levels and elevations in the indoor concentrations of particles and biomarkers were evaluated using four approaches for distinguishing activity levels: diurnal differences, the number of occupants, self-estimated occupancy, and activity strength. The concentrations of particles, protein, endotoxin and (1 --> 3)-beta-D-glucan in all three size fractions (PM < 2.5 microm, PM10-2.5, and PM >10 microm) were found, in most cases, to be significantly elevated during the day, and with higher activity levels in the room. The coarser fractions of particle mass and bioaerosols were more strongly correlated with human activity levels. Activity strength was the most statistically robust measure for relating human activities to indoor bioaerosol levels. While self-estimated activity and analysis of diurnal differences both offer reasonable (but not perfect) alternatives to activity strength, the number of occupants appears to be a weaker indicator for homes.
  • Article
    Full-text available
    During the first randomized intervention trial (RESPIRE: Randomized Exposure Study of Pollution Indoors and Respiratory Effects) in air pollution epidemiology, we pioneered application of passive carbon monoxide (CO) diffusion tubes to measure long-term personal exposures to woodsmoke. Here we report on the protocols and validations of the method, trends in personal exposure for mothers and their young children, and the efficacy of the introduced improved chimney stove in reducing personal exposures and kitchen concentrations. Passive diffusion tubes originally developed for industrial hygiene applications were deployed on a quarterly basis to measure 48-hour integrated personal carbon monoxide exposures among 515 children 0-18 months of age and 532 mothers aged 15-55 years and area samples in a subsample of 77 kitchens, in households randomized into control and intervention groups. Instrument comparisons among types of passive diffusion tubes and against a continuous electrochemical CO monitor indicated that tubes responded nonlinearly to CO, and regression calibration was used to reduce this bias. Before stove introduction, the baseline arithmetic (geometric) mean 48-h child (n=270), mother (n=529) and kitchen (n=65) levels were, respectively, 3.4 (2.8), 3.4 (2.8) and 10.2 (8.4) p.p.m. The between-group analysis of the 3355 post-baseline measurements found CO levels to be significantly lower among the intervention group during the trial period: kitchen levels: -90%; mothers: -61%; and children: -52% in geometric means. No significant deterioration in stove effect was observed over the 18 months of surveillance. The reliability of these findings is strengthened by the large sample size made feasible by these unobtrusive and inexpensive tubes, measurement error reduction through instrument calibration, and a randomized, longitudinal study design. These results from the first randomized trial of improved household energy technology in a developing country and demonstrate that a simple chimney stove can substantially reduce chronic exposures to harmful indoor air pollutants among women and infants.
  • Article
    The short-term effects of particulate matter (PM) on mortality and morbidity differ by geographic location and season. Several hypotheses have been proposed for this variation, including different exposures with air conditioning (AC) versus open windows. Bayesian hierarchical modeling was used to explore whether AC prevalence modified day-to-day associations between PM10 and mortality, and between PM2.5 and cardiovascular or respiratory hospitalizations, for those 65 years and older. We considered yearly, summer-only, and winter-only effect estimates and 2 types of AC (central and window units). Communities with higher AC prevalence had lower PM effects. Associations were observed for cardiovascular hospitalizations and central AC. Each additional 20% of households with central AC was associated with a 43% decrease in PM2.5 effects on cardiovascular hospitalization. Central AC prevalence explained 17% of between-community variability in PM2.5 effect estimates for cardiovascular hospitalizations. Higher AC prevalence was associated with lower health effect estimates for PM.
  • Article
    The association between total daily mortality and air pollution was investigated for a 1-year period (September 1985 through August 1986) in St. Louis and in the counties in eastern Tennessee surrounding Kingston/Harriman. The purpose of this study was to evaluate the relative importance of various measures of particulate and gaseous air pollution as predictors of daily mortality. Concentrations of inhalable particles (PM10), fine particles (PM2.5), the elemental composition of these particles, and aerosols acidity were measured daily during the period of study. The effect of each air pollutant on daily mortality was estimated after controlling for meteorologic and seasonal influences. Total mortality in St. Louis was found to increase 16% (95% CI-1 to 33%) for each 100 micrograms/m3 increase in PM10, and by 17% (95% CI-12 to 57%) in eastern Tennessee. Positive but progressively weaker associations were found with PM2.5, sulfate, and aerosol acidity concentrations in both communities. Associations with gaseous pollutants--sulfur dioxide, nitrogen dioxide, and ozone--were all far from statistical significance. Because of the short monitoring period for daily particulate air pollution, the power of this study to detect associations was limited. Nevertheless, statistically significant associations with PM10 were found in St. Louis, and, more importantly, the estimated effects were consistent between the two communities studied and with other reported analyses of the effects of particles on daily mortality. These data suggest that the acidity of particles is not as important in associations with daily mortality as the mass concentrations of particles.
  • Article
    The objective of this study was to determine the effects of passive smoking on functional lung growth in children and adolescents. It was hypothesized that passive smoking might reduce lung function growth, especially in susceptible children. The assumption was that those most susceptible would be children who started with low lung function, as it had been shown that they had slower growth of lung function, and start to decline earlier. There were 138 non-Hispanic Caucasian children and adolescents, ages 5 through 15, who had at least three satisfactory longitudinal lung function tests over a 13 year period in the Tucson epidemiological study of airway obstructive diseases. Those who started in childhood with normal function did not show any effect of passive smoking, nor did females who started with low lung function. Males starting with low lung function whose parents smoked showed definite changes. Their forced expiratory volume in 1 second (FEV1) grew even more slowly between ages 13 through 16, related primarily to continuous parental smoking. They also had higher rates of decline for FEV1 to forced vital capacity (FVC) ratio and maximum flow at 50% vital capacity to FVC ratios than either the low function group without passive smoking or the normal function groups. This was independent of any symptoms or diagnoses present in this male low function group.
  • Article
    Full-text available
    To identify the indoor air quality issues about which Californians most often sought advice from a health department or a public information agency and to evaluate how well these agencies met the public's needs, members of the California Interagency Working Group (IWG) on Indoor Air Quality kept records of inquiries they received over a 30-month period from mid-1985 through 1987. Members of the IWG answered calls from residents of a least 49 of California's 58 counties. IWG members received more public inquiries about residences than about offices, educational institutions, commercial buildings, or medical facilities. However, each call about a residence probably represented fewer people at risk of exposure to a real or a potential problem than did calls about other types of buildings. Homeowners themselves asked the majority of the questions about residences, whereas a large number of the inquiries about office buildings were made, not by affected office workers, but by building managers, contractors, consultants, or company health and safety officers. The leading topics of concern in the residences were asbestos, chemical and biological contamination, and radon. In offices, chemical contamination, the ventilation system, biological contamination, asbestos, and tobacco smoke were the most frequently mentioned sources of problems. Callers often reported experiencing headaches, allergy symptoms, nose or throat irritation, and respiratory tract problems in connection with their complaints. IWG members directed a third of the calls elsewhere, of which half were referred to consultants or testing laboratories. The IWG's experience in the State of California could help other health departments prepare to face the public's increasing concern about indoor air pollution.
  • Article
    Airborne transmission of infectious agents and associations of indoor air pollutants with respiratory illnesses are well documented. We hypothesized that energy conservation measures that tighten buildings also increase risks of respiratory infection among building occupants. At four Army training centers during a 47-month period, incidence rates of febrile acute respiratory disease were compared between basic trainees in modern (energy-efficient design and construction) and old barracks. Rates of febrile acute respiratory disease were significantly higher among trainees in modern barracks (adjusted relative risk estimate, 1.51; 95% confidence interval, 1.46 to 1.56), and relative risks were consistent at the four centers. These results support the hypothesis that tight buildings with closed ventilation systems significantly increase risks of respiratory-transmitted infection among congregated, immunologically susceptible occupants.
  • Article
    The concentration of house-dust mites (Dermatophagoides spp.) was investigated for four seasons in three locations in each of 50 Danish apartments. Simultaneously the absolute humidity was recorded and the previously known correlation between mite counts and indoor humidity was confirmed. It appeared, however, that apartments which had a low absolute indoor humidity in the winter period (due to low household load of water vapour) did not contain noticeable concentrations of house-dust mites in the summer and autumn despite the fact that the indoor absolute humidity in these apartments could be high enough to allow for a high peak-population of mites. Because of this it is suggested that in a temperate climate avoidance measures against house-dust mites should be supplemented at least by a drying out period in the winter, when this process is convenient to perform because of the low outdoor absolute humidity.
  • Article
    Thirty single-family homes with either high (> or = 2000 ng/g) or low (< or = 1000 ng/g) house-dust mite (HDM) allergen levels in mattress dust were examined for ventilation, thermal climate, and air quality (formaldehyde and total volatile organic compounds (TVOC). Elevated concentrations of HDM allergen in mattress and floor dust were associated with the difference in absolute humidity between indoor and outdoor air, as well as with low air-change rates of the home, particularly the bedroom. No correlation was found between concentration of TVOC or formaldehyde in bedroom air and HDM allergen concentration. In regions with a cold winter climate, the air-change rate of the home and the infiltration of outdoor air into the bedroom appear to be important for the infestation of HDM.
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    The study compares societal risk ratings by inhabitants of two countries which differ markedly in terms of geography, economics, politics, and ethnic background, but which are similar as regards media coverage. The two populations were represented by a sample of French students and a sample of Burkina Faso intellectuals. The overall Burkinabè mean ratings appeared much closer to the mean observed in France (and in the United States-roughly 40 out of 100) than the means reported for other countries like Norway or Hungary. The correlation between Burkinabè and French ratings was very high: .852. The findings argue in favor of a practically totally determinant effect of the media in risk perception.
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    To examine the relation between ventilation rate and occurrence of symptoms of the eyes, nose, throat, and skin as well as general symptoms such as lethargy and headache, often termed the sick building syndrome. A cross sectional population based study was carried out in 399 workers from 14 mechanically ventilated office buildings without air recirculation or humidification, selected randomly from the Helsinki metropolitan area. The ventilation type and other characteristics of these buildings were recorded on a site visit and the ventilation in the rooms was assessed by measuring the airflow through the exhaust air outlets in the room. A questionnaire directed at workers inquired about the symptoms and perceived air quality and their possible personal and environmental determinants (response rate 81%). The outcomes were weekly work related symptoms experienced during the previous 12 months and symptom groups defined either by their anatomical location or hypothesised mechanism. In logistic regression analysis, the adjusted odds ratio (OR) for any symptom of interest was 3.03 (95% confidence interval (95% CI) 1.13 to 8.10) in the very low ventilation category of below 5 l/s per person and 2.24 (0.89 to 5.65) in the high ventilation category of over 25 l/s per person compared with the reference (15- < 25 l/s). The ORs for ocular (1.27, 1.11 to 1.46), nasal (1.17, 1.06 to 1.29), skin symptoms (1.18, 1.05 to 1.32), and lethargy (1.09, 1.00 to 1.19) increased significantly by a unit decrease in ventilation from 25 to 0 l/s per person. The results suggest that outdoor air ventilation rates below the optimal (15 to 25 l/s per person) increase the risk of the symptoms of sick building syndrome with the sources of pollutants present in mechanically ventilated office buildings. The Finnish guideline value is 10 l/s per person.
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    A critical review was conducted of the quantitative literature linking indoor air pollution from household use of biomass fuels with acute respiratory infections in young children, which is focused on, but not confined to, acute lower respiratory infection and pneumonia in children under two years in less developed countries. Biomass in the form of wood, crop residues, and animal dung is used in more than two fifths of the world's households as the principal fuel. Medline and other electronic databases were used, but it was also necessary to secure literature from colleagues in less developed countries where not all publications are yet internationally indexed. The studies of indoor air pollution from household biomass fuels are reasonably consistent and, as a group, show a strong significant increase in risk for exposed young children compared with those living in households using cleaner fuels or being otherwise less exposed. Not all studies were able to adjust for confounders, but most of those that did so found that strong and significant risks remained. It seems that the relative risks are likely to be significant for the exposures considered here. Since acute lower respiratory infection is the chief cause of death in children in less developed countries, and exacts a larger burden of disease than any other disease category for the world population, even small additional risks due to such a ubiquitous exposure as air pollution have important public health implications. In the case of indoor air pollution in households using biomass fuels, the risks also seem to be fairly strong, presumably because of the high daily concentrations of pollutants found in such settings and the large amount of time young children spend with their mothers doing household cooking. Given the large vulnerable populations at risk, there is an urgent need to conduct randomised trials to increase confidence in the cause-effect relationship, to quantify the risk more precisely, to determine the degree of reduction in exposure required to significantly improve health, and to establish the effectiveness of interventions.
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    In a study in 29 health centre districts in Japan 91 540 non-smoking wives aged 40 and above were followed up for 14 years (1966-79), and standardised mortality rates for lung cancer were assessed according to the smoking habits of their husbands. Wives of heavy smokers were found to have a higher risk of developing lung cancer and a dose-response relation was observed. The relation between the husband's smoking and the wife's risk of developing lung cancer showed a similar pattern when analysed by age and occupation of the husband. The risk was particularly great in agricultural families when the husbands were aged 40-59 at enrolment. The husbands' smoking habit did not affect their wives' risk of dying from other disease such as stomach cancer, cervical cancer, and ischaemic heart disease. The risk of developing emphysema and asthma seemed to be higher in non-smoking wives of heavy smokers, but the effect was not statistically significant. The husband's drinking habit seemed to have no effect on any causes of death in their wives, including lung cancer. These results indicate the possible importance of passive or indirect smoking as one of the causal factors of lung cancer. They also appear to explain the long-standing riddle of why many women develop lung cancer although they themselves are non-smokers. These results also cast doubt on the practice of assessing the relative risk of developing lung cancer in smokers by comparing them with non-smokers.
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    Higher indoor concentrations of air pollutants due, in part, to lower ventilation rates are a potential cause of sick building syndrome (SBS) symptoms in office workers. The indoor carbon dioxide (CO2) concentration is an approximate surrogate for indoor concentrations of other occupant-generated pollutants and for ventilation rate per occupant. Using multivariate logistic regression (MLR) analyses, we evaluated the relationship between indoor CO2 concentrations and SBS symptoms in occupants from a probability sample of 41 U.S. office buildings. Two CO2 metrics were constructed: average workday indoor minus average outdoor CO2 (dCO2, range 6-418 ppm), and maximum indoor 1-h moving average CO2 minus outdoor CO2 concentrations (dCO2MAX). MLR analyses quantified dCO2/SBS symptom associations, adjusting for personal and environmental factors. A dose-response relationship (p < 0.05) with odds ratios per 100 ppm dCO2 ranging from 1.2 to 1.5 for sore throat, nose/sinus, tight chest, and wheezing was observed. The dCO2MAX/SBS regression results were similar.
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    We analyzed 1994 sick leave for 3,720 hourly employees of a large Massachusetts manufacturer, in 40 buildings with 115 independently ventilated work areas. Corporate records identified building characteristics and IEQ complaints. We rated ventilation as moderate (approximately 25 cfm/person, 12 ls-1) or high (approximately 50 cfm/person, 24 ls-1) outdoor air supply based on knowledge of ventilation systems and CO2 measurements on a subset of work areas, and used Poisson regression to analyze sick leave controlled for age, gender, seniority, hours of non-illness absence, shift, ethnicity, crowding, and type of job (office, technical, or manufacturing worker). We found consistent associations of increased sick leave with lower levels of outdoor air supply and IEQ complaints. Among office workers, the relative risk for short-term sick leave was 1.53 (95% confidence 1.22-1.92) with lower ventilation, and 1.52 (1.18-1.97) in areas with IEQ complaints. The effect of ventilation was independent of IEQ complaints and among those exposed to lower outdoor air supply rates the attributable risk of short-term sick leave was 35%. The cost of sick leave attributable to ventilation at current recommended rates was estimated as $480 per employee per year at Polaroid. These findings suggest that net savings of $400 per employee per year may be obtained with increased ventilation. Thus, currently recommended levels of outdoor air supply may be associated with significant morbidity, and lost productivity on a national scale could be as much as $22.8 billion per year. Additional studies of IEQ impacts on productivity and sick leave, and the mechanisms underlying the apparent association are needed.
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    Associations have been found between day-to-day particulate air pollution and increased risk of various adverse health outcomes, including cardiopulmonary mortality. However, studies of health effects of long-term particulate air pollution have been less conclusive. To assess the relationship between long-term exposure to fine particulate air pollution and all-cause, lung cancer, and cardiopulmonary mortality. Vital status and cause of death data were collected by the American Cancer Society as part of the Cancer Prevention II study, an ongoing prospective mortality study, which enrolled approximately 1.2 million adults in 1982. Participants completed a questionnaire detailing individual risk factor data (age, sex, race, weight, height, smoking history, education, marital status, diet, alcohol consumption, and occupational exposures). The risk factor data for approximately 500 000 adults were linked with air pollution data for metropolitan areas throughout the United States and combined with vital status and cause of death data through December 31, 1998. All-cause, lung cancer, and cardiopulmonary mortality. Fine particulate and sulfur oxide--related pollution were associated with all-cause, lung cancer, and cardiopulmonary mortality. Each 10-microg/m(3) elevation in fine particulate air pollution was associated with approximately a 4%, 6%, and 8% increased risk of all-cause, cardiopulmonary, and lung cancer mortality, respectively. Measures of coarse particle fraction and total suspended particles were not consistently associated with mortality. Long-term exposure to combustion-related fine particulate air pollution is an important environmental risk factor for cardiopulmonary and lung cancer mortality.
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    We studied the effects of removing small airborne particles in an office building without unusual contaminant sources or occupant complaints. We conducted a double-blind crossover study of enhanced particle filtration in an office building in the Midwest United States in 1993. We replaced standard particle filters, in separate ventilation systems on two floors, with highly efficient filters on alternate floors weekly over 4 weeks. Repeated-measures models were used to analyze data from weekly worker questionnaires and multiple environmental measurements. Bioaerosol concentrations were low. Enhanced filtration reduced concentrations of the smallest airborne particles by 94%. This reduction was not associated with reduced symptoms among the 396 respondents, but three performance-related mental states improved; for example, the confusion scale decreased (-3.7%; 95% confidence limits (CL) = -6.5, -0.9). Most environmental dissatisfaction variables also improved; eg, "stuffy" air, -5.3% (95% CL = -10.3, -0.4). Cooler temperatures within the recommended comfort range were associated with remarkably large improvement in most outcomes; for example, chest tightness decreased -23.4% (95% CL = -38.1, -8.7) for every 1 degrees C decrease. Benefits of enhanced filtration require assessment in buildings with higher particulate contaminant levels in studies controlling for temperature effects. Benefits from lower indoor temperatures need confirmation.
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    Chemicals identified as endocrine-disrupting compounds (EDCs) have widespread consumer uses, yet little is known about indoor exposure. We sampled indoor air and dust in 120 homes, analyzing for 89 organic chemicals identified as EDCs. Fifty-two compounds were detected in air and 66 were detected in dust. These are the first reported measures in residential environments for over 30 of the compounds, including several detected at the highest concentrations. The number of compounds detected per home ranged from 13 to 28 in air and from 6 to 42 in dust. The most abundant compounds in air included phthalates (plasticizers, emulsifiers), o-phenylphenol (disinfectant), 4-nonylphenol (detergent metabolite), and 4-tert-butylphenol (adhesive) with typical concentrations in the range of 50-1500 ng/m3. The penta- and tetrabrominated diphenyl ethers (flame retardants) were frequently detected in dust, and 2,3-dibromo-1-propanol, the carcinogenic intermediate of a flame retardant banned in 1977, was detected in air and dust. Twenty-three pesticides were detected in air and 27 were detected in dust, the most abundant being permethrins and the synergist piperonyl butoxide. The banned pesticides heptachlor, chlordane, methoxychlor, and DDT were also frequently detected, suggesting limited indoor degradation. Detected concentrations exceeded government health-based guidelines for 15 compounds, but no guidelines are available for 28 compounds, and existing guidelines do not consider endocrine effects. This study provides a basis for prioritizing toxicology and exposure research for individual EDCs and mixtures and provides new tools for exposure assessment in health studies.
  • Article
    With the aim of identifying health-relevant exposures in buildings, an epidemiological study “Dampness in Buildings and Health” (DBH) started in the year 2000 in Sweden. The health focus of the study is on asthma and allergic symptoms among small children and their parents. The first step in the study was an epidemiological cross-sectional questionnaire on housing and health involving 14,077 preschool children in the county of Värmland in Sweden (March–April 2000). Self-reported moisture-related problems in the building were strongly associated with asthma, allergic symptoms, and airway infections among children and adults. Other factors associated with symptoms among the children were allergic heredity, smoking in the family, male sex, urban living, short breast feeding, pet keeping, daycare attendance, non-farming life and some food habits. The second step in the study was a nested case-control study including 198 children with symptoms and 202 healthy controls. A detailed clinical examination by physicians in parallel with extensive inspections and measurements in the subjects' homes were conducted from October 2001 to April 2002. The influence of selection bias in case-control studies has been studied, and questionnaires on self-reported symptoms and building characteristics have been validated. Identified risk factors for allergic symptoms are, e.g., inspector-observed dampness, a low ventilation rate, endotoxin, Penicillium and phthalates in dust. In the third phase, a 5-year follow-up study will be carried out during 2005. The same questionnaire as used in DBH-phase 1 will be distributed to the 10,852 children/parents who responded to the first questionnaire in 2000. Finally, in a fourth phase, controlled experimental studies in climate chambers and in vitro tests regarding findings from DBH-Phase 2 are planned to be conducted during 2004–08.