Air exchange rates and migration of VOCs in basements and residences.

UNLABELLED: 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/m(3), respectively; maximum concentrations were 54, 888, 1117, and 134 µg/m(3). 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. PRACTICAL IMPLICATIONS: Few IAQ studies have examined basements. A sizable volume of air can flow between the basement and living area, and AERs in these two zones can differ considerably. In many residences, the basement contains significant emission sources and contributes a large fraction of VOC concentrations found in the living area. Exposures can be lowered by removing VOC sources from the basement; other exposure management options, such as local ventilation or isolation, are unlikely to be practical.

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

UNLABELLED: 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/m(3) (mean = 150 µg/m(3); median = 91 µg/m(3)); 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. PRACTICAL IMPLICATIONS: Total target VOC concentrations in the Detroit homes ranged from 14 to 2274 lg/m3, generally lower than found in earlier studies. However, a subset of houses had elevated concentrations, and levels of 1,4-dichlorobenzene, naphthalene, and benzene reached levels commensurate with excess individual cancer risks of 10(-2), 10(-3), and 10(-4), respectively. VOC concentrations varied mostly due to between-residence and season effects. The most important sources included cigarette smoking, vehicle-related emissions, building renovation, solvents, household products, and pesticides.

Concentrations and risks of p-dichlorobenzene in indoor and outdoor air.

UNLABELLED: p-dichlorobenzene (PDCB) is a chlorinated volatile organic compound that can be encountered at high concentrations in buildings owing to its use as pest repellent and deodorant. This study characterizes PDCB concentrations in four communities in southeast Michigan. The median concentration outside 145 homes was 0.04 µg/m(3), and the median concentration inside 287 homes was 0.36 µg/m(3). The distribution of indoor concentrations was extremely skewed. For example, 30% of the homes exceeded 0.91 µg/m(3), which corresponds to a cancer risk level of 10(-5) based on the California unit risk estimate, and 4% of homes exceeded 91 µg/m(3), equivalent to a 10(-3) risk level. The single highest measurement was 4100 µg/m(3). Estimates of whole-house emission rates were largely consistent with chamber test results in the literature. Indoor concentrations that exceed a few µg/m(3) indicate the use of PDCB products. PDCB concentrations differed among households and the four cities, suggesting the importance of locational, cultural, and behavioral factors in the use patterns of this chemical. The high PDCB levels found suggest the need for policies and actions to lower exposures, for example, sales or use restrictions, improved labeling, and consumer education. PRACTICAL IMPLICATIONS: Distributions of p-dichlorobenzene concentrations in residences are highly right-skewed, and a subset of houses has very elevated concentrations that are equivalent to an excess cancer risk of 10(-3) or higher based on the California unit risk effect estimate. House-to-house variation is large, reflecting differences in use practices. Stronger policies and educational efforts are needed to eliminate or modify indoor usage practices of this chemical.

Sources, concentrations, and risks of naphthalene in indoor and outdoor air.

UNLABELLED: Naphthalene is a ubiquitous pollutant, and very high concentrations are sometimes encountered indoors when this chemical is used as a pest repellent or deodorant. This study describes the distribution and sources of vapor-phase naphthalene concentrations in four communities in southeast Michigan, USA. Outdoors, naphthalene was measured in the communities and at a near-road site. Indoors, naphthalene levels were characterized in 288 suburban and urban homes. The median outdoor concentration was 0.15 µg/m(3), and a modest contribution from rush-hour traffic was noted. The median indoor long-term concentration was 0.89 µg/m(3), but concentrations were extremely skewed and 14% of homes exceeded 3 µg/m(3), the chronic reference concentration for non-cancer effects, 8% exceeded 10 µg/m(3), and levels reached 200 µg/m(3). The typical excess individual lifetime cancer risk was about 10(-4) and reached 10(-2) in some homes. Important sources include naphthalene's use as a pest repellent and deodorant, migration from attached garages and, to lesser extents, cigarette smoke and vehicle emissions. Excessive use as a repellent caused the highest concentrations. Naphthalene presents high risks in a subset of homes, and policies and actions to reduce exposures, for example, sales bans or restrictions, improved labeling, and consumer education, should be considered. PRACTICAL IMPLICATIONS: Long-term average concentrations of naphthalene in most homes fell into the 0.2-1.7 µg/m(3) range reported as representative in earlier studies. The highly skewed distribution of concentrations results in a subset of homes with elevated concentrations and health risks that greatly exceed US EPA and World Health Organization (WHO) guidelines. The most important indoor source is the use of naphthalene as a pest repellant or deodorant; secondary sources include presence of an attached garage, cigarette smoking, and outdoor sources. House-to-house variation was large, reflecting differences among the residences and naphthalene use practices. Stronger policies and educational efforts are needed to eliminate or modify indoor usage practices of this chemical.

Particulate matter concentrations in residences: an intervention study evaluating stand-alone filters and air conditioners.

UNLABELLED: This study, a randomized controlled trial, evaluated the effectiveness of free-standing air filters and window air conditioners (ACs) in 126 low-income households of children with asthma. Households were randomized into a control group, a group receiving a free-standing HEPA filter placed in the child's sleeping area, and a group receiving the filter and a window-mounted AC. Indoor air quality (IAQ) was monitored for week-long periods over three to four seasons. High concentrations of particulate matter (PM) and carbon dioxide were frequently seen. When IAQ was monitored, filters reduced PM levels in the child's bedroom by an average of 50%. Filter use varied greatly among households and declined over time, for example, during weeks when pollutants were monitored, filter use was initially high, averaging 84±27%, but dropped to 63±33% in subsequent seasons. In months when households were not visited, use averaged only 34±30%. Filter effectiveness did not vary in homes with central or room ACs. The study shows that measurements over multiple seasons are needed to characterize air quality and filter performance. The effectiveness of interventions using free-standing air filters depends on occupant behavior, and strategies to ensure filter use should be an integral part of interventions. PRACTICAL IMPLICATIONS: Environmental tobacco smoke (ETS) increased particulate matter (PM) levels by about 14 µg/m3 and was often detected using ETS-specific tracers despite restrictions on smoking in the house as reported on questionnaires administered to caregivers. PM concentrations depended on season, filter usage, relative humidity, air exchange ratios, number of children, outdoor PM levels, sweeping/dusting, and presence of a central air conditioner (AC). Free-standing air filters can be an effective intervention that provides substantial reductions in PM concentrations if the filters are used. However, filter use was variable across the study population and declined over the study duration, and thus strategies are needed to encourage and maintain use of filters. The variability in filter use suggests that exposure misclassification is a potential problem in intervention studies using filters. The installation of a room AC in the bedroom, intended to limit air exchange ratios, along with an air filter, did not lower PM levels more than the filter alone.

Sources and migration of volatile organic compounds in mixed-use buildings.

UNLABELLED: We examined concentrations and migration of volatile organic compounds (VOCs) in ten mixed-use buildings in southeast Michigan, USA. In an office and work zone in each building, air exchange rates (AERs) were measured using perfluorocarbon tracers, and over 96 VOC species were measured by GC/MS over a 7-day period. VOCs were then apportioned to sources in offices, work zones, and outdoors using a two-zone mass balance model. AERs averaged 3.9 h (0.2-14.2 h) in offices and 1.9 h (0.4-3.5 h) in work zones. The dominant VOCs included aromatics, terpenes and alkanes. VOC concentrations were uniform in the smaller spaces, and more variable in some of the very large spaces. Apportionments depended on the VOC and building, but emissions in industrial zones of buildings often migrated to office areas where they frequently accounted for the bulk of VOC concentrations. Outdoor sources accounted for most benzene and carbon tetrachloride, and a small fraction of aromatic and aliphatic compounds. This study shows that pollutant migration can be a significant and not uncommon problem in mixed-use buildings, and it demonstrates the need for better control of emissions and pollutant migration. PRACTICAL IMPLICATIONS: Pollutant exposures in industrial, commercial, and institutional buildings arise from indoor and outdoor sources that can be identified, apportioned, and controlled with knowledge of emission sources and building airflows. We show that multi-tracer techniques are an effective and practical means of determining airflows and exchange rates in large buildings. In examining a set of mixed-use buildings, a substantial fraction of VOC exposures in otherwise relatively 'clean' offices is due to pollutant migration from 'dirty' zones of the building. This indicates the need for corrective actions to minimize exposures of office workers that are unwanted and probably unknown to building managers. These actions should include better control of emissions, isolation or control of air and pollutant flows between building zones, and documentation of the effectiveness of such measures when strong emission sources are present.

Microtubule-affinity regulating kinase (MARK) is tightly associated with neurofibrillary tangles in Alzheimer brain: a fluorescence resonance energy transfer study.

Paired helical filaments, the main structural components of the neurofibrillary tangles in Alzheimer disease, consist of phosphorylated tau protein. Because the levels and degree of phosphorylation are significantly higher in paired helical filament (PHF)-derived tau than in normal adult tau, and because phosphorylation of tau severely disrupts microtubule stability, it is postulated that tau phosphorylation is an important step in PHF formation. The kinases and/or phosphatases that act in vivo to help induce such a pathological state of tau, however, are not yet known. In this study we implicate the non-proline directed kinase MARK in PHF-tau phosphorylation, by virtue of its close intermolecular association with the phosphorylated Ser262 epitope on PHF-tau as assessed by fluorescence resonance energy transfer. Moreover, because this tight enzyme-substrate association is observed in neurofibrillary tangles in Alzheimer tissue, we suggest that PHF-tau phosphorylation may occur to some extent on assembled PHF filaments.

Synthesis and turnover of brain phosphoglycerides- results, methods of calculation and interpretation.

The important problem of membrane assembly and disassembly can be studied by measurements of rates of tunrover of labeled components. After intracerebral injections of ethanolamine and glycerol into mice, we have found rapid and slow turnover pools of 1,2-diacyl-sn-glycero-3-phosphorylethanolamine (diacyl-GPE) and 1,2-diacyl-sn-glycero-3-phosphorylcholine (diacyl-GPC). We have described the methods for calculation of half-lives for two or more pools and for the calculation of the relative size of the pools. For mice injected between 5 and 8 weeks of age, the rapid turnover pools have a half-life of 1.5 and 1.8 days for diacyl-GPC and diacyl-Ge respectively. Corresponding half-lives for the slow turnover pools are 20 and 27 days. The slow turnover pools include 74% of the diacyl-GPC and 86% of the diacyl-Ge. These turnover rates are in agreement with the flux of fatty acids through the diacylglycerol pools. We have proposed that the rapid turnover pool may be the phosphoglycerides that are exchangable with cytosol carrier proteins and that the slow turnover may represent the catabolism of membrane segments including the intrinsic proteins.

Evaluation of the utility of abdominal CT scans in the diagnosis, management, outcome and information given at discharge of patients with non-traumatic acute abdominal pain.

OBJECTIVES: The role of CT imaging in the diagnosis and management of acute abdominal pain is well established, but its utility is limited in a minority of cases. The aim of this study was to quantify the degree to which radiological and clinical findings differ. Interobserver variability in CT reporting was also assessed. METHODS: Clinical data and CT reports were analysed retrospectively for any discrepancies by comparing CT diagnosis, clinical diagnosis as stated on the discharge summary and final diagnosis (based on consensus review of all information). Blinded review of all CT imaging was performed to determine interobserver variability. RESULTS: 120 consecutive scans fulfilled the inclusion criteria (114 patients; 79 women; mean age 55 years). The correct clinical diagnosis was made in 87.5% of cases based on CT findings. The lack of intravenous contrast limited diagnostic interpretation in 6 of the 15 discrepant cases. CT was unable to define early inflammatory changes in three patients and early caecal carcinoma in one. A right paraduodenal internal hernia was difficult to detect in another patient. Interobserver agreement was 93%, but with a low kappa value of 0.27. A paradox exists due to an imbalance in the positive and negative agreement of 96% and 31%, respectively. CONCLUSIONS: The utility of CT imaging in the diagnosis and management of patients presenting with acute abdominal pain is confirmed, but is limited in a minority of cases where poor negative interobserver agreement exists. Good communication to the reporting radiologist of the relevant patient history and clinical question becomes important.

Broadband ground-plane cloak.

The possibility of cloaking an object from detection by electromagnetic waves has recently become a topic of considerable interest. The design of a cloak uses transformation optics, in which a conformal coordinate transformation is applied to Maxwell's equations to obtain a spatially distributed set of constitutive parameters that define the cloak. Here, we present an experimental realization of a cloak design that conceals a perturbation on a flat conducting plane, under which an object can be hidden. To match the complex spatial distribution of the required constitutive parameters, we constructed a metamaterial consisting of thousands of elements, the geometry of each element determined by an automated design process. The ground-plane cloak can be realized with the use of nonresonant metamaterial elements, resulting in a structure having a broad operational bandwidth (covering the range of 13 to 16 gigahertz in our experiment) and exhibiting extremely low loss. Our experimental results indicate that this type of cloak should scale well toward optical wavelengths.

A case of endobronchial actinomycosis.

Actinomycosis is an infectious disease caused by certain Actinomyces species. Actinomyces are Gram-positive, non-spore forming organisms characterized by obligate or facultative anaerobic rods that normally inhabit anaerobic niches of the human oral cavity. Cervicofacial, abdominal, pelvic and thoracic infections of Actinomyces are not uncommon, but endobronchial actinomycosis is rarely reported. Endobronchial actinomycosis can be misdiagnosed as unresolving pneumonia, endobronchial lipoma or malignancies. Endobronchial actinomycosis should be included in the differential diagnosis of any endobronchial mass. We report a case of a 43-year-old man who presented with a productive cough and pulmonary consolidation at the right lower lobe on chest radiograph. Fiberoptic bronchoscopy revealed obstruction of the right superior segment of the lower bronchus with an exophytic endobronchial mass. Endobronchial actinomycosis was confirmed by demonstration of sulfur granules in the bronchoscopic biopsy of the mass. Intravenous administration of penicillin G followed by oral amoxacillin/clavulanic acid therapy for 3 months resulted in improving symptoms. Infiltrative consolidation on the chest X-ray was markedly decreased.

Aequorea green fluorescent protein: simultaneous analysis of wild-type and blue-fluorescing mutant by flow cytometry.

Aequorea green fluorescent protein (GFP) has been expressed in a variety of cell lines and host organisms. A recent report (Heim et al.: Proc Natl Acad Sci USA 91:12501-12504, 1994) has documented that a GFP mutant with a single amino acid substitution (tyrosine 66 to histidine; Y66H-GFP) elicits altered spectral properties. Whereas wild-type GFP emits with a maximum at approximately 509 nm (green fluorescence), Y66H-GFP fluoresces with a maximum at approximately 448 nm (blue fluorescence). In this study we employed available argon and krypton ion laser lines to investigate the impact of laser excitation wavelength on the detection of Y66H-GEP by flow cytometry. Using transiently transfected 293 cells, a cellular subpopulation with elevated blue fluorescence was detectable with excitation at 407 nm, but not with ultraviolet (UV), 458 nm, or 488 nm excitation. The blue-fluorescing cells were further documented to express Y66H-GFP by immunoblot analysis of sorted cells. Finally, we demonstrated the simultaneous analysis of both wild-type and Y66H-GFP in cotransfected 293 cells using 407 nm excitation while collecting blue fluorescence at 460 +/- 20 nm (Y66H-GFP) and green fluorescence at 525 +/- 25 nm (wild-type GFP). These studies illustrate the potential for assessing differential gene expression by simultaneously analyzing multiple GFP species with multiparameter flow cytometry.

Mechanistic scheme and effect of "extended sigh" as a recruitment maneuver in patients with acute respiratory distress syndrome: a preliminary study.

OBJECTIVE: To devise a new form of sigh ("extended sigh") capable of providing a sufficient recruiting pressure x time, and to test it as a recruitment maneuver in patients with acute respiratory distress syndrome. DESIGN: Prospective uncontrolled clinical trial. SETTING: Medical intensive care unit of a university-affiliated hospital. PATIENTS: Twenty consecutive patients diagnosed with acute respiratory distress syndrome (18 men, 2 women, age 59 +/- 10 yrs). INTERVENTIONS: From baseline settings of tidal volume (Vt) 8 mL/kg and positive end-expiratory pressure (PEEP) 10 cm H2O on volume control mode with the high pressure limit at 40 cm H2O, the Vt-PEEP values were changed to 6-15, 4-20, and 2-25, each step being 30 secs (inflation phase). After Vt-PEEP 2-25, the mode was switched to continuous positive airway pressure of 30 cm H2O for a duration of 30 secs (pause), after which the baseline setting was resumed following the reverse sequence of inflation (deflation phase). This extended sigh was performed twice with 1 min of baseline ventilation between. MEASUREMENTS AND RESULTS: Airway pressures and hemodynamic parameters were traced at each step during the extended sigh. Arterial blood gases and physiologic parameters were determined before the extended sigh (pre-extended sigh), at 5 mins after two extended sighs (post-extended sigh), and then every 15 mins for 1 hr. In our average patient, the recruiting pressure x time of the inflation phase was estimated to be 32.8-35.4 cm H2O x 90 secs. Compared with the inflation phase, inspiratory pause pressure of the deflation phase was lower at Vt-PEEP 6-15 (28.9 +/- 2.7 cm H2O vs. 27.3 +/- 2.8 cm H2O) and 4-20 (31.8 +/- 2.9 cm H2O vs. 31.1 +/- 2.9 cm H2O; both p <.05). Compared with pre-extended sigh, Pao2 (81.5 +/- 15.3 mm Hg vs. 104.8 +/- 25.0 mm Hg; p <.001) and static respiratory compliance both increased post-extended sigh (27.9 +/- 7.9 mL/cm H2O vs. 30.2 +/- 9.7 mL/cm H2O; p =.009). Improvement in these parameters was sustained above pre-extended sigh for the duration of the study. Major hemodynamic or respiratory complications were not noted during the study. CONCLUSION: We present a new form of sigh (i.e., extended sigh) capable of achieving an augmented recruiting pressure x time through a prolonged inflation on a gradually increased end-expiratory pressure. In view of the sustained effect and absence of major complications in our patients, extended sigh could be a useful recruitment maneuver in acute respiratory distress syndrome.

Aequorea green fluorescent protein analysis by flow cytometry.

The isolation and expression of the cDNA for the green fluorescent protein (GFP) from the bioluminescent jellyfish Aequorea victoria has highlighted its potential use as a marker for gene expression in a variety of cell types (Chalfie et al.: Science 263: 802-805, 1994). The longer wavelength peak (470 nm) of GFP's bimodal absorption spectrum better matches standard fluorescein filter sets; however, it has a considerably lower amplitude than the major absorption peak at 395. In an effort to increase the sensitivity of GFP with routinely available instrumentation, Heim et al. (Nature 373:663-664, 1995) have generated a GFP mutant (serine-65 to threonine; S65T-GFP) which possesses a single absorption peak centered at 490 nm. We have constructed this mutant in order to determine whether it or wild-type GFP (wt-GFP) afforded greater sensitivity when excited near their respective absorption maxima. Using the conventionally available 488 nm and ultraviolet (UV) laser lines from the argon ion laser as well as the 407 nm line from a krypton ion laser with enhanced violet emission, we were able to closely match the absorption maxima of both the S65T and wild-type forms of Aequorea GFP and analyze differences in fluorescence intensity of transiently transfected 293 cells with flow cytometry. The highest fluorescence signal was observed with 488 nm excitation of S65T-GFP relative to all other laser line/GFP pairs. The wt-GFP fluorescence intensity, in contrast, was significantly higher at 407 nm relative to either 488 nm or UV. These results were consistent with parallel spectrofluorometric analysis of the emission spectrum for wt-GFP and S65T-GFP. The relative contribution of cellular autofluorescence at each wavelength was also investigated and shown to be significantly reduced at 407 nm relative to either UV or 488 nm.

Respiratory and haemodynamic effects of the prone position at two different levels of PEEP in a canine acute lung injury model.

This study was designed to examine whether the oxygenation response in the prone position differs in magnitude depending on the level of positive end-expiratory pressure (PEEP) applied in the supine position, and whether cardiac output (CO) increases in the prone position. In seven supine dogs, acute lung injury was established by saline lavage (arterial oxygen tension (Pa,O2)/inspiratory oxygen fraction (FI,O2) 17.8+/-9.6 kPa (134+/-72 mmHg)), and inflection point (Pflex) of the respiratory system was measured (6.6+/-1.4 cmH2O). Pa,O2/FI,O2 and CO of the supine and prone positions were obtained under the application of low PEEP and then under optimal PEEP (2 cmH2O below and above Pflex, respectively). The net increase in Pa,O2/FI,O2 by prone positioning was greater at low PEEP (27.3+/-12.0 kPa (205+/-90 mmHg)) than at optimal PEEP (4.4+/-13.0 kPa (33+/-98 mmHg)) (p=0.006). CO decreased significantly with optimal PEEP in the supine position (2.4+/-0.5 versus 3.1+/-0.4 L x min(-1) at baseline, p<0.001), and increased to 3.4+/-0.6 and 3.6+/-0.7 L x min(-1) in the prone position at 5 min and 30 min, respectively (both p=0.018). When the dogs were turned supine at optimal PEEP, CO again decreased (2.4+/-0.5 L x min(-1), p<0.001). In conclusion, the prone position augmented the effect of relatively low positive end-expiratory pressure on oxygenation, and attenuated the haemodynamic impairment of relatively high positive end-expiratory pressure in a canine acute lung injury model.