Collection of aerosolized human cytokines using Teflon® filters

BACKGROUND

Collection of exhaled breath samples for the analysis of inflammatory biomarkers is an important area of research aimed at improving our ability to diagnose, treat and understand the mechanisms of chronic pulmonary disease. Current collection methods based on condensation of water vapor from exhaled breath yield biomarker levels at or near the detection limits of immunoassays contributing to problems with reproducibility and validity of biomarker measurements. In this study, we compare the collection efficiency of two aerosol-to-liquid sampling devices to a filter-based collection method for recovery of dilute laboratory generated aerosols of human cytokines so as to identify potential alternatives to exhaled breath condensate collection.

METHODOLOGY/PRINCIPAL FINDINGS

Two aerosol-to-liquid sampling devices, the SKC® Biosampler and Omni 3000™, as well as Teflon® filters were used to collect aerosols of human cytokines generated using a HEART nebulizer and single-pass aerosol chamber setup in order to compare the collection efficiencies of these sampling methods. Additionally, methods for the use of Teflon® filters to collect and measure cytokines recovered from aerosols were developed and evaluated through use of a high-sensitivity multiplex immunoassay. Our results show successful collection of cytokines from pg/m(3) aerosol concentrations using Teflon® filters and measurement of cytokine levels in the sub-picogram/mL concentration range using a multiplex immunoassay with sampling times less than 30 minutes. Significant degradation of cytokines was observed due to storage of cytokines in concentrated filter extract solutions as compared to storage of dry filters.

CONCLUSIONS

Use of filter collection methods resulted in significantly higher efficiency of collection than the two aerosol-to-liquid samplers evaluated in our study. The results of this study provide the foundation for a potential new technique to evaluate biomarkers of inflammation in exhaled breath samples.

Effects of endotoxin exposure on childhood asthma risk are modified by a genetic polymorphism in ACAA1

Background

Polymorphisms in the endotoxin-mediated TLR4 pathway genes have been associated with asthma and atopy. We aimed to examine how genetic polymorphisms in innate immunity pathways interact with endotoxin to influence asthma risk in children.

Methods

In a previous analysis of 372 children from the Boston Home Allergens and the Connecticut Childhood Asthma studies, 7 SNPs in 6 genes (CARD15, TGFB1, LY96, ACAA1, DEFB1 and IFNG) involved in innate immune pathways were associated with asthma, and 5 SNPs in 3 genes (CD80, STAT4, IRAK2) were associated with eczema. We tested these SNPs for interaction with early life endotoxin exposure (n = 291), in models for asthma and eczema by age 6.

Results

We found a significant interaction between endotoxin and a SNP (rs156265) in ACAA1 (p = 0.0013 for interaction). Increased endotoxin exposure (by quartile) showed protective effects for asthma in individuals with at least one copy of the minor allele (OR = 0.39 per quartile increase in endotoxin, 95% CI 0.15 to 1.01). Endotoxin exposure did not reduce the risk of asthma in children homozygous for the major allele.

Conclusion

Our findings suggest that protective effects of endotoxin exposure on asthma may vary depending upon the presence or absence of a polymorphism in ACAA1.

Temporal changes in the prevalence of childhood asthma and allergies in urban and rural areas of Cyprus: results from two cross sectional studies

BACKGROUND

The prevalence of childhood asthma and allergies in Cyprus was significantly higher in urban compared to rural areas back in the year 2000, against a background of an overall low prevalence (e.g. current wheeze 6.9%) by comparison to northern European countries. In this study we aimed to assess temporal changes in the prevalence of asthma and allergies in Cyprus after an 8-year interval and to examine whether any differential changes have occurred in urban and rural parts of the island.

METHODS

During the academic years 1999-2000 and 2007-2008, the parents of 7-8 year old children residing in the same set of urban and rural areas completed the ISAAC core questionnaire. In addition to providing prevalence estimates of allergic diseases in 2000 and 2008, changes between the two periods were expressed as odds ratios estimated in multiple logistic regression models adjusting for survey participants' characteristics.

RESULTS

The prevalence of current wheeze was higher in 2008 (8.7%, 95% confidence interval 7.5%-9.9%, n = 2216) than the previously recorded figure in 2000 (6.9%, 95% CI 6.2%-7.6%, OR = 1.25, 95% CI: 1.02-1.53, n = 4944). Significant increases were also seen in the prevalence of lifetime asthma (11.3% vs. 17.4%, OR = 1.59, CI: 1.36-1.86), eczema (6.8% vs. 13.5%, OR = 1.91, CI: 1.59-2.29) and allergic rhinoconjuctivitis (2.6% vs. 5.2%, OR = 1.82, CI: 1.39-2.41). The prevalence of current wheeze nearly doubled between 2000 and 2008 in rural areas (5.4% vs. 9.7%, OR 1.81, CI: 1.24-2.64) while no significant change was observed in urban areas (7.5% vs. 8.4%, OR 1.08, CI: 0.84-1.37); p value for effect modification = 0.04. Rises in asthma and rhinitis prevalence, but not eczema were also more pronounced in rural compared to urban areas.

CONCLUSIONS

The prevalence of allergic diseases in Cyprus is still on the rise; recent increases appear more pronounced among children living in rural areas possibly indicating recent environmental and lifestyle changes in these communities.

Clinical study of multiple breath biomarkers of asthma and COPD (NO, CO(2), CO and N(2)O) by infrared laser spectroscopy

Breath analysis is a powerful non-invasive technique for the diagnosis and monitoring of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Exhaled nitric oxide (NO) and carbon monoxide (CO) are markers of airway inflammation and can indicate the extent of respiratory diseases. We have developed a compact fast response quantum cascade laser system for analysis of multiple gases by tunable infrared absorption spectroscopy. The ARI breath analysis instrument has been deployed in a study of exhaled breath from patients with asthma or COPD. A total of 173 subjects participated, including both adult and pediatric patients. Patients in asthma or COPD exacerbations were evaluated twice-during the exacerbation and at a follow-up visit-to compare variations in breath biomarkers during these events. The change in exhaled NO levels between exacerbation and 'well' visits is consistent with spirometry data collected. Respiratory models are important for understanding the exchange dynamics of nitric oxide and other species in the lungs and airways. At each patient's visit, tests were conducted at four expiratory flow rates. We have applied a trumpet model with axial diffusion to the multi-flow exhaled nitric oxide data, obtaining NO alveolar concentrations and airway fluxes. We found higher airway fluxes for those with more severe asthma and during exacerbation events. The alveolar concentrations from the model were higher in adults with asthma and COPD, but this trend was less clear among the pediatric subjects.

Origin of exhaled breath particles from healthy and human rhinovirus-infected subjects

BACKGROUND

Exhaled breath studies suggest that humans exhale fine particles during tidal breathing, but little is known of their physical origin in the respiratory system during health or disease.

METHODS

Particles generated by 3 healthy and 16 human rhinovirus (HRV)-infected subjects were counted using an optical particle counter with nominal diameter-size bins ranging between 0.3 and 10 μm. Data were collected from HRV-infected subjects during tidal breathing. In addition, data from healthy subjects were collected during coughs, swallows, tidal breathing, and breathing to total lung capacity (TLC) and residual volume (RV). Using general additive models, we graphed exhaled particle concentration versus airflow during exhalation. Exhaled particles were collected from expired air on gelatin filters and analyzed for HRV via quantitative PCR.

RESULTS

HRV-infected subjects exhaled from 0.1 to 7200 particles per liter of exhaled air during tidal breathing (geometric mean = 32 part/L). A small fraction (24%) of subjects exhaled most (81%) of the particles measured and 82% of particles detected were 0.300-0.499 μm. Minute ventilation, maximum airflow during exhalation, and forced expiratory volume 1 second (FEV(1) % predicted) were positively correlated with particle production. No human rhinovirus was detected in exhaled breath samples. Three healthy subjects exhaled less than 100 particles per liter of exhaled air during tidal breathing and increased particle concentrations more with exhalation to RV than with coughing, swallowing, or rapid exhalation.

CONCLUSIONS

Submicron particles were detected in the exhaled breath of healthy and HRV-infected subjects. Particle concentrations were correlated with airflow during the first half of exhalation, and peaked at the end of exhalation, indicating both lower and upper airways as particle sources. The effect of breathing maneuver suggested a major contribution from lower airways, probably the result of opening collapsed small airways and alveoli.

Home characteristics as predictors of bacterial and fungal microbial biomarkers in house dust

BACKGROUND

Measurement of fungal and bacterial biomarkers can be costly, but it is not clear whether home characteristics can be used as a proxy of these markers, particularly if the purpose is to differentiate specific classes of biologic exposures that have similar sources but may have different effects on allergic disease risk.

OBJECTIVE

We evaluated home characteristics as predictors of multiple microbial biomarkers, with a focus on common and unique determinants and with attention to the extent of their explanatory ability.

METHODS

In 376 Boston-area homes enrolled in a cohort study of home exposures and childhood asthma, we assessed the relationship between home characteristics gathered by questionnaire and measured gram-negative bacteria (GNB) (endotoxin and C10:0, C12:0, and C14:0 3-hydroxy fatty acids), gram-positive bacteria (GPB) (N-acetyl muramic acid), and fungal biomarkers [ergosterol and (1→6) branched, (1→3) β-D glucans] in bed and family room dust.

RESULTS

Home characteristics related to dampness were significant predictors of all microbial exposures; water damage or visible mold/mildew in the home was associated with a 20-66% increase in GNB levels. Report of cleaning the bedroom at least once a week was associated with reduced GNB, GPB, and fungi. Presence of dogs or cats predicted increases in home bacteria or fungi. The proportion of variance in microbial biomarkers explained by home characteristics ranged from 4.2% to 19.0%.

CONCLUSIONS

Despite their associations with multiple microbial flora, home characteristics only partially explain the variability in microbial biomarker levels and cannot substitute for specific microbial measurements in studies concerned with distinguishing effects of specific classes of microbes.

Quantitative assessment of airborne exposures generated during common cleaning tasks: a pilot study

BACKGROUND

A growing body of epidemiologic evidence suggests an association between exposure to cleaning products with asthma and other respiratory disorders. Thus far, these studies have conducted only limited quantitative exposure assessments. Exposures from cleaning products are difficult to measure because they are complex mixtures of chemicals with a range of physicochemical properties, thus requiring multiple measurement techniques. We conducted a pilot exposure assessment study to identify methods for assessing short term, task-based airborne exposures and to quantitatively evaluate airborne exposures associated with cleaning tasks simulated under controlled work environment conditions.

METHODS

Sink, mirror, and toilet bowl cleaning tasks were simulated in a large ventilated bathroom and a small unventilated bathroom using a general purpose, a glass, and a bathroom cleaner. All tasks were performed for 10 minutes. Airborne total volatile organic compounds (TVOC) generated during the tasks were measured using a direct reading instrument (DRI) with a photo ionization detector. Volatile organic ingredients of the cleaning mixtures were assessed utilizing an integrated sampling and analytic method, EPA TO-17. Ammonia air concentrations were also measured with an electrochemical sensor embedded in the DRI.

RESULTS

Average TVOC concentrations calculated for 10 minute tasks ranged 0.02 - 6.49 ppm and the highest peak concentrations observed ranged 0.14-11 ppm. TVOC time concentration profiles indicated that exposures above background level remained present for about 20 minutes after cessation of the tasks. Among several targeted VOC compounds from cleaning mixtures, only 2-BE was detectable with the EPA method. The ten minute average 2- BE concentrations ranged 0.30 -21 ppm between tasks. The DRI underestimated 2-BE exposures compared to the results from the integrated method. The highest concentration of ammonia of 2.8 ppm occurred during mirror cleaning.

CONCLUSIONS

Our results indicate that airborne exposures from short-term cleaning tasks can remain in the air even after tasks' cessation, suggesting potential exposures to anyone entering the room shortly after cleaning. Additionally, 2-BE concentrations from cleaning could approach occupational exposure limits and warrant further investigation. Measurement methods applied in this study can be useful for workplace assessment of airborne exposures during cleaning, if the limitations identified here are addressed.

Research findings from nonpharmaceutical intervention studies for pandemic influenza and current gaps in the research

In June 2006, the Centers for Disease Control and Prevention released a request for applications to identify, improve, and evaluate the effectiveness of nonpharmaceutical interventions (NPIs)-strategies other than vaccines and antiviral medications-to mitigate the spread of pandemic influenza within communities and across international borders (RFA-CI06-010). These studies have provided major contributions to seasonal and pandemic influenza knowledge. Nonetheless, key concerns were identified related to the acceptability and protective efficacy of NPIs. Large-scale intervention studies conducted over multiple influenza epidemics, as well as smaller studies in controlled laboratory settings, are needed to address the gaps in the research on transmission and mitigation of influenza in the community setting. The current novel influenza A (H1N1) pandemic underscores the importance of influenza research.

Multiple microbial exposures in the home may protect against asthma or allergy in childhood

BACKGROUND

Experimental animal data on the gram-negative bacterial (GNB) biomarker endotoxin suggest that persistence, dose, and timing of exposure are likely to influence its effects on allergy and wheeze. In epidemiologic studies, endotoxin may be a sentinel marker for a microbial milieu, including gram-positive bacteria (GPB) as well as GNB, that may influence allergy and asthma through components (pathogen-associated molecular patterns) that signal through innate Toll-like receptor pathways.

OBJECTIVE

To determine the influence of current GNB and GPB exposures on asthma and allergic sensitization in school-aged children.

METHODS

We examined the relationship between bacterial biomarkers and current asthma and allergic sensitization in 377 school-aged children in a birth cohort study. We then evaluated the effects of school-aged endotoxin, after controlling for exposure in early life.

RESULTS

Exposure to GNB was inversely associated with asthma and allergic sensitization at school age [for >median endotoxin: prevalence odds ratio (POR)=0.34, 95% CI=0.2-0.7, for current asthma and prevalence ratio=0.77, 95% CI=0.6-0.97, for allergic sensitization]. In contrast, elevated GPB in the bed was inversely associated with current asthma (POR=0.41, 95% CI=0.2-0.9) but not with allergic sensitization (POR=1.07, 95% CI=0.8-1.4). School-aged endotoxin exposure remained protective in models for allergic disease adjusted for early-life endotoxin.

CONCLUSION

Both GNB and GPB exposures are associated with decreased asthma symptoms, but may act through different mechanisms to confer protection. Endotoxin exposure in later childhood is not simply a surrogate of early-life exposure; it has independent protective effects on allergic disease.

Multicomponent Breath Analysis With Infrared Absorption Using Room-Temperature Quantum Cascade Lasers

Breath analysis is a powerful noninvasive technique for the diagnosis and monitoring of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Nitric oxide (NO) and carbon monoxide (CO) are markers of airway inflammation and can indicate the extent of respiratory diseases. We have developed a compact fast response laser system for analysis of multiple gases by infrared absorption. The instrument uses room temperature quantum cascade lasers to simultaneously measure NO, CO, carbon dioxide (CO(2)) and nitrous oxide (N(2)O) in exhaled breath. Four breath flow rates are employed to explore their exchange dynamics in the lungs and airways. We obtain 1-s detection precisions of 0.5-0.8 parts-per-billion (ppb) for NO, CO, and N(2)O with an instrument response time of less than 1 s. The breath analysis system has been demonstrated in a preliminary study of volunteers. It is currently deployed in a trial clinical study.

Airborne influenza virus detection with four aerosol samplers using molecular and infectivity assays: considerations for a new infectious virus aerosol sampler

As a first step in conducting studies of airborne influenza transmission, we compared the collection performance of an SKC Biosampler, a compact cascade impactor (CCI), Teflon filters, and gelatin filters by collecting aerosolized influenza virus in a one-pass aerosol chamber. Influenza virus infectivity was determined using a fluorescent focus assay and influenza virus nucleic acid (originating from viable and non-viable viruses) was measured using quantitative PCR. The results showed that the SKC Biosampler recovered and preserved influenza virus infectivity much better than the other samplers - the CCI, Teflon, and gelatin filters recovered only 7-22% of infectious viruses compared with the Biosampler. Total virus collection was not significantly different among the SKC Biosampler, the gelatin, and Teflon filters, but was significantly lower in the CCI. Results from this study show that a new sampler is needed for virus aerosol sampling, as commercially available samplers do not efficiently collect and conserve virus infectivity. Applications for a new sampler include studies of airborne disease transmission and bioterrorism monitoring. Design parameters for a new sampler include high collection efficiency for fine particles and liquid sampling media to preserve infectivity. Practical Implications New air samplers are needed to study infectious airborne viruses and learn about airborne disease transmission. As a first step in designing a new air sampler to collect influenza virus we evaluated four commercial samplers and determined necessary design parameters for a new collector.

Characterization of occupational exposures to cleaning products used for common cleaning tasks--a pilot study of hospital cleaners

BACKGROUND

In recent years, cleaning has been identified as an occupational risk because of an increased incidence of reported respiratory effects, such as asthma and asthma-like symptoms among cleaning workers. Due to the lack of systematic occupational hygiene analyses and workplace exposure data, it is not clear which cleaning-related exposures induce or aggravate asthma and other respiratory effects. Currently, there is a need for systematic evaluation of cleaning products ingredients and their exposures in the workplace. The objectives of this work were to: a) identify cleaning products' ingredients of concern with respect to respiratory and skin irritation and sensitization; and b) assess the potential for inhalation and dermal exposures to these ingredients during common cleaning tasks.

METHODS

We prioritized ingredients of concern in cleaning products commonly used in several hospitals in Massachusetts. Methods included workplace interviews, reviews of product Materials Safety Data Sheets and the scientific literature on adverse health effects to humans, reviews of physico-chemical properties of cleaning ingredients, and occupational hygiene observational analyses. Furthermore, the potential for exposure in the workplace was assessed by conducting qualitative assessment of airborne exposures and semi-quantitative assessment of dermal exposures.

RESULTS

Cleaning products used for common cleaning tasks were mixtures of many chemicals, including respiratory and dermal irritants and sensitizers. Examples of ingredients of concern include quaternary ammonium compounds, 2-butoxyethanol, and ethanolamines. Cleaning workers are at risk of acute and chronic inhalation exposures to volatile organic compounds (VOC) vapors and aerosols generated from product spraying, and dermal exposures mostly through hands.

CONCLUSION

Cleaning products are mixtures of many chemical ingredients that may impact workers' health through air and dermal exposures. Because cleaning exposures are a function of product formulations and product application procedures, a combination of product evaluation with workplace exposure assessment is critical in developing strategies for protecting workers from cleaning hazards. Our task based assessment methods allowed classification of tasks in different exposure categories, a strategy that can be employed by epidemiological investigations related to cleaning. The methods presented here can be used by occupational and environmental health practitioners to identify intervention strategies.

Inactivation of poxviruses by upper-room UVC light in a simulated hospital room environment

In the event of a smallpox outbreak due to bioterrorism, delays in vaccination programs may lead to significant secondary transmission. In the early phases of such an outbreak, transmission of smallpox will take place especially in locations where infected persons may congregate, such as hospital emergency rooms. Air disinfection using upper-room 254 nm (UVC) light can lower the airborne concentrations of infective viruses in the lower part of the room, and thereby control the spread of airborne infections among room occupants without exposing occupants to a significant amount of UVC. Using vaccinia virus aerosols as a surrogate for smallpox we report on the effectiveness of air disinfection, via upper-room UVC light, under simulated real world conditions including the effects of convection, mechanical mixing, temperature and relative humidity. In decay experiments, upper-room UVC fixtures used with mixing by a conventional ceiling fan produced decreases in airborne virus concentrations that would require additional ventilation of more than 87 air changes per hour. Under steady state conditions the effective air changes per hour associated with upper-room UVC ranged from 18 to 1000. The surprisingly high end of the observed range resulted from the extreme susceptibility of vaccinia virus to UVC at low relative humidity and use of 4 UVC fixtures in a small room with efficient air mixing. Increasing the number of UVC fixtures or mechanical ventilation rates resulted in greater fractional reduction in virus aerosol and UVC effectiveness was higher in winter compared to summer for each scenario tested. These data demonstrate that upper-room UVC has the potential to greatly reduce exposure to susceptible viral aerosols. The greater survival at baseline and greater UVC susceptibility of vaccinia under winter conditions suggest that while risk from an aerosol attack with smallpox would be greatest in winter, protective measures using UVC may also be most efficient at this time. These data may also be relevant to influenza, which also has improved aerosol survival at low RH and somewhat similar sensitivity to UVC.

Evaluating building-related symptoms using the US EPA BASE study results

In order to develop baseline data about United States office buildings, the United States Environmental Protection Agency conducted the Building Assessment Survey Evaluation (BASE) study, a systematic survey of 100 randomly selected United States office buildings, in the 1990s. This paper analyzes the self-reported work-related symptoms and job and workplace characteristics of 4326 respondents and compares results to the National Institute for Occupational Safety and Health's (NIOSH) study of 80 'complaint' buildings. Four distinct groups of symptoms, representing 'tiredness', 'mucosal irritation', 'neuropsychological', and 'lower respiratory' conditions emerged from factor analysis of work-related symptoms. The symptom grouping is identical for both surveys. Although the prevalence of each symptom is significantly higher in the NIOSH than in the BASE sample, there is overlap of the symptom distributions. In the BASE survey, 45% of the work force reported at least one work-related health symptom; 20% reported at least three symptoms. These findings imply that it is counterproductive to dichotomize buildings into healthy vs. unhealthy; instead the prevalence of health problems related to buildings span a continuum.

PRACTICAL IMPLICATIONS

These results indicate that most office buildings have occupants who report building-related symptoms. This paper provides practical guidance for the comparison of building prevalences to the BASE normative data. Work-related symptom distributions and symptom groups can improve investigators' ability to identify IEQ problems.

Influenza virus in human exhaled breath: an observational study

Background

Recent studies suggest that humans exhale fine particles during tidal breathing but little is known of their composition, particularly during infection.

Methodology/Principal Findings

We conducted a study of influenza infected patients to characterize influenza virus and particle concentrations in their exhaled breath. Patients presenting with influenza-like-illness, confirmed influenza A or B virus by rapid test, and onset within 3 days were recruited at three clinics in Hong Kong, China. We collected exhaled breath from each subject onto Teflon filters and measured exhaled particle concentrations using an optical particle counter. Filters were analyzed for influenza A and B viruses by quantitative polymerase chain reaction (qPCR). Twelve out of thirteen rapid test positive patients provided exhaled breath filter samples (7 subjects infected with influenza B virus and 5 subjects infected with influenza A virus). We detected influenza virus RNA in the exhaled breath of 4 (33%) subjects–three (60%) of the five patients infected with influenza A virus and one (14%) of the seven infected with influenza B virus. Exhaled influenza virus RNA generation rates ranged from <3.2 to 20 influenza virus RNA particles per minute. Over 87% of particles exhaled were under 1 µm in diameter.

Conclusions

These findings regarding influenza virus RNA suggest that influenza virus may be contained in fine particles generated during tidal breathing, and add to the body of literature suggesting that fine particle aerosols may play a role in influenza transmission.

Reproducibility and validity of a handheld spirometer

BACKGROUND

Handheld spirometers have several advantages over desktop spirometers, but worries persist regarding reproducibility and validity of data from handheld spirometers. We undertook an independent examination of the EasyOne handheld spirometer.

METHODS

The laboratory testing included reproducibility and validity testing with a waveform generator. We used standard American Thoracic Society waveforms for in-line testing, calibration adaptor testing, and testing during compression of the mouthpiece. The clinical testing involved repeated tests with 24 spirometry-naïve volunteers and comparison to spirometry results from laboratory (volume-sensing dry rolling seal) spirometer.

RESULTS

The EasyOne exceeded standard thresholds for acceptability with the American Thoracic Society waveforms. In-line testing yielded valid results from the EasyOne. Between the EasyOne and the reference spirometer readings the mean +/- SD difference was 0.03 +/- 0.23 L for forced vital capacity (FVC) and -0.06 +/- 0.09 L for forced expiratory volume in the first second (FEV(1)). The calibration adaptor showed no appreciable problems. Extreme compression of the mouthpiece reduced the measured values. In clinical testing the coefficients of variation and limits of agreement were, respectively, 3.3% and 0.24 L for FVC, 2.6% and 0.18 L for FEV(1), and 1.9% and 0.05 for the FEV(1)/FVC ratio. The EasyOne readings were lower than those from the reference spirometer; the differences were: -0.12 L for FVC, -0.17 L for FEV(1), and -0.02 for FEV(1)/FVC. The limits of agreement were within criteria for FVC but not for the FEV(1), possibly due to a training effect.

CONCLUSION

The EasyOne spirometer yielded generally reproducible results that were generally valid, compared to the values from the laboratory spirometer. The use of the EasyOne in clinical, occupational, and research settings seems justified.

Characterization of UVC light sensitivity of vaccinia virus

Interest in airborne smallpox transmission has been renewed because of concerns regarding the potential use of smallpox virus as a biothreat agent. Air disinfection via upper-room 254-nm germicidal UV (UVC) light in public buildings may reduce the impact of primary agent releases, prevent secondary airborne transmission, and be effective prior to the time when public health authorities are aware of a smallpox outbreak. We characterized the susceptibility of vaccinia virus aerosols, as a surrogate for smallpox, to UVC light by using a benchtop, one-pass aerosol chamber. We evaluated virus susceptibility to UVC doses ranging from 0.1 to 3.2 J/m(2), three relative humidity (RH) levels (20%, 60%, and 80%), and suspensions of virus in either water or synthetic respiratory fluid. Dose-response plots show that vaccinia virus susceptibility increased with decreasing RH. These plots also show a significant nonlinear component and a poor fit when using a first-order decay model but show a reasonable fit when we assume that virus susceptibility follows a log-normal distribution. The overall effects of RH (P < 0.0001) and the suspending medium (P = 0.014) were statistically significant. When controlling for the suspending medium, the RH remained a significant factor (P < 0.0001) and the effect of the suspending medium was significant overall (P < 0.0001) after controlling for RH. Virus susceptibility did not appear to be a function of virus particle size. This work provides an essential scientific basis for the design of effective upper-room UVC installations for the prevention of airborne infection transmission of smallpox virus by characterizing the susceptibility of an important orthopoxvirus to UVC exposure.

Exposure to dust mite allergen and endotoxin in early life and asthma and atopy in childhood

BACKGROUND

There has been no longitudinal study of the relation between concurrent exposure to dust mite allergen and endotoxin in early life and asthma and atopy at school age.

OBJECTIVES

To examine the relation between exposure to dust mite allergen and endotoxin at age 2 to 3 months and asthma, wheeze, and atopy in high-risk children.

METHODS

Birth cohort study of 440 children with parental history of atopy in the Boston metropolitan area.

RESULTS

In multivariate analyses, early exposure to high levels of dust mite allergen (> or =10 microg/g) was associated with increased risks of asthma at age 7 years (odds ratio [OR], 3.0; 95% CI, 1.1-7.9) and late-onset wheeze (OR, 5.0; 95% CI, 1.5-16.4). Exposure to endotoxin levels above the lowest quartile at age 2 to 3 months was associated with reduced odds of atopy at school age (OR, 0.5; 95% CI, 0.2-0.9). In contrast with its inverse association with atopy, endotoxin exposure in early life was associated with an increased risk of any wheeze between ages 1 and 7 years that did not change significantly with time (hazard ratio for each quartile increment in endotoxin levels, 1.23; 95% CI, 1.07-1.43).

CONCLUSION

Among children at risk of atopy, early exposure to high levels of dust mite allergen is associated with increased risks of asthma and late-onset wheeze. In these children, endotoxin exposure is associated with a reduced risk of atopy but an increased risk of wheeze.

CLINICAL IMPLICATIONS

Early endotoxin exposure may be a protective factor against atopy but a risk factor for wheeze in high-risk children.

The validation of work-related self-reported asthma exacerbation

OBJECTIVE

To determine the validity of work-related self-reported exacerbation of asthma using the findings from serial peak expiratory flow (PEF) measurements as the standard.

METHODS

Adults with asthma treated in a health maintenance organisation were asked to conduct serial spirometry testing at home and at work for 3 weeks. Self-reported respiratory symptoms and medication use were recorded in two ways: a daily log completed concurrently with the serial PEF testing and a telephone questionnaire administered after the PEF testing. Three researchers evaluated the serial PEF records and judged whether a work relationship was evident.

RESULTS

95 of 382 (25%) working adults with asthma provided adequate serial PEF data, and 13 of 95 (14%) were judged to have workplace exacerbation of asthma (WEA) based on these data. Self-reported concurrent medication use was the most valid single operational definition, with a sensitivity of 62% and a specificity of 65%.

CONCLUSIONS

A work-related pattern of self-reported asthma symptoms or medication use was usually not corroborated by serial PEF testing and failed to identify many people who had evidence of WEA based on the serial PEF measurements.

Partial questionnaire designs, questionnaire non-response, and attributable fraction: applications to adult onset asthma

The attributable fraction (AF) is often used to explore the policy implications of an association between a disease and an exposure. To date, there have been no proposed estimators of AF in the context of partial questionnaire designs (PQD). The PQD, first proposed in a public health context by Wacholder is often used to enhance response rates in questionnaires. It involves eliciting responses from each subject on preassigned subsets of questions, thereby reducing the burden of response. We propose a computationally efficient method of estimating logistic (or more generally, binary) regression parameters from a PQD model where there is non-response to the questionnaire and the rates of non-response differ between sub-populations. Assuming a log-linear model for the distribution of missing covariates, we employ the methods of Wacholder to motivate consistent estimating equations, and weight each subject's contribution to the estimating function by the inverse probability of responding to the questionnaire. We also propose techniques for goodness-of-fit to assist in model selection. We then use the PQD regression estimates to derive an estimate of AF similar to that proposed by Bruzzi. Finally, we demonstrate our methods using data obtained from a study on adult occupational asthma, conducted within a Massachusetts HMO. Although we concentrate on a particular type of missing data mechanism, other missing data techniques can be incorporated into AF estimation in a similar manner.

Case-by-case assessment of adult-onset asthma attributable to occupational exposures among members of a health maintenance organization

OBJECTIVE

In a general population of employed persons with health insurance, what proportion of adult-onset asthma is caused by occupational exposures?

METHOD

We conducted a 2-year prospective study to identify adult-onset asthma among health maintenance organization (HMO) members. Telephone interviews regarding occupational exposures, symptoms, medication use, and triggers were used to assess likelihood of work-related asthma for each case. Weighted estimating equations were used to adjust the proportion of asthma attributable to workplace exposures for factors associated with interview participation.

RESULTS

Overall, 29% (95% confidence interval, 25-34%) of adult-onset asthma was attributable to workplace exposures; 26% (21-30%) and 22% (18-27%) of cases had asthma attributable to occupational irritant and sensitizer exposures, respectively.

CONCLUSIONS

Occupational exposures, including irritants, are important causes of adult-onset asthma.