Outdoor Allergens

Outdoor allergens are an important part of the exposures that lead to allergic disease. Understanding the role of outdoor allergens requires a knowledge of the nature of outdoor allergen-bearing particles, the distributions of their source, and the nature of the aerosols (particle types, sizes, dynamics of concentrations). Primary sources for outdoor allergens include vascular plants (pollen, fern spores, soy dust), and fungi (spores, hyphae). Nonvascular plants, algae, and arthropods contribute small numbers of allergen-bearing particles. Particles are released from sources into the air by wind, rain, mechanical disturbance, or active discharge mechanisms. Once airborne, they follow the physical laws that apply to all airborne particles. Although some outdoor allergens penetrate indoor spaces, exposure occurs mostly outdoors. Even short-term peak outdoor exposures can be important in eliciting acute symptoms. Monitoring of airborne biological particles is usually by particle impaction and microscopic examination. Centrally located monitoring stations give regional-scale measurements for aeroallergen levels. Evidence for the role of outdoor allergens in allergic rhinitis is strong and is rapidly increasing for a role in asthma. Pollen and fungal spore exposures have both been implicated in acute exacerbations of asthma, and sensitivity to some fungal spores predicts the existence of asthma. Synergism and/or antagonism probably occurs with other outdoor air particles and gases. Control involves avoidance of exposure (staying indoors, preventing entry of outdoor aerosols) as well as immunotherapy, which is effective for pollen but of limited effect for spores. Outdoor allergens have been the subject of only limited studies with respect to the epidemiology of asthma. Much remains to be studied with respect to prevalence patterns, exposure and disease relationships, and control

The Characterization of Upper-Room Ultraviolet Germicidal Irradiation in Inactivating Airborne Microorganisms

In this study, we explored the efficacy of upper-room ultraviolet germicidal irradiation (UVGI) in reducing the concentration of Serratia marcescens and Mycobacterium bovis bacille Calmette-Guérin (BCG) aerosols in enclosed places. We constructed a facility (4.5 m x 3 m x 2.9 m) in which both ceiling- and wall-mounted UV fixtures (UV output: 10W and 5W respectively) were installed. The use of ceiling- and wall-mounted UV fixtures (total UV output: 15W) without mixing fan reduced the concentration of S. marcescens aerosols by 46% (range: 22-80%) at 2 air changes per hour (ACH) and 53% (range: 40-68%) at 6 ACH. The use of ceiling- and wall-mounted UV fixtures with mixing fan increased the UV effectiveness in inactivating S. marcescens aerosols to 62% (range: 50-78%) at 2 ACH and to 86% (81-89%) at 6 ACH. For BCG aerosols, UV effectiveness in inactivating BCG aerosols at 6 ACH were 52% (range: 11-69%) by ceiling-mounted UV fixture only (total UV output: 10W) and 64% (51-83%) by both ceiling- and wall-mounted UV fixtures (total UV output: 15W). Our results indicated that the equivalent ventilation rate attributable to upper-room UVGI for BCG aerosols ranged from 1 ACH to 22 ACH for ceiling-mounted UV fixtures and from 6.4 ACH to 28.5 ACH for ceiling- and wall-mounted UV fixtures. Both generalized linear and generalized additive models were fitted to all our data. The regression results indicated that the number of UV fixtures, use of mixing fan, and air exchange rate significantly affected UV effectiveness (p < 0.01, 0.01, 0.01 respectively). However, the strain difference (S. marcescens vs. BCG) appeared less important in UV effectiveness (p = 0.26). Our results also indicated that UV effectiveness increased at higher temperature ((italic)p(/italic) < 0.01), lower dry-bulb temperature ((italic)p(/italic) = 0.21), and colder air from a supply grill located near the ceiling (p = 0.22)

Sampling and analysis of biological aerosols

The extreme particle size range and enormous heterogeneity of airborne biological particles make sampling a significant challenge. Three major sampler types available include gravity devices, impactors and suction samplers. Gravity methods, while most commonly used, are neither qualitatively or quantitatively accurate and of very limited use. Impaction samplers (rotating, centrifugal) accelerate air by rotating the collecting surface or with a fan. Particles are collected from measured volumes of air but these devices preferentially sample particles larger than 10 [mu]m. Suction samplers, which efficiently collect particles of a wide size range from measured volumes of air, include slit samplers, cascade impactors, filtration devices and liquid impingers. Suction samplers can retrieve viable particles by direct impaction on culture media, or by subsequent culture of impinger fluid or filter eluates. Nonviable particles can often be identified by microscopic examination of slides, filters or filtrates of impinger fluids. Immunoassays and biochemical assays can be used with impinger fluid and filter eluates to assess antigen and toxin levels in measured air samples.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26961/1/0000528.pd

Populations and determinants of airborne fungi in large office buildings

Bioaerosol concentrations in office environments and their roles in causing building-related symptoms have drawn much attention in recent years. Most bioaerosol studies have been cross-sectional. We conducted a longitudinal study to examine the characteristics of airborne fungal populations and correlations with other environmental parameters in office environments. We investigated four office buildings in Boston, Massachusetts, during 1 year beginning May 1997, recruiting 21 offices with open workstations. We conducted intensive bioaerosol sampling every 6 weeks resulting in 10 sets of measurement events at each workstation, and recorded relative humidity, temperature, and CO2 concentrations continuously. We used principal component analysis (PCA) to identify groups of culturable fungal taxa that covaried in air. Four major groupings (PCA factors) were derived where the fungal taxa in the same groupings shared similar ecological requirements. Total airborne fungal concentrations varied significantly by season (highest in summer, lowest in winter) and were positively correlated with relative humidity and negatively related to CO2 concentrations. The first and second PCA factors had similar correlations with environmental variables compared with total fungi. The results of this study provide essential information on the variability within airborne fungal populations in office environments over time. These data also provide background against which cross-sectional data can be compared to facilitate interpretation. More studies are needed to correlate airborne fungi and occupants' health, controlling for seasonal effects and other important environmental factors

Comparative recoveries of airborne fungus spores by viable and non-viable modes of volumetric collection

The suitability of viable and non-viable volumetric collectors as prevalence indicators for potentially allergenic airborne fungi was studied during 124 paired exposures of the Burkard (Hirst) spore trap and a modified, wind-oriented Andersen sampler. Overall, viable recoveries of several Cladosporium form species varied directly with microscopic spore counts (p≤0.0001). However, as spore levels rose, culture plate data progressively underestimated prevailing concentrations (recoveries falling below 5% at levels above 500 spores/M 3 ). Viable collections yielded low estimates of prevalence (20–40%) even at modest Cladosporium levels (< 100 spores/M 3 ) and substantially understated the abundance and regularity in air of several additional taxa. Spores typical of Penicillium and Aspergillus form species were not sought in spore trap deposits. Careful examination of these failed to reveal typical arthrospores or Fusarium macrospores despite substantial recoveries of corresponding growth in culture. Correlations in the occurrence patterns of arthrospore-forming and non-sporulating colonies with those of Coprinus and ‘other basidiospores’ (excluding Ganoderma) were noted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43291/1/11046_2004_Article_BF00440755.pd

Acute respiratory effects on workers exposed to metalworking fluid aerosols in an automotive transmission plant

Exposure to metalworking fluids has been linked to modest cross-shift reductions in FEV 1 and occupational asthma. To identify responsible agents, we measured personal exposures to thoracic particulate (TP), viable plus nonviable thoracic bacteria (BAC), and vapor phase nicotine (VPN) (as a surrogate for tobacco particulate) among 83 machinists exposed to soluble oils and 46 dry assemblers working in an automotive transmission machining plant using biocides infrequently. The participants completed interviews and performed pre- and postshift spirometry on Monday and Thursday of the same week in each of three rounds of data collection (June 1992, January 1993, June 1993). Generalized estimating equations were used to combine information across rounds in multiple regression models of cross-shift and cross-week changes in forced expiratory volume, I second (FEV 1 ) and forced vital capacity (FVC). Mean seniority was 19 years among machinists. Mean personal TP levels were 0.41 mg/m 3 in machinists and 0.13 mg/m 3 in assemblers. Six of the 83 machinists and none of the 46 assemblers experienced a greater than 19% cross-shift decrement in FEV 1 or FVC at least once (p = .07). In regression models using either TP or BAC, among subjects with lower baseline (Monday preshift) FEV 1 /FVC ratios, increasing exposure was significantly associated with increasing cross-shift decrements in FEV 1 and FVC in linear models, and with increased likelihood of a 10% or greater cross-shift decrement in FEV 1 or FVC in logistic models. Adjustment of TP for VPN did not affect models significantly. We conclude that clinically important cross-shift decrements in pulmonary function are associated with exposure to metalworking fluid aerosols within a high-seniority population. Am. J. Ind. Med. 31:510–524, 1997. © 1997 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34816/1/4_ftp.pd

Fungal Levels in the Home and Allergic Rhinitis by 5 Years of Age

Studies have repeatedly demonstrated that sensitization to fungi, such as Alternaria, is strongly associated with allergic rhinitis and asthma in children. However, the role of exposure to fungi in the development of childhood allergic rhinitis is poorly understood. In a prospective birth cohort of 405 children of asthmatic/allergic parents from metropolitan Boston, Massachusetts, we examined in-home high fungal concentrations (> 90th percentile) measured once within the first 3 months of life as predictors of doctor-diagnosed allergic rhinitis in the first 5 years of life. In multivariate Cox regression analyses, predictors of allergic rhinitis included high levels of dust-borne Aspergillus [hazard ratio (HR) = 3.27; 95% confidence interval (CI), 1.50–7.14], Aureobasidium (HR = 3.04; 95% CI, 1.33–6.93), and yeasts (HR = 2.67; 95% CI, 1.26–5.66). The factors controlled for in these analyses included water damage or mild or mildew in the building during the first year of the child’s life, any lower respiratory tract infection in the first year, male sex, African-American race, fall date of birth, and maternal IgE to Alternaria > 0.35 U/mL. Dust-borne Alternaria and non-sporulating and total fungi were also predictors of allergic rhinitis in models excluding other fungi but adjusting for all of the potential confounders listed above. High measured fungal concentrations and reports of water damage, mold, or mildew in homes may predispose children with a family history of asthma or allergy to the development of allergic rhinitis