The relation between fungal propagules in indoor air and home characteristics.

BACKGROUND: Questionnaires are commonly used in epidemiologic studies to obtain information about house characteristics in order to predict the household aeroallergen exposure levels. However, the reliability of the predictions made with the questionnaires has not been evaluated. To address this issue, we compared objectively measured fungal propagules including the most frequently isolated mold genera (i.e., Alternaria, Aspergillus, Cladosporium, Penicillium, etc.) in a large sample of homes and compared these measured values to the questionnaire-determined household characteristics. METHODS: As part of a prospective cohort study on the relation between residential allergen exposure and development of asthma in neonates, fungal air samples were collected from infant bedrooms and main living areas in 1000 homes in the Northeast USA, from December 1996 to January 1999. A Burkard portable air sampler was used in combination with DG-18 and MEA agars. A questionnaire was used to obtain information on host and house characteristics that may have an impact on the presence of fungal propagules in the air. This included information on observation of moisture problems (e.g., water leakage or damage, and mold or mildew growth), ventilation and heating facilities, building age and type, number of occupants, annual household income, presence of pets and pests, cleaning regimens, etc. RESULTS: The number of CFU/m3 air collected on MEA was significantly higher than on DG-18 (means, respectively, 1033.5 and 846.0 CFU/m3) (P < 0.0005). However, there was no significant difference between the numbers of CFU/m3 air collected from the main living area and from the infant bedroom. There was only a very weak relationship between the house characteristics, as described by questionnaire, and the presence of fungal propagules in indoor air. Only the temperature, relative humidity, season, and cats inside homes had a statistically significant impact on the presence of fungal propagules in indoor air. CONCLUSION: The presence of fungal propagules in indoor air cannot be reliably predicted by home characteristics. Actual measurements are required for fungal exposure assessment, and the use of only one medium to collect samples in one location in a home might be adequate to represent residential levels of fungi in indoor air.

Indoor, outdoor, and regional summer and winter concentrations of PM10, PM2.5, SO4(2)-, H+, NH4+, NO3-, NH3, and nitrous acid in homes with and without kerosene space heaters.

Twenty-four-hour samples of PM10 (mass of particles with aerodynamic diameter < or = 10 microm), PM2.5, (mass of particles with aerodynamic diameter < or = 2.5 microm), particle strong acidity (H+), sulfate (SO42-), nitrate (NO3-), ammonia (NH3), nitrous acid (HONO), and sulfur dioxide were collected inside and outside of 281 homes during winter and summer periods. Measurements were also conducted during summer periods at a regional site. A total of 58 homes of nonsmokers were sampled during the summer periods and 223 homes were sampled during the winter periods. Seventy-four of the homes sampled during the winter reported the use of a kerosene heater. All homes sampled in the summer were located in southwest Virginia. All but 20 homes sampled in the winter were also located in southwest Virginia; the remainder of the homes were located in Connecticut. For homes without tobacco combustion, the regional air monitoring site (Vinton, VA) appeared to provide a reasonable estimate of concentrations of PM2.5 and SO42- during summer months outside and inside homes within the region, even when a substantial number of the homes used air conditioning. Average indoor/outdoor ratios for PM2.5 and SO42- during the summer period were 1.03 +/- 0.71 and 0.74 +/- 0.53, respectively. The indoor/outdoor mean ratio for sulfate suggests that on average approximately 75% of the fine aerosol indoors during the summer is associated with outdoor sources. Kerosene heater use during the winter months, in the absence of tobacco combustion, results in substantial increases in indoor concentrations of PM2.5, SO42-, and possibly H+, as compared to homes without kerosene heaters. During their use, we estimated that kerosene heaters added, on average, approximately 40 microg/m3 of PM2.5 and 15 microg/m3 of SO42- to background residential levels of 18 and 2 microg/m3, respectively. Results from using sulfuric acid-doped Teflon (E.I. Du Pont de Nemours & Co., Wilmington, DE) filters in homes with kerosene heaters suggest that acid particle concentrations may be substantially higher than those measured because of acid neutralization by ammonia. During the summer and winter periods indoor concentrations of ammonia are an order of magnitude higher indoors than outdoors and appear to result in lower indoor acid particle concentrations. Nitrous acid levels are higher indoors than outdoors during both winter and summer and are substantially higher in homes with unvented combustion sources.

Comparisons of seasonal fungal prevalence in indoor and outdoor air and in house dusts of dwellings in one Northeast American county.

Fungi cause allergies and many other adverse health effects. In this study, we characterized the nature and seasonal variation of fungi inside and outside homes in the Greater New Haven, Connecticut area. Three indoor air samples (in the living room, bedroom, and basement) and one outdoor sample were collected by the Burkard portable air sampler. House dust samples were collected in the living room by a vacuum cleaner. The mold concentrations varied widely from house to house in both indoor and outdoor air. No significant difference (p>0.05) in concentration and type of fungi between living room and bedroom or by season was observed. Both concentration and type of fungi were significantly higher (p<0.05) in the basement than other indoor areas and outdoor air in winter. The type of fungi in living room, bedroom, and outdoor air were found to have significant changes among seasons, but there was no significant difference for the basement among seasons. Cladosporium spp. was dominant in both indoor and outdoor air in summer. Penicillium and Aspergillus were dominant in indoor air in winter, but neither was dominant in any season in outdoor air. The type of fungi and their concentrations in house dust samples were not representative of those isolated in indoor air. In dust samples, more Mucor, Wallemia, and Alternaria species, but less Aspergillus, Cladosporium, and Penicillium species were found in all seasons. Air sampling in spring or fall in every suspected house is suggested for year-round fungal exposure assessment.