Establishing Site Specific Reference Levels for Fungi in Outdoor Air for Building Evaluation

Abstract

Culturable airborne fungal spore sampling at five building sites during 2002-2003 provided a bank of outdoor data (102 samples total) to evaluate differences in levels of individual species of airborne fungi during the morning and afternoon hours. A minimum of 15 (outdoor) air samples was collected at each site, and data were segregated into morning (before noon) and afternoon subsets. Significant differences in airborne levels for all detected fungal types between the morning and afternoon subsets were determined for each site, using a direct calculation of probability. Significance was defined by differences in frequency of detection above the combined median (p=0.90 or greater) for the respective fungal type. The levels of various species of fungi in the outdoor air varied significantly between morning and afternoon data sets at all five sites, with no pattern by species, time of day, or location. Levels of Penicillium, Aspergillus, or other fungal species associated with problematic buildings if detected outdoors, can be significantly greater in the morning or afternoon (or exhibit no significant difference) on any given day. The data does not indicate laboratory analysis as a major contributor to the variability exhibited in bioaerosols, and underscores the necessity of collecting sufficient number of samples in the outdoor air in both the morning and afternoon to prevent bias when comparing a suspect indoor environment to outdoor conditions.

Comparison of mold concentrations quantified by MSQPCR in indoor and outdoor air sampled simultaneously

“…They stated that "the number of CFU/m 3 in the indoor and outdoor air varied widely" and the "low predictive value …limits their use in epidemiological studies." Spicer and Gangloff (2005) showed that "the levels of fungi in the outdoor air varied significantly between morning and afternoon …with no pattern by species, time of day or location. "…”

Verifying Interpretive Criteria for Bioaerosol Data Using (Bootstrap) Monte Carlo Techniques

“…The high frequency of nondetect values precludes the necessity of substitution of an arbitrary value based on a limit of detection, as any potential negative bias affects all data equally. (9,22) The BMC analysis randomly selected a data point from the base field data and calculated the associated NP/P ratio. The process was repeated 10,000 times, and the frequency distribution of the various values of NP/P produced an estimate of probability the descriptor is useful.…”

“…For example, each fungal type/species can be considered independently, with comparison of the frequency of each type (however defined) across indoor and outdoor zones irrespective of other microbial types that may be detected. (21,22) This is fundamentally different from the more common practice of comparing relative differences of fungal types detected within the control zone to relative differences of fungal types detected in a suspect indoor environment. The latter approach by rank order analysis is usually performed by simple inspection of the data but can also be formalized through utilization of Spearman's rank order correlation.…”

“…(1−3,5−7,9−21) Consequently, a fundamental contributor to the wide variability in guidelines for bioaerosol data interpretation stems from differences in the nature of the data generated by a Journal of Occupational and Environmental Hygiene February 2008 85 particular sampling methodology, as well as how data may be truncated and/or processed to allow use of a particular descriptor. (5,16,22,23) As an example, an investigation comparing a suspect indoor environment with the outdoor air using differences in the ratio of phylloplane to nonphylloplane fungi (as discussed herein) must first define (limit) the types of fungi to be considered phylloplane and nonphylloplane fungi. Data for the designated species must then be combined into the respective grouping and each resulting group treated as a single contaminant.…”

“…Not only does the species makeup of each group potentially alter the data (phylloplane and nonphylloplane species may vary among studies), but once established, comparison of nonphylloplane and phylloplane fungi across zones may in fact be comparing very different organisms identified within the same group. (3,5,6,22) Even if the types of fungi determined to be relevant were universally agreed on, there is no consistent procedure in which data from a suspect indoor environment and an (outdoor air) control zone is compared. For example, each fungal type/species can be considered independently, with comparison of the frequency of each type (however defined) across indoor and outdoor zones irrespective of other microbial types that may be detected.…”