Aspergillis_in_Environment

Asp f 1 Allergen in Office Environments

Survey of Asp f 1 Allergen in Office Environments - Ryan, Timothy J., Whitehead, Lawrence W., Connor, Thomas H., and Burau, Keith D., Applied Occupational and Environmental Hygiene, 16:679-684, 2001.

Background:

The study of indoor fungal allergens is still in its infancy. Thus neither safe nor acceptable threshold levels of fungal allergens have been determined for indoor air quality (IAQ) standards. However recent events have made it possible to study the role of fungal allergens in the etiology of Sick Building Syndrome (SBS). Increased prevalence of the year-round present mold Penicillium chrysogenum and SBS in school buildings has been documented. Recent data link Sick Building Syndrome (SBS) to serum Ig-E specific to Penicillium chrysogenum. These findings indicate the potential use of standard immunological tests in the study of office air quality. More cause for investigation of indoor aeroallergens comes from data showing that any type of allergen can cause sensitization to asthma, an increasingly common chronic disease.

Amino acid sequencing has been performed for Aspergillus Asp f 1 (Asp f 1) allergen. Accurate study of the prevalence of this allergen in non-industrial occupational work settings is now possible. One study of Asp 1 f found it present in dust of 5% of houses examined at a concentration of 38 ng/g dust.

Purpose:

The purpose of this study was to determine background levels of Asp f 1 in non-domestic buildings without SBS complaints. Thus an acceptable background level of Asp f 1 could be estimated for purposes of IAQ standards. Increases in interior moisture and the effect on Asp f 1 levels were also studied in this experiment.

Materials and Methods:

1) Study Design:

Offices, research laboratories, and classrooms in 30 university buildings were studied for Asp f 1 levels. Rooms with mold growth risk factors (usually water intrusion history) were included to increase the probability of allergen release from fungal growth. Four variables were included within each building:

·       A moist location (basement level) termed "Wet"

·       A dry location (second story or higher) termed "Dry"

·       Dry periods (based on lack of rainfall) termed "Hi"

·       Wet periods (based on no or little rainfall) termed "Low"

Samples of airborne allergens were collected for four conditions as follows:

·       Hi/Dry

·       Hi/Wet

·       Low/Dry

·       Low/Wet

2) Environmental Measurements:

The following were measured:

·       RH of room and floor

·       T of room and floor

·       Moisture content of room materials

·       Dew points calculated for rooms and floor

3) Allergen Sampling and Quantification:

·       Airborne samples were collected with a high volume sampling pump (Eberline Model RAP-1) @ 50 l/m on Whatman glass fiber filters.

·       Filters were then prepared for analysis of fungus – both identification and quantification.

·       Vigorously sweeping an area for 10" with a hand broom was considered aggressive sampling. Airborne particles generated were collected on filter papers.

·       A hand-held vacuum cleaner was used to collect bulk dust samples that were then sieved.

All samples collected as above (filter extracts and sieved dust) were sent for analysis in outside laboratories. Examination was by 2-site ELISA for quantification of the Asp f 1 allergen.

4) Microbial Sampling and Quantification:

Only A. fumigatus (Asp f 1) was identified and quantitated in CFU/g of dust.

5) Data Analysis:

Both descriptive point estimates and their variability were calculated on data and log-transformed data. Normality of the log-transformed data was tested with the Shapiro-Wilk "W" statistic. The variables of climate condition and sample location were compared with 2-sample t-tests. The RH, dew point, and relative moisture were compared across both location and climate as defined under "1) study design" above.

Results:

In summary:

· Airborne levels of Asp f 1 tested for were >1.2 ng/m³ in this study.

· No significant levels of Asp f 1 allergen were found in these non-industrial office buildings.

· No significant levels of Asp f 1 allergen were found even when Asp f 1 was detectable by culture methods used.

· The airborne levels of Asp f 1 did not change when environmental moisture changed. This was true when there were increases in interior moisture and in levels of Asp f 1 from dust sampled during wet conditions.

Discussion:

The majority of the discussion consists of possible explanations of the unexpected results of low levels of Asp f 1. Much higher levels of Cladosporium Alternaria, and Penicillium were observed relative to Asp f 1. The authors conclude that in spite of possible inefficient collection methods, a lack of allergen production is the reason for low allergen collection.

Conclusion:

Asp f 1 allergen is absent from these non-industrial work buildings. It is possible that levels might increase with moisture in facilities experiencing water-related SBS problems. Asp f 1 did not increase in concentration above lower levels of the study’s detection even when microbial blooms were temporally associated with interior moisture increases. The authors emphasize that these findings do not exclude Asp f 1 as being involved in SBS under unusual building environmental conditions.

Recommendations:

The authors make 4 recommendations:

· Asp f 1 levels should be examined in buildings where there is water intrusion.

· Asp f 1 levels should be examined in buildings where both Asp f 1 and high moisture occur simultaneously.

· More efficient dust recovery techniques should be sought out.

· The efficiency of current dust recovery methods should be determined.

Editorial note: This report represents a relatively new area of occupational hygiene with minimal scientific background information yet available. At the other end of the occupational hygiene spectrum are areas such as lung disease associated with mineral dust exposure or solvent exposures. It is likely that more studies of the roles of fungal and other allergens in SBS (Sick Building Syndrome) will be performed due to the apparently increasing incidence of asthma that is thought to be a predisposing factor to SBS. – Susan G. Shami, ScD

By: Susan G. Shami, ScD