Seasonal Distribution of Airborne Alternaria Spores

Abstract

RATIONALE: Alternaria is one of the most recognizable of all spore types known to cause allergy. It is also the fungus most likely to cause a positive skin test. To investigate the yearly variation of airborne Alternaria spores we conducted the following.METHODS: Airborne spores were collected every 4 hours during the months of March thru October from 1998 to 2005 in Kansas City. Spores were collected on silicon grease coated glass slides using a Burkard volumetric sampler set atop a 5 story building. Slides were stained and preserved with Calberlas stain in glycerin jelly and counted microscopically at 1000x. Spore numbers were entered into an Access database and counts were displayed as spores per cubic meter of air.RESULTS: The distribution of airborne Alternaria spores was very consistent from year to year. Counts start low in the early spring (mean < 10 per cubic meter) and increase steadily until September (mean > 1500 spores per cubic meter). As temperatures decline spore counts then decrease until low levels are again achieved. The highest mean Alternaria count is achieved 245 days into the year (usually September 2). The greatest daily mean observed during the 8 year period was 6988 spores per cubic meter in both 2001 and 2002 and occurred on September 2 and September 3 respectively.CONCLUSIONS: Airborne Alternaria spores are consistently found in the Midwestern United States. Levels rise from low winter and spring levels to peak in early September. RATIONALE: Alternaria is one of the most recognizable of all spore types known to cause allergy. It is also the fungus most likely to cause a positive skin test. To investigate the yearly variation of airborne Alternaria spores we conducted the following. METHODS: Airborne spores were collected every 4 hours during the months of March thru October from 1998 to 2005 in Kansas City. Spores were collected on silicon grease coated glass slides using a Burkard volumetric sampler set atop a 5 story building. Slides were stained and preserved with Calberlas stain in glycerin jelly and counted microscopically at 1000x. Spore numbers were entered into an Access database and counts were displayed as spores per cubic meter of air. RESULTS: The distribution of airborne Alternaria spores was very consistent from year to year. Counts start low in the early spring (mean < 10 per cubic meter) and increase steadily until September (mean > 1500 spores per cubic meter). As temperatures decline spore counts then decrease until low levels are again achieved. The highest mean Alternaria count is achieved 245 days into the year (usually September 2). The greatest daily mean observed during the 8 year period was 6988 spores per cubic meter in both 2001 and 2002 and occurred on September 2 and September 3 respectively. CONCLUSIONS: Airborne Alternaria spores are consistently found in the Midwestern United States. Levels rise from low winter and spring levels to peak in early September.