title: Concentrations of the major birch tree allergen Bet v 1 in pollen and respirable fine particles in the atmosphere.
abstract: BACKGROUND
  Birch tree pollen allergens are an important cause of early spring hay fever and allergic asthma. Pollen counts provide a guide for individuals with birch pollen allergy. However, birch pollen, because of its size, has a low probability of entering the lower airways to trigger asthma. Yet birch pollen allergens are known to be associated with respirable particles present in the atmosphere.
  
  
  OBJECTIVE
  We sought to determine the concentration of major allergen Bet v 1 in birch pollen and respirable particles in the atmosphere during the birch pollen season.
  
  
  METHODS
  We used a two-site monoclonal antibody-based assay (ELISA) to quantitate Bet v 1 in pollen extracts and high-volume air sampler filters collecting particles larger and smaller than 7.2 microm.
  
  
  RESULTS
  Bet v 1 (0.006 ng) is detectable per birch pollen grain, of which 0.004 ng is present in aqueous extracts (13.9% of soluble proteins). Atmospheric Bet v 1 concentrations are correlated with birch pollen counts. Heavy rainfall tended to wash out pollen and particles, indicated by a mean daily Bet v 1 concentration of 0.12 ng/m3 (20 pollen equivalents), but light rainfall produced a dramatic increase in allergen-loaded respirable particles with Bet v 1 concentrations of 1.2 ng/m3 (200 pollen equivalents).
  
  
  CONCLUSIONS
  These results highlight the different environmental risk factors for hay fever and allergic asthma in patients sensitized to Bet v 1. Light rainfall causes an increase in respirable particles; hence, this is an important risk factor for asthma.
authors.affiliation: Pollen and Allergen Research Group, School of Botany, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: G F
authors.initials: GF
authors.lastname: Schäppi
authors.forename: C
authors.initials: C
authors.lastname: Suphioglu
authors.forename: P E
authors.initials: PE
authors.lastname: Taylor
authors.forename: R B
authors.initials: RB
authors.lastname: Knox
mesh_terms: D000397:Air Pollution / Q000032:analysis; D000485:Allergens / Q000032:analysis*; D052179:Antigens, Plant; D002452:Cell Count; D005374:Filtration / Q000295:instrumentation; D006801:Humans; D010940:Plant Proteins / Q000032:analysis*; D011058:Pollen / Q000737:chemistry* / Q000166:cytology
chemical_list: D000485:Allergens; D052179:Antigens, Plant; D010940:Plant Proteins; C061312:Bet v 1 allergen, Betula