IgE sensitization to potent allergens may occur at average airborne concentrations <0.1-1 ng/m3. Measured levels in parallel samples or job categories show however an often high variability that cannot be explained by sampling or assay errors. We therefore focused on characteristics of allergenic particles.
Airborne dust was collected in bakeries with a low-flow (2 L/min per filter) parallel sampling unit (PSU), and allergens of wheat and fungal a-amylase measured by EIA. Total numbers of wheat flour and amylase particles were estimated, as collected on the filters or inhaled during the work day.
High CV values for amylase could be explained by a high (>90%) allergen content of the enzyme particles, of which each (diameter 10-20 mm) would contain 0.8-8 ng of allergen, and 4-8-hr monitoring, even at ‘high’ amylase exposure, would lead to Poisson-distributed numbers of <5-10 amylase particles per sample. As a consequence, sensitizing time-weighted average levels of <1 ng/m3 correspond to inhalation of <1 inhaled amylase particle per day. In contrast, the estimated number of wheat flour particles in the same samples was >100,000/filter, with approximately 100 pg allergen per particle.
The quantum nature of allergen exposure should be taken into account in airborne measurements and exposure-sensitization analyses. Sensitization at average levels of <1 ng/m3 may be due to incidentally inhaled ‘peaks’ of <10-100 allergen particles, followed by days or even weeks without exposure. Calculations for allergenic particles from mites, pets and pollen suggest that similar conclusions apply to exposure and sensitization to many common and work-related allergens.
- AAAAI 2014 (70th)