Background: Asthma attacks and mortality due to inhalation of soybean antigens in Barcelona, Spain have been well documented. A new control scheme was adopted in the city to avoid the emission and dispersion of soybean dust into the atmosphere during unloading. We studied soybean allergen emission during unloading and at 3 industrial sites and compared the results obtained.

Methods: Over a period of 31 months, 628 paired air samples from 3 plants (A, B, C) involved in soybean manipulation in Barcelona harbor were collected. Samples were analyzed by a radiometric competitive inhibition assay (RCIA) and the enzyme-linked immunosorbent assay (ELISA). A Bland-Altman plot was used to compare the soybean concentrations measured by each assay.

Results: The median values for the 628 samples were 5535 U/m3 (range, 370-18 416 751) for the RCIA and 9955 U/m3 (range, 400-22 349 059) for the ELISA. Plant A had the lowest emission levels and the lowest Spearman rank correlation coefficient (0.409). The
correlation coeffi cients were 0.747 and 0.794 for plants B and C. Soybean aeroallergen concentrations differed by plant. The highest variability in values was seen for plant A, which had the lowest allergen concentrations.

Conclusions: The competitive assays described are useful tools for the measurement of soybean allergen emission levels at industrial sites.
These methods may be used to monitor unloading and the impact of environmental interventions.

Key words: Competitive inhibition assay. Soybean. Aeroallergen. Asthma. Emission. Risk.