Epidemic soybean asthma and public health: new control systems and initial evaluation in Barcelona, 1996-98

To evaluate the new measures adopted to control the risks from soybean unloading operations in the Port of Barcelona, after an episode of epidemic asthma in June 1996.

After an initial cautionary suspension of all soybean unloading operations, they were subsequently resumed under restrictive criteria for time, flux, simultaneity, and meteorological conditions. Emission filtration systems based on either micro pore size filters or polytetrafluoroethylene membranes on tetratex filters showed promising results.

Allergen emission underwent a very important decrease to levels 95% to 98% lower. Emissions from the two plants with unloading operations are in the same order of magnitude as the processing plant that does not unload soybean. Allergen concentration levels presented fluctuations initially, but the new filters decreased mean values; despite increased unloading, allergen levels did not increase-mean allergen levels on unloading days (67 U/m(3)) and on days without unloading operations (63 U/m(3)) are similar. A panel of patients detected a cluster of increased symptoms during unloading operations on a day with suboptimal meteorological conditions and comparatively low allergen levels (225-415 U/m(3)). Since the June 1996 episode, no further asthma outbreak has been detected.

The evaluation shows the effectiveness of the new filters in the control of soybean dust emission. With a systematic control programme, industrial soybean operations may function near urban centres without public health risks. These data may be useful in the development of future standards for allergenic agents.