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Filtration technology arrests asthma allergen

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Measures to abolish the threat of asthma to public health from soybean dust have been so successful that they could underpin future control standards for allergens, according to an evaluation in Barcelona. Success was achieved by combining knowledge and skills across a wide range of sectors and agencies.

The initial alert was an asthma epidemic in June 1996 traced to dust from ships unloading soybeans in the port, near the city. A significant benefit was introducing dry filtration technology in late 1997 to reduce emissions. This took the form of micropore size filter sleeves or special filters in series with PTFE membrane filter cartridges to replace standard filter sleeves in the unloading process. Once new operating licences were granted, in June 1998, the relatively crude control of emissions by limiting unloading brought in in June 1996 was lifted, and the pilot phase ran until December 1998.

Four indicators were used to evaluate effectiveness. Soybean dust emissions, available from 1997, dropped 96–98% between summers 1998 and 1999. Airborne dust load measured at one site in the port fell drastically (mean (median) 1089 (731) RAST U/m3 in June 1996 v 59 (35) U/m3 June-December 1998)). No asthma epidemics were recorded in four city hospitals, and sentinel surveillance from the end of 1997 with a panel of high risk asthma sufferers uncovered just one cluster of symptoms, coinciding with unloading in adverse weather.

Similar problems with soybean dust have emerged elsewhere, including outside Spain, but no legislation has been developed to control the public health risk. That may change.