Association between soybean dust exposure, allergic sensitization and respiratory symptoms

The purpose of this study was to correlate soybean dust (SD) exposure, skin reactivity to soybean hull (SH) allergens, and symptoms of asthma and/or a llergic rhinitis. A group of 365 subjects with asthma and/or allergic rhini tis and a control group of 50 individuals without respiratory symptoms were studied. The level of exposure to SD is defined as follows: 1) direct (DE) ; 2) indirect (ID), and 3) urban (UE). All subjects completed standard ques tionnaires. Skin tests with a SH extract and with common allergens were per formed by the prick technique (SPT). Fifty-six (15.3%) patients and no subj ects from control group had positive SPT (histamine index greater than or e qual to 0.5) with a SH allergen extract. The percentages of positive SPT to SH extract were 38.7%, 20.3% and 8.4% in subjects with DE, IE and UE, resp ectively (p<0.001). Monosensitization to SH was absent in all subjects. The percent of subjects with positive SPTs to mites (p<0.01), pollen (p<0.01) and molds (p<0.05) were higher in subjects with a positive SPT to SH versus those with a negative SPT to SH. Sixty-six percent of subjects with DE and 13.6% of subjects with IE or UE reported respiratory symptoms after SD inh alation (Odds Ratio: 12.67 [2.4 - 74.9], p<0.001). Compared to subjects exc lusively sensitized to mites, patients sensitized to SH presented significa ntly different clinical characteristics. Soybean production has been increa sing in Argentina during the last 20 years, determining an increase in the population exposed to chronic SD inhalation. This fact determines a high ri sk of sensitization and triggering of respiratory symptoms in atopic subjec ts. This study demonstrates that there is: 1) a high prevalence of skin rea ctivity to SH in subjects with asthma and/or allergic rhinitis from Argenti na and that this prevalence is associated with the level of exposure to SD, and 2) an association between sensitivity to SH and severity of asthma. Me asures to avoid release and inhalation of SD in rural areas from Argentina are needed.