The overall goal of this project is to further understand the determinants and extent of respiratory disease among workers exposed to mixed grain, corn, and soybean dust. This study is designed to assess the relative contribution of specific exposures (concentration of total and respirable particulate dust, type of vegetable dust-mixed grain vs. corn vs. soybean, and level of airborne endotoxin) and their interaction with other known risk factors on the development of respiratory symptoms and airflow obstruction. This study will allow us to evaluate the safety of the threshold limit value that is currently recommended for cereal (wheat, rye, barley, and oats) grain handlers and determine whether these same threshold limit values should be recommended for noncereal grain and vegetable (corn and soybean) handlers. We will determine if respirable levels of endotoxin are more clearly related to the development of airflow obstruction than are gravimetric measures of total and respirable dust and also whether workers exposed to corn and soybean dust have a higher prevalence of chronic respiratory disorders. We will accomplish this by conducting a population-based, cross-sectional study among workers in livestock feed grain elevators, corn, mills, and soybean processing plants in Iowa. We will perform environmental measures of particulate exposures at the work site, obtain a medical and occupational history, and access spirometric function (baseline and after four hours of work). Similar measures of respiratory risks, symptoms, and function will be made on an appropriate community-based, unexposed working population. In addition to accomplishing the specific aims of this proposal, this population-based, cross-sectional study will allow us to establish a representative cohort of exposed workers for future investigations.
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