The common denominator for respiratory disorders among agricultural workers was exposure to organic dust which was recognized to be a complex mixture of vegetable particles and fragments, microorganisms and their products, insects and insect fragments, feed additives including fish meal and antibiotics, and avian and rodent proteins. While the vegetable dust itself was by far the most important exposure, individual circumstances of growing, storage and subsequent use of the product from which the organic dust arose, influenced specific exposures. In certain situations, like animal confinement housing, irritant gases including ammonia and hydrogen sulfide co-existed with an organic dust to further vary respiratory exposure.