In conclusion, based on the 15-yr follow-up study, accelerated chronic loss of pulmonary function in relation to airborne endotoxin exposure was observed. The chronic functional
losses were significantly associated with across-shift drops of FEV1 and byssinosis or chest tightness at work. Although reporting symptoms apparently varied from time to time, the
consistency of respiratory symptoms may provide important information regarding permanent obstructive impairments in cotton workers. Further study is required to identify the factors
that determine the consistent presence of cotton dustrelated syndromes.