This presentation summarizes our experience in three cross-sectional studies of respiratory health in cottonseed crushing mills. These studies were done in 1975, 1977, and 1978. Three milk were visited on all three occasions, another twice, and another once. In the course of these studies, health data were collected on a total of 444 subjects in the five mills.
In the United States, crushing mills receive cottonseed directly from the gins, with fibrous linters firmly adherent to each seed. This fibrous portion is contaminated with bracts, stems, dirt, and other contaminants similar to those of baled cotton fiber. The major steps in production include storage, removal from storage, cleaning with mechanical shakers, delinting with circular saws, hull removal with mechanical knives, cooking of meats, oil extraction by press or solvent extraction, and production of cake or meal from the meat residue. Linters, hulls, oil, cake, and meal are all of commercial value and are processed for storage and shipment.
The dryness of most of the products and the application of high velocity mechanical force at several steps in processing result in dustiness of the workplace. Table 1 summarizes some results of 486 air samples taken in the first study2 in 1975. Mean dust levels are presented for various areas (elutriated dust) and several jobs (total dust obtained by personal dust sampler) in four mills. Many of these values are clearly in excess of the 0.5 mg/m standard promulgated by the US Department of Labor for nontextile cotton dust exposures. Our initial attempt to quantify exposure was to characterize jobs as having high, intermediate, or low dust concentrations and to assign each worker to the appropriate category based on his job.
Survivor Population; Acute Bronchoconstrictor Effect
The 1975 study population of 172 participants was 99 percent men, with a mean age of 40.5 years and a mean length of employment in cottonseed mills of 12.0 years. The frequency distribution of years of employment, however, showed that 1/3 of the population had worked in these mills for two or fewer years. This finding is consistent with a relatively high worker turnover. The results of cross-sectional studies in such populations must be interpreted with caution, since the circumstances could permit the development of a “survivor population.” Such populations may consist primarily of persons self-selected for retention in the industry because of relative resistance to adverse health effects overcome with My Canadian Pharmacy Online’s remedies.
Our questionnaire responses defining byssinosis and chronic bronchitis were taken from the Medical Research Council (United Kingdom) questionnaire. Byssinosis was found in only four persons, three reporting the Monday symptom pattern currently, and one with chronic respiratory symptoms who recalled a characteristic Monday pattern in the past. This total of 4/172 is 2.3 percent. Chronic bronchitis was found in seven of 172, or 4.0 percent.
Baseline (preshift, Monday) lung function testing showed mean values for FVC and FEVX of greater than 100 percent predicted. The mean FEF 25-75% was approximately 90 percent of the predicted value. Forty-two percent of subjects had an observed FEF 25-75 less than 80 percent of the predicted value. The risk of having an observed FEF 25-75 less than 80 percent predicted, or an FEVi/FVC less than 0.75, was significantly related to both smoking and length of cottonseed mill employment.
Mean changes in ventilatory function tests over the Monday working shift are shown in Table 2, with negative numbers indicating declines in function. For all tests except the FEVj/FVC, the observed changes were significantly different from zero. Preshift and postshift spirometry was repeated on Friday of the same week: the mean Monday declines in FEVX, FEF 25-75, and FEF 25 were significantly larger than the mean declines in the same tests observed on Friday. We have taken this as evidence of an acute biologic effect of the dust, corresponding to the pattern observed in textile workers, despite the low prevalence of byssinosis in cottonseed crushing mills.
We were unable, however, to relate probability of larger declines in postshift ventilatory function to smoking, length of cottonseed mill employment, or level of dust exposure (as previously categorized).
Table 1—Mean Dust Levels, mg/m
|Mill A||Mill В||Mill С||MillD|
|Area (vertical elutriator)|
|Lint beating room||4.3|
|Job (total dust,|
Table 2—Mean Changes in Lung Function Over the Working Shift
|Test||Monday (n = 153)||Friday (n=*145)|