Long-term exposure to organic dust is known to cause respiratory symptoms and airflow obstruction, mostly studied in grain workers and in cotton industry workers. In workers exposed to grain dust, significant dose-response relationships were reported by Huy et al for chronic phleghm production, breathlessness on exertion, FEVi, FVC, and total dust exposure in workers. Few studies in the animal feed industry have been reported. One study showed both acute, across-shift, and preshift effects of feed dusts on lung function and respiratory symptoms canadianhealthcaremallinc.com canadian health & care mall. Another recent cross-sectional study among 315 workers in the Dutch animal feed industry confirmed the long-term effects on lung function, but failed to show a relation between the level of exposure and symptom prevalence. Similar to other studies on organic dusts, endotoxin was suggested to be an important factor in both acute and chronic respiratory impairment.
In this article, results will be presented from a cross-sectional study among 194 workers involved in animal feed processing, with emphasis on respiratory symptoms and lung function measured by flow-volume curves and input impedance testing. Recent investigations showed that impedance measurement by the forced oscillation technique is able to measure the distribution and magnitude of airway resistance along the respiratory system. Moreover the technique was shown to be suitable in early diagnosis of airflow obstruction to irritants in an occupational setting and of airflow obstruction due to inorganic dust. In this study, impedance measurements were applied along with flow volume curves to (1) detect and localize airflow obstruction caused by animal feed dust/endotoxin, and (2) to relate respiratory symptoms to the outcome of both types of lung function measurements.
In a cross-sectional study, male white workers (n=205) from five grain elevators of the same agricultural cooperation in the Netherlands were studied. Characteristics of the study population are summarized in Table 1. Written informed consent was obtained from each worker (participation rate, 88 percent). Subjects were asked to complete the British Medical Research Council questionnaire on respiratory complaints at home before lung function measurements. Additional questions were asked concerning job history and exposure. Exposure to organic dust and endotoxin was measured to estimate present and historic cumulative exposure.
Table 1—Characteristics of Animal Feed Workers and Controls (Mean ± SEM)
|Age, yr||38.9 (1.5)||42.3 (0.8)|
|Length, cm||178.2 (0.9)||176.4 (0.6)|
|Weight, kg||78.2 (2.2)||78.1 (1.9)|
|Years in industry||14.1 (1.4)||16.3 (0.7)|
|Years exposed||0.9 (0.4)||16.3 (0.7)|
|Years smoked||9.8 (1.0)||12.2 (0.6)|
|Pack-years||6.5 (1.3)||9.5 (0.7)|
|Current||16 (26%)||53 (40%)|
|Past||18 (30%)||58 (44%)|
|Never||27 (44%)||22 (17%)|
|FVC, L||5.63 (0.12)||5.37 (0.11)|
|FEVb L||4.51 (0.11)||4.16 (0.11)|
|FEVi/FVC, %||80.6 (1.00)||77.3 (0.70)|
|PEF, L/s||12.34 (0.25)||11.14 (0.25)|
|MMEF, L/s||4.45 (0.18)||3.67 (0.12)|
|MMEF75, L/s||9.54 (0.34)||8.41 (0.26)|
|R8, hPa.s/L||2.23 (0.08)||2.73 (0.10)|
|FD, hPa.s/L||0.29 (0.05)||0.03 (0.06)|
|X8, hPa.s/L||-0.03 (0.03)||-0.19 (0.05)
|f0, Hz||8.46 (0.18)||10.41 (0.42)|