Differences between exposure groups were most pronounced for FEF25. Interestingly, all impedance parameters were significantly different between exposure groups. R8 and fo increased at higher exposure while X8 decreased with higher exposure (Table 3). Frequency dependence of oscillatory resistance became more negative with increasing exposure. Roughly, similar differences between exposure groups and lung function parameters were observed when workers were stratified into three groups with respect to endotoxin exposure. Difference in effects on lung function between present dust and endotoxin exposure was not observed, because few subjects changed between groups when classified to endotoxin exposure with group sizes equal to dust exposure (data not shown). No interaction was observed between exposure and smoking when including an interaction term. purchase antibiotics online
Lung function was clearly inversely related to cumulative exposure after adjustment for age, height, and smoking (Table 4). Among flow volume parameters, only the FEF25, however, reached statistical significance (p<0.05). On the other hand, all impedance parameters were significantly related to cumulative inspirable organic dust and endotoxin exposure. The estimated cumulative exposure to endotoxin appeared to be more strongly related to lung function decrements than cumulative dust levels. This is reflected in consistently higher regression coefficients, although statistical significance is higher only for frequency dependence (Table 4). No interaction was observed between exposure and smoking.
Most respiratory symptoms were related to age and smoking habits in a logistic regression analysis. Prevalence of chronic bronchitis and (ever) wheezing ranged from 7 percent in the control workers to 32 percent in the highest exposure group (>9 mg/m) (Fig 1). Smoking and age-adjusted odds ratios indicated significant differences in reported symptoms (chronic bronchitis, wheezing) between production and control workers. Moreover, a clear exposure-re-sponse relationship was present, since prevalence of respiratory symptoms increased with exposure. Endotoxin exposure revealed similar relationships (data not shown).
Table 4—Relation Between Cumulative Dust and Endotoxin Exposure and Spirometric/Impedance Values, After Adjustment for Age, Height, Weight, Pack-years, and Years A/ter Quitting Smoking (n=135)
|Lung Function Parameter||Estimated Cumulative Exposure|
|Dust,У * g/m||EndotoxinУ * g/m|
Figure 1. Prevalence of respiratory symptoms vs present exposure categories. Significance was tested by multiple linear regression (see Methods); asterisk indicates p<0.05; number sign, p<0.01.