Lung Function Among Workers in the Soft Tissue Paper-Producing Industry: Results

In a third step, odds ratios and p values for the clinically relevant threshold FVC < 80% predicted were calculated for the different exposure subgroups in a logistic regression model incorporating factory, age, sex, body mass index, and smoking habits. All reported p values are two sided, those < 0.05 were considered as significant. The statistical analyses were performed using the SPSS version 10 (SPSS; Chicago, IL) and SAS version 8.1 (SAS Institute; Cary, NC). there
Ambient Monitoring
The results of the ambient monitoring of dust and fiber concentrations are presented in Table 2. The mean concentrations for inhalable dusts were 12.4 mg/m. Maximum concentrations found were 30 mg/m inhalable dust during the production process at the machines and 96 mg/m during cleaning the machines with pressured air. Measurements of the respirable dust fraction in five of nine companies yielded mean concentrations of 0.28 mg/m with a maximum of 1.78 mg/m. The mean ratio of respi-rable to inhalable fraction was 4.5%. The maximum of the fiber concentrations was 1.5 million fibers per cubic meter. Mean fiber concentrations were 420,000 fibers/per cubic meter (Table 2). The mean cumulative exposure index based on these ambient monitoring results and duration of exposure was 27.7 dust-years for workers with moderate exposure and 112.7 dust-years for workers from the production units. The corresponding results for fiber-years were 0.9 and 3.9, respectively.
Lung Function Analysis
With relation to cumulative dust exposure FEV1 decreased significantly in workers with > 25 dust-years from 107.3% (reference) to 101.0% predicted (Table 3). Corresponding results with FEV1 decrease of 5.2% were observed with relation to cumulative fiber exposure (Table 3). The parameter estimates show a dose-response relationship, which is pronounced between the categories < 25 dust-years and 25 to 100 dust-years (Table 4). Cumulative exposure to < 3 fiber-years already leads to a significant reduction of FEV1 (Table 4). Both evaluations showed a small increase of mean FEV1% predicted in the subgroup with the highest cumulative exposure (Table 3).
Table 2—Ambient Monitoring for Inhalable, Respirable, and Fiber Concentrations

Variables Inhalable

Dust,

mg/m

Respirable

Dust,

mg/m

Fibers/m
Measurements, No. 148 33 95
Mean ± SD 12.4 ± 18.8 0.28 ± 0.38 420,000 ± 392,000
Minimum 0.04 < DL < DL
Maximum 96.1 1.78 1,500,000
90% quantile 21.3 0.84 1,080,000

Table 3—FEV1, FVC, FEV1%F’VC, and No. and Percentage of Cases With FVC < 80% Predicted for Different Dust/Fiber-Exposure Categories and Smoking Status

Variables No. Exposure FEV1, Mean ± SD FVC, Mean ± SD FEV1% FVC, Mean ± SD FVC < 80%, No. (%)
Control subjects 189 0 107.3 ± 15.8 105.4 ± 13.2 82.7 ± 8.3 2 (1.0)
Dust-years, mg/m X years 230 < 25 103.5 ± 14.4 103.8 ± 15.1 81.5 ± 7.4 17 (7.4)
347 25-100 101.0 ± 18.1 99.0 ± 15.5 81.0 ± 9.3 36 (10.4)
281 > 100 103.0 ± 17.9 96.9 ± 18.3 83.4 ± 8.3 42 (15.3)
Fiber-years, fibers/cm X years 605 < 3 102.1 ± 16.5 100.7 ± 15.6 81.5 ± 8.4 58 (9.1)
253 >3 102.8 ± 18.5 97.1 ± 18.4 82.8 ± 8.7 37 (15.0)
Smoking habits 462 Never 105.9 ± 16.6 101.8 ± 16.0 82.7 ± 8.3 35 (7.6)
492 Smoker 100.0 ± 16.7 99.6 ± 16.7 81.5 ± 8.4 54(11.0)
93 Former 106.7 ± 17.5 106.7 ± 17.5 82.8 ± 8.7 8 (8.9)

Table 4 —Results of Different Multiple Regression Models: Changes in Function Adjusted for Factory, Body Mass Index, Age, Sex, and Smoking Habits

Variables FEV1 FVC FEV1%FVC FVC < 80%
Exposure I

Parameter

Estimate

I

p Value*

I

Parameter

Estimate

p Value* I

Parameter

Estimate

I

p Value*

Odds Ratio p Value t
Control subjects 0 0 Reference 0 Reference 0 Reference 1 Reference
Dust-years, mg/m X years < 25 – 0.991 0.5480 – 1.218 0.4335 0.965 0.4700 9.304 0.0043
25-100 – 5.231 0.0006 – 5.853 < 0.0001 1.061 0.3876 11.692 0.0011
> 100 – 6.618 < 0.0001 – 7.807 < 0.0001 2.278 0.0954 16.311 0.0002
Controls subjects 0 0 Reference 0 Reference 0 Reference 1 Reference
Fiber-years, fibers/cm X < 3 – 3.600 0.0100 – 4.045 0.0021 1.037 0.3567 11.449 0.0010
years > 3 – 6.813 0.0002 – 8.281 < 0.0001 2.603 0.0757 17.355 0.0002
Smoking habitsj Never 0 Reference 0 Reference 0 Reference 1 Reference
Smoker – 5.556 < 0.0001 – 1.957 0.0553 – 3.120 0.0003 1.363 0.2014
Former 0.104 0.9573 2.162 0.2405 – 2.357 0.1297 0.800 0.6082
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