Pulmonary effects of intermittent, seasonal exposure to high concentrations of cotton dust

Table 1 Demographic characteristics, smoking habits, and exposure levels of the studied subjects

Variables	Exposed workers	Unexposed subjects
	(n = 51)	(n = 51)
Age (yr)1	40.7 ± 11.54	40.2 ± 12.1
Height (cm)1	169 ± 4.84	170.3 ± 4.8
Weight (kg)1	70.1 ± 9.74	73.5 ± 12.1
Duration of exposure or employment (yr)1	10.7 ± 7.84	9.5 ± 5.2
Marital status2
Single	5 (10%)4	9 (18%)
Married	46 (90%)4	42 (82%)
Smoking2
Yes	31 (61%)4	28 (55%)
No	20 (39%)4	23 (45%)
Light3	21 (41%)4	19 (37%)
Heavy	10 (20%)4	9 (18%)
Cotton exposure (mg/m3)
Ginning section	35.2 ± 11.6	NA
Fed section	14.9 ± 6.2	NA
Seed separator area	18.5 ± 10.1	NA
Outdoor	6.8 ± 4.2	NA

¹Independent sample T test;

²χ² or Fisher’s exact test;

³Light: < 5 cigarettes per day, heavy: ≥ 5 cigarettes per day;

⁴No significant differences exist between the exposed and unexposed subjects (P > 0.05). NA: Not available.

Table 2 Frequency (%) of respiratory symptoms in the exposed and unexposed subjects¹n (%)

Symptoms	Exposed	Unexposed
	(n = 51)	(n = 51)
Cough	19 (37)b	2 (4%)
Phlegm	19 (37)b	4 (8%)
Productive cough	4 (8)	0
Wheezing during a cold	21 (41)b	5 (10%)
Wheezing apart from colds	14 (27)b	3 (6%)
Wheezing accompanied by Shortness of breath	7 (14)d	0
Shortness of breath	8 (16)d	1 (2%)
Byssinosis grade 1/2	9 (17.6)b	0
Byssinosis grade I	3 (6)	0
Byssinosis grade II	2 (4)	0

¹χ² or Fisher’s exact test;

^bP < 0.001;

^dP < 0.01.

Table 3 Changes in pulmonary function test parameters of the exposed and unexposed subjects

Parameters	Exposed workers (n = 51)					Referent group
	Preshift1	Postshift1	End of season2	End of shift end of workweek3	After 48 h of exposure free period4	(n=51)
VC	78.9 ± 16.3b	76.6 ± 17d	73.2 ± 16.6f	78.8 ± 16.3h	76.1 ± 16.3	85.5 ± 13.5
FVC	84.8 ± 12.6b	85.2 ± 12.9	86.2 ± 16.5	85.5 ± 12.8	84.8 ± 12.6	81 ± 4.4
FEV1	79.7 ± 13.7b	78.3 ± 12.4d	74.6 ± 13.1f	76.7 ± 11.7h	79.1 ± 13.7	90.1 ± 10.5
FEV1/FVC	94.1 ± 14.5b	89.3 ± 20.2	89.3 ± 20.2	90.6 ± 12h	94.1 ± 14.5	107.6 ± 14.5

¹At the beginning of work season (prior to and end of first shift of workweek);

²At end of the work season;

³At end of shift at end of workweek;

⁴48 h after exposure ceased;

^bP < 0.05 vs the referent group;

^dP < 0.05 vs preshift;

^fP < 0.05 vs preshift;

^hP < 0.05 vs after 48 h of exposure free period. VC: Vital capacity; FVC: Forced vital capacity; FEV: Forced expiratory volume.

Table 4 Association between exposure to cotton dust and duration of exposure with changes in the pulmonary function test parameters¹ (n = 51)

Period of time	Parameters	Independent variable	Adjusted R2	β
At the beginning of work season	VCb	Duration of exposure	0.23	-0.5
	FVCb		0.4	-0.65
	FEV1b		0.21	-0.48
	FEV1/FVCd		0.16	0.42
During the work shift	FVCa	Duration of exposure	0.06	-0.28
During the work shift	FEV1d	Dust concentration	0.14	0.4
During the work season	VCd	Dust concentration	0.1	0.4
	FVCd		0.1	0.32
	FEV1a		0.06	0.28

¹Multiple linear regression analysis;

^bP < 0.001;

^dP < 0.01;

^aP < 0.05. VC: Vital capacity; FVC: Forced vital capacity; FEV: Forced expiratory volume.

Table 5 Comparison of the subjects with normal spirogram, possibly restrictive, obstructive or mixed pattern for both groups¹

Period of time		Spirogram pattern n (%)
		Normal	Restrictive	Obstructive	Mixed
Before exposure, at the start of the work season	Exposed	40 (87.4)	6 (11.8)	5 (9.8)	0
	Unexposed	45 (88.2)	4 (7.8)	2 (3.9)	0
After exposure, at the start of the work season	Exposed	39 (76.5)	4 (7.8)	8 (15.7)	0
	Unexposed	45 (88.2)	4 (7.8)	2 (3.9)	0
At the end of the work season2	Exposed	27 (53)	6 (11.8)	18 (35.3)	0
	Unexposed	45 (88.2)	4 (7.8)	2 (3.9)	0

¹χ² or Fisher’s exact test; ²significant difference exists between the exposed and unexposed groups (P < 0.001).