Table 4.

Standardized incidence ratios (SIR) and rate ratio (RR) trends for lung cancer among cotton textile production unit workers by dust exposure category.

Exposure category	Obs	SIR	95% CI	RR	95% CI	χ2 test for trend
Male
None* (N = 2511)	42	1.01	0.73–1.36	1 (reference)		χ2 = 9.68;p = 0.02
Low (N = 656)	10	1.91	0.92–3.51	1.89	0.85–3.85
Medium (N = 481)	7	1.30	0.52–2.69	1.29	0.49–2.91
High (N = 529)	4	0.77	0.21–1.96	0.76	0.20–2.10
Very high (N = 574)	2	0.24	0.03–0.86	0.24	0.03–0.91
Female
None (N = 2140)	2	0.92	0.11–3.30	1 (reference)		χ2 = 4.68;p = 0.20
Low (N = 1350)	3	2.38	0.49–6.91	2.58	0.30–30.9
Medium (N = 1410)	3	2.17	0.45–6.35	2.36	0.27–28.2
High (N = 1371)	2	1.28	0.16–4.63	1.39	0.10–19.2
Very high (N = 1910)	1	0.55	0.01–3.08	0.60	0.01–11.5

None * – using the maintenance employment group as the reference category.