Table 4 Individual and meta‐analysis results for Group I sub‐cohort studies of occupational TCE exposure and non‐Hodgkin's lymphoma by lowest and highest TCE exposure categories.

Reference and level of exposure	Type of risk estimate	Lowest exposure category		Highest exposure category
		Risk estimate	95% CI	Risk estimate	95% CI
Anttila et al, 199528
TCE exposed sub‐cohort
Low: <100 μmol/l uTCA
High: ⩾100 μmol/l uTCA	SIR	2.01	0.65 to 4.69	1.40	0.17 to 5.04
Axelson et al, 199427
TCE exposed sub‐cohort (⩾2 years of exposure and 10 years of latency)
Low: <50 mg/l mean uTCA
High: ⩾100 mg/l mean uTCA	SIR	1.64	0.20 to 5.92	8.33	0.22 to 46.43
Hansen et al, 200125
Low: individual mean exposure (<19 mg/m3)
High: individual mean exposure (⩾19 mg/m3)	SIR	3.90	1.10 to 10.0	3.2	1.10 to 10.0
Morgan et al, 199830*
TCE exposed sub–cohort
Low: approx <50 ppm
High: approx. ⩾50 ppm	SMR	1.79	0.22 to 6.46	0.50	0.01 to 2.79
Summary risk estimate: random effects model	SRRE	2.33	1.39 to 3.91	2.11	0.76 to 5.84
Test for heterogeneity	p value	0.63		0.109

*Results for lymphosarcoma, reticulosarcoma.