Table 2

Biological exposures and lung cancer risk

Exposure	Cumulative exposure	Cases	Controls	OR^* (95% CI)
Organic dust	Never	6487	8940	1.00 (reference)
	First quartile	1549	1770	1.05 (0.96 to 1.15)
	Second quartile	1875	1914	1.15 (1.06 to 1.25)
	Third quartile	1634	1804	1.12 (1.03 to 1.22)
	Fourth quartile	1755	1845	1.24 (1.14 to 1.35)
	Test for trend, p value^†			<0.001
Endotoxin	Never	8509	11 305	1.00 (reference)
	First quartile	1241	1276	1.08 (0.98 to 1.19)
	Second quartile	1113	1175	1.08 (0.98 to 1.20)
	Third quartile	1230	1268	1.12 (1.02 to 1.23)
	Fourth quartile	1207	1249	1.23 (1.12 to 1.36)
	Test for trend, p value^†			<0.001
Contact with animals	Never	11 158	14 001	1.00 (reference)
	First quartile	661	627	1.10 (0.97 to 1.26)
	Second quartile	463	512	1.05 (0.90 to 1.21)
	Third quartile	488	563	1.07 (0.93 to 1.24)
	Fourth quartile	530	570	1.15 (1.00 to 1.32)
	Test for trend, p value^†			0.081

↵* ORs are adjusted for age, sex, study, cigarette pack-years, time since quitting smoking, and ever employment in a ‘list A job’.
↵† p Values for trend result from a logistic regression model with exposure as a continuous variable.