. 2015 Sep 22;15:941. doi: 10.1186/s12889-015-2237-9

Table 2.

Odds ratio between lung cancer and ever having been employed in the construction industry, the reference unexposed category being either all workers outside the construction industry or all blue collar workers outside the construction industry, stratified by duration and sector of the industry, in the pooled set of two studies conducted in Montreal, Canada

	All workers			Blue collar workers^a
	Ca/Co^b (1,593/1,427)	OR^c	95 % CI^d	Ca/Co (1,313/1,081)	OR	95 % CI
Never in the construction industry	1179/1106	1.00	-	932/793	1.00	-
Ever in the construction industry	414/321	1.15	0.94–1.41	381/288	1.11	0.90–1.38
Sector of the construction industry
Building, industrial, heavy construction^e	249/195	1.26	0.98–1.62	227/170	1.23	0.94–1.61
Trades contracting^f	202/163	1.02	0.78–1.33	187/152	0.98	0.74–1.29
Duration in the construction industry
≥ 10 years	268/206	1.13	0.89–1.44	250/193	1.08	0.84–1.39
≥ 20 years	173/138	1.10	0.82–1.46	161/130	1.05	0.78–1.41
≥ 30 years	100/81	1.11	0.77–1.60	95/76	1.08	0.74–1.58

^aAt least 50 % of the entire working lifetime spent in blue collar occupations (as defined by Ahrens et al., 1998 [40])

^bNumber of cases/number of controls

^cOdds ratio adjusted for age, median family income for census tract, comprehensive smoking index, respondent status, education level and ethnicity and a binary indicator for studies

^d95 % confidence interval

^eBuilding, industrial, heavy construction: codes 40 (building, developing and general contracting industries), 41 (industrial and heavy construction industries from the Canadian Standard Industrial Classification of 1980 [34] and codes 404 (building construction), 406 (highway, bridge and street construction) and 409 (other constructions) from the Canadian Standard Industrial Classification of 1970 [33].

^fTrade contracting industries: codes 42 (trade contracting industries), 44 (service industries incidental to construction from the Canadian Standard Industrial Classification of 1980 [34] and code 421 (special trade contractors) from the Canadian Standard Industrial Classification of 1970 [33].