. 2015 Oct 9;124(5):611–618. doi: 10.1289/ehp.1409238

Table 2.

Associations between driving farm equipment and the overall lung cancer risk among farmers and female spouses of farmers, Agricultural Health Study.

Exposure	Farmers		Spouses of farmers
Exposure	Cases^a (n = 281) (n)	RR^b (95% CI)	Cases^a (n = 165) (n)	RR^b (95% CI)
Diesel tractors^c
No/< monthly	32	1.00	121	1.00
≥ Monthly ≥ 1 season	26	1.19 (0.71, 2.01)	34	0.71 (0.48, 1.06)
Weekly ≥ 1 season	121	1.11 (0.74, 1.68)
Daily in one season	51	1.21 (0.75, 1.95)
Daily in both seasons	35	1.48 (0.87, 2.50)
p for trend^d		0.18
Gasoline tractors^c
No/< monthly	91	1.00	128	1.00
≥ Monthly ≥ 1 season	56	0.87 (0.62, 1.22)	27	0.67 (0.44, 1.04)
≥ Weekly ≥ 1 season	90	1.07 (0.79, 1.44)
Daily in one season	12	1.03 (0.56, 1.89)
Daily in both seasons	13	1.20 (0.66, 2.19)
p for trend^d		0.49
Combines or other types of crop harvesters^c
No/< monthly	87	1.00	149	1.00
1–10 days	57	1.11 (0.78,1.58)	12	0.74 (0.41, 1.34)
11–30 days	89	1.11 (0.78,1.57)
≥ 31 days	30	0.80 (0.51,1.26)
p for trend^d		0.57
Trucks^c
No or < monthly	83	1.00	108	1.00
≥ Monthly ≥ 1 season	41	0.85 (0.58, 1.23)	47	0.82 (0.57, 1.16)
≥ Weekly ≥ 1 season	69	0.89 (0.65, 1.24)
Daily in one season	15	1.01 (0.58, 1.76)
Daily in both seasons	52	0.80 (0.55, 1.15)
p for trend^d		0.31
^aCase counts do not sum to total counts because of missing values for exposure variables. ^bFor farmers, rate ratios were adjusted for age, pack-years (nonsmokers, < 20, 20–39, 40–59, ≥ 60, missing), state, race, level of education, and current exposure to animals and stored grain (no, one exposure, both exposures); for spouses: rate ratios were adjusted for age, pack-years (nonsmokers, < 20, 20–39, ≥ 40, missing), level of education, and exposure to farm animals in the year before enrollment. ^cThe frequency of use of farm equipment in the year was not collected by the spouses’ questionnaire. ^dTest for trend, p-value obtained by treating the categorical variable as ordinal.