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

Table 3.

Associations between driving farm equipment and the overall lung cancer risk, by exposure to endotoxin-related activities, among farmers and female spouses of farmers, Agricultural Health Study.

Population/exposure Nonexposed to endotoxin-related activitiesa Exposed to endotoxin-related activitiesa p for interactiond
Casesb (n) RRc (95% CI) Casesb(n) RRc (95% CI)
Farmers
Diesel tractors
No/lowe 72 1.00 107 1.00 0.63
Intermediatef 10 0.99 (0.50, 1.93) 41 1.11 (0.77, 1.61)
Highg 6 1.83 (0.79, 4.25) 29 1.19 (0.78, 1.81)
Gasoline tractors
No/lowe 82 1.00 155 1.00 0.33
Intermediatef/highg 6 1.63 (0.71, 3.75) 19 0.99 (0.61, 1.60)
Combines or other types of crop harvesters
0 day 49 1.00 38 1.00 0.43
1–30 days 33 1.38 (0.88, 2.17) 113 0.94 (0.41, 2.18)
≥ 31 days 6 0.80 (0.34, 1.89) 24 0.72 (0.14, 3.76)
Trucks
No/lowe 64 1.00 129 1.00 0.50
Intermediatef 4 0.70 (0.25, 1.91) 11 1.38 (0.74, 2.56)
Highg 18 0.84 (0.49, 1.41) 34 0.88 (0.59, 1.30)
Spouses
Diesel tractors
No/< monthly 75 1.00 46 1.00 0.01
≥ Monthly 19 1.24 (0.75, 2.07) 15 0.41 (0.23, 0.73)
Gasoline tractors
No/< monthly 82 1.00 46 1.00 0.16
≥ Monthly 13 0.93 (0.52, 1.67) 14 0.51 (0.28, 0.93)
Combines or other types of crop harvesters
0 day 94 1.00 55 1.00 0.66
≥ 1 day 5 0.87 (0.35, 2.13) 7 0.66 (0.30, 1.45)
Trucks
No/< monthly 72 1.00 36 1.00 0.78
≥ Monthly 23 0.86 (0.53, 1.37) 24 0.77 (0.46, 1.30)
aEndotoxin-related activities were defined by current exposure to animals or stored grain in farmers and exposure to farm animals in the year before enrollment in spouses. bCase counts do not sum to total counts because of missing values for exposure variables. cFor farmers: rate ratios were adjusted for age, cigarette pack-years (non-smokers, < 20, 20–39, 40–59, ≥ 60, missing), state, race, and level of education; for spouses: rate ratios were adjusted for age, pack-years (non-smokers, < 20, 20–39, ≥ 40, missing), and level of education. dp for interaction was obtained from the likelihood ratio test by adding cross-product terms between each category of exposure and the variable reflecting potential exposure to endotoxins. eNo or low exposure was defined by driving < daily in one season. fIntermediate exposure: daily driving in one season. gHigh exposure: daily driving in both seasons.