Breast cancer risk by exposure to benzene in a breast cancer case-control study
| Exposure metrics | Cases n=2383 | Controls n=2502 | OR* (95% CI) |
| n (%) | n (%) | ||
| Ever exposed to benzene | |||
| Never | 2268 (95.2) | 2382 (95.2) | |
| Ever | 115 (4.8) | 120 (4.8) | 1.00 (0.8 to 1.3) |
| Duration of exposure (in years)† | |||
| >0–5 | 42 (1.8) | 41 (1.6) | 1.07 (0.7 to 1.7) |
| >5–10 | 25 (1.0) | 19 (0.8) | 1.36 (0.7 to 2.5) |
| >10 | 48 (2.0) | 60 (2.4) | 0.82 (0.6 to 1.2) |
| p Trend¶ | 0.691 | ||
| Crude average intensity (concentration in air) (mg/m3)† | |||
| >0–<1 | 92 (3.9) | 99 (4.0) | 0.95 (0.7 to 1.3) |
| ≥1 | 23 (0.9) | 21 (0.8) | 1.21 (0.7 to 2.2) |
| p Trend¶ | 0.849 | ||
| Intensity weighted by duration (mg/m3)† | |||
| >0–1 | 92 (3.9) | 99 (3.9) | 0.95 (0.7 to 1.3) |
| >1 | 23 (0.9) | 21 (0.9) | 1.21 (0.7 to 2.2) |
| p Trend¶ | 0.849 | ||
| Crude average frequency (h/wk)† | |||
| >1–≤10 | 33 (1.4) | 28 (1.1) | 0.93 (0.5 to 1.6) |
| >10–<20 | 48 (2.0) | 46 (1.8) | 1.10 (0.7 to 1.7) |
| ≥20 | 34 (1.4) | 46 (1.8) | 0.93 (0.6 to 1.5) |
| p Trend¶ | 0.962 | ||
| Average frequency weighted by duration (h/wk)† | |||
| >1–≤10 | 34 (1.4) | 28 (1.1) | 0.96 (0.5 to 1.6) |
| >10–<20 | 47 (2.0) | 46 (1.8) | 1.08 (0.7 to 1.6) |
| ≥20 | 34 (1.4) | 46 (1.8) | 0.93 (0.6 to 1.5) |
| p Trend¶ | 0.940 | ||
| Average latency (years)† | |||
| 0–20 | 10 (0.4) | 12 (0.5) | 0.94 (0.4 to 2.2) |
| >20 | 105 (4.4) | 108 (4.3) | 1.00 (0.8 to 1.3) |
| p Trend¶ | 0.991 | ||
| Cumulative exposure (h*mg*years/wk*m3)†,‡ | |||
| >0–33 | 58 (2.4) | 59 (2.4) | 1.00 (0.7 to 1.5) |
| >33 | 57 (2.4) | 61 (2.4) | 0.99 (0.7 to 1.4) |
| p Trend¶ | 0.960 | ||
| Highest intensity*frequency (mg*h/m3*wk)†,§ | |||
| I level | 95 (4.0) | 102 (4.1) | 0.96 (0.7 to 1.3) |
| II level | 20 (0.8) | 18 (0.7) | 1.21 (0.6 to 2.3) |
| p Trend¶ | 0.872 | ||
| Crude average probability† | |||
| ≥1–<10% | 63 (2.6) | 54 (2.2) | 1.28 (0.9 to 1.9) |
| ≥10–<50% | 36 (1.5) | 44 (1.8) | 0.73 (0.5 to 1.2) |
| ≥50–<90% | 11 (0.5) | 17 (0.7) | 0.77 (0.4 to 1.7) |
| ≥90% | 5 (0.2) | 5 (0.2) | 1.20 (0.3 to 4.3) |
| p Trend¶ | 0.565 | ||
| Average probability weighted by duration† | |||
| ≥1–<10% | 63 (2.6) | 54 (2.2) | 1.28 (0.9 to 1.9) |
| ≥10–<50% | 37 (1.6) | 44 (1.8) | 0.76 (0.5 to 1.2) |
| ≥50–<90% | 10 (0.5) | 17 (0.7) | 0.71 (0.3 to 1.6) |
| ≥90% | 5 (0.2) | 5 (0.2) | 1.20 (0.3 to 4.3) |
| p Trend¶ | 0.542 | ||
↵* Adjusted for age, study site, education, body mass index (BMI), age at menarche, menopausal status, age at menopause (in postmenopausal women), number of full-term births, age at first full-term birth, breastfeeding, family history of breast cancer and previous screening mammography.
↵† Never exposed to benzene used as referent.
↵‡ Cumulative exposure: product of frequency, intensity, and duration of exposure summed across all jobs. Cutpoint=median in exposed controls: I level=≤4, II level=>4.
↵§ Product of scores for intensity*frequency: I level=≤4, II level=>4.
↵¶ p For trend in ever exposed to benzene.