table 2.
Breast cancer risk by exposure to benzene in a breast cancer case-control study
| Exposure metrics | Cases n= 2383 n (%) |
Controls n = 2502 n (%) |
ORa (95%CI) |
|---|---|---|---|
| Ever exposed to benzene | |||
| Never | 2268 (95.2) | 2382 (95.2) | |
| Ever | 115 (4.8) | 120 (4.8) | 1.00 (0.8–1.3) |
| Duration of exposure (in yrs)b | |||
| >0 – 5 | 42 (1.8) | 41 (1.6) | 1.07 (0.7–1.7) |
| >5 – 10 | 25 (1.0) | 19 (0.8) | 1.36 (0.7–2.5) |
| >10 | 48 (2.0) | 60 (2.4) | 0.82 (0.6–1.2) |
| p trend e | 0.691 | ||
| Crude average intensity (concentration in air) (mg/m3)b | |||
| >0 – <1 | 92 (3.9) | 99 (4.0) | 0.95 (0.7–1.3) |
| ≥1 | 23 (0.9) | 21 (0.8) | 1.21 (0.7–2.2) |
| p trend e | 0.849 | ||
| Intensity weighted by duration (mg/m3)b | |||
| >0 – l | 92 (3.9) | 99 (3.9) | 0.95 (0.7–1.3) |
| >1 | 23 (0.9) | 21 (0.9) | 1.21 (0.7–2.2) |
| p trend e | 0.849 | ||
| Crude average frequency (hrs/wk)b | |||
| >1 – ≤10 | 33 (1.4) | 28 (1.1) | 0.93 (0.5–1.6) |
| >10 – <20 | 48 (2.0) | 46 (1.8) | 1.10 (0.7–1.7) |
| ≥20 | 34 (1.4) | 46 (1.8) | 0.93 (0.6–1.5) |
| p trend e | 0.962 | ||
| Average frequency weighted by duration (hrs/wk)b | |||
| >1 – ≤10 | 34 (1.4) | 28 (1.1) | 0.96 (0.5–1.6) |
| >10 – <20 | 47 (2.0) | 46 (1.8) | 1.08 (0.7–1.6) |
| ≥20 | 34 (1.4) | 46 (1.8) | 0.93 (0.6–1.5) |
| p trend e | 0.940 | ||
| Average latency (yrs)b | |||
| 0 – 20 | 10 (0.4) | 12 (0.5) | 0.94 (0.4–2.2) |
| >20 | 105 (4.4) | 108 (4.3) | 1.00 (0.8–1.3) |
| p trend e | 0.991 | ||
| Cumulative exposure(hrs*mg*yrs/wk*m3)b,c | |||
| >0 – 33 | 58 (2.4) | 59 (2.4) | 1.00 (0.7–1.5) |
| >33 | 57 (2.4) | 61 (2.4) | 0.99 (0.7–1.4) |
| p trend e | 0.960 | ||
| Highest intensity*frequency(L*hrs/mo*wk)b,d | |||
| I level | 95 (4.0) | 102 (4.1) | 0.96 (0.7–1.3) |
| II level | 20 (0.8) | 18 (0.7) | 1.21 (0.6–2.3) |
| p trend e | 0.872 | ||
| Crude average probabilityb | |||
| ≥1 – <10% | 63 (2.6) | 54 (2.2) | 1.28 (0.9–1.9) |
| ≥10 – <50% | 36 (1.5) | 44 (1.8) | 0.73 (0.5–1.2) |
| ≥50 – <90% | 11 (0.5) | 17 (0.7) | 0.77 (0.4–1.7) |
| ≥90% | 5 (0.2) | 5 (0.2) | 1.20 (0.3–4.3) |
| p trend e | 0.565 | ||
| Average probability weighted by durationb | |||
| ≥1 – <10% | 63 (2.6) | 54 (2.2) | 1.28 (0.9–1.9) |
| ≥10– <50% | 37 (1.6) | 44 (1.8) | 0.76 (0.5–1.2) |
| ≥50 – <90% | 15 (0.5) | 17 (0.7) | 0.71 (0.3–1.6) |
| ≥90% | 5 (0.2) | 5 (0.2) | 1.20 (0.3–4.3) |
| p trend e | 0.542 |
a
Adjusted for age, study site, education, 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
b
Never exposed to benzene used as referent
c
Product of scores for intensity*frequency: level I=≤4, level II=>4
d
Cumulative exposure: product of frequency, intensity, and duration of exposure summed across all jobs. Cutpoint=median in exposed controls
e
p for trend in ever exposed to benzene