Duration and concentration of occupational exposure2-150 to formaldehyde relative to risk of nasopharyngeal cancer by histological type
| Exposure to formaldehyde | Controls (n=244) n | Cases | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| All epithelial | Undifferentiated and non-keratinising | Differentiated squamous cell | Epithelial | ||||||||||
| (n=196) n | OR2-151 (95% CI) | (n=54) n | OR2-151 (95% CI) | (n=118) n | OR2-151 (95% CI) | (n=24) n | OR2-151 (95% CI) | ||||||
| Unexposed | 165 | 117 | 1.0 (reference) | 36 | 1.0 (reference) | 69 | 1.0 (reference) | 12 | 1.0 (reference) | ||||
| Ever exposed | 79 | 79 | 1.3 (0.8 to 2.1) | 18 | 0.9 (0.4 to 2.0) | 49 | 1.5 (0.8 to 2.7) | 12 | 3.1 (1.0 to 9.6) | ||||
| Maximum exposure (ppm): | |||||||||||||
| <0.10 | 56 | 60 | 1.4 (0.8 to 2.4) | 14 | 1.0 (0.4 to 2.4) | 35 | 1.6 (0.8 to 3.0) | 11 | 4.0 (1.2 to 13.1) | ||||
| 0.10–0.50 | 19 | 14 | 0.9 (0.4 to 2.3) | 3 | 0.5 (0.1 to 3.1) | 10 | 1.2 (0.4 to 3.3) | 1 | 1.5 (0.2 to 13.9) | ||||
| >0.50 | 4 | 5 | 1.6 (0.3 to 7.1) | 1 | 1.5 (0.2 to 14.7) | 4 | 2.1 (0.4 to 12.3) | 0 | 0 | ||||
| Trend test | p=0.57 | p=0.72 | p=0.32 | p=0.46 | |||||||||
| Duration (y): | |||||||||||||
| 1–5 | 41 | 24 | 0.8 (0.4 to 1.6) | 8 | 0.7 (0.3 to 2.2) | 12 | 0.8 (0.3 to 2.0) | 4 | 2.0 (0.4 to 9.8) | ||||
| 6–17 | 19 | 26 | 1.6 (0.7 to 3.4) | 6 | 1.0 (0.2 to 3.9) | 17 | 1.8 (0.7 to 4.3) | 3 | 4.0 (0.9 to 18.6) | ||||
| ⩾18 | 19 | 29 | 2.1 (1.0 to 4.5) | 4 | 1.2 (0.3 to 4.8) | 20 | 2.5 (1.1 to 5.9) | 5 | 4.2 (0.8 to 21.5) | ||||
| Trend test | p=0.070 | p=0.82 | p=0.033 | p=0.036 | |||||||||