Table 5.
Case-control studies of formaldehyde exposure and nasopharyngeal cancer
| Authors (Years), Country | Characteristics of cases and controls | Exposure assessment | Exposure categories | OR (95% CI) |
|---|---|---|---|---|
| Marsh et al. (2007), USA [22] | 7 incidental cases who died from nasopharyngeal cancer during 1945–2003; case was matched on exact age race, sex, and year of birth (±2 years) to four controls from the members of the cohort. | Evaluation of formaldehyde exposure while accounting for potential confounding or effect modification by smoking or external (non-Wallingford) employment. | Silver smithing | |
| Never | 1.0 (Ref) | |||
| Ever | 14.41 (1.30–757.8) | |||
| p-trend | 0.024 | |||
| Silver smithing or other metal work | ||||
| Never | 1.0 (Ref) | |||
| Ever | 7.31 (1.08–82.1) | |||
| p-trend | 0.047 | |||
| Olsen et al. (1984), Denmark [32] | 754 cases from the Danish Cancer Registry including 266 nasopharyngeal cancers; controls were 2465 patients with cancers of the colon, rectum, prostate and breast; frequency matched by sex, age (± 5 years) and year of diagnosis (± 5 years) | Record linkage with pension fund with compulsory membership; job title from Central Pension Registry; exposure assessed blindly as certain, probable, unlikely, unknown | Men | 0.7(0.3–1.7) |
| Women | 2.6(0.3–21.9) | |||
| Vaughan et al. (1986), USA [33] | 285 incidental cases identified by the local Cancer Surveillance System, aged 20–74 years, including 27 cases of cancer of nasopharynx; controls were 552 identified by random-digit dialing | Job–exposure linkage system based on industry and occupation, resulting in four categories: high, medium, low and background | Low exposure | 1.2 (0.5–3.3) |
| Medium or High | 1.4 (0.4–4.7) | |||
| Exposure years | ||||
| 1–9 | 1.2 (0.5–3.1) | |||
| 10+ | 1.6 (0.4–5.8) | |||
| Exposure scores | ||||
| 5~ 19 | 0.9 (0.5–5.7) | |||
| 20+ | 2.1 (0.6–7.8) | |||
| Roush et al. (1987), USA [29] | 173 nasopharyngeal cancers registered at the Connecticut Tumor Registry; Controls were 605 men who died during the same period, selected by random sampling without matching or stratification | Job title, industry, specific employment, year of employment, obtained from death certificates and city directories to determine occupation at 1, 10, 20, 25, 30, 40 and 50 years prior to death | Probably exposed for most of working | 2.7 (1.1–6.6) |
| life | 1.2 (0.5–3.2) | |||
| + exposure > 20 years before death | 2.9 (1.1–7.6) | |||
| + exposure to high level for some years | 4.0 (1.3–12.3) | |||
| + exposure to high level > 20 years before death | ||||
| West et al. (1993), Philippines [30] | 104 incidental cases (76 men, 28 women) histologically confirmed; 104 hospital controls matched for sex, age and hospital ward type and 101 community controls matched for sex, age and neighborhood | Occupational history; occupation classified as likely or unlikely to involve exposure to formaldehyde; duration of exposure; 10-year lag period; years since first exposure; age at start of exposure | Exposure year | |
| < 15 years | 2.7 (1.1–6.6) | |||
| > 15 years | 1.2 (0.5–3.2) | |||
| < 15 years (10-year lag) | 2.9 (1.1–7.6) | |||
| > 15 years (10-year lag) | 4.0 (1.3–12.3) | |||
| Vaughan et al. (2000), USA [31] | 196 men and women from five cancer registries, aged 18–74 years controls were 244 population based selected by random digit dialing, and frequency matched by sex, cancer registry and age (5-year groups) | Structured telephone interviews; occupational exposures assessed by a job–exposure matrix | Duration (years) | |
| 1–5 | 0.9 (0.4–2.1) | |||
| 6–17 | 1.9 (0.9–4.4) | |||
| > 18 | 2.7 (1.2–6.0) | |||
| p-trend | 0.014 | |||
| Cumulative exposure (ppm-years) | ||||
| 0.05–0.4 | 0.9 (0.4–2.0) | |||
| 0.4–1.10 | 1.8 (0.8–4.1) | |||
| > 1.10 | 3.0 (1.3–6.6) | |||
| p-trend | 0.03 | |||
| Armstrong et al. (2000), Malaysia [34] | 282 histologically confirmed cases of nasopharyngeal carcinoma in Chinese men and women from four centers who had lived in the area for > 5 years;One Chinese control selected by multistage area sampling per case, matched by age and sex | Structured in-home interviews; Occupational exposures assessed by a job–exposure matrix |
Any (unadjusted) | 1.24 (0.67–2.32) |
| Any (adjusted) | 0.71 (0.34–1.41) | |||
| Hildesheim et al. (2001), Taipei [35] | 375 histologically confirmed hospital cases (31% women), aged < 75 years; 325 community controls, individually matched on sex, age (5 years) and district of residence | Structured in person interviews; occupational exposures assessed by an industrial hygienist | Ever exposed | 1.4 (0.93–2.2) |
| Duration | ||||
| 1–10 years | 1.3 (0.69–2.3) | |||
| > 10 years | 1.6 (0.91–2.9) | |||
| p-trend | 0.08 |
OR, Odds ratio