Occupational exposure to wood dust and formaldehyde and risk of nasal, nasopharyngeal, and lung cancer among Finnish men

Our plain-English summary of Occupational exposure to wood dust and formaldehyde and risk of nasal, nasopharyngeal, and lung cancer among Finnish men, by S.S. Siew, T. Kauppinen, P. Kyyrönen, et al (Cancer Management and Research, 2012).

The study

• Authors: S.S. Siew, T. Kauppinen, P. Kyyrönen, P. Heikkilä, E. Pukkala
• Journal: Cancer Management and Research
• Published: 2012;4:223-32
• Cited by: 43 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Controversy exists over whether or not occupational inhalation exposure to wood dust and/or formaldehyde increases risk for respiratory cancers. The objective of this study was to examine the risk of nasal, nasopharyngeal, and lung cancer in relation to occupational exposure to wood dust and formaldehyde among Finnish men. The cohort of all Finnish men born between the years 1906 and 1945 and in employment during 1970 was followed up through the Finnish Cancer Registry for cases of cancers of the nose (n = 292), nasopharynx (n = 149), and lung (n = 30,137) during the period 1971-1995. The subjects' occupations, as recorded in the population census in 1970, were converted to estimates of exposure to wood dust, formaldehyde, asbestos, and silica dust through the Finnish job-exposure matrix. Cumulative exposure (CE) was calculated based on the prevalence, average level, and estimated duration of exposure. The relative risk (RR) estimates for the CE categories of wood dust and formaldehyde were defined by Poisson regression, with adjustments made for smoking, socioeconomic status, and exposure to asbestos and/or silica dust. Men exposed to wood dust had a significant excess risk of nasal cancer overall (RR, 1.59; 95% confidence interval [CI], 1.06-2.38), and specifically nasal squamous cell carcinoma (RR, 1.98; 95% CI, 1.19-3.31). Workers exposed to formaldehyde had an RR of 1.18 (95% CI, 1.12-1.25) for lung cancer. There was no indication that CE to wood dust or formaldehyde would increase the risk of nasopharyngeal cancer. Occupational exposure to wood dust appeared to increase the risk of nasal cancer but not of nasopharyngeal or lung cancer. The slight excess risk of lung cancer observed for exposure to formaldehyde may be the result of residual confounding from smoking. In summary, this study provides further evidence that exposure to wood dust in a variety of occupations may increase the risk of nasal cancer.

In plain English

This study asked whether workplace exposure to wood dust and formaldehyde was linked to cancers of the nose, the nasopharynx (the upper throat behind the nose) and the lung. Asbestos was not the focus. It was one of the exposures the lung cancer analysis adjusted for. The authors followed about 1.2 million Finnish men born between 1906 and 1945 who were working at the 1970 census, using the national cancer registry for 1971 to 1995. Exposures were estimated from each man's 1970 job using a national job-exposure matrix, not measured person by person. Men exposed to wood dust had a higher risk of nasal cancer (relative risk 1.59; 95% confidence interval 1.06 to 2.38) and of nasal squamous cell carcinoma (1.98; 1.19 to 3.31). No excess nasopharyngeal cancer was seen with either exposure. Formaldehyde exposure was associated with a slightly raised lung cancer risk (1.18; 1.12 to 1.25). In the lung cancer model, the highest asbestos category had a relative risk of 1.29 (1.19 to 1.38). The authors concluded that wood dust appears to raise nasal cancer risk but not nasopharyngeal or lung cancer risk. They called the formaldehyde results inconclusive.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Registry-based cohort study of a national census population, with exposures assigned by a job-exposure matrix and analysed by standardized incidence ratios and Poisson regression
• Who was studied: All 1.2 million economically active Finnish men born between 1906 and 1945 who took part in the 31 December 1970 population census, followed for cancer from 1971 to 1995. There were 292 nasal, 149 nasopharyngeal and 30,137 lung cancer cases. Cancer patients with no census record (676 cases) were excluded.
• Exposure: Occupational inhalation exposure to wood dust (mg/m3-years) and formaldehyde (ppm-years), estimated from each man's 1970 census occupation using the Finnish job-exposure matrix (FINJEM). Exposure was assumed to run from age 20 to 65 in the same job, with a 20-year latency. Asbestos (fibers/cm3-years) and silica dust were included as co-exposures in the lung cancer models, and smoking was adjusted for using occupation-level smoking prevalence.
• Main results:
  • Men exposed to wood dust had a significantly elevated relative risk of nasal cancer of 1.59 (95% CI 1.06–2.38), and the risk did not vary by cumulative exposure level.
  • Men exposed to wood dust had a relative risk of nasal squamous cell carcinoma of 1.98 (95% CI 1.19–3.31).
  • Of 22 nasal adenocarcinoma cases, three were exposed to wood dust.
  • No excess of nasopharyngeal cancer was seen among workers exposed to wood dust or to formaldehyde.
  • No increased lung cancer risk was found with wood dust exposure. In Table 3 the relative risk for any wood dust exposure was 0.93 (95% CI 0.87–0.98).
  • Workers with any cumulative exposure to formaldehyde had a slightly elevated lung cancer relative risk of 1.18 (95% CI 1.12–1.25). In the stratified analysis, the excess was absent in the higher cumulative exposure group (1.0 ppm-years or more).
  • In the lung cancer model, the highest asbestos exposure category (2 fibers/cm3-years or more) had a relative risk of 1.29 (95% CI 1.19–1.38), and the highest silica dust category had 1.39 (95% CI 1.16–1.65).
  • Among the 32 occupations with wood dust or formaldehyde exposure, construction carpenters were the only occupation with a significantly increased standardized incidence ratio for lung cancer: 1.19 (95% CI 1.14–1.25). No occupation had a significantly elevated ratio for nasal or nasopharyngeal cancer.
• The authors' conclusion: The authors concluded that occupational exposure to wood dust appears to raise the risk of nasal cancer but not of nasopharyngeal or lung cancer. They called the formaldehyde results inconclusive and said the modest lung cancer association with formaldehyde may result from residual confounding by smoking or other occupational exposures.
• Limitations the authors state:
  • The occupation-level smoking data (1978–1991) were to some extent too recent for cancers diagnosed between 1971 and 1995.
  • Because the study used aggregate rather than individual data, residual confounding may influence the relative risk estimates.
  • Specific wood types were not distinguished, so the nasal squamous cell carcinoma finding could be partly due to chance.
  • Mixed exposure to more than one species of wood was very common, which complicates exposure assessment.
  • Nasopharyngeal cancer was rare and formaldehyde exposure in Finland fairly low, which could make an excess risk harder to detect.

Topics

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Lung Cancer, Cancer Registry, Cumulative Exposure, Relative Risk, confidence interval, Squamous Cell Carcinoma, Confounding.

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