Substance Profiles Report on Carcinogens, Eleventh Edition

Wood dust is known to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in humans. An association between wood dust exposure and cancer of the nasal cavity has been observed in many case reports, cohort studies, and case-control studies that specifically addressed nasal cancer. Strong and consistent associations with cancer of the nasal cavities and paranasal sinuses were observed both in studies of people whose occupations are associated with wood dust exposure and in studies that directly estimated wood dust exposure. Risks were highest for adenocarcinoma, particularly among European populations. Studies of U.S. populations showed similar significant positive associations. A pooled analysis of 12 case-control studies showed that the estimated relative risk of adenocarcinoma was very high (45.5) among men with the greatest exposure and that the risk increased with duration of exposure (Demers et al. 1995). The association between wood dust exposure and elevated nasal cancer risk in a large number of independent studies and with many different occupations in many countries strongly supports the conclusion that the increased risk is caused by wood dust rather than by simultaneous exposure(s) to other substances, such as formaldehyde or wood preservatives. Other types of nasal cancer (squamous-cell carcinoma of the nasal cavity) and cancer at other sites, including cancer of the nasopharynx and larynx and Hodgkin’s disease, have been associated with exposure to wood dust in several epidemiologic studies. However, these findings were positive in some, but not all, studies, and the overall epidemiologic evidence is not strong enough or consistent enough to allow firm conclusions about the role of wood dust exposure in the development of cancer at these other sites (IARC 1995, NTP 2000). There is inadequate evidence for the carcinogenicity of wood dust from studies in experimental animals. No tumors attributable to beech wood dust exposure were found in inhalation studies in female Sprague-Dawley rats, female Wistar rats, or male Syrian golden hamsters or in intraperitoneal injection studies in female Wistar rats. Similarly, inhalation exposure to wood dust did not significantly affect the incidence of tumors induced by simultaneous exposure to other compounds, including formaldehyde in female Sprague-Dawley rats, sidestream cigarette smoke in female Wistar rats, or Nnitrosodiethylamine in male Syrian golden hamsters. However, each of these studies suffers from various limitations, such as small numbers of animals or dose groups, short study duration, or inadequate data reporting (IARC 1995). Dermal exposure to a methanol extract of beech wood dust resulted in a significant dose-related increase in the incidence of skin tumors (squamous-cell carcinoma and papilloma) and mammary tumors (adenocarcinoma, adenoacanthoma, and mixed tumors) in female NMRI mice (IARC 1995).