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Moulds, bacteria and cancer among Finns: an occupational cohort study
  1. A Laakkonen1,
  2. P K Verkasalo2,
  3. A Nevalainen2,
  4. T Kauppinen1,
  5. P Kyyrönen3,
  6. E I Pukkala3
  1. 1
    Finnish Institute of Occupational Health, Helsinki, Finland
  2. 2
    National Public Health Institute, Department of Environmental Health, Kuopio, Finland
  3. 3
    Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Helsinki, Finland
  1. Dr A Laakkonen, Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, FI-00250 Helsinki, Finland; aarne.laakkonen{at}


Background: Some environmental moulds and bacteria produce carcinogenic toxins.

Aim: To study associations between work-related exposure to moulds and bacteria and cancers in Finland.

Methods: A cohort of all economically active Finns in the population census in 1970 were followed-up for 30 million person-years. Subsequent cancer cases were identified through record linkage with the Finnish Cancer Registry. Observed and expected numbers of cancer cases were calculated by occupation, sex, birth cohort and period of observation. Exposures to moulds of agricultural and industrial origin and to bacteria of non-human origin were estimated with the Finnish Job–Exposure Matrix.

Results: Men with the highest mould and bacterial exposure had a reduced relative risk for lung cancer (RR 0.7, 95% CI 0.6 to 0.9 for moulds and RR 0.9, 95% CI 0.8 to 1.0 for bacteria). Women in the highest mould and bacterial exposure category had RRs of 3.1 (95% CI 1.0 to 9.2) and 2.6 (95% CI 1.5 to 4.7) for cervical cancer, respectively. The respective RRs for lip cancer were 2.4 (95% CI 1.2 to 5.1) and 1.6 (95% CI 1.2 to 2.2).

Conclusions: Exposures at the investigated concentrations to either moulds or bacteria are unlikely to be major risk factors of cancer, although suggestions of risk increases were observed for some cancer types. It has been suggested previously that the decreased risk for lung cancer is due to the protective effect of endotoxins.

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  • Competing interests: None declared.