Doctoral defence of M.Sc. Madar Talibov on November 4, 2016

Doctoral defence of M.Sc. Madar Talibov

Occupational Exposures and Risk of Adult Leukemia: A population-based study in the Nordic countries

The field of science of the dissertation is Epidemiology.

The opponent is Bengt Järvholm (Umeå University, Sweden). Docent Susanna Lehtinen-Jacks acts as the custos.

The language of the dissertation defence is English.

Occupational Exposures and Risk of Adult Leukemia: A population-based study in the Nordic countries

Leukemia is a cancer of blood. Its four major types are acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL). While a number of genetic, life-style, therapeutic and environmental factors have been linked to an increased risk of leukemia, the evidence to date is inconsistent on majority of these factors. The aim of this study was to evaluate associations between various occupational agents and adult leukemia. The study was based on the Nordic Occupational Cancer Studies (NOCCA), which includes 14.9 million persons from the Nordic countries. Occupational information and cancer cases were identified from national cancer registries.

In Study I, leukemia incidences (18 811 AML, 20 462 CLL and 15 570 other non-specified leukemia) in 53 occupational categories were compared to corresponding incidences in general population. In Study II, risk of AML associated with occupational exposure to solvents was assessed in a matched case-control study based on 15 332 AML cases and 76 660 controls. In Study III, risk of AML following occupational exposure to low-frequency magnetic fields (ELF-MF) and electrical shocks was evaluated in a matched case-control setting consisting of 13 435 AML cases and 67 175 controls. In Study IV, reliability of NOCCA job-exposure matrix (NOCCA-JEM) was assessed by comparing NOCCA-JEM based cosmic radiation dose estimates to individual dose estimates from Radiation and Nuclear Safety Authority, Finland (STUK) among 5 022 Finnish airline workers (1 535 cockpit and 3 487 cabin crew members).

Study I showed that AML incidence among drivers and food workers, CLL incidence among farmers and clerical workers, and incidence of other non-specified leukemia among seamen, other health workers, chemical process workers, and sales agents was slightly elevated. On the other hand, AML incidence among forestry workers and seamen, CLL incidence among seamen, and incidence of other non-specified leukemia among fishermen was significantly reduced compared to general population. Study IV demonstrated large disagreement between NOCCA-JEM and individual dose estimates.

In conclusion, observed small leukemia excess in some occupational categories maybe associated with exposure to specific occupational agents. However, studies on solvent, ELF-MF and electrical shocks exposures did not demonstrate any association with adult leukemia. A large disagreement between NOCCA-JEM and individual dose estimates from STUK suggested that NOCCA-JEM can lead to cosmic radiation exposure misclassification in NOCCA studies.

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The dissertation is published in the publication series of Acta Universitatis Tamperensis; 2220, Tampere University Press, Tampere 2016. ISBN 978-952-03-0247-4, ISSN 1455-1616. The dissertation is also published in the e-series Acta Electronica Universitatis Tamperensis; 1720, Tampere University Press 2016. ISBN 978-952-03-0248-1, ISSN 1456-954X.