Epidemiological study (observational study)

Incidence of selected cancers in Swedish railway workers, 1961-79 epidem.

By: Floderus B, Törnqvist S, Stenlund C

Published in: Cancer Causes Control 1994; 5 (2): 189-194

Aim of study (acc. to author)

The incidence of leukemia, lymphoma, tumors of the brain, breast, and the pituitary gland was investigated among railway workers in Sweden.

Further details

The present study is a re-analysis of the study of Floderus et al (1993) in which the 1961-1979 incidence data showed no increase in risk for leukemia and brain tumors for railway workers. In the present study, follow-up was divided into two 10-year periods 1961-1969 and 1970-1979 because the structural change in the railway industry could mean that a large proportion of subjects in the exposure groups was exposed to high levels of EMF only during the very first period, and that this could dilute a potential effect.

Endpoint/type of risk estimation

Type of risk estimation:

incidence

Exposure

- 16 2/3 Hz (train)
- magnetic field
- occupational

Exposure groups

Group	Description
Group 1	engine drivers
Group 2	conductors
Group 3	engine drivers and conductors
Group 4	railway workers (station masters, train dispatcher, railroad assistants and linemen)
Group 5	workers in the railway industry

Population

Group:
- men
Age: 20–64 years
Characteristics: railway workers employed in 1960
Observation period: 1960 - 1979
Study location: Sweden
Data source: Cancer Environment Registry

Other:

17,150,940 person-years in 1961-1969 and 19,056,600 person-years in 1970-1979

Results (acc. to author)

Overall, there seem to be elevated estimates for the exposure groups during the first decade, which are not seen during the second period of follow-up.
For the first decade 1961-1969, engine drivers and conductors combined had an relative risk (RR) of 1.9 (CI 0.9-4.0) for chronic lymphocytic leukemia, of 1.4 (CI 0.4-4.3) for acute myeloid leukemia, and 1.0 (CI 0.5-1.9) for lymphoma. For all brain tumors, the RR was 1.2 (CI 0.8-1.9), with a higher risk estimate for those below age 30 (RR 12.2, CI 2.8-52.5). Three cases of breast cancer and nine cases of tumors of the pituitary gland occurred among engine drivers and conductors (RR 4.9, CI 1.6-11.8; RR 3.2, CI 1.6-6.2, respectively).
The authors conclude that the results give some support to the hypothesis of an association between EMF and certain types of cancers in railway workers.

Limitations (acc. to author)

Occupation was only defined at baseline in 1960, therefore a potential occupational change is not incorporated.

Study funded by

National Board of Occupational Safety and Health; Sweden

Grundy A et al. (2016): Occupational exposure to magnetic fields and breast cancer among Canadian men
Sun JW et al. (2013): Electromagnetic field exposure and male breast cancer risk: a meta-analysis of 18 studies
Röösli M et al. (2007): Mortality from neurodegenerative disease and exposure to extremely low-frequency magnetic fields: 31 years of observations on Swiss railway employees
Park SK et al. (2004): Ecological study on residences in the vicinity of AM radio broadcasting towers and cancer death: preliminary observations in Korea
Minder CE et al. (2001): Leukemia, brain tumors, and exposure to extremely low frequency electromagnetic fields in Swiss railway employees
Alfredsson L et al. (1996): Cancer incidence among male railway engine-drivers and conductors in Sweden, 1976-90
Tynes T et al. (1994): Leukemia and brain tumors in Norwegian railway workers, a nested case-control study
Floderus B et al. (1993): Occupational exposure to electromagnetic fields in relation to leukemia and brain tumors: a case-control study in Sweden
Balli-Antunes M et al. (1990): The mortality from malignancies of haematopoietic and lymphatic systems (MHLS) among railway engine drivers. Is exposure to low frequency electromagnetic fields associated with an increase of mortality from MHLS?