Epidemiological study (observational study)

Occupational Exposure to Electromagnetic Field and Breast Cancer Risk in a Large, Population-Based, Case-Control Study in the United States epidem.

By: McElroy JA, Egan KM, Titus-Ernstoff L, Anderson HA, Trentham-Dietz A, Hampton JM, Newcomb PA

Published in: J Occup Environ Med 2007; 49 (3): 266-274

Aim of study (acc. to author)

A population-based case-control study was conducted in the USA to investigate occupational exposure to electromagnetic fields and breast cancer risk.

Further details

Exposure was assessed according to the job exposure scheme of Coogan et al. (publication 1912) which is based on strength of potential magnetic field source, proximity of workstation to the source and how frequently a worker is at the workstation proximate to the source.

Endpoint/type of risk estimation

breast cancer

Type of risk estimation:

incidence

(odds ratio (OR))

Exposure

- 50/60 Hz
- magnetic field
- occupational

Assessment

interview: occupational history beginning at age 14 for any job held for at least 1 year with at least 4 hours/week
job exposure matrix

Exposure groups

Group	Description
Reference group 1	exposure: background
Group 2	exposure: low
Group 3	exposure: medium
Group 4	exposure: high
Group 5	premenopausal women, exposure: background
Group 6	premenopausal women, exposure: low
Group 7	premenopausal women, exposure: medium
Group 8	premenopausal women, exposure: high
Group 9	postmenopausal women, exposure: background
Group 10	postmenopausal women, exposure: low
Group 11	postmenopausal women, exposure: medium
Group 12	postmenopausal women, exposure: high
Group 13	high potential for exposure: computer programmer
Group 14	high potential for exposure: assembler, electrical accessories
Group 15	medium potential for exposure: bookkeeper
Group 16	medium potential for exposure: data entry clerk
Group 17	medium potential for exposure: accounting clerk
Group 18	medium potential for exposure: telephone operator
Group 19	medium potential for exposure: accountant
Group 20	medium potential for exposure: payroll clerk

Population

Group:
- women
Age: 20–69 years
Observation period: not specified
Study location: USA (Massachusetts, New Hampshire and Wisconsin)

Case group

Characteristics: breast cancer
Data source: cancer registries

Control group

Selection:
- population-based
Matching:
- sex
- 5-year age group

Study size

	Cases	Controls
Eligible	8,066	10,161
Participants	6,429	7,683
Participation rate	80 %	76 %
Evaluable	6,213	7,390

Statistical analysis method:

logistic regression

(adjustment:

age
residential area
in second analysis adjusted for age, state and gynecological factors

)

Results (acc. to author)

A statistically not significant, slighly increased risk for breast cancer was observed for low, medium and high occupational exposure compared with the reference group. A statistically significant increased risk was found for data entry clerks.
The authors concluded that their findings, taken together with previous studies (publications 1912, 6826, 10719, 10081, 1048, 1060, and 10438), suggest that occupational exposure to electromagnetic fields might be associated with a slight elevation in breast cancer risk.

Limitations (acc. to author)

It is difficult to derive accurate exposure assessment from occupational data.

Study funded by

National Institutes of Health (NIH), Maryland, USA

Zhang Y et al. (2016): Meta-analysis of extremely low frequency electromagnetic fields and cancer risk: a pooled analysis of epidemiologic studies
Zhao G et al. (2014): Relationship between exposure to extremely low-frequency electromagnetic fields and breast cancer risk: a meta-analysis
Koeman T et al. (2014): Occupational extremely low-frequency magnetic field exposure and selected cancer outcomes in a prospective Dutch cohort
Li W et al. (2013): Occupational Exposure to Magnetic Fields and Breast Cancer Among Women Textile Workers in Shanghai, China
Chen Q et al. (2013): A Meta-Analysis on the Relationship between Exposure to ELF-EMFs and the Risk of Female Breast Cancer
Chen C et al. (2010): Extremely low-frequency electromagnetic fields exposure and female breast cancer risk: a meta-analysis based on 24,338 cases and 60,628 controls
Forssen UM et al. (2005): Occupational magnetic fields and female breast cancer: a case-control study using Swedish population registers and new exposure data
Kliukiene J et al. (2004): Residential and occupational exposures to 50-Hz magnetic fields and breast cancer in women: a population-based study
Kliukiene J et al. (2003): Follow-up of radio and telegraph operators with exposure to electromagnetic fields and risk of breast cancer
Labreche F et al. (2003): Occupational exposures to extremely low frequency magnetic fields and postmenopausal breast cancer
van Wijngaarden E et al. (2001): Population-based case-control study of occupational exposure to electromagnetic fields and breast cancer
Kliukiene J et al. (1999): Incidence of breast cancer in a Norwegian cohort of women with potential workplace exposure to 50 Hz magnetic fields
Floderus B et al. (1999): Occupational magnetic field exposure and site-specific cancer incidence: a Swedish cohort study
Coogan PF et al. (1996): Occupational exposure to 60-hertz magnetic fields and risk of breast cancer in women