Epidemiological study

Parental occupational exposure to low-frequency magnetic fields and risk of leukaemia in the offspring: findings from the Childhood Leukaemia International Consortium (CLIC) epidem.

By: Talibov M, Olsson A, Bailey H, Erdmann F, Metayer C, Magnani C, Petridou E, Auvinen A, Spector L, Clavel J, Roman E, Dockerty J, Nikkilä A, Lohi O, Kang A, Psaltopoulou T, Miligi L, Vila J, Cardis E, Schüz J

Published in: Occup Environ Med 2019; 76 (10): 746-753

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Aim of study (acc. to author)

The association between parental occupational exposure to extremely low frequency magnetic fields and the risk of leukemia in their offspring was studied in a pooled analysis of the Childhood Leukemia International Consortium (CLIC).

Further details

Two analytical approaches were used. First, a pooled analysis was performed including 11 case-control studies from 8 countries. Second, a meta-analysis was conducted based on individual risk estimates of the 11 case-control studies and further case-control studies (Smulevich et al. (1999), Feychting et al. (2000), Pearce et al. (2003) und Reid et al. (2011)).

Endpoint/type of risk estimation

childhood leukemia: acute lymphatic leukemia (B- and T-cell lineages), acute myeloid leukemia

Type of risk estimation:

incidence

(odds ratio (OR))

Exposure

- occupational

Assessment

job exposure matrix: developed by Turner et al. (2014)

Exposure groups

Group	Description
Reference group 1	paternal occupational exposure: ≤ 0.2 µT
Group 2	paternal occupational exposure: > 0.2 µT
Reference group 3	paternal occupational exposure: < 0.1 µT
Group 4	paternal occupational exposure: 0.1 - ≤ 0.2 µT
Group 5	paternal occupational exposure: > 0.2 - ≤ 1 µT
Group 6	paternal occupational exposure: > 1 µT
Reference group 7	maternal occupational exposure: ≤ 0.2 µT
Group 8	maternal occupational exposure: > 0.2 µT
Reference group 9	maternal occupational exposure: ≤ 0.1 µT
Group 10	maternal occupational exposure: > 0.1 - ≤ 0.2 µT
Group 11	maternal occupational exposure: > 0.2 µT

Population

Group:
- children
- children in utero
Age: 0–14 years
Observation period: 1989 - 2011
Study location: Finland, France, Germany, Greece, Italy, New Zealand, UK, USA
Data source: The Childhood Leukemia International Consortium
Exclusion criteria: Down's syndrome

Study size

Type	Value
Total	26,822

Other:

overall 9,723 children with leukemia and 17,099 controls; analyzed: 8,420 children with ALL and 16,453 controls, 926 children with AML and 12,246 controls

Statistical analysis method:

unconditional logistic regression
heterogeneity test, Forest plots, sensitivity tests

(adjustment:

child: age, sex; education of either parent, case accrual time, study

)

Results (acc. to author)

No statistically significant association between paternal or maternal occupational exposure to extremely low frequency magnetic fields and the risk for leukemia in their offspring was found. Similar results were observed for ALL or AML or in the highest exposure category.
The meta-analysis showed an increased overall risk of leukemia with borderline significance for paternal exposure (OR 1.11, CI 1.00-1.22) but not for maternal exposure (OR 1.04, CI 0.92-1.17).
The authors concluded that they did not find any associations between parental occupational exposure to extremely low frequency magnetic fields and childhood leukemia in the large international dataset.

Study funded by

not stated/no funding

Zhang Y et al. (2016): Meta-analysis of extremely low frequency electromagnetic fields and cancer risk: a pooled analysis of epidemiologic studies
Keegan TJ et al. (2012): Case-control study of paternal occupation and childhood leukaemia in Great Britain, 1962-2006
Reid A et al. (2011): Risk of childhood acute lymphoblastic leukaemia following parental occupational exposure to extremely low frequency electromagnetic fields
Hug K et al. (2010): Parental occupational exposure to extremely low frequency magnetic fields and childhood cancer: a German case-control study
Pearce MS et al. (2007): Paternal occupational exposure to electro-magnetic fields as a risk factor for cancer in children and young adults: a case-control study from the North of England
Ali R et al. (2004): A case-control study of parental occupation, leukemia, and brain tumors in an industrial city in Taiwan
Infante-Rivard C et al. (2003): Maternal occupational exposure to extremely low frequency magnetic fields during pregnancy and childhood leukemia
McKinney PA et al. (2003): Parental occupation at periconception: findings from the United Kingdom Childhood Cancer Study
Feychting M et al. (2000): Parental occupational exposure to magnetic fields and childhood cancer (Sweden)
Sorahan T et al. (1999): Maternal occupational exposure to electromagnetic fields before, during, and after pregnancy in relation to risks of childhood cancers: findings from the Oxford Survey of Childhood Cancers, 1953-1981 deaths
Smulevich VB et al. (1999): Parental occupation and other factors and cancer risk in children: II. Occupational factors
Infante-Rivard C et al. (1991): Acute lymphoblastic leukaemia among Spanish children and mothers' occupation: a case-control study
Shu XO et al. (1988): A population-based case-control study of childhood leukemia in Shanghai