Case-control study on occupational exposure to extremely low-frequency electromagnetic fields and glioma risk

Exposure to extremely low-frequency electromagnetic fields (ELF-EMF) was in 2002 classified as a possible human carcinogen, Group 2B, by the International Agency for Research on Cancer (IARC) at WHO. In the international Interphone study on mobile phone use and glioma risk, glioma was associated with occupational ELF-EMF exposure in recent time windows. The authors concluded that such exposure may play a role in late stage carcinogenesis of glioma.

We assessed life time occupations in case-control studies during 1997-2003 and 2007-2009 on e.g. use of wireless phones and glioma risk. An ELF-EMF Job-Exposure Matrix was used for associating occupations with ELF exposure (μT). Cumulative exposure (μT-years), average exposure (μT), and maximum exposed job (μT) were calculated.

Cumulative exposure gave for astrocytoma grade IV (glioblastoma multiforme) in the time window 1-14 years before diagnosis odds ratio (OR) = 1.9, 95% confidence interval (CI) = 1.4-2.6, p linear trend <0.001, and in the time window 15+ years OR = 0.9, 95% CI = 0.6-1.3, p linear trend = 0.44 in the highest exposure categories 2.75+ and 6.59+ μT-years, respectively.

We concluded that we found an increased risk in late stage (promotion/progression) of astrocytoma grade IV for occupational ELF-EMF exposure. No statistically significant interaction was found between exposure to ELF-EMF and use of wireless phones (exposure to radiofrequency radiation; RF-EMF). They were independent risk factors for astrocytoma grade IV.