Febrero 2006

Two more Interphone studies

Interphone is the multinational series of case-control studies to assess whether radiofrequency radiation exposure from cell phones is associated with the cancer risk. Another two Interphone studies have been published. (For others, see “What’s New April, May, and September ’05). The first is from five areas of the UK, and addresses the risk of glioma in relation to cell phone use. The Odds Ratio (OR) for regular phone use was 0.94, which is consistent with no increased risk. There was a significantly increased OR of 1.24 for reported phone use on the same side as the tumour, but there was a significantly reduced risk on the opposite side. This is consistent with recall bias, seen when knowledge of the tumour site influences information given about which side of the head was usually used for phoning. The main weakness of the study was the low response rate - 51% for patients with glioma and 47% for controls.

The second was from Germany, and looked at cases of glioma and meningioma. Like the UK study, the overall use of a cell phone was not associated with brain tumour risk. The ORs for glioma and meningioma were 0.98 and 0.84 respectively. Among persons who had used a cell phone for 10 years or more, the OR was 2.20, although the risk was not statistically significant, since the 95% confidence intervals were 0.94 and 5.11. This result was based on 12 cases. The participation rates were 79.6% for glioma cases and 62.7 % for controls.

Reference: Hepworth SJ, Schoemaker MJ, Muir KR, Swerdlow AJ, et al. (2006): Mobile phone use and risk of glioma in adults: case-control study. BMJ (published online 20 January)

Schuz J, Bohler E, Berg G, Schlehofer B, et al. (2006): Cellular phones, Cordless phones, and the risks of glioma and meningioma (Interphone study group, Germany). Am J Epidemiol (published on-line January 27).

And two more papers from Hardell and colleagues

Hardell and colleagues have added to their lengthy list of publications with two recent papers. The first pools results from two separate studies with similar methodology, and examines the risk of benign brain tumours in users of analogue and digital cell phones, and also in cordless phone users. Many results are reported. In the multivariate analysis there was a statistically significant increased risk for acoustic neuroma in analogue phone users. The OR was 2.5. The second paper reported the results of their latest case-control study. The paper concentrates on malignant tumours. The authors found increased risks in all of the user groups, even after multivariate analysis (although the risk was not statistically significant in digital phone users). These results contrast markedly with the results emerging from the various Interphone studies.

For more on the Interphone studies, and those of Hardell et al., see "Research-Epidemiology".

Reference: Hardell L, Carlberg M, Mild KH (2006a): Pooled analysis of two case-control studies on the use of cellular and cordless telephones and the risk of benign brain tumours diagnosed during 1997-2003. Int J Oncol 228:509-518.

Hardell L, Carlberg M, Mild KH (2006b): Case-control study of the association between the use of cellular and cordless telephones and malignant brain tumours diagnosed during 2000-2003. Environ Res 100:232-241.

Four genotoxic studies with varied results

A study by Sakuma and colleagues has failed to show and evidence of DNA damage in cells exposed to radiofrequency radiation (RFR). The RFR exposure was from the International Mobile Telecommunication system (IMT-2000). The cells were exposed for either 2 or 24 hours at SARs between 0.8 and 8 W/kg. There were no significant differences between RFR-exposed and sham-exposed cells in the alkaline comet assay, an indicator of DNA damage.

Baohong et al. report that RFR exposure (1.8 GHz, SAR 3 W/kg) with chemical mutagens mitomycin C and 4-nitroquinoline-1-oxide had greater effects on DNA damage in human lymphocytes than those seen with the chemical mutagens alone.

Finnie found no effect on the proto-oncogene c-fos in rat brain cells after the animals had been exposed to RFR for 60 minutes (900 MHz, SAR 4W/kg).

Lee and colleagues used serial analysis of gene expression to assess the effect of 2.45 GHz RFR on cultured human HL-60 cells (SAR 10 W/kg). They found that a large number of genes altered their expression after 2 and 6 hours exposure.

For more, see "Research - Toxicological -cancer studies".

References: Sakuma N, Komatsubara Y, Takeda H, Hirose H, et al. (2006): DNA strand
breaks are not induced in human cells exposed to 2.1425 GHz band CW and W-CDMA
modulated radiofrequency fields allocated to mobile radio base stations.
Bioelectromagnetics 27:51-57.

Baohong W, Jiliang H, Lifen J, Deqiang L, et al. (2005): Studying the synergistic damage effects induced by 1.8 GHz radiofrequency field radiation (RFR) with four chemical mutagens on human lymphocyte DNA using comet assay in vitro. Mutat Res 578:149-157.

Finnie JW (2005): Expression of the immediate early gene, c-fos, in mouse brain after acute global system for mobile communication microwave exposure. Pathology 37:231-3.

Lee S, Johnson D, Dunbar K, Dong H, et al. (2005): 2.45 GHz radiofrequency fields alter gene expression in cultured human cells. FEBS Letters 579:4829-4836.

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