Mobile phone base station towers boost cell reception, not childhood cancer risk, a British study has shown.
Children whose mothers lived near a high-output cell phone antenna mast while pregnant were no more likely to develop childhood cancer than those who lived farther away, found Paul Elliott of Imperial College London and colleagues. The researchers reported their findings online in the British Medical Journal.
It's possible that the study, despite being the largest of its kind, may have missed a small effect for certain less common childhood cancers, noted John F. Bithell of the University of Oxford, England in an accompanying editorial. However, overall the anxiety about environmental risk from cell tower proximity is likely unfounded, he concluded.
"Moving away from a mast, with all its stresses and costs, cannot be justified on health grounds in the light of current evidence," he warned in BMJ.
Levels of individual exposure to radiofrequencies are much lower from cell towers than from mobile phones themselves, he said. The largest study to date found no increased risk from use of cell phones at any "plausible" level.
Thus, what patients should worry about is not the frequencies they're exposed to, but the way they use the phone, Bithell suggested.
"The risks are dwarfed by the well known dangers of distraction while using mobile phones, especially when driving-even when using hands-free equipment," he wrote in the editorial.
But because of the high levels of public concern, Elliott's group conducted a study looking at all 1,397 cases of central nervous system cancer, leukemia, and non- Hodgkin's lymphomas in children up to age 4 years in the U.K. national cancer registry from 1999 to 2001.
Another 5,588 children from the U.K. national birth registry, matched by sex and date of birth to the experimental group, served as controls.
What the researchers found was that childhood cancer cases didn't have mothers that lived any closer to cell towers at the time of birth than did controls. Total power output of base stations within 700 meters of the mother's address at time of birth was likewise similar for cases and controls. A measurement known as modelled power density -- the best estimate of in utero exposure, according to Bithell -- at the mother's home address was also no different between cases and controls.
After making adjustments for small area measures of education level, socioeconomic deprivation, population density, and population mixing, the researchers found no difference between the lowest modelled power density exposure and intermediate exposure or the highest exposure for brain and central nervous system cancers.
Likewise, for leukemia and non-Hodgkin's lymphoma, intermediate modelled power density exposure and the highest exposure during pregnancy didn't appear to increase risk compared with the lowest exposure.
The researchers noted that these findings counter reports of apparent clusters of small numbers of cancer cases living near mobile phone antennas, which "are subject to possible selection and reporting biases."
The size and national scope of their study would avoid these biases, but the study could not account for the weakening of radiofrequency field strength inside of the home or individual exposures or exposure from other sources of electromagnetic fields, such as maternal use of cell phones.