Does long-term cell phone use lead to brain tumors?

Islamabad, Jan 20 : The highest-quality research data available suggests that long-term exposure to microwaves from cellular phones may lead to an increased risk of brain tumors, reports a paper in the November/December issue of Journal of Computer Assisted Tomography.

Although debate continues, independent studies with long-term follow-up strongly suggest an increased risk of brain tumors related to the use of cellular or cordless phones. "We conclude that the current standard of exposure to microwave during mobile phone use is not safe for long-term exposure and needs to be revised," conclude the study authors, led by R.B. Dubey of Apeejay College of Engineering, Sohna, Gurgaon, India.

There is increasing public concern about the potential cancer risks from microwave emissions related to wireless phones -- not only cellular phones and base stations (transmission tower antennae), but also home cordless phones. Some studies have reported that long-term wireless phone users have increased rates of brain tumors, including malignant gliomas and benign acoustic neuromas. However, other studies have found no association.

To gain insight into the controversy, Dubey and colleagues performed an in-depth analysis of research on the health risks associated with microwave exposure from wireless phones. To date, only eleven published studies have provided data on the risk of developing brain tumors in long-term cell phone users -- ten years or longer.

The largest data source was a series of studies called the Interphone studies, which were largely funded by the wireless communications industry. Based on data from thirteen countries, the Interphone studies concluded that cell phone exposure did not increase the risk of brain tumors. In addition to possible bias associated with industry funding, the studies had some important flaws, including relatively short durations of cell phone use.

However, an independent series of studies led by Swedish cancer specialist Dr. Lennart Hardell reached a different conclusion. Dr. Hardell's studies included more patients who had used a cell phone for ten years or longer and were performed without financial support from the wireless industry. The findings suggested that the more hours of cellular phone use over time, the higher the risk of developing brain tumors. Risk also increased along with the level of power from the wireless device, years since first use, total exposure, and younger age when starting wireless phone use.

Based on an analysis of pooled data from different studies, researchers write, "[L]ong-term cell phone usage can approximately double the risk of developing a glioma or acoustic neuroma in the more exposed brain hemisphere" -- that is, on the side where the user typically holds the phone to the ear. That conclusion is consistent even with data on the long-term cell phone users from the Interphone studies.

It's unclear exactly how exposure to microwave radiation from cell phones may increase brain cancer risk. However, studies have shown that the cell signal is absorbed up to two inches in the adult skull. There is special concern about the risks in younger age groups, as cell phone signals penetrate much deeper into the brain in children.

Further studies are needed to definitively determine the risk of brain cancer and other health effects related to long-term use. Meanwhile, Dr. Dubey and coauthors suggest some steps that cell phone users can take to reduce exposure. These include limiting the number and length of calls, restricting children's cell phone use, communicating by text instead of voice, and wearing an "air tube" headset (not a regular wired headset) rather than holding the phone to the ear.

The researchers also urge adoption of newer phones and other technologies to reduce exposure, and call for government action to revise standards for microwave exposure.

"The precautionary principle clearly applies in this case, since the problem is possible but not certain and low cost ameliorating actions are easily implemented by industry," Dubey and coauthors conclude. "With over 3 billion people using cell phones and with children among the heaviest users, it is time for governments to mandate precautionary measures to protect their citizens."

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