Fresh concerns over cell phones, cancer link
SCIENTISTS have long been worried about the possible harmful effects of regular cellular phone use, but so far no study has managed to produce clear results. Currently, cell phones are classified as carcinogenic category 2b- potentially carcinogenic to humans- by the International Agency for Research on Cancer (IARC).
A new Tel Aviv University, Israel, study, though, may bring bad news.
To further explore the relationship between cancer rates and cell phone use, Dr. Yaniv Hamzany of Tel Aviv University's Sackler Faculty of Medicine and the Otolaryngology Head and Neck Surgery Department at the Rabin Medical Center, looked for clues in the saliva of cell phone users. Since the cell phone is placed close to the salivary gland when in use, he and his fellow researchers, including departmental colleagues Profs. Raphael Feinmesser, Thomas Shpitzer and Dr. Gideon Bahar and Prof. Rafi Nagler and Dr. Moshe Gavish of the Technion in Haifa, hypothesized that salivary content could reveal whether there was a connection to developing cancer.
Comparing heavy mobile phone users to non-users, they found that the saliva of heavy users showed indications of higher oxidative stress- a process that damages all aspects of a human cell, including DNA- through the development of toxic peroxide and free radicals. More importantly, it is considered a major risk factor for cancer.
The findings have been reported in the journal Antioxidants and Redox Signaling.
For the study, the researchers examined the saliva content of 20 heavy-user patients, defined as speaking on their phones for a minimum of eight hours a month. Most participants speak much more, Hamzany says, as much as 30 to 40 hours a month. Their salivary content was compared to that of a control group, which consisted of deaf patients who either do not use a cell phone, or use the device exclusively for sending text messages and other non-verbal functions.
Compared to the control group, the heavy cell phone users had a significant increase in all salivary oxidative stress measurements studied.
'This suggests that there is considerable oxidative stress on the tissue and glands which are close to the cell phone when in use,' he says. The damage caused by oxidative stress is linked to cellular and genetic mutations, which cause the development of tumors.
This field of research reflects longstanding concerns about the impact of cell phone use, specifically the effects of radiofrequency non-ionizing electromagnetic radiation on human tissue located close to the ear, say the researchers. And although these results don't uncover a conclusive 'cause and effect' relationship between cellular phone use and cancer, they add to the building evidence that cell phone use may be harmfaul in the long term, and point to a new direction for further research.
One potential avenue of future research would be to analyze a person's saliva prior to exposure to a cell phone, and then again after several intense minutes of exposure. This will allow researchers to see if there is an immediate response, such as a rise in molecules that indicate oxidative stress, Hamzany says.
However, a very big study published in October 2011 showed no link between mobile phones and cancer. The study published in British Medical Journal found there is no link between long-term use of mobile phones and tumours of the brain or central nervous system.
In what is described as the largest study on the subject to date, Danish researchers found no evidence that the risk of brain tumours was raised among 358,403 mobile phone subscribers over an 18-year period.
The number of people using mobile phones is constantly rising with more than five billion subscriptions worldwide in 2010. This has led to concerns about potential adverse health effects, particularly tumours of the central nervous system.
Previous studies on a possible link between phone use and tumours have been inconclusive particularly on long-term use of mobile phones. Some of this earlier work took the form of case control studies involving small numbers of long-term users and were shown to be prone to error and bias.
The International Agency for Research on Cancer (IARC) recently classified radio frequency electromagnetic fields, as emitted by mobile phones, as possibly carcinogenic to humans.
The only cohort study investigating mobile phone use and cancer to date is a Danish nationwide study comparing cancer risk of all 420,095 Danish mobile phone subscribers from 1982 until 1995, with the corresponding risk in the rest of the adult population with follow-up to 1996 and then 2002. This study found no evidence of any increased risk of brain or nervous system tumours or any cancer among mobile phone subscribers.
So researchers, led by the Institute of Cancer Epidemiology in Copenhagen, continued this study up to 2007 (GUARDIAN).
They studied data on the whole Danish population aged 30 and over and born in Denmark after 1925, subdivided into subscribers and non-subscribers of mobile phones before 1995. Information was gathered from the Danish phone network operators and from the Danish Cancer Register.