The AIIMS professor and his team of neurologists recently analysed results of 22 case-controlled studies conducted globally on 48,452 participants from 1966 to 2016 that reported the results for the risk of brain tumour.
Of this, 10 were funded by government, seven had mixed-funding from phone industry, government and mobile manufacturers and at least three studies were solely funded by the phone industry.
Results of this analysis, which has been published in medical journal Neurological Sciences, states that while government funded studies have a quality score of 7 or 8, all studies by phone industry and mixed sources have a score of 5 or 6. Lower quality score points to increased risk of selection or measurement bias that can affect results.
AIIMS research shows studies with higher quality score show a trend towards harm, while lower quality score studies show a trend towards protection. "It is baffling how certain studies even propound that mobile phone use can protect against brain tumour," said a researcher.
Meta-analysis, according to sources of funding, clearly shows a consistent increase in risk of brain tumour with mobile phone use of more than 10 years. While summary estimate of government funded studies shows a 1.64 times increase in odds, mixed funded studies shows a 1.05 times increase in the odds of risk of brain tumours, the AIIMS research states.
It clarifies that data for more than 10 years of use were not available for phone industry funded studies, a major weakness from the point of view of analysing a possible link between mobile phone radiation and the risk of brain tumour on long-term use.
Dr Prasad said the association between mobile phone use and the risk of brain tumour is beset with controversies. The AIIMS paper provides an insight into the underlying reasons for this. "Our aim is not to denigrate the technology that has revolutionised the way we communicate. We want people to avoid non-essential use to reduce the risk of health hazards such as brain tumour," he added.
Mobile phones emit radio waves, a form of non-ionizing radiation, from their antennas. Tissues nearest to the antenna can absorb this energy. These radio waves are classified as possibly carcinogenic to human by the International Agency for Research on Cancer (IARC). Children, who have soft tissues near the ear, are at the highest risk of brain tumour, say doctors.
"You should use wireless hands-free system (headphone, headset) with a low power bluetooth emitter to reduce radiation risk to the head. Keeping calls short or send text messages instead, especially in the case of children, adolescents and pregnant women, is advised," a doctor add.
Brain tumour is just one of the potential health hazards from radiation exposure. Many top scientific institutions have been commissioned by the Union government to investigate its link with irreversible infertility - use of cell phones by men is associated with a decrease in semen quality, interference with other gadgets including pace makers, tinnitus and ear damage, and neuro-degenerative diseases.
In 2011, an inter-ministerial committee had said mobile phone towers should not be installed near high-density residential areas, schools, playgrounds and hospitals after reviewing available research, some of which held that radiation from mobile phones and towers posed serious health risks, including loss of memory, lack of concentration, disturbance in the digestive system and sleep disturbances.
The committee pointed to research which claimed that disappearance of butterflies, bees, insects and sparrows from big cities could be due to radiation from mobile phone towers. However, cellphone operators have been resisting curbs on installing towers saying there is still no evidence on the cause-and-effect relationship between exposure and health hazard, a fact conceded by many senior scientists.