Energy from cellphone towers may trigger pain in amputees

Cellphone towers and other technologies that emit electromagmetic fields may cause amputees to feel pain in their injured limbs, a new study has found for the first time.
Until now there was no scientific evidence to back the stories of people who reported aberrant sensations and neuropathic pain around towers that produce radio-frequency electromagnetic fields (EMFs).
"Our study provides evidence, for the first time, that subjects exposed to cellphone towers at low, regular levels can actually perceive pain," said senior author Mario Romero-Ortega, an associate professor at The University of Texas at Dallas.
Most of the research into the possible effects of cellphone towers on humans has been conducted on individuals with no diagnosed, pre-existing conditions.

The team hypothesised that the formation of neuromas - inflamed peripheral nerve bundles that often form due to injury - created an environment that may be sensitive to EMF-tissue interactions.
To test this, the team randomly assigned 20 rats into two groups - one receiving a nerve injury that simulated amputation, and the other group receiving a sham treatment.

Researchers then exposed the subjects to a radiofrequency electromagnetic antenna for 10 minutes, once per week for eight weeks.
The antenna delivered a power density equal to that measured at 39 metres from a local cellphone tower - a power density that a person might encounter outside of occupational settings.

Researchers found that by the fourth week, 88 per cent of subjects in the nerve-injured group demonstrated a behavioural pain response, while only one subject in the sham group exhibited pain at a single time point, and that was during the first week.
After growth of neuroma and resection - the typical treatment in humans with neuromas who are experiencing pain - the pain responses persisted.
"Many believe that a neuroma has to be present in order to evoke pain. Our model found that electromagnetic fields evoked pain that is perceived before neuroma formation; subjects felt pain almost immediately," Romero-Ortega said.

Researchers also performed experiments at the cellular level to explain the behavioural response.
That led researchers to explore the protein TRPV4, which is known to be a factor in heat sensitivity and the development of allodynia - experience of pain from a non-painful stimulation of the skin, such as light touch - which some subjects displayed.
"It is highly likely that TRPV4 is a mediator in the pain response for these subjects," Romero-Ortega said.
Romero-Ortega said since the research produced pain responses similar to those in anecdotal reports and a specific human case, the results "are very likely" generalisable to humans.

The study was published in the journal PLOS ONE.