Specific Absorption Rate (SAR)

Specific absorption rate is the measure of the rate at which energy is absorbed by the body when exposed to a radio frequency (RF) in electromagnetic field. The term is not restricted to the absorption of Electromagnetic Feild (EMF) and can be used in terms of absorption of other forms of energy by tissue, including ultrasound. In short SAR is the power absorbed per mass of tissue and its unit is Watts per kilogram (W/kg).

Why the term was in news recently?

  • An Inter-ministerial committee was set up by the government under Ministry of Communications & Information Technology to examine the effect of EMF Radiation from base stations and mobile phones on human health and environment and to suggest safety limits for exposure to radio frequency energy produced by mobile hand-sets i.e. Specific Absorption Rate (SAR) levels of exposure from a mobile hand-set and disclosure of information for the hand-sets.

What is the SAR limit suggested by the committee?

  • It has suggested SAR limit for mobile handsets of 1.6 watt/kg averaged over a 6 minutes period and taken over a volume containing a mass of 1 gram of human tissue.

What is the importance of keeping the radio frequency levels under control?

  • In the current context, with the boom in communication technology and expanse of mobile network the exposure of humans to the EM field has increased drastically. Quite a number of law suits and writ petitions have been filed by individuals / groups alleging health effect of radiation.

What is the effect of EMF on human health?

  • As per studies human beings are bio electrical systems. The heart and the brain are regulated by internal bioelectrical signals. Environmental exposures to EMF can interact with fundamental biological processes in the human body and in some cases this may cause discomfort. In a human body due to the proximity of a mobile phone to the head, the head is the targeted recipient of the electro-magnetic energy from many wireless systems whose impulses are transmitted to other organs and parts. A high frequency signal modulated at certain low frequency or a signal i.e. pulsed may have harmful effects than an un-modulated study carrier, as reported in literature.
  • Modulation signals are one important component in the delivery of EMF signals to which cells, tissues, organs and individuals can respond biologically. Modulating signals have a specific beat defined by how the signal varies periodically over time. Modulation signals may interfere with normal, nonlinear biological functions.
  • People who are chronically exposed to low level wireless antenna emissions and users of mobile handsets have reported feeling several unspecific symptoms during and after its use, ranging from burning and tingling sensation in the skin of the head, fatigue, sleep disturbance, dizziness, lack of concentration, ringing in the ears, reaction time, loss of memory, headache, disturbance in digestive system and heart palpitation etc.
  • There are reports indicating adverse health effects of cell phones which emit electro-magnetic radiation, with a maximum value of 50% of their energy being deposited when held close to the head. However, The  effects of long term exposure to wireless  technology including emissions from cell phones and whole body exposure to RF transmission from cell tower antenna is simply not known yet with certainty.
  • Scientific studies as yet have not been able to confirm a cause-and-effect relationship. The research has not so far separated these symptoms from electromagnetic radiation hence all the above symptoms can also be attributed to stress.

What is Electro-pollution ? What is its impact on environment? 

  • The electromagnetic radiation pervading the environment is now increasingly realized and this has added to the list of another pollutant in the environment i.e. electro-pollution.
  • Some Studies reported that mortality at communication towers over 200 ft. may be a threat to the healthy population of birds and electromagnetic radiation from cell phone towers may probably be the reasons for the vanishing butterflies, bees, insects and sparrows.  Some other Studies have also shown that there seems to be effects on birds exposed to the electromagnetic field radiation and losing navigational ability. They get disoriented and begin to fly in different direction. However, these studies were unable to find a direct link of exposure of EMF radiation to adverse effects on birds.