## Wednesday, September 11, 2013

### Of Cellphone Radiation and Sparrows

[UPDATE: Harmful but not lethal an article from the print edition of today's The Hindu newspaper has some content from the essay below.]

A wave has a wavelength, usually thought of as the length of a successive crest and trough. When continuous and unobstructed, a wave repeats this ‘crest+trough unit’ endlessly. If we stand at a location, how many such crest+trough units pass us in a given time determines the frequency of the wave. Longer the wavelength, shorter the frequency of a wave.

Sea waves and sound waves require medium (matter) to propagate. But electromagnetic (EM) radiation are waves that don’t require a medium to propagate. Sunlight is an example, called the visible radiation. All such EM waves we put to use can be placed in a slot in the electromagnetic spectrum, a continuous band of several wavelengths (and hence, frequencies) as shown in the accompanied graphics.

In photoelectric effect electrons are released from metals subjected to EM radiation bombardment. Importantly, this effect depends on the frequency of the incident radiation and not on its intensity. This was shown in 1905 by Einstein and is a direct proof of the quantized nature of electromagnetic radiation. In 1922, he won his Nobel for this proof. Take home point? Higher the radiation frequency of the EM wave, greater the ‘damage’ caused by that radiation.

EM spectrum is split into two zones; ionizing and non-ionizing radiation. If we take the visible radiation (Sunlight) to be approximately in the center, the radiation spectrum to the right of this starting from the ultraviolet radiation including X-rays and gamma-rays , are ionizing radiation. These radiation with higher frequencies (hence with more energy) are capable of knocking-off few electrons from the atoms of the object they pass through, resulting in ionization (electrically neutral atoms by losing electrons become ions). When the objects are live human tissue, such ionization is harmful as we learnt painfully by 1945. X-ray machines emanate X-rays and long-term exposure to this is definitely harmful for humans. Hence radiologist advice against taking X-rays in general, for children. Ultraviolet rays, for instance, have higher frequency than visible blue light and are harmful to human body. Considerable melanin on the skin can give a temporary protection hence advertisements for products that claim to increase the skin melanin content.

Cell phone radiation is in the microwave range of the electromagnetic spectrum, next to radiation from microwave ovens. Microwave radiation falls in frequency between visible radiation (Sunlight) and radio waves (used as carrier by radio and TV programs). All the radiation to the left of visible radiation are termed non-ionizing radiation; due to their lower frequencies they don’t have sufficient energy to knock-off electrons from atoms of the objects they pass through. But they could heat the objects.

Holding a cellphone to the ears and conversing for an hour results in heating of the ears and the brain region exposed to the radiation. This heating can result in macro-level changes within the brain like dilation of blood vessels (called vaso-dilation, wherein temporary additional blood flow is directed to the overheated region for cooling) and even haemorrhage. Importantly, neither this heating nor the microwave radiation results in ionization of brain atoms or DNA mutation. Prolonged exposure (over several hours) resulting in sustained heating is suspected to possibly affect at the DNA level. But as such there is no evidence of such DNA mutation in research literature. The one study that linked cellphone radiation to possible DNA mutation in rats is invalidated as those results were not reproducible.

All over the World, the radiation absorbed by the body from a cellphone antenna during talking is measured in Specific Absorption Rate (SAR) values. Prescribed safe SAR values are enforced in the manufacture of cellphones. In India a committee, comprising representatives from the Health Ministry, Department of Biotechnology and Member Secretary, DoT recommend SAR values for cellphones operating in India not to exceed 1.6 Watts/kg. Violating such standards would lead to health hazards. Such cellphones should strictly be banned.

Also, microwave radiation is not carcinogenic. Exposure to cellphone radiation and only that in time directly leads to DNA mutations and growth of cancerous tumours in humans or living things is a conjecture not yet proved with scientific results. Proof, in this context, is difficult to obtain either way. One could only deduce from experimental evidence that are repeatable and data, some general conclusions with limits of applicability. As of today, propositions like ‘cellphone microwave radiation cause cancer or brain tumour’ is not based on scientific evidence. Contrary unsubstantiated claims and doubts are just that.

A chief concern among the public as per media reports of a certain variety is cellphone radiation to cause decline in sparrow population, disruption to bee and squirrel habitat and so on.

Sparrows are ‘affected’ by cellphone radiation just like any other living being. Tying a cellphone in operation to a sparrow’s body can lead to heating of the sparrow, which in itself is uncomfortable. Beyond this there is no correlation between cellphone radiation -- whether from the hand-held devices or towers -- and decline in sparrow population. There are two other valid reasons for their decline. Increase in garbage and insecticides. Sparrows feed insects to their young-ones. Rampant insecticide uses in fields – this can be verified to be on the increase over the last several decades – have reduced insect population and/or have infected them. Shortage of food this way leads to sparrow decline. A second reason is due to this ‘food’ shortage, sparrows have begun to scavenge in garbage. Over the decades garbage (at least in heavily populated cities) has increased several folds. This results in the increase in crow population; crows hunt down sparrows as competitors for their food. These two plausible reasons for decline in sparrows can be verified with ornithologists.

There has been news about sparrow eggs breaking when kept in contact with a cell phone in operation for considerable time. This is neither surprising nor alarming. Eggs break for several reasons. In this case they break because prolonged absorption of microwaves from the cellphone heats them causing macro cracks on the brittle shell. The same can be observed if the eggs are placed inside a microwave oven or for that matter on any hot surface for sufficient time. Cellphone microwave radiation due to the resulting heating when absorbed for a while can pop corn kept nearby, as one could verify at home.

No evidence exists that the microwaves cause DNA mutation in the egg yolk or cause irreparable damage to atoms. As can be verified, talking over your cellphone at home doesn’t break the eggs in the kitchen, an otherwise quick albeit messy way to make omelettes for breakfast. Prolonged exposure also doesn’t result in such breakage. If this were true, eggs randomly should pop-off in nests all over a region due to incessant cellphone microwave radiation noise.

Anecdotal evidence is not scientific proof; media reports are not peer-reviewed research results. Critical thinking is a welcome asset in understanding reality.

***

References:

Electromagnetic pollution from phone masts. Effects on wildlife
http://www.sciencedirect.com/science/article/pii/B9780444522726002099

(To date, there is no clear evidence for adverse health effects of RF-EMF, as long as limit values are not exceeded. This is partly due to the facts that (1) results of experimental studies have not been replicated and (2) the number of persons who have been exposed over a long time period has been limited.)

Another research paper
http://www.sciencedirect.com/science/article/pii/S0928468009000030

Good website with info.
http://www.ehso.com/ehshome/cellphonecancer.php