Caught in radiation trap
KOLKATA: Constables on duty at Gariahat crossing are exposed to radio frequency (RF)radiation level that is 500 times more than the safe limit for short time exposure.
For a traffic police posted at the Gurusaday Road-Syed Amir Ali Avenue intersection, it's 120 times more.
For bhelpuri and ice-cream vendors in front of South City Mall, the exposure to radiation is 80 times the safe limit.
The extensive network of fixed cellular wireless antennas in the city has turned its streets into a radiation minefield with recorded levels making a mockery of the safety standard set by the government. Adopting the international standards, the maximum permissible RF exposure from radiation source - base station antennas - was set as 9.2 watt per square metre (W/m{+2}) at 1,800 MHz in India before 2012. A revised amendment has reduced the RF radiation to one tenth the previous value concerning the health hazard of citizens, thus setting the limit as 0.92 W/m{+2} at 1,800 MHz and 0.47 W/m{+2} at 900 MHz.
Measurement of street-level electromagnetic radiation show that even at a distance of 80 metre from a cell site, exposure to RF radiation is dangerously high. If one considers 1-10 W/m{+2} as safe limit for exposure, then a field study by students of electronics and telecommunication engineering (ETCE) department at Jadavpur University shows that few pockets in the city are safe.
Of the 33 locations where readings were taken, the metre read below 10 W/m{+2}{+ }only at two places: in front of the Indian Association for Cultivation of Science and Acharya Prafulla Chandra Roy Polytechnic College. The remaining 31 locations recorded readings ranging between 20 W/m{+2} and 5,000 W/m{+2}.
In addition to the 33 sites, measurements were recorded inside three buildings in Salt Lake, including a hospital. At all three locations, RF exposure was well above the prescribed norm. At the third and fourth floor of Kolkata Heart Clinic Hospital, the readings were 200 W/m{+2} and 400 W/m{+2}, respectively. At the entrance of Gold Castle Loop, the reading was 3,500 W/m{+2}. The measurement of RF radiation on the roof of a residential building at BL block with a cell site located 50 metre away was 5,000 W/m{+2}.
"There have been several articles about ailments from RF radiation exposure. But the quantum of RF radiation in the city was not mentioned. We had discussed the radiation issue in class and students were curious to know if the hazard was for real. That is when the owner of a company called us to find out the radiation level in the office located at Elgin Road. Once we did the study, we decided to map some more areas to find out what the average radiation in the city was like," recounted ETCE department professor Iti Saha Misra.
Armed with an HF 35 C radiation detector that operates within frequency range 800 MHz - 2.5 GHz and measures the radiation power density in W/m2, the JU research team comprising PhD scholar Anindita Kundu and B. ETCE students Bindita Choudhuri, Banishree Ghosh and Jyotibdha Acharya set out to measure the RF radiation at various locations in the city. The findings left them astounded.
The analysis of the data showed that while high radiation was detected when a cell site was located in the vicinity, there was a quantum jump in radiation level at locations that were overlapped by multiple base stations. Researchers said the high-power density in a place may occur due to two factors: high transmitting power or high gain of the transmitting antenna. Another major factor that emerged from the study was that radiation was most in the direction at which the antennas of a cell site pointed.
"Antennas installed at very low height with high gain cause large radiation power density at the ground level. Also, very high directive antennas installed in close proximity may cause high received cumulative radiation though the distance may be in excess of 300 metre. These cases were observed in many places. Obviously, such installation should be avoided in densely populated areas," said Misra.
"There are no guidelines for long-term RF exposure concerning health hazards. Herein lies the significance for surveying the present cellular base station RF radiation in the city area and their impact on human health where population density is very high," Misra added.
Interestingly, the study also observed that phone calls could be made and received with complete voice clarity where radiation power density was as low as 2-3 W/m{+2} in an indoor building surrounded by thick walls. So careful planning in installation of base stations can ensure that calls be made without unnecessarily high RF radiation.
Radiation Exposure is predominantly determined by the following parameters:
* Distance from antenna: More the distance from transmitting antennas, less is the receiving power density
* Line of sight to antenna or straight line radiation from transmitter to receiver antenna
* Type of antennas: Omni directional (equal radiation in all directions); directional (radiation is higher in a specified direction)
* Number: How many antennas are installed)
* Power: How much is the transmitting power in watt
* Orientation of antennas
* Capacity of antenna site: number of channels, frequencies
* Total reflection of environment and other multipath phenomena
Examples:
* The building housing Charu Medical Hall in Jadavpur that has several antennas on the roof recorded considerably low reading below the building. But when the detector was moved south west to the building and the measurement taken at Jadavpur subway entrance, the maximum reading recorded was 1,000 W/m2. Incidentally, the antennas were pointing in towards the subway
* The building opposite Ice Skating Rink has one large antenna installed at the top. There is high radiation observed in the opposite side. While it is 1500 W/m2 outside Bally High Apartments opposite Ice Skating Rink, 1,250 outside CCFC, 220 outside Haldiram's and 150 outside Hindustan Copper
* The building beside Mizoram House has many antennas installed on a single tower at the top of the building, Large radiation density was observed along the horizontal direction. At Mizoram House, the measurement was 1,300 W/m{+2} while that at the building next to Birla Temple was 350 W/m{+2}.
* Multiple antennas on a building opposite South City Mall causes power density of 900-1,000 W/m{+2} in some direction. In front of South City Mall, the reading was 800 W/m{+2}
On May 31, 2013, Iti Saha Mishra drove from Gariahat in south Kolkata to Hedua in north Kolkata and took readings along the way. Here's what the metre read:
Gariahat-Golpark crossing: 1,000
Gariahat Tram Depot: 1,400
Ballygunge Phanri crossing - 800
Park Circus crossing on Surawardy Avenue: 2,000
Lady Brabourne College: 50
Chittaranjan Medical College: 100
Entally-Moulali crossing: 1,200
NRS Hospital: 400-500
Sealdah flyover: 900-1,000
College Street: 350
Thanthania Kalibari: 250
Amherst St police station: 1,000
Loha Patti: 1,800
Bethune College gate: 70
(All Measurement in W/m{+2}{+ })
Country Power Density (W/m{+2})
US:10
Canada:3
Australia:2
Belgium (ex Wallonia): 1.2
India:0.92
New Zealand:0.5
Belgium:0.24
Poland:0.1
China:0.1
Italy:0.1
Switzerland:0.095
Russia: 0.02
Bulgaria:0.02
Hungary:0.02
http://timesofindia.indiatimes.com/city/kolkata/Caught-in-radiation-trap/articleshow/20468794.cms
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