Emissão de radiação eletromagnética não ionizante na cidade do Natal: caracterização, avaliação e modelamento com base na intensidade do campo elétrico e na taxa de exposição

Abstract

The electromagnetic waves used in the telecommunication systems until the 1980’s were considered by the governments environmental control organs as apparently “clean” forms of energy, whose effects weren’t considered any harmful to people’s health. The development of the mobile cellular telecommunication, beginning in the 1990’s, and the frenetic construction of antennas in the cities’ urban areas scared the population in general and turned the attention of the world’s scientific community to the theme. In a poor Brazilian State, such as Rio Grande do Norte – RN (GDP:R$ 51,4 billion in 2013) , the amount of cellular phones in operation went from 340.000 in 2002 to 4.6 million phones in 2014. In RN the number of cellular lines overcomes its own population, with a density of 128.98 accesses for each 100 inhabitants. Natal, the capital city of the State, with 850.000 inhabitants, already has 885 radio base stations of the cellular systems in 167.26 km² of urban area. The data is from ANATEL (august 2015). The objective of this work is to make a diagnosis about the actual situation of the emission of non-ionizing electromagnetic radiation in all urban area of the city of Natal. The methodology used took into account measurements of the intensity of the radiation taken in 160 different sites throughout the city. This radiation was measured in the range of 88MHz to 2.400 MHz. The collected data was compared to the limits of exposure of the ICNIRP (International Commission on Non Ionization Protection). The ICNIRP parameters used as reference were: “intensity of electric field” and “exposure ratio”. The telecommunication services researched were: TV broadcasting, FM radio broadcasting, cellular systems and WLAN (IEE 802.11bg). The obtained results allowed the drawing of a map comparing the data between the measured values and the limits of exposure to RNI defined by ICNIRP and ANATEL. The evaluation criteria used was the parameters Intensity of Electric Field and Exposure Ratio (ER). Results: according to the measurements taken, 48.48% of the outdoor electromagnetic exposure in the municipality of Natal are originated from TV transmitters. Similarly, in 77.2% of the researched locations, the intensity of the electric field originated from TVs overcomes all the rest of the wireless telecommunication services, including the cellular system. Based on the information that the radiation emitted by the TV transmitters is the most relevant in the city, a model to estimate the intensity of the electric field resulting from this service in any point in town was developed. This model was developed based on multivariate regression techniques. The final equations obtained allowed the estimative of the electric field with a level of precision R2> 0,9 and p<0,1. It was found that the exponent RF propagation attenuation in Natal varies between 2.6 and 2.8.The average Exposure Rate (ER) to NIR observed in the researched frequency rate was of 4.43.10-3, while the maximum value was of 7.67. 10- Conclusions: The results of the study demonstrated that the levels of electromagnetic exposure to NIR in outdoor environments in the city of Natal are lower than the security limits set by ICNIRP and ANATEL. The services that contribute most to NIR in Natal are 1-TV, 2- Cellular System and 3-FM Radios.